This PDF file contains the front matter associated with SPIE Proceedings Volume 8915, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Non-contact and remote measurements of vital physical signals are important for reliable and comfortable physiological self-assessment. In this paper, we provide a new video-based methodology for remote and fast measurements of vital physical signals such as cardiac pulse and breathing rate. A webcam is used to track color video of a human face or wrist, and a Photoplethysmography (PPG) technique is applied to perform the measurements of the vital signals. A novel sequential blind signal extraction methodology is applied to the color video under normal lighting conditions, based on correlation analysis between the green trace and the source signals. The approach is successfully applied in the measurement of vital signals under the condition of different illuminating in which the target signal can also be found out accurately. To assess the advantages, the measuring time of a large number of cases is recorded correctly. The experimental results show that it only takes less than 30 seconds to measure the vital physical signals using presented technique. The study indicates the proposed approach is feasible for PPG technique, which provides a way to study the relationship of the signal for different ROI in future research.

Photodynamic therapy (PDT) of cancer works via direct cytotoxicity, causing damage to tumor vasculature and stimulating the body’s anti-tumor immune response. PDT outcome depends on the parameters used; therefore an in vivo tumor response monitoring system is useful for optimization of the treatment protocol. The combined use of diffuse optical spectroscopy and diffuse correlation spectroscopy allows us to measure the tissue oxygen saturation (StO₂) and relative blood flow (rBF) in tumors. These parameters were measured before and after PDT in mouse tumor models and were calculated as ratios relative to the baseline in each tumor (rStO₂ and rBF). Readings were also measured in drugonly control tumors. In responders (mice with tumor eradication), significant PDT-induced decreases in both rStO₂ and rBF levels were observed at 3h post-PDT. The rStO₂ and rBF readings in these mice remained low until 48h post-PDT, with recovery of these parameters to baseline values observed 2 weeks after PDT. In non-responders (mice with partial or no response), the rStO₂ and rBF levels decreased less sharply at 3h post-PDT, and the rBF values returned toward baseline values at 48h post-PDT. By comparison, the rStO₂ and rBF readings in drug-only control tumors showed only fluctuations about the baseline values. Thus tumor response can be predicted as early as 3h post-PDT. Recovery or sustained decreases in rStO₂ and rBF up till 48h post-PDT were correlated to long-term tumor control. Diffuse optical measurements can thus facilitate early assessment of tumor response to PDT to aid in treatment planning.

There exist a multitude of therapeutic options for the treatment of both benign and malignant tumors, where several of these options induce temperature changes in the tissue from several degrees centigrade to temperatures that ablate the region of interest (ROI). Recent advances in optical imaging technologies, namely optical coherence tomography (OCT) and Fiber Bragg Gratings (FBG), may provide the necessary hardware/software components to both monitor and quantify the direct biological response to temperature-mediated cancer therapies. Preliminary research has been conducted to identify and analyze the trends in temperature measurements from FBG's placed within phantoms that mimic the optical characteristics of human tissue. Shifts of the Bragg wavelength at selected temperature intervals depict the temperature of the phantom relative to room temperature. The scattering properties of tissue were achieved in the phantom by using 0.665 g of titanium dioxide (TiO₂ - Titanium (IV) oxide, anatase) nanopowder, with a particle size smaller than 25 nm, which was mixed into 475 mL of Penecro’s Versagel (hydrocarbon material). This mixture imitates the tissue’s index of refraction of ~1.4. Shifts in the Bragg wavelength were measured using a spectrum analyzer at temperature intervals at approximately 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C and 60°C. The results show that the relative Bragg wavelength is directly proportional to any increase or decrease of temperature in the phantom. In the case of these experiments, it was observed that the change in the bragg wavelength shift increased the phantom’s temperature was also increased with respect to the temperature set by the hot plate. The FBG regions that monitored temperature variations within the tissue-mimicking phantoms were also imaged, via OCT, to investigate temperature induced changes in the OCT images including investigation of changes in the OCT envelope statistics. This data may provide the base line to detect changes in the biological response to temperature variations, based solely on OCT images, and ultimately provide suitable imaging metric(s) to predict therapeutic outcome.

Concentrator photovoltaic (CPV) technology has come a long way, with multi-junction solar cell efficiencies now reaching up to 44.4%. Front contact grid design, crucial for improving efficiency, is typically performed for uniform illumination, but this does not account for the real world conditions of non-homogeneous irradiance distributions. In this work, we aim to optimize finger spacing for a linear grid under non-uniform illumination by using Simulation Program with Integrated Circuit Emphasis (SPICE) analysis. A two-dimensional distributed resistance model is used to simulate a lattice matched, triple-junction solar cell whose design parameters are determined by curve-fitting current-voltage curves from each sub-cell to a two-diode equivalent-circuit model. Cell efficiency is considered to be a unimodal function that varies with finger spacing so a golden-section search optimization algorithm is used to determine the optimal spacing. Various Gaussian profiles are used to simulate non-uniform illumination and their effects on device performance. Designs based on optimal spacing for non-uniform illumination show an efficiency increase of more than 0.5% absolute at concentrations greater than 500 suns.

One of the challenges associated with forecasting and evaluating concentrating photovoltaic system (CPV) performance in diverse locations is the lack of high-quality spectral solar resource data. Various local atmospheric conditions such as air mass, aerosols, and atmospheric gases affect daily CPV module operation. A multi-channel filter radiometer (MFCR) can be used to quantify these effects at relatively low cost. The proposed method of selectively sampling the solar spectrum at specific wavelength channels to spectrally reconstruct incident irradiance is described and extensively analyzed. Field spectroradiometer (FSR) measurements at the University of Ottawa's CPV testing facility (45.42°N, 75.68°W) are fed into our model to mimic the outputs from the MCFR. The analysis is performed over a two year period (2011-2012), using 46,564 spectra. A recommendation is made to use four aerosols channels at 420, 500, 780, and 1050 nm, one ozone channel at 610 nm and one water vapour channel at 940 nm, all of which can be measured with ubiquitous Si photodiodes. A simulation of this MFCR channel configuration produces an RMS error under 1.5% over 96% of the 350-1830 nm range, when compared with the FSR, for the 2012 data set in Ottawa.

A polycrystalline Cu(In,Ga)Se₂ (CIGS) single junction solar cell model is developed with dependencies on the molar fraction of In and Ga with a 0.8 eV Shockley-Read-Hall (SRH) trap level above the valence band. The simulated performance of this solar cell over molar fraction compares well to data published in the literature using the SRH minority carrier lifetime to fit the trend in open circuit voltage. The material parameters are then used as a foundation for a numerical model of a monocrystalline CIGS solar cell grown on a GaAs substrate with an emphasis on modeling the CIGS/GaAs interface where a molar fraction gradient in CIGS forms due to lattice mismatch induced inter-diffusion of Ga and In from the substrate and CIGS layers. Without strain effects due to the lattice mismatch, the CIGS monocrystalline solar cell has an efficiency of 18.6% under the AM1.5G spectrum (1000 W/m²) with a short circuit current density of 36.5 mA/cm², an open circuit voltage of 0.66 V and a fill factor of 77.4%. However, when reasonable strain effects are considered, such as the formation of strained induced interface defects and threading dislocation densities (TDD), the efficiency degrades to 6% for TDD < 1x10⁷ cm^-2. The models are able to reproduce a similar structure’s measured performance using a TDD of 1.5×10⁷ cm^-2 and a surface recombination velocity of 10⁸ cm/s at the CdS/CIGS interface.

Heterojunctions are inherent in and essential to all molecular electronic devices. In organic solar cells, in particular, heterojunctions play a defining role in all of the major electrical processes and particularly in stability. The p-type organic molecule diindenoperylene (DIP) is an interesting photoactive organic molecule that forms inherently unstable interfaces within organic solar cell devices. Using scanning probe microscopies, supported by x-ray scattering, we examined the stability of inorganic/organic interfaces at both charge extraction electrodes. The DIP morphology can be stabilized by: 1. roughening the ITO surface, which disrupts the molecular packing, 2. using an interlayer such as PEDOT:PSS, which modifies the surface energy, or 3. depositing a dielectric layer, LiF, which pins the DIP grain boundaries. Any combination of the approaches would lead to significant improvements in solar cell lifetime.

Concentrator photovoltaic (CPV) solar energy systems use optics to concentrate direct normal incidence (DNI) sunlight onto multi-junction photovoltaic (MJPV) cells fabricated from III-V compound semiconductors on germanium substrates. The MJPV receiver, which integrates cell and bypass diode, is then mated with its concentrating optic to form a channel, and several such channels form a CPV module, in which the receivers are connected electrically in series. The two ends of the module receiver string are brought out to a single pair of electrical connections, at which point the lightcurrent- voltage (L-I-V) response of the entire module can be tested. With commercial CPV modules commonly sealed against outdoor exposure, there are no other accessible test points, and field installation on trackers further complicates access to performance data. There are many physical phenomena influencing module performance, and in early development and commercialization some of these may not yet be completely under control. Unambiguous diagnosis of such phenomena from one full-module L-I-V curve is problematic. Simple, fast test methods are needed to develop more detailed information from full-module on-tracker testing, without opening up modules in the field. We describe a test protocol, using a simple optical shutter array constructed to fit mechanically over the module. When module L-I-V curves are recorded for each of various combinations of open and closed shutters, the information can be used to identify one or more anomalous channels, and to further identify the kind of anomaly present, such as optical misalignment, conductor failure, series or shunt resistance, and so on. Simulated results from anomaly models can be compared with the measured results to identify the anomalous behaviour. Results herein are compared with direct single-channel measurements to verify the technique. The L-I-V response curves were obtained in continuous real time, an approach found to be more helpful than single-shot capture in understanding field response. A triangular wave function generator is used to drive the DC power supply, and a four-channel digital sampling oscilloscope displays and stores the real time response. Where modules exhibit unstable or intermittent response under certain conditions, this is immediately obvious in real-time display.

Various space division multiplexing (SDM) schemes are currently investigated as a way to overcome the capacity limit of data links. We here focus on mode division multiplexing (MDM) in a multi-mode fiber (MMF). Towards long-haul data transmission, for which signal amplification is a key enabling component, we investigate a simple approach to precisely control the mode-dependent gain (MDG) between the co-propagating LP₀₁ and LP₁₁ modes of an erbium-doped few-mode fiber amplifier (MM-EDFA) by engineering a multi-ring doping profile. In practice, the mode dependent loss of the few-mode transmission fiber must be taken into account in order to equalize the gain for all modal channels. In a step towards practical implementation of MM-EDFA for long-haul SDM, we extend the single ring doping approach to incorporate multi-ring and multi-level doping. Through numerical simulations we study the optimization of the width and doping level of each ring so as to control the MDG. We further discuss the possibility of modal gain equalization through zero-differential modal gain (ZDMG) points in a single stage MM-EDFA, or via tuning of pump powers in a dual-stage MM-EDFA configuration.

Extensive research effort is ongoing in energy-efficient Internet-based communications. Optical Flow Switching (OFS) and Optical Burst Switching (OBS) offer potentially efficient alternatives to IP-router-based networks for large data transactions, but significant challenges remain. OFS requires each user to install expensive core network technology, limiting application to highly specialized nodes. OBS can achieve higher scalability but burst assembly/disassembly procedures reduce power efficiency. Finally both OFS and OBS use all-optical switching technologies for which energy efficiency and flexibility remain subject to debate. Our study aims at combining the advantages of both OBS and OFS while avoiding their shortcomings. We consider using a two-way resource reservation protocol for periodic concatenations of large (e.g. 1 Mb) packets or Media Frames (MFs). These chains of MFs (MFCs) are semi-transparent with a periodicity referred to as the “transparency degree”. Each MFC is assembled and stored at an end-user machine during the resource reservation procedure and is then switched and buffered electronically along its path. The periodic configuration of each MFC enables interleaving of several chains using buffering only to align the MFs in each MFC in time, largely reducing the buffer requirements with respect to OBS. This periodicity also enables a simple scheduling algorithm to schedule large transactions with minimal control plane processing, achieving link utilization approaching 99.9%. In summary, results indicate that implementing optical burst switching techniques in the electronic domain is a compelling path forward to high-throughput power-efficient networking.

We present the experimental results for a Raman amplifier that operates at 1810 nm and is pumped by a Raman fiber laser at 1680 nm. Both the pump laser and the Raman amplifier is polarization maintaining. A challenge when scaling Raman amplifiers to longer wavelengths is the increase in transmission loss, but also the reduction in the Raman gain coefficient as the amplifier wavelength is increased. Both polarization components of the Raman gain is characterized, initially for linearly co-polarized signal and pump, subsequently linearly polarized orthogonal signal and pump. The noise performance of the amplifier is also investigated for both configurations. Our results show an on/off gain exceeding 20 dB at 1810 nm for which the obtained effective noise figure is below 3 dB.

In optically-routed networks, different wavelength channels carrying the traffic to different destinations can have quite different optical signal-to-noise ratios (OSNRs) and signal is differently impacted by various channel impairments. Regardless of the data destination, an optical transport system (OTS) must provide the target bit-error rate (BER) performance. To provide target BER regardless of the data destination we adjust the forward error correction (FEC) strength. Depending on the information obtained from the monitoring channels, we select the appropriate code rate matching to the OSNR range that current channel OSNR falls into. To avoid frame synchronization issues, we keep the codeword length fixed independent of the FEC code being employed. The common denominator is the employment of quasi-cyclic (QC-) LDPC codes in FEC. For high-speed implementation, low-complexity LDPC decoding algorithms are needed, and some of them will be described in this invited paper. Instead of conventional QAM based modulation schemes, we employ the signal constellations obtained by optimum signal constellation design (OSCD) algorithm. To improve the spectral efficiency, we perform the simultaneous rate adaptation and signal constellation size selection so that the product of number of bits per symbol × code rate is closest to the channel capacity. Further, we describe the advantages of using 4D signaling instead of polarization-division multiplexed (PDM) QAM, by using the 4D MAP detection, combined with LDPC coding, in a turbo equalization fashion. Finally, to solve the problems related to the limited bandwidth of information infrastructure, high energy consumption, and heterogeneity of optical networks, we describe an adaptive energy-efficient hybrid coded-modulation scheme, which in addition to amplitude, phase, and polarization state employs the spatial modes as additional basis functions for multidimensional coded-modulation.

In this paper, the possibility of interleaving optical wavelengths of a WDM system among M cores is investigated. This technique results in wider channel spacing in each core and non-overlapping spectra among cores, which leads to significant reduction in nonlinear impairments and inter-core crosstalk. In the proposed architecture, a single WDM data is transmitted over M cores and a single in-line amplifier, which reduces the system cost. The impact of crosstalk between cores of a multi-core fiber on the system performance is studied.

Space-division multiplexing enables fiber capacity increase beyond the limits imposed on single mode fibers by the nonlinear Shannon limit. The capacity increase has to be implemented in a cost and energy efficient way in order to enable a commercially viable solution. Optical amplifiers using multi mode fiber as an active medium achieve better pump power efficiency than multi core fiber based amplifiers due to the higher density of modes. In addition, module optimization approaches can be implemented to further reduce the cost and energy per transported bit. Mutli mode fibers also posess a better capacity upgrade potential than multi core fibers due to the higher density of modes. Multiple input / multiple output processing can be deployed for signal equalization at the receiver, if mode coupling occurs during propagation along the link. An approach using adaptive optical filters for realization of the equalization function in the optical domain enables low installation costs and capacity upgrade on demand by adding transponders for the individual channels.

A novel architecture for generating incoherent, 2-dimensional wavelength hopping-time spreading optical CDMA codes is presented. The architecture is designed to facilitate the reuse of optical source signal that is unused after an OCDMA code has been generated using fiber Bragg grating based encoders. Effective utilization of available optical power is therefore achieved by cascading several OCDMA encoders thereby enabling 3dB savings in optical power.

With the advent of digital signal processing (DSP) in optical transmitters and receivers, the ability to finely tune the ratio of pre and post dispersion compensation can be exploited to best mitigate the nonlinear penalties caused by the Kerr effect. A portion of the nonlinear penalty in optical communication channels has been explained by an increase in peak to average power ratio (PAPR) inherent in highly dispersed signals. The standard approach for minimizing these impairments applies 50% pre dispersion compensation and 50% post dispersion compensation, thereby decreasing average PAPR along the length of the cable, as compared with either 100% pre or post dispersion compensation. In this paper we demonstrate that simply considering the net accumulated dispersion, and applying 50/50 pre/post dispersion is not necessarily the best way to minimize PAPR and subsequent Kerr nonlinearities. Instead, we consider the cumulative dispersion along the entire length of the cable, and, taking into account this additional information, derive an analytic formula for the minimization of PAPR. Alignment with simulation and experimental measurements is presented using a commercially available 100Gb/s dual-polarization binary phase-shift-keying (DP-BPSK) coherent modem, with transmitter and receiver DSP. Measurements are provided from two different 5000km dispersion managed Submarine test-beds, as well as a 3800km terrestrial test-bed with a mixture of SMF-28 and TWRS optical fiber. This method is shown to deviate significantly from the conventional 50/50 method described above, in dispersion managed communications systems, and more closely aligns with results obtained from simulation and data collected from laboratory test-beds.

The capability of a directly modulated laser (DML) can be dramatically enhanced through precise control of the drive current waveform based on digital signal processing (DSP) and a digital-to-analog convertor (DAC). In this paper, a novel method to pre-compensate fiber dispersion for metro and regional networks is described for a bit rate of 10.709 Gb/s using a DML. A look-up table (LUT) for the drive current is optimized for dispersion mitigation. The entries of the LUT are determined based on the effects of the DML adiabatic and transient chirp on pulse propagation, the nonlinear mapping between the input current and the output optical power, and the bandwidth of the DML package. A DAC operating at 2 samples per bit (21.418 GSa/s with 6 bit resolution) converts the digital samples at the output of the LUT to an analog current waveform driving the DML. Experimental results for a bit rate of 10.709 Gb/s and on-off keying demonstrate a transmission reach of 252 km using a DML intended for 2.5 Gb/s operation and 608 km using a chirp managed laser intended for 10 Gb/s operation. Using this approach (DSP + DAC), the generation of 10.709 Gb/s differential phase shift keying (DPSK) and 56 Gb/s 16-ary quadrature amplitude modulation, sub-carrier multiplexed (QAM SCM) optical signals using the direct modulation of a passive feedback laser is also presented. 6-bit DACs operating at sampling rates of 21.418 GSa/s and 28 GSa/s, respectively, was used to generate the requisite analog current waveform.

A novel scheme to simultaneously provide UWB, 60-GHz millimeter-wave (mmW), and baseband services over a wavelength division multiplexing (WDM) passive optical network (PON) is proposed and demonstrated. In the proposed system, an OOK Gaussian pulse signal is modulated on the optical carrier and then converted to an OOK UWB impulse signal at an edge filter, a baseband signal and a 30-GHz signal are then modulated on the same optical carrier. By employing polarization multiplex technique, the UWB and baseband signal will have orthogonal polarization directions and the spectrum interference between the two signals is avoided. By suppressing the optical carrier, a frequencydoubled mmW signal at 60 GHz is generated by beating the two 1st order sidebands at a photodetector (PD). Error-free transmission of a UWB signal at 2.5 Gbps and a wired baseband signal at 2.5 and 5 Gbps over a 25-km single-mode fiber (SMF) is achieved. A frequency-doubled mmW signal at 60 GHz is also obtained.

In a today’s world, information technology has been identified as one of the major factors driving economic prosperity. Datacenters businesses have been growing significantly in the past few years. The equipments in these datacenters need to be efficiently connected to each other and also to the outside world in order to enable effective exchange of information. This is why there is need for highly scalable, energy savvy and reliable network connectivity infrastructure that is capable of accommodating the large volume of data being exchanged at any time within the datacenter network and the outside network in general. These devices that can ensure such effective connectivity currently require large amount of energy in order to meet up with these increasing demands. In this paper, an overview of works being done towards realizing energy aware optical networks and interconnects for datacenters is presented. Also an OCDMA approach is discussed as potential multiple access technique for future optical network interconnections. We also presented some challenges that might inhibit effective implementation of the OCDMA multiplexing scheme.

We describe the design and characterization of a silicon nanophotonic waveguide (SNW) and its use in a reconfigurable microwave photonic filter (MPF). The SNW is dispersion tailored for efficient on-chip four-wave-mixing. We use the onchip four-wave-mixing to increase the number of taps in our multiple tap delay line MPF. The tap levels are controlled by a programmable filter. Using a 12 mm long SNW reduces the footprint by five orders of magnitude compared to silica highly nonlinear fiber while only requiring approximately two times more input power.

We demonstrate a range of novel functions based on a high index doped silica glass CMOS compatible platform. This platform has promise for telecommunications and onchip WDM optical interconnects for computing.

Optical information processing has traditionally been demonstrated using 3D free-space optical systems employing bulk optical components. These systems are bulky and unstable due to the stringent alignment tolerances that must be met. Taking advantage of the alignment accuracy offered by planar light circuits, these issues may be overcome by confining the light in a planar slab waveguide. The limitation on scaling, consequent on the loss of one dimension is offset by the nanoscale component footprints attainable in a silicon integration platform. A key component of this free-space-opticson- a-chip concept is a waveguide lens. Waveguide lenses are of general utility but our specific application is their use to implement the complex crossover interconnections of a switch fabric. The graded refractive index of the lens is engineered by patterning the silicon layer of silicon on insulator slab waveguides into a dense distribution of cylinders; either solid (silicon) or voids (air); using a single etch step. The cylinders have variable diameters and are placed on a regular square or hexagonal grid with sub-wavelength pitch. In the case of voids, the patterned silicon may be suspended in air to form the core of a symmetric slab waveguide. Solid cylinders must be supported by the Si02 layer leading to an asymmetric waveguide of reduced effective index range. Advantageously, the patterning of the metamaterial region within the slab-waveguide requires only a single etch step. Photonic wire feeder waveguides at different positions around the lens may be used to launch light into the lenses or collect light from the lenses. A method is developed to determine the local effective media index of a periodic metamaterial in terms of the parameters of its unit cell. This method is used as a calibration to lay out a metamaterial with graded parameters. The operation of a metamaterial Lüneburg lens telescope is verified by FDTD simulations and shown to be capable of near zero insertion loss and crosstalk. The careful approximation of the graded index of the Lüneburg lens by a metamaterial introduces minimal impairments.

We report on a design and simulation of silicon on insulator apodized surface diffraction grating fiber to chip coupler by sub-wavelength structure which is compatible with 193 nm laser DUV lithography. The structure of designed fiber to chip coupler consists of two parts: a relatively large tapered segment and a segment with the surface diffraction grating having sub-wavelength structure. The first segment adjusts cross-section of silicon on insulator wire single mode waveguide to standard single mode fiber diameter and the second one is designed for vertical coupling to the fiber. Four types of surface diffraction grating apodization by sub-wavelength structure are designed and simulated. The simulation of the fiber-to-chip coupler is performed by FDTD simulation method. The simulation results of coupling effects for each apodization of surface diffraction grating are evaluated and compared with each other.

The rapid proliferation of Electron Multiplying Charge Coupled Devices (EMCCDs) in recent years has revolutionized low light imaging applications. EMCCDs in particular show promise to enable the construction of versatile space astronomy instruments while space-based observations enable unique capabilities such as high-speed accurate photometry due to reduced sky background and the absence of atmospheric scintillation. The Canadian Space Agency is supporting innovation in EMCCD technology by increasing its Technology Readiness Level (TRL) aimed at reducing risk, cost, size and development time of instruments for future space missions. This paper will describe the advantages of EMCCDs compared to alternative low light imaging technologies. We will discuss the specific issues associated with using EMCCDs for high-speed photon counting applications in astronomy. We will show that a careful design provided by the CCD Controller for Counting Photons (CCCP) makes it possible to operate the EMCCD devices at rates in excess of 10 MHz, and that levels of clock induced charge and dark current are dramatically lower than those experienced with commercial cameras. The results of laboratory characterization and examples of astronomical images obtained with EMCCD cameras will be presented. Issues of radiation tolerance, charge transfer efficiency at low signal levels and life time effects on the electron-multiplication gain will be discussed in the context of potential space applications.

An experimental characterization of broadband semiconductor optical amplifiers (SOAs) at 1360 nm is reported. In addition to their inherent small size, fast dynamics, and feasibility of integration with other optoelectronic components, the relevance of the multi quantum well (MQW) asymmetric SOAs here reported relies on the achievement of a flat and broad 3 dB amplification bandwidth. SOAs are composed of nine _In1-xGa_xAs_yP_1-y 0.2% tensile strained MQW layers separated by latticed matched InP barriers. The asymmetry of the active region is based on the difference of the molar concentrations, with Ga (x) ranging from 0.46 to 0.47 and As (y) ranging from 0.89 to 0.94. Devices under test have 7 degrees tilt cleaved facets and feature different geometries: ridge widths from 2 to 4 μm in steps of 0.25 μm, and cavity lengths of 600, 900, 1200, and 1500 μm. Fabry-Pérot (FP) lasers with the same material composition as the SOAs and within the same wafer are used as test structures for parameters extraction, providing a feedback mechanism for further design improvement. The ridge width of the FP lasers varies from 2 to 8 μm, in steps of 2 μm. All the devices have been designed and characterized at the Photonics Technology Laboratory, Centre for Research in Photonics, fabrication was done at Canadian Photonics Fabrication Centre (CPFC), Canada and supported by CMC Microsystems. Devices under test are DC-biased and temperature controlled at 25°C. A single pass gain of 13.5 dB is measured for a 3 dB bandwidth of 60 nm centred at 1360 nm. Light-current plots obtained from the FP lasers show that the threshold current varies with the cavity length, with a minimum of 80 mA for a cavity length of 600 μm and a ridge width of 2 μm. A thermal roll-off occurring at high injection currents is observed, especially with the smallest cavity length. In conclusion, asymmetric MQW SOAs featuring different ridge widths and cavity lengths have been

Tunable optical delay devices have numerous applications in optical communications [1] and have been successfully implemented using slow light elements and fiber or waveguide gratings. There has been considerable interest in siliconon- insulator (SOI) as a technology platform for compact integration of optical signal processing systems. SOI-based delay lines have been realized using coupled ring resonators [2], photonic crystals [3], and various Bragg grating-based configurations including single or coupled chirped sidewall gratings [4,5] as well as tapered rib waveguide gratings [6]. By linearly chirping the period in sidewall gratings, relatively small delays (a few ps) over a bandwidth of tens of nm were demonstrated [4]; with tapered waveguides, significantly larger delays (300-500 ps) were obtained, albeit over a narrower bandwidth (< 2 nm) [6]. On the other hand, some signal processing applications may require large delays (e.g., tens to hundreds of ps) over large bandwidths (several to tens of nm). Several designs have been proposed to meet these requirements, e.g., a step-chirped rib waveguide grating providing 50 ps delay over 15 nm [7] or complementary apodized sidewall gratings providing up to 275 ps over 3 nm [8], however, they have not been realized experimentally. In this paper, we demonstrate discretely tunable optical delay lines that provide tens of ps delay (up to 65 ps) in steps of 15-32 ps over bandwidths of several tens of nm (35-70 nm). The devices are fabricated on SOI using electron beam lithography and implemented through two different approaches: serial sidewall Bragg grating arrays and the step-chirped sidewall Bragg gratings.

The 2x2 optical switch is a crucial component to the future of optical communications and integrated optics. Optical switches on the silicon-on-insulator (SOI) platform have shown advantages in terms of device footprint and switching speed. However, due to the intrinsic properties of SOI rib waveguides, these devices suffer from a strong wavelength and polarization dependent response. Our work presents an SOI based Mach-Zehnder interferometer (MZI) switch which is both polarization and wavelength insensitive over a large bandwidth of 1260-1360 nm. We have completed detailed analyses on the polarization and wavelength performance of the MZI, and obtained optimized parameters in a novel design to reduce the crosstalk f or transverse electric (TE) and transverse magnetic (TM) modes over the wavelength range 1260-1360 nm. Our simulations suggest that we successfully obtained a polarization and wavelength insensitive MZI. A crosstalk level below -18 dB is achieved for both the TE and TM modes in the on-state and the off-state, across the 100 nm bandwidth. Such a polarization and wavelength insensitive switch has a variety of applications in wavelength division multiplexing and other communication systems.

A fully-etched grating coupler with improved back re ection and bandwidth is demonstrated in this paper. It can also be made in compact patterns with much smaller footprints than conventional, fully-etched grating couplers with long adiabatic tapers. Sub-wavelength gratings were employed to form the e ective index areas between the major gratings. Our grating has a measured 3-dB bandwidth of 64.37 nm with a back re ection of -14 dB.

We demonstrated 2×2 broadband adiabatic 3-dB couplers based on silicon rib waveguides. Functioning as 50/50 optical power splitters, these devices can be used in optoelectronic applications. Fabricated using siliconon-insulator technology, we demonstrated the performance of the adiabatic 3-dB couplers by integrating two couplers into an unbalanced Mach-Zehnder Interferometer (MZI). Measurements of the MZI were made over a 100 nm wavelength range. Extinction ratios in excess of 33.4 dB were obtained over the wavelength range from 1520 nm to 1600 nm, for light injected into Input Port1 and measured at Output Port2, i.e., the cross port response.

The goal of this research is to introduce the design and simulation of a novel 2×2 SOI integrated photonic phased array switch. Under-etched NEMS-operated slot waveguides are used as the active phase shifters offering the benefits of compact size and low power consumption. The design of the NEMS-operated phase shifter has been validated by numerical analysis and simulation. The finite difference mode three-dimensional full-vectorial solver of FIMMPROP is used for the simulation. The designed NEMS-operated phase shift element is only 349 μm in length, exhibits an excess loss of about 1.1 dB and provides a phase shift of 180°. Straight transition slot waveguide couplers with high efficiency of about 96.7% have been designed to couple the NEMS-operated phase shifters to standard unslotted waveguides. The 2×2 MMI (multimode interference) couplers used in the switch element feature a compact size of 4μm × 61.2 μm, have a small excess loss of about 0.155 dB and minimal imbalance of about -0.004 dB. The NEMS-operated phase shifters are located on the sides of the switch with their outermost electrode bond pads. Optical interferogram response is utilized for the testing of the designed phase shifters.

Single-etch grating couplers provide efficient light coupling from optical fibers to photonic waveguides while having a very low fabrication complexity. Here, the use of a coupling coefficient profile solution permits an efficient optimization of the grating apodization profile and yields a simulated -4.8 dB coupling at 1550 nm. A very compact way to reduce back-reflections by up to 8 dB, by inserting a simple anti-reflective section, is also numerically investigated. Some proximity effects and minimum features of the 248 nm deep-ultraviolet lithography had a detrimental effect on the fabricated designs and the best experimental results were -7.5 dB. Nonetheless, these gratings, requiring a single-etch step fabrication process, should be useful when using e-beam prototyping.

A universal design methodology for grating couplers based on the silicon-on-insultator platform is presented in this paper. Our design methodology accomodates various etch depths, silicon thickness (e.g., 220 nm, 300 nm), incident angles, and cladding materials (e.g., silicon oxide or air), and has been verified by simulations and measurement results. Further more, the design methodology presented can be applied to a wide range, from 1260 nm to 1675 nm, of wavelengths.

Silicon photonics is going trough a terrific expansion driven by several applications, from chip wiring to integrated sensors and telecommunications. Some applications, e.g. intra and inter chip connections and sensing, require long parallel waveguides for wiring or for connecting grating couplers (GCs) to devices situated in sensing micro-channels. In well packed photonics chips there are often long wiring waveguides parallel for several mm, so loss can be caused by light coupled back and forth between them (cross-talk), by scattering, wall roughness, mode mismatch, etc. This work aims to investigate cross-talk for long parallel waveguides, and to propose methods to reduce cross-talk loss when high integration density is required. We have designed and fabricated about 200 testing structures exploiting e-beam on silicon on insulator (SOI) chip, in order to test several parameters and to find out dominant loss mechanisms. All devices have been tested and measured using an automatic optical bench, in the wavelength range between 1500-1600 nm. Achieved results are promising, since they allow for comparing cross-talk for short as well as long interaction lengths (up to 5 mm), different waveguide width pairs, several separation distances, and for TE and TM polarization. For smaller gaps, having not symmetric pair of waveguides is very beneficial, since it results in a lower power coupling, e.g. about 20/14 dB of crosstalk reduction for TE/TM waveguides after 5 mm of propagation and gap of 0.5 μm. This can be very useful for the design of integrated photonics chips requiring high-density packaging of devices and waveguides.

Photonic Integrated Circuits (PICs) enable photons as data carriers at a very high speed. PIC market opportunities call for reduced wafer dimensions, power consumption and cost as well as enhanced reliability. The PIC technology development must cater for the latter relentless traits. In particular, monolithic PICs are sought as they can integrate hundreds of components and functions onto a single chip. InGaAsP/InP laterally-coupled distributed feedback (LC-DFB) lasers stand as key enablers in the PIC technology thanks to the compelling advantages their embedded high-order surface-gratings have. The patterning of the spatial corrugation along the sidewalls of the LC-DFB ridge, has been established to make the epitaxial overgrowth unnecessary thereby reducing the cost and time of manufacturing, and ultimately increasing the yield. LC-DFBs boast a small footprint synonymous of enhanced monolithic integrate-ability. Nonetheless, LC-DFBs suffer from the adverse longitudinal spatial hole burning (LSHB) effects materialized by typically quite high threshold current levels. Indeed, the carrier density longitudinal gradient- responsible for modes contending for the available material gain in the cavity- may be alleviated somewhat by segmenting the LC-DFB electrode into two or three reasonably interspaced longitudinal sections. In this work we report on the realization and performance of various electrode partition configurations. At room temperature, the experimental characterization of many as-cleaved LC-DFB devices provides ample evidence of superior performance such as a narrow linewidth (less than 400 kHz), a wide wavelength tune-ability (over 4 nm) and a hop-free single mode emission (side mode suppression ratio (SMSR) exceeding 54dB).

We demonstrate the generation of dual-wavelength noiselike pulses in an Er³⁺ fiber laser. A ring cavity configu­ ration including a polarizer as saturable absorber induces a first series of pulses at the wavelength of 1550 nm via nonlinear polarization rotation. From the Raman gain of these pump pulses emerges a second series of Stokes pulses at 1650 nm. With an adequate control of the polarization states in the cavity, the Stokes pulses contain 67% of the total energy and reach a bandwidth of 84 nm in the U-band.

Propagation of large-wavevector bulk plasmonic waves in multilayer hyperbolic metamaterials (HMMs) with two levels of structuring is theoretically studied. It is shown that when the parameters of a subwavelength metal-dielectric multilayer (“substructure”) are modulated (“superstructured”) on a larger, wavelength scale, the propagation of bulk plasmon polaritons in the resulting multiscale HMM is subject to photonic band gap phenomena. A great degree of control over such plasmons can be exerted by varying the superstructure geometry. As an example, Bragg reflection and Fabry-Perot resonances are demonstrated in multiscale HMMs with periodic superstructures. More complicated, aperiodically ordered superstructures are also considered, with fractal Cantor-like multiscale HMMs exhibiting characteristic self-similar spectral signatures in the high-k band. The multiscale HMM concept is shown to be a promising platform for using high-k bulk plasmonic waves as a new kind of information carriers, which can be used in far-field subwavelength imaging and plasmonic communication.

Various approaches for the optical detection of chiral compounds have been developed due to their natural optical activity. Since the advantages of second harmonic generation (SHG) on noble-metal nanoparticles (NPs) have been observed, it would be interesting to study the nonlinear phenomena from chiral compounds attached Ag NPs. In the present work, we fabricated chiral-modified Ag NPs based on the self-assembly process of cysteine and Ag, and carried out the investigation on SHG on modified and unmodified Ag NPs. For modified Ag NPs, either L-Cysteine (L-C) or D-Cysteine (D-C), as a pair of enantiomers, was applied on top of the Ag NPs. The resulting chiral-modified monolayers of L-C/Ag NPs and D-C/Ag NPs exhibit a reversed optical rotation difference (ORD) at linearly ±45° polarization of SH, where no such difference exists for Ag NPs alone. SHG efficiently probes and discriminates L-C from D-C monolayers on the modified Ag NPs, which constitutes a simple and sensitive optical diagnostic of chiral molecules.

Nonlinear absorption is investigated in a poly (3-hexylthiophene) (P3HT) PCBM fullerene blend, one of the most popular organic solar cell’s materials. We observe three-photon absorption in the bulk hetero junction photodiode configuration. The output photocurrent of the photodiode is interpreted in terms of the three-photon absorption properties of the P3HT:PCBM blend at 1550 nm.

We look at the relationship between the preparation method of Si and Ge nanostructures (NSs) and the structural, electronic, and optical properties in terms of quantum confinement (QC). QC in NSs causes a blue shift of the gap energy with decreasing NS dimension. Directly measuring the effect of QC is complicated by additional parameters, such as stress, interface and defect states. In addition, differences in NS preparation lead to differences in the relevant parameter set. A relatively simple model of QC, using a ‘particle-in-a-box’-type perturbation to the effective mass theory, was applied to Si and Ge quantum wells, wires and dots across a variety of preparation methods. The choice of the model was made in order to distinguish contributions that are solely due to the effects of QC, where the only varied experimental parameter was the crystallinity. It was found that the hole becomes de-localized in the case of amorphous materials, which leads to stronger confinement effects. The origin of this result was partly attributed to differences in the effective mass between the amorphous and crystalline NS as well as between the electron and hole. Corrections to our QC model take into account a position dependent effective mass. This term includes an inverse length scale dependent on the displacement from the origin. Thus, when the deBroglie wavelength or the Bohr radius of the carriers is on the order of the dimension of the NS the carriers ‘feel’ the confinement potential altering their effective mass. Furthermore, it was found that certain interface states (Si-O-Si) act to pin the hole state, thus reducing the oscillator strength.

Under the proviso that the existing tight-binding (TB) and effective mass (EM) theoretical models provide a good description of the Ge dot energy gap versus dot diameter, this work investigates the effect of nanoparticle size and the size distribution on the near infrared PL spectrum obtained from self-assembled Ge dots grown on a thin layer of TiO₂ or SiO₂ on Si. For the as-grown samples, the dot PL emission occupies a wide near-infrared band between 0.8 and 1 eV. The PL efficiency versus dot size for four samples was obtained in three steps. Firstly, the PL spectrum was converted to an intensity plot versus dot diameter rather than energy by taking the PL emission from each dot to occur at the dot bandgap calculated using the TB or EM model. Secondly, a numerical form for the physical size distribution of that sample was obtained by performing a least-squares fit of a Gaussian to the dot size distribution measured by atomic force microscopy or transmission electron microscopy. Finally, the PL efficiency versus dot size was calculated using the fitted Gaussian dot size distribution to normalize the PL intensity distribution obtained in the first step. Although the absolute intensities of the PL from the samples vary, the calculated curves are all well-fitted by straight lines on a log-log plot with essentially the same slope for all samples, which indicates that under weak confinement there is a universal power-law increase in PL efficiency with decreasing dot size.

Maker Fringe measurements are a common method for measuring the second-order non-linear coefficient of materials. Typically these measurements are made with laser sources that have pulse lengths exceeding 10 ps. In this presentation we will explore the use of a femtosecond source in a Maker Fringe measurement. We will look at how femtosecond Maker Fringes differ from those made with longer pulse sources. We will compare our theoretical calculations to experiments performed in poled silica.

Whispering Gallery Modes (WGMs) have been widely studied for the past 20 years for various applications, including biological sensing. While the different WGM-based sensing approaches reported in the literature enable useful sensor characteristics, at present this technology is not yet mature, mainly for practical reasons. Our work has been focused on developing a simple, yet efficient, WGM-based sensing platform capable of being used as a dip sensor for in-vivo biosensing applications. We recently demonstrated that a dye-doped polymer microresonator, supporting WGMs, positioned onto the tip of a suspended core Microstructured Optical Fiber can be used as a dip sensor. In this architecture, the resonator is located on an air hole next to the fiber core at the fiber’s tip, enabling a significant portion of the sphere to overlap with the guided light emerging from the fiber tip. This architecture offers significant benefits that have never been reported in the literature in terms of radiation efficiency, compared to the standard freestanding resonators, which arise from breaking the symmetry of the resonator. In addition to providing the remote excitation and collection of the WGMs' signal, the fiber also allows easy manipulation of the microresonator and the use this sensor in a dip sensing architecture, alleviating the need for a complex microfluidic interface. Here, we present our recent results on the microstructured fiber tip WGM-based sensor, including its lasing behavior and enhancement of the radiation efficiency as a function of the position of the resonator on the fiber tip. We also show that this platform can be used for clinical diagnostics and applying this technology to the detection of Troponin T, an acute myocardial infarction biomarker, down to a concentration of 7.4 pg/mL.

We studied theoretically and experimentally the induction of electromagnetic forces in one-dimensional photonic crystals with localized defects when light impinges transversally to the defect layer. The theoretical calculations indicate that the electromagnetic forces increases at a certain frequency that coincide with a defect photonic state. The photonic structure consists of a microcavity like structure formed of two one-dimensional photonic crystals made of free-standing porous silicon, separated by variable air gap and the working wavelength is 633 nm. The force generation is made evident by driving a laser light by means of a chopper; the light hits the photonic structure and induces a vibration and the vibration is characterized by using a very sensitive vibrometer.

We present four refractometric sensing platforms based on whispering gallery mode (WGM) modulated fluorescence spectra from active microsphere or capillary microresonators and scattered surface plasmon (SP) spectra from rough thin metal coatings and metal nanoparticles in waveguide and fibre dip configurations, respectively. Redshifts of the detected spectra upon increasing sample refractive index are demonstrated for each platform; label-free bio-sensing is also demonstrated.

A frequency comb is the optical spectrum formed by a train of optical pulses and comprises a series of equally spaced spectral lines. Ytterbium and Erbium based fiber lasers can produce frequency combs in the region of 1.0 and 1.5 μm respectively. The frequency comb based on an Erbium doped fiber is especially interesting because it emission is centered in the spectral region of optical fiber communications. In this work we use a frequency comb based on an Erbium doped fiber optically filtered by stimulated Brillouin scattering in an optical fiber to generate optical reference frequency in the regions of optical fiber telecommunications and microwaves. The study of the stability of the isolated tooth are performed, resulting two orders of magnitude better than the stability of the pump laser used. This result is the calibration of telecommunication wavelength meters. Also, we analyze some applications based on the Brillouin filtering technique.

This paper reports on the development and testing of a direct reading radon detector assembled from consumer electronics at very low cost. An electrostatic concentrator constructed by metalizing a plastic funnel is used to focus charged radon progeny onto the exposed surface of an optical image sensor from a webcam. Alpha particles emitted by the collected progeny strike the image sensor, generating sufficient charge to completely saturate one or more pixels The high voltage required by the concentrator is generated using a simple Cockcroft-Walton charge pump. A personal computer is used to analyze the webcam data. Alpha particles were counted at a rate of 5.2 counts/ hour at a radon concentration of 159 Bq/ m³.

We propose a plasmonic gold nanodipole array on silicon, forming a Schottky contact thereon, and covered by water. The behavior of this array under normal excitation has been extensively investigated. Trends have been found and confirmed by identification of the mode propagating in nanodipoles and its properties. This device can be used to detect infrared radiation below the bandgap energy of the substrate via internal photoelectric effect (IPE). Also we estimate its responsivity and detection limit. Finally, we assess the potential of the structure for bulk and surface (bio) chemical sensing. Based on modal results an analytical model has been proposed to estimate the sensitivity of the device. Results show a good agreement between numerical and analytical interpretations.

A novel biosensing platform based on long-range surface plasmon waveguides is demonstrated for selective biosensing. The sensor consists of gold waveguides embedded in CYTOP with a microfluidic channel. Gold surfaces were modified by forming a self-assembled monolayer (SAM) and further they were functionalized by proper receptor (antibodies) with carbodiimide chemistry. Investigation of biochemical interactions were performed with human immunoglobulin (Ig). Human immunoglobulin M (IgM) kappa chain (IgM-κ) was tested on the waveguide, functionalized with anti-human immunoglobulin-kappa specific chain (anti-Igκ). As a negative control, human IgM lambda chain (IgM-λ) was tested on anti-Igκ surface. The response for IgM- sample was 0.173 dBm and that for IgM-λ was 0.033. The ratio of the responses ΔS(IgM-κ)/ ΔS(IgM-λ) was found to be 5.3.

Applications that involve the use of hydrogen gas (H2) have an inherent risk in that hydrogen is combustible in air and hence accurate detection of its concentration is critical for safe operation. Long-Range Surface Plasmon Polaritons (LRSPPs) are optical surface waves that are guided along thin metal films or stripes which are symmetrically cladded by a dielectric and have been demonstrated to be highly sensitive for biological and chemical sensing. The sensor presented here consists of a gold (Au) stripe suspended on an ultrathin Cytop membrane. This architecture is referred to as the membrane waveguide and has previously been demonstrated to support LRSPP propagation. Hydrogen sensing is achieved by overlaying a palladium (Pd) patch on a straight waveguide section, which induces a measureable insertion loss change under the presence of hydrogen. The design and optimization of the sensor through finite element method (FEM) simulation will be discussed. This will include the design of the optimal waveguide geometry along with the design of an integrated grating coupler for broadside light coupling. In addition, details on the fabrication process are presented.

This paper presents the use of Terahertz (THz) SPR near-field sensor to characterize materials such as PMMA and those used in organic light emitting diode (OLED). The SPR device contains 2D periodic circular or square hole array in 500 nm Al on an 5 mm-thick intrinsic silicon, and was fabricated by photolithography and wet etching. For THz spectrum measurement, the SPR device with and without thin (PMMA) film on it is placed at the focus of the THz beam in transmission THz Time Domain Spectroscopy (TDS), where the spectrum is obtained from the Fourier-transformed sample and reference THz pulses. The transmission is obtained from the ratio between the sample spectrum and reference spectrum, whereas the phase change is the phase difference between the two spectra. To avoid overlap with water absorption lines, the optimal SPR device design has a period of 320 μm and square holes of 150 μm side length. The theoretical SPR frequencies in the THz range are determined for the metal-silicon modes and metal-air modes (0.9375 THz for mode (0, 1) at the metal-air interface). The measurement results confirmed the theoretical SPR frequencies for metal-silicon mode and demonstrate a shift to 0.9211 THz due to 2 μm of PMMA layer on the surface.

Incorporation of a solid-state gain medium in the cladding of a Long Range Surface Plasmon Polariton (LRSPP) waveguide in order to create a single-mode near-infrared laser source is proposed. LRSPP Bragg gratings based on stepping the width of the metal strip are used to form the laser’s cavity. Three laser configurations are presented: The first 2 lasers employ DBRs (Distributed Bragg Reflectors) in ECL (External Cavity Laser) architecture while the third is based on the DFB (Distributed Feedback) configuration. All 3 configurations are thermally tunable by heating the gratings directly by injecting current. The lasers are convenient to fabricate leading to inexpensive sources that could be used in optical integrated circuits or waveguide biosensors.

This paper is devoted to examining the ability of a coaxial fiber-optic sensor (FOS) in detecting weak fluorescent light and weak fluorescence “turn-on” in the presence of trace heavy metal ion Pb²⁺. The captured fluorescent signal is detected by the Ocean Optics QE65000 spectrometer. The stock solutions include Pb²⁺ acetate in water (0.01 M) and a small molecule probe in water. The preliminary experiment shows that this FOS offers the Pb²⁺ detection limit (DL) of 1.26×10^-4 mg/mL. The advantages, limitations and further improvements of this coaxial FOS are discussed in comparison with the bench-top instruments in terms of the abilities of signal light capture and stray excitation light suppression.

In this paper we propose and demonstrate a non-intrusive measurement method for internal pressure and water flow in hydraulic pipeline systems. Fiber Bragg Gratings are used to measure deformations in the external side of pipes under different working conditions for two different experiments. In the first experiment