This PDF file contains the front matter associated with SPIE Proceedings Volume 8431, including the Title Page, Copyright Information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Conventional SOI waveguide technology, serving as the foundation of near-IR photonics, meets its limitation in mid-IR due to high loss associated with the buried oxide. Silicon-on-sapphire (SOS) waveguides are considered as a good mid-IR alternative, because the transparency window of sapphire is up to 6 μm and SOS waveguides are compatible with SOI technology. We show that properly-designed SOS waveguides can facilitate frequency band conversion between near-IR and mid-IR. An indirect mid-IR detection scheme is proposed and the mid-IR signal is down-converted to telecommunication wavelength (1.55 μm) through SOS waveguides and indirectly detected by near-IR detectors. The performance of the indirect mid-IR detection scheme is discussed. Particularly we model and compare the noise performance of the indirect detection with direct detection using state-of-the-art mid-IR detectors. In addition to advantages of room temperature and high-speed operation, the results show that the proposed indirect detection can improve the electrical signal-to-noise ratio up to 50dB, 23dB and 4dB, compared to direct detection by PbSe, HgCdTe and InSb detectors respectively. The improvement is even more pronounced in detection of weak MWIR signals. In order to further boost the performance, we also investigate mechanisms to increasing the conversion efficiency in SOS waveguide wavelength converters. The conversion efficiency can be improved by periodically cascading SOS waveguide sections with opposite dispersion characteristics to achieve quasi-phase-matching. Conversion efficiency enhancement over 30dB and the conversion bandwidth increased by 2 times are demonstrated, which may facilitate the fabrication of parametric oscillators that can improve the conversion efficiency by 50dB.

We propose an efficient four-wave-mixing-based wavelength conversion scheme in a silicon nanowire ring whereby no dispersion engineering of the nanowire is required. Instead, we rely on the spatial variation of the Kerr susceptibility around the ring to quasi-phase-match the wavelength conversion process for TE polarized fields. We show through numerical modeling that in the absence of dispersion engineering this quasi-phase-matched wavelength conversion approach can outperform 'conventional' wavelength conversion by as much as 10 dB.

We compare the energy performance of four-wave mixing in nanowires and slow-light photonic crystals and outline the regimes where each platform exhibits salient advantages and limitations, including analysis of the impact of future fabrication improvement. These results suggest a route towards energy efficient silicon integrated photonics.

We report a Germanium lateral pin photodiode integrated with selective epitaxy at the end of silicon waveguide. A very high optical bandwidth estimated at 120GHz is shown, with internal responsivity as high as 0.8A/W at 1550nm wavelength. Open eye diagram at 40Gb/s was obtained under zero-bias at wavelength of 1.55μm.

Group IV mid-infrared photonics is attracting more research interest lately. The main reason is a host of potential applications ranging from sensing, to medicine, to free space communications and infrared countermeasures. The field is, however, in its infancy and there are several serious challenges to be overcome before we see progress similar to that in the near-infrared silicon photonics. The first is to find suitable material platforms for the mid-infrared. In this paper we present experimental results for passive mid-infrared photonic devices realised in silicon-on-insulator, silicon-on-sapphire, and silicon on porous silicon. We also present relationships for the free-carrier induced electro-refraction and electro-absorption in silicon and germanium in the mid-infrared wavelength range. Electro-absorption modulation is calculated from impurity-doping spectra taken from the literature, and a Kramers-Kronig analysis of these spectra is used to predict electro-refraction modulation. We examine the wavelength dependence of electro-refraction and electro-absorption, finding that the predictions suggest longer-wave modulator designs will in many cases be different than those used in the telecom range.

Grating couplers have shown promising performance in terms of coupling efficiency and alignment tolerances as an interface between optical fibers and nanometric silicon-on-insulator (SOI) waveguides. In this paper we review our previous work, where the implementation of a fiber to chip grating coupler in micrometric rib SOI waveguide was demonstrated for the first time, showing measured coupling efficiency of -2.2dB for transverse-electric (TE) polarization. We also propose a new grating design that achieves a calculated coupling efficiency of -2dB for transverse-magnetic (TM) light.

Label-free photonic biosensors fabricated on silicon-on-insulator (SOI) can provide compact size, high evanescent field strength at the silicon waveguide surface, and volume fabrication potential. However, due to the large thermo optic coefficient of water-based biosamples, the sensors are temperature-sensitive. Consequently, active temperature control is usually used. However, for low cost applications, active temperature control is often not feasible. Here, we use the opposite polarity of the thermo-optic coefficients of silicon and water to demonstrate a photonic slot waveguide with a distribution of power between sample and silicon that aims to give athermal operation in water. Based on simulations, we made three waveguide designs close to the athermal point, and asymmetric integrated Mach- Zehnder interferometers for their characterization. The devices were fabricated on SOI with a 220 nm device layer and 2 μm buried oxide, by electron beam lithography of hydrogen silsesquioxane (HSQ) resist, and etching in a Cl₂/HBr/O₂/He plasma. With Cargile 50350 fused silica matching oil as top cladding, the group index of the three guides varies from 1.9 to 2.8 at 1550 nm. The temperature sensitivity of the devices varied from -70 to -160 pm/K under the same conditions. A temperature sensitivity of -2 pm/K is projected with water as top cladding.

Grating couplers are the best solution for testing nano-photonic circuits. Their main benefit is that they allow access via an optical fiber from the top and therefore there is no need to dice the chip and prepare the facets crucially. In the PLATON project grating couplers were designed to couple TM mode into and out of the SOI waveguides. Simulations came up with a grating coupler layout capable of theoretical coupling losses lower than 3dB for 1550 nm in TM configuration. A fully etched grating structure was chosen for fabrication simplicity and the optimal filling factor was found. The structures were fabricated using proximity error correction (PEC) and show a uniform coupling efficiency for all couplers. Therefore they are well-suited for all applications which demand for stable fiber-to-chip coupling. The spectral response of the structures was measured from 1500 to 1580 nm with 2 nm step and measuring the fiber-tofiber losses of three straight waveguides equipped with three grating couplers with different gap widths. The optimal grating period exhibits adequate coupling losses of 3.23 dB per coupler at 1557 nm, being therefore the most promising design.

In this work, a technique for precise position control of individual transmission channels in a triple-cavity resonator device is proposed. The resonator design is based on Si photonic crystal (PhC) and liquid crystal technologies. By filling of the particular air grooves in one-dimensional, Si-Air PhC with nematic liquid crystal, an efficient coupled Fabry- Pérot resonator can be realized in which a wide stop band is used for broad frequency channel separation and high out-of- band reflection. By random tuning of the refractive index in all coupled cavities, a continuous individual tuning of the central channel (or edge channels) up to 25% of the total channel spacing is demonstrated. Additionally, an approach for precise controllable improvement of transmission up to 100% is demonstrated for the edge channels with decrease of the channel spacing 1%. Based on the proposed design, a prototype triple-channel filter was fabricated on Silicon-On-Insulator platform and optimized to the desired operational mode.

In this work, we revisit the operation principles of Bragg reflectors assisted directional couplers. We show that an efficient narrow band forward coupling operation can be achieved by an appropriate engineering of the Bragg grating waveguides dispersion properties. Our theoretical analysis reveals the existence of a minimum Bragg grating coupling strength for co-directional phase matching. This threshold coupling condition is an essentially new aspect of Bragg grating asymmetric directional couplers as compared to conventional co-directional couplers and Bragg reflectors. The threshold condition is analytically determined, and a coupled mode theory four-wave model is successfully applied to describe the behavior of the investigated device. It is shown that the optimal operation is achieved with only one Bragg grating distributed along one of the two waveguides. A numerical validation of the results of coupled mode theory is performed for the case of shallow-etched Silicon on Insulator (SOI) ridge waveguides with Bragg grating assisted coupling. The selectivity is a factor of 5.5 higher than that obtained in the conventional approach of asymmetric directional couplers where III-V waveguides with different alloy compositions are coupled vertically. The proposed design is shown to be compatible with existing micronano- fabrication technology.

We present first experimental results of a high-speed silicon optical modulator based on carrier depletion in interleaved PN junctions oriented in the waveguide direction. The modulator is integrated in a ring resonator of radius 50 μm. The modulator is characterized using a laser beam at 1.55 μm for TE and TM polarizations, and extinction ratios as high as 11 dB and 10 dB in in TE- and TM-polarizations, respectively, obtained between 0 and -10 V. At 10 Gbit/s extinction ratios of 4.1 dB and 2.7 dB for TE- and TM-polarization, respectively, are experimentally demonstrated.

Slow light optical modulators are attracting ever more attention in the field of silicon photonics owing to their capacity to shrink the footprint of conventional rib waveguide based carrier depletion modulators while maintaining similar drive voltages. Nonetheless, the integration of future photonics components with advanced complementary-metal-oxide-semiconductor (CMOS) electronics will require drive voltages as low as 1V. Here, we demonstrate that the use of slow light provides an attractive solution to reduce the driving power of carrier depletion-based Mach-Zehnder modulators so that they fulfill the consumption requirements of future CMOS electro-photonics transceivers. Preliminary characterization results show that our 1mm-long slow light device features a data transmission rate of 5 Gbit/s with ~5.7 dB extinction ratio under a 1V drive voltage with 12dB insertion loss. Further measurements show that higher transmission speeds are achievable while sustaining the drive voltage close to current CMOS requirements.

We calculate the conduction band electron scattering rates from the Γ-valley into the indirect valleys in germanium, and use this to determine the strength of the indirect absorption in Ge/SiGe quantum well heterostructures. This is done as a function of the in-plane compressive strain in the Ge quantum wells, which results from pseudomorphic growth on a SiGe virtual substrate. This compressive strain results in the Δ valleys becoming available as destination states for scattering, which leads to a reduction in the Γ-valley lifetime. We calculate the indirect absorption and lifetime broadening of excitonic peaks, and show that indirect absorption decreases as the Ge fraction in the virtual substrate increases. We conclude that the Ge fraction of the SiGe virtual substrate should be approximately 95% or larger for optimum electroabsorption performance of Ge/SiGe quantum wells.

High speed Ge multiple quantum well (MQWs) electro-absorption (EA) modulator is reported. Device development procedures from the epitaxial growth of high quality Ge MQWs by LEPECVD technique, fabrication, and characterization of optoelectronic device are described.

We discuss the development of label-free, real-time and low-cost biosensors based on planar photonic bandgap (PBG) structures. We propose a novel power-based readout technique where the PBG shift is indirectly tracked by simply exciting the photonic sensing structure with a filtered broadband source and measuring the output power with a power meter. Therefore, the use of either tunable lasers or spectrum analyzers to continuously acquire the transmission spectrum of the structure, as done for other spectrum-based sensing techniques, is avoided. We have used this technique both for the sensing of refractive index variations as well as for the label-free detection of antibodies, showing high sensitivities and low detection limits, which demonstrate its high potential for the development of label-free, real-time and low-cost photonic biosensors. Furthermore, the use of broadband sources and detectors for the readout of the photonic sensors will also allow their integration, thus achieving a completely electrically accessed photonic biosensing device.

Silicon photonic biosensors based on evanescent wave detection have revealed themselves as the most promising candidates for achieving truly point-of-care devices as they can overcome the limitations of current analytical techniques. Advantages such as miniaturization, extreme sensitivity, robustness, reliability, potential for multiplexing and mass production at low cost can be offered. Among the existing integrated optical sensors, the interferometric ones are the most attractive due to their extreme sensitivity for label-free and real-time evaluations with detection limits close to 10^-7- 10^-8 in bulk refractive index. In this article we will review the recent progress in the most common interferometric waveguide biosensors (Mach-Zehnder interferometers, Young interferometers, Hartman interferometers, dual polarization interferometers and bimodal optical waveguides). In particular, we will focus on the description of their optical structures and their applicability for bioanalytical detection.

We will discuss the latest progress in our work on using complementary metal-oxide semiconductor (CMOS) photonics for optical manipulation of dielectric microparticles and submicrometer particles in a microfluidic channel. Specifically, we will review optical trapping and routing of particles using silicon nitride waveguide-based directional couplers and multimode-interference (MMI)-based couplers. Our experiments reveal that microparticles can be directionally coupled from one waveguide to another waveguide via evanescent light coupling over submicrometer gap spacing. We also observe that microparticles can be preferentially transported to the larger field-intensity output-port of a 1×2 MMI optical power splitter. We thus envision that these photonic components, along with other photonic components that have previously been demonstrated with functionalities of optical manipulation of particles in fluids, constitute basic building blocks of CMOS optofluidic "particle circuits" for particle manipulation and biosensing.

We present a novel wavelength multiplexing concept for an integrated label-free biosensor array employing silicon photonic Mach-Zehnder interferometers as sensors. Microring resonators act as wavelength selective elements in the near infrared wavelength region. The radii of the microring resonators differ to obtain resonance wavelengths that are allocated equally within the free spectral range. By choosing a wavelength where a certain microring is in resonance, an individual interferometer is addressed. Wire Bragg gratings terminate the interferometer arms and reflect the light back. The ring resonator, which dropped the light, now couples the light back into the input waveguide, where it propagates in opposite direction. A standard fiber optic circulator between the tunable laser source and the in/output separates the incoming from the outgoing light. In this work, the characteristics of the entire device are discussed. The design based on FEM and 3D-FDTD simulations as well as measurements of the nanophotonic key components namely micro ring resonators, Mach-Zehnder interferometers, and photonic wire Bragg gratings are presented. Measurements of combinations of the key components demonstrate the applicability of the reflectors in photonic circuits. Finally, for proof-of-concept, we successfully performed experiments with fluids of different refractive index differences rinsed over the sensor array.

The realization of on-chip optical interconnects requires the integration of active micro-optical devices with microelectronics. However, it is not clear yet how silicon photonics could be integrated within CMOS chips. In this context the non-crystalline forms of silicon, such as laser-annealed polycrystalline and hydrogenated amorphous silicon (a-Si:H), can deserve some advantages as they can be included almost harmlessly everywhere in a CMOS typical run-sheet, yielding low-cost and flexible fabrication. In particular, a-Si:H can be deposited using the CMOS-compatible low temperature plasma enhanced chemical vapour deposition (PECVD) technique, which brings clear advantages particularly for a back-end photonic integrated circuit (PIC) integration. However, till now a-Si:H has been mainly considered for the objective of passive optical elements within a photonic layer at λ=1.55 μm. Only a small number of examples have been reported, in fact, on waveguide integrated active devices. In this paper we detail about an effective refractive index variation obtained through an electrically induced carrier depletion in an as-deposited a-Si:H-based p-i-n waveguiding device. For this device switch-on and switch-off times of ~2 ns were measured allowing a modulation rate higher than 150 MHz.ÿÿ

We present the experimental results of an error-free high-speed silicon optical modulator based on carrier depletion in a lateral 1.8 mm-long PIPIN diode embedded in a Mach-Zehnder interferometer. At 10 Gbit/s, the silicon optical modulator provides a large extinction ratio of 8.1 dB simultaneously with a low optical loss of 6 dB. The silicon modulator is a key element required to build and integrate photonic high performance data links.

We propose a Si Mach-Zehnder interferometer (MZI) optical modulator with multi-cascade p/n junctions along waveguides. So far a single p/n junction is set horizontally across the waveguide or vertically in the thickness direction. Compared with these types of MZIs, the newly proposed structure operates at low voltage because the depletion region expands from the p/n junctions at the both edges of the p or n type neutral region along the waveguide and the reverse bias voltage required to deplete the whole region becomes low. Furthermore, the doping concentration of the p and n regions can be reduced because there is no constraint on the width of the depletion region, while in the case of the horizontal or vertical junction type, the doping concentration must be high so that the depletion-region width is within the width or the height of the waveguide. The low doping concentration results in the low junction capacitance and leads to the higher operation speed. In this paper the detailed characteristics of the newly proposed MZI modulator have been simulated. The operation voltage of the proposed device is only 1.5V at 13dB (95%) modulation for the arm length of 5mm, while in the case of vertical junction, the operation voltage is 8V at the same modulation and for the same arm length.

A Si photonics platform is described, co-integrating advanced passive components with Si modulators and Ge detectors. This platform is developed on a 200mm CMOS toolset, compatible with a 130nm CMOS baseline. The paper describes the process flow, and describes the performance of selected electro-optical devices to demonstrate the viability of the flow.

We report on a new and very cost effective way to integrate PIN photo detectors into a standard CMOS process. Starting with lowly p-doped (intrinsic) EPI we need just one additional mask and ion implantation in order to provide doping concentrations very similar to standard CMOS substrates to areas outside the photoactive regions. Thus full functionality of the standard CMOS logic can be guaranteed while the photo detectors highly benefit from the low doping concentrations of the intrinsic EPI. The major advantage of this integration concept is that complete modularity of the CMOS process remains untouched by the implementation of PIN photodiodes. Functionality of the implanted region as host of logic components was confirmed by electrical measurements of relevant standard transistor as well as ESD protection devices. We also succeeded in establishing an EPI deposition process in austriamicrosystems 200mm wafer fabrication which guarantees the formation of very lowly p-doped intrinsic layers, which major semiconductor vendors could not provide. With our EPI deposition process we acquire doping levels as low as 1•10¹²/cm³. In order to maintain those doping levels during CMOS processing we employed special surface protection techniques. After complete CMOS processing doping concentrations were about 4•10¹³/cm³ at the EPI surface while the bulk EPI kept its original low doping concentrations. Photodiode parameters could further be improved by bottom antireflective coatings and a special implant to reduce dark currents. For 100×100μm² photodiodes in 20μm thick intrinsic EPI on highly p-doped substrates we achieved responsivities of 0.57A/W at λ=675nm, capacitances of 0.066pF and dark currents of 0.8pA at 2V reverse voltage.

In the past, the suitability of Er for Si-based light emission was already investigated in detail. However, much less attention has been paid to Nd with its main electroluminescence (EL) line around 900 nm. In this study we compare the electrical and EL properties of Er- and Nd-implanted metal-oxide-semiconductor (MOS) structures where the dielectric stack is composed of the implanted SiO₂ layer and a SiON buffer layer. Regarding the EL, the EL spectrum, the EL decay time and the EL efficiency were measured. The electrical characterization comprises current-voltage and capacitance-voltage measurements. Although the EL efficiency of Nd-implanted devices is by a factor of 5 to 10 lower than that of Er-based, the emission wavelength of Nd has some advantages compared to that of Er. Finally, based on these results the suitability of these two types of light emitters for integrated photonic devices is discussed.

Carbon nanotubes are more and more considered for future use in microelectronics. On the other hand, the use of optics to overcome the limitation of metallic interconnects start to be considered as a viable solution. Carbon nanotubes are promising candidate to bridge the gap between optics and microelectronics, thanks to their ability to emit, modulate and detect light in the wavelength range of silicon transparency. In this proceeding, we will rst underline the use of carbon nanotube for photonics. We will then show that thin lm doped with semiconducting carbon nanotubes displays strong optical gain at a wavelength of 1.3 μm. Finally, we will report the integration of carbon nanotube thin layer with silicon waveguide, and present the successfull coupling of their absorption and emission properties. This leds to the demonstration of temperature independent emission from carbon nanotubes in silicon at a wavelength of 1.3 μm.

The convergence of photonics and microelectronics within a single chip is still lacking of a monolithical on-chip optical amplifier. Rare-earth doped slot waveguides show a large potential as on-chip source. Slot waveguides with silicon nanocrystals embedded in a dielectric host matrix can increase the light confinement in the active layer and allow electrical injection. In this work, horizontal slot waveguides formed by two thick silicon layers separated by a thin erbium doped silicon rich silicon oxide layer are studied as on-chip optical amplifiers. The waveguides are grown in a CMOS line with the active material grown by low-pressure chemical vapor deposition. Optical tests are performed and light propagation in the slot waveguides is observed. Using the cut-back technique, spectra propagation losses are evaluated. Room temperature electroluminescence is observed at 1.54 μm. Transmitted optical signal resonant with Er absorption is studied as a function of the injected current for different probing laser wavelengths.

Room temperature direct gap electroluminescence (EL) from a Ge/Si_0.15Ge_0.85 MQW waveguide was experimentally studied. The dependence of the EL intensity on the injection current and temperature was measured. The direct gap EL from Ge/SiGe MQWs was shown to be transverse-electric (TE) polarized, confirming that the EL originates from recombination with a HH state.

The design, optical characterization and sensoristic capability provided by a complementary metal-oxide-semiconductor (CMOS) compatible integrated sensor based on a μ-disk resonator cavity are reported. The working principle of the presented device consists in monitoring the changes in the effective refractive index of the supported optical modes induced by variations of the refractive index of the surrounding material. The detection system has been designed on the base of a high quality factor (Q=1.4×10⁴) Si-rich Si₃N₄ (SRSN) μ-disk - emitting in the VIS under optical pumping - bottom coupled to a low loss passive stoichiometric Si₃N₄ waveguide (WG), with losses values under 1 dB/cm measured in the same spectral region. The PL emission in the VIS range provided by the SRSN enable the use of Si-based detectors, easily integrable using the current CMOS standard technology. Proof of concept measurements performed on the coupled device revealed a good sensitivity of 51.79 nm/RIU (Refractive Index Unit), in accordance with the simulated data, and a minimum detection limit of 1.1 × 10^-3 RIU.

For the fabrication of photonic devices the sol-gel technique is a potentially lucrative alternative to methods such as physical vapor or chemical vapor deposition because of its solution-processability, low cost and relative ease of production. In this work we harness this potential by developing based photonic devices which incorporate highly luminescent CdSe@ZnS core-shell semiconductor quantum dots (QDs) doped within inorganic (TiO₂, ZrO₂) or hybrid organic-inorganic sol-gel films. As a pre-requisite to the formation of such devices, luminescent waveguides emitting between green and red have been obtained and their optical properties have been characterized. The photochemical stability of these waveguides was found to highly dependent on the exact sol-gel material used. QDs:Titania based composites were found to be inherently photo-unstable due to photoelectron injection into the bulk matrix and subsequent nanocrystal oxidation. In comparison, zirconia composites were significantly more robust with high photoluminescence retained up to annealing temperatures of 300 °C. Despite this difference in photo-chemical stability, both titania and zirconia composite waveguides exhibited amplified stimulated emission (ASE) with one-photon and two-photon optical pumping, however only zirconia based waveguides exhibited long term photostability. This Zirconia based films have been used for the realization of distributed feedback lasers and Bragg micro-cavities.

As optical components continue to replace electronics in ultrafast signal processing applications, a growing interest in further miniaturization and integration of photonic devices on a single chip is observed. Therefore, optical waveguides of high refractive index contrast of core and cladding materials are developed since a couple of years. They can have a very small cross section and also bending radius, enabling the development of ultra-compact photonic integrated devices and circuits. Silicon-On-Insulator (SOI) waveguides ("photonic wires") and devices are the most prominent examples. A corresponding technology for Lithium Niobate-On-Insulator (LNOI) waveguides is still in its infancy, though LN offers - in contrast to SOI - excellent electro-optic, acousto-optic, and nonlinear optical properties. Moreover, it can be easily doped with rare-earth ions to get a laser active material. Therefore, LNOI photonic wires will enable the development of a wide range of extremely compact, active integrated devices, including electro-optical modulators, tunable filters, nonlinear (periodically poled) wavelength converters, and amplifiers and lasers of different types. The state-of-the-art of LNOI films as platform for high-density integrated optics is reviewed. Using a full-wafer technology (3" diameter), sub-micrometer thin LN films are obtained by high-dose He⁺ ion implantations, crystal-bonding to a low-index substrate (preferably SiO₂) and cleaving by a special annealing step ("ion-beam-slicing"). Various LNOI structures, also combined with metallic layers, are presented. Based on such platforms, photonic wires and micro-photonic devices are developed using different micro- and nano-structuring techniques. To be specific, the fabrication and characterization of LNOI photonic wires with cross-section < 1 μm², and periodically poled LNOI photonic wires for second harmonic generation are reported in detail.

Er-doped (100-x) SiO₂ - x SnO₂ glass-ceramic monoliths were prepared using a sol-gel processing. The thermally induced growth of SnO₂ nanocrystals was followed by Raman spectroscopic measurements. Using x-ray crystallography, the average crystal size was determined to be about 5nm for a heat-treatment at 1000°C. Analysis of the photoluminescence data shows that the amount of Er³⁺ ions incorporated in the SnO₂ nanocrystals can be controlled by the tin dioxide concentration. In addition, spectroscopic evidence is provided of a transfer of energy from SnO₂ nanocrystals to erbium ions within the silica matrix, thus confirming the crystalline environment of the rare-earth ions.

In this paper we discuss the use and implementation of on-chip filtered optical feedback in order to tune the emission wavelength of a semiconductor ring laser. In this device, a directional coupler is used to couple part of the light emitted by the laser to a feedback section integrated on the same chip. The feedback section contains two arrayed waveguide gratings and a set of semiconductor optical amplifiers to provide filtering of particular longitudinal modes sustained by the ring cavity. Each of the two counter-propagating modes supported by the ring laser is coupled back into the same direction after filtering in the feedback section. We show that, for appropriate currents injected into the semiconductor optical amplifiers, the emission wavelength can be tuned and that single mode operation in both directions is achieved. We use a rate equation model in order to demonstrate tuning of the device theoretically.

Confinement of light at submicron wavelengths is of great importance for highly specific sensing of bio-molecules and for compact photonic circuits based on waveguiding. Currently this confinement can be achieved through the well established high index contrast silicon on insulator (SOI) platform. However this material combination requires light at wavelengths beyond 1 micron where the component cost of the InP based lasers and photodetectors are very expensive. It is thus of great interest to develop a similar platform that could operate in the range of 850 nm where low cost lasers (e.g. Vertical Cavity Surface Emitting Lasers as used in optical mice) and detectors (e.g., as used in camera phones) are readily available. A possible high index material suited to this application is Gallium Phosphide which has a bandgap of 2.26 eV and refractive index of ~ 3.2 at this wavelength. For the highest index contrast, GaP should be grown on a substrate with low index of refraction such as quartz (n=1.5) or sapphire (1.7). We report on the design and characteristics of GaP waveguides grown on c-plane (0001) sapphire substrates using metalorganic vapour phase epitaxy. Growth parameters such as substrate temperature and, in particular, the V:III ratio are reviewed with respect to their effect on the nucleation, surface roughness and uniformity of the films. Modal analysis and the design of a grating coupler at wavelengths around 850 nm have been designed for GaP on sapphire using vectorial finite element method in order to validate the feasibility of GaP waveguides.

In this work, we demonstrate successful interfacing between metallic nanoparticle (MNP) chain supporting localized surface plasmons (LSP) and silicon-on-insulator (SOI) waveguides. We show that the optical energy carried by a TE SOI waveguide mode at telecom wavelengths can be efficiently transferred into MNP chains deposited on the waveguide top, whatever the number of metallic particles (from 5 to 50). Especially in short chains, most of the energy can be transferred into the fourth or fifth MNP of the chains. Predictions from theoretical models are fully corroborated by transmission and near-field measurements.

A novel silicon optical modulator based on surface plasmon resonance is proposed and the light modulation characteristics investigated theoretically. By utilizing Marcatili's approximation for the rectangular waveguide analysis, the propagation loss and the modulation depth are evaluated. It is expected that the modulation depth of 10 dB can be achieved for a modulator with less than 100-μm in length.

We demonstrate low-loss silicon slot waveguides filled with single and dual atomic layer deposited oxide layers. Propagation losses less than 5 dB/cm and 8 dB/cm are achieved for the waveguides with single (Al₂O₃) and double (Al₂O₃-TiO₂) layers, respectively. The devices are fabricated using low-temperature CMOS compatible processes. The geometries allow nonlinearities nearly two orders of magnitude smaller than plain silicon waveguides.

We report on the realization and characterization of a silicon-based integrated optical platform which implements a vertical coupling scheme between a Whispering-gallery type microresonator and a buried dielectric waveguide. The vertical coupling allows for the separation of the resonator and the waveguide into different planes, which enables one to realize the optical components in different materials/thicknesses. The high optical quality of this cavity micro-optical system follows from the accurate planarization of the waveguide topography, which is achieved by multiple depositions-and- reflows of a borophosphosilicate glass over strip waveguides. Importantly, we demonstrate the feasibility of our approach for wafer-scale mass fabrication of freestanding planar resonators suspended in air and coupled to integrated bus waveguides. This opens the door for the realization of stable all-integrated resonator systems for optomechanical and metrological applications and has the potential to substitute today's complicated fiber-taper coupling schemes.

Silica microspheres were made by melting the tip of a standard telecom fiber and were coated with a 70SiO₂ - 30 HfO₂ sol-gel derived glass activated by 0.3 mol % of Er³⁺ ions. The samples were coated using a dip coating apparatus. The thickness of the coating was estimated to be around 1 μm. The whispering gallery modes of the coated resonator were studied using a full taper - microsphere coupling setup. Upon excitation at 1480 nm sharp peaks at wavelengths 1540- 1565 nm were observed. They were attributed to the whispering gallery modes of the microsphere falling in the wavelength range of the erbium emission.

We present a single-lithography Mach-Zehnder interferometer sensor circuit, with integrated low back-reflection input and output grating couplers. The low back-reflection is accomplished by a duty cycle apodization optimized for coupling light between single-mode silica fibers and the nanometric silicon-on-insulator (SOI) rib-waveguides. We discuss the design, fabrication, and characterization of the circuit. The apodization profile of the gratings is algorithmically generated using eigenmode expansion based simulations and the integrated waveguides, splitters, and combiners are designed using finite element simulations. The maximum simulated coupling efficiencies of the gratings are 70% and the multimode interference splitters and combiners have a footprint of only 19.2×4.5 μm². The devices are fabricated on an SOI wafer with a 220 nmdevice layer and 2 μm buried oxide, by a single electron beam lithography and plasma etching. We characterize the devices in the wavelength range from 1460-1580 nm and show a grating pass-band ripple of only 0.06 dB and grating coupling efficiency of 40% at 1530 nm. The integrated Mach-Zehnder interferometer has an extinction ratio of -18 dB at 1530 nm and between -13 and -19 dB over the whole 1460-1580 nm range.

We report on the development of a UV-lithography manufacturing process for low loss single mode light waveguides in a novel polymer and the characterization of the fabricated components in a broad wavelength range from 808 nm to 1550 nm. The main focus of this work lies in providing a quick and cost efficient production technique for single mode waveguides and low loss integrated optical circuits. To achieve this goal we chose a novel photo-structurable polymer host-guest-system consisting of SU8 and a low refractive dopant monomer. Near and far-field measurements at different wavelengths show that the mode propagating within a well designed integrated waveguide structure and the mode of a standard fiber can exhibit a mode overlap value of approximately 1 and suffer only very low coupling losses. We demonstrate excess loss of 0.14 dB/cm for 808 nm, 0.33 dB/cm for 1310 nm and 2.86 dB/cm for 1550 nm. Typical insertion loss values of straight waveguides with a length of 36 mm are 0.9 dB for 808 nm, 1.5 dB for 1310 nm and 10.4 dB for 1550 nm. Polarization dependent loss was found to be less than 0.2 dB on sets of test structures of 36 mm length. We measured material attenuation in the novel polymer material before cross-linking of approximately 0.04 dB/cm for 808 nm and around 0.20 dB/cm for 1310 nm respectively. The presented production technique is suitable to provide low loss and low cost integrated optical circuits for sensor and communication applications in a broad wavelength range.

We propose the biosensor chip using optical ring resonators. Although the detection of biomarkers for the diagnosis of diseases generally requires high sensitivity of the order of 10^-9 g/ml, the detection sensitivity of our device was of the order of 10^-7 g/ml. In this paper, we show that 10 or 100 times higher sensitivity than the previous biosensor is accomplished by the following three strategies; (1) using slot-type waveguides, (2) using silicon nitride (SiN) as the waveguide core, (3) improvement of measurement system.

In this work an antenna-coupled diode-based microbolometer implemented in a 0.35μm CMOS technology with a low-cost maskless micromachining post-process is proposed. The device is suspended above the substrate on an oxide membrane by removing the silicon underneath. It is composed of an antenna connected to a matched load, which heats up proportionally to the captured electromagnetic radiation, and heat sensing elements. These elements consist of several series polysilicon diodes placed near the antenna load, while an identical set of diodes is also included as a reference to track ambient temperature variations. Theoretical calculations and preliminary temperature characterization of polysilicon diodes have been performed. Different antenna sizes have been used so as to obtain detectors for 0.5THz, 1.0THz, and 2.0THz frequency operation. Thanks to the use of a standard CMOS technology, in the same chip a custom designed readout circuit has been integrated with the objective to maximize the performance of the detectors through signal amplification and filtering.

A conventional Arrayed Waveguide Grating (AWG) has been tailored for non-conventional applications such as Astro-Photonics, Life-science and spectroscopy where the input signal can have information over the full continuum of light/spectrum, compared to discrete optical channels in optical communication systems. The material system chosen for the AWG design is silicon-nitride/SiO₂/Si (Si₃N₄-SiO₂-Si) for it's relatively high refractive index, which for a given channel spacing allowing a more compact device than Silicon-on-Silica. While existing conventional AWGs cannot be utilized in spectroscopy when the input is a continuum, due to the fixed output waveguides where the centre wavelength λ_c and therefore rest of the wavelength channels have been assigned to predetermined output waveguides, the device under development has no output waveguides permitting to utilize the entire-image plane of the output star-coupler. The output of the AWG can then be re-imaged onto a detector array to sample the entire output spectrum, such as the 2-D infrared arrays used in astronomy. The designed AWG can resolve up to 40 spectral channels with wavelength spacing 0.4nm (50GHz), adjacent channel cross-talk level < -25dB at the ITU grid (25GHz) and non-uniformity ~ 2.5dB. The modeled mean spectral resolving power, R, at the flat image-plane is ~ 12,200.

The use of photonic integrated circuits made of polymer materials represents a solution for obtaining low-cost immunosensors for fast clinical diagnosis. In this paper are presented the simulation studies of a photonic integrated sensor on silicon substrate based on the configuration of Young interferometer. The core and cladding materials of the photonic sensor are polymeric materials. This sensor works for the detection of the surrounding medium refractive index variation and also for the detection of a thin adsorbed layer on the sensor surface. Simulations are performed using the Beam Propagation Method and 2D mode solvers for obtaining the relation between the variation of the surrounding refractive index or the presence of an adsorbed layer and the displacement of the interference fringe position. From this dependence one can calculate the sensor sensitivity and also one can estimate the detection limit. In order to obtain reliable results it is necessary to have waveguides which presents single mode operation regime both on the horizontal and vertical direction. Rib waveguides which are more prone for satisfying single mode condition were considered. The suppression of the higher order modes on the vertical direction by leakage in the silicon substrate is made by adjusting the thickness of the silicon dioxide buffer layer.

An approximate method of modeling of Raman generation in silicon-on-insulator(SOI) rib waveguide with DBR/F-P resonator including nonlinear effects such as Raman amplification and free-carrier absorption (FCA), is presented. In our detailed theoretical model, we consider coupled set of differential equations for pump signal and Stokes signal inside the laser cavity. In threshold analysis of steady-state Raman laser operation, we assume that the pump signal distribution is determined from linear equations. An analytical formula relating threshold pump power to the system parameters is obtained. The analysis of the above threshold operation is based on an energy theorem and threshold field approximation. In exact energy conservation relation, we approximate the pump and Stokes field distributions by these proportional to linear field distribution existing at the threshold, obtaining an approximate, semi-analytical expression related the Raman output power (i.e. the output power of Stokes lasing) to the pump power and system parameters. With this formula, the laser characteristics revealing the optimal rib waveguide geometry and the optimal coupling coefficients, which provide the maximal power efficiency, can be obtained.

The series of Nd³⁺-doped Si-rich SiO₂ thin films with different excess Si content were deposited by magnetron co-sputtering of three different (SiO₂, Si and Nd₂O₃) targets under a plasma of pure argon at 500 °C. The Si excess content in the samples was monitored via a power applied on Si cathode. The films were submitted to the rapid thermal annealing (RTA) at 900, 1000 and 1100 °C, respectively. It was observed a phase separation and a formation of Si nanoclusters embedded in oxide host. The Si excess, remaining after a RTA-1100 °C annealing, was found to be negligible, confirmed nearly complete phase separation. The Nd³⁺ photoluminescence (PL) property was explored as a function of Si excess and/or annealing temperature. The most efficient Nd³⁺ PL emission was found for the samples with about 4.7% of Si excess. These optimal samples, submitted to RTA-900 °C-1 min treatment and conventional annealing at 900°C for 1 h in nitrogen flow, demonstrated comparable Nd³⁺ PL intensities. This offers future application of RTA treatment to achieve an efficient emission from the materials doped with rare-earth ions.

In this paper, the composition profiles within intermixed AlInGaAs-based multiple quantum wells structure are analyzed by secondary ion mass spectrometry and the bandgap blue shift is found to be mainly attributed to the interdiffusion of In and Ga between the quantum wells and barriers. Based on these results, AlInGaAs-based single quantum well structures with various compressive strain (CS) levels are then investigated and we report an enhancement of the bandgap shift by increasing the compressive strain level in the SQW. For instance, at an annealing temperature of 850°C, the photoluminescence blue shift can reach more than 110 nm for the sample with 1.2%-CS SQW, but only 35 nm with 0.4%-CS SQW. The indium composition ratios are designed to be 0.59 and 0.71 for the 0.4% and 1.2%-CS quantum wells, respectively, as opposed to 0.53 for the lattice-matched barrier. This relatively larger atomic compositional gradient between the CS quantum well and barrier is expected to facilitate the atomic interdiffusion and lead to the more pronounced bandgap shift.

A wafer level packaging LED with photo-sensor which is fabricated on thin poly-silicon membrane located on the corner of silicon cavity is presented in this paper. The wafer substrate was fabricated with (100) orientation silicon wafer and a cavity was etched on the top of the wafer with wet chemical anisotropic etching process for mounting a LED chip. A thin polysilicon membrane was fabricated on the corner of the cavity and a MSM (Metal Semiconductor Metal) type photo-sensor was fabricated on the thin polysilicon membrane. The photo-sensor fabrication and LED packaging were completed on wafer level. The embedded photo-sensor in a wafer level packaging LED is designed to measure light intensity of a LED. The membrane structure photo-sensor can sense the light of the mounted LED directly, so it can measure accurate light intensity of the wafer level packing LED.

The design of an optical amplifier based on an Er³⁺-doped chalcogenide microsphere evanescently coupled with a tapered optical fiber is illustrated. The physical phenomena as the main transitions among the erbium energy levels, the amplified spontaneous emission and the most important secondary transitions, pertaining to the ion-ion interactions, have been modeled in a 3D numerical code. The model is based on the coupled mode theory and the rate equations. The device has been designed and optimized by varying the fiber-microsphere gap, the thickness of erbium doped region, the fiber taper angle, the erbium concentration, the pump and signal powers. The simulation results highlight that the amplification system here proposed could be a good candidate to obtain a highly efficient and compact amplifier in midinfrared wavelength range.

Spectra of fields for applications of polymeric 3D micro/nanostructures is rapidly widening thus demanding the development of versatile precise and efficient fabrication methods that can be used to process a variety of materials and could be implemented to form tiny devices on a variety of surfaces without influencing their structural quality. We present the latest results obtained using laser lithography approach: 3D polymeric structures with submicrometer spatial resolution on different opaque surfaces such as semiconductors (Si) and various metals (Cr, Al, Fe, Ti). The photostructuring was performed using a range of photosensitive materials such as acrylate based AKRE23, acrylated biodegradable PEG-DA-258, epoxy based mr-NIL 6000, hybrid organic-inorganic SZ2080 and Ormocore b59.

In order to create thermally tunable filter, we fabricate integrated micro-ring resonators with specific polymers. Their high index contrast (Δn ~ 0.15 at the wavelength of 1550 nm) allows to make small size waveguides (typically with cross sections of 1.2 × 1.5 μm²). We study the impact of different ring radii and gaps on the response of filters. Compared to the state of the art with polymers, we have obtained ring resonators with good characteristics. These results and the high thermo-optic coefficient of polymers enable us to plan the creation of thermally tunable resonators. For that purpose, we develop a thermal model of the polymer waveguide behaviour in order to minimize the electrical consumption of a tunable filter. First experiments of thermal tunability of the micro-ring filter are also reported to work on a range of 40 °C giving a 5 nm shift of the dropped wavelength.

Doping of the lead telluride and related alloys with the group III impurities results in appearance of the unique physical features of a material, such as persistent photoresponse, enhanced responsive quantum efficiency (up to 100 photoelectrons/incident photon), radiation hardness and many others. We present the physical principles of operation of the photodetecting devices based on the group III-doped IV-VI including the possibilities of a fast quenching of the persistent photoresponse, construction of the focal-plane array, new readout technique, and others. The advantages of infrared photodetecting systems based on the group III-doped IV-VI in comparison with the modern photodetectors are summarized. The spectra of the persistent photoresponse have not been measured so far because of the difficulties with screening the background radiation. We report on the observation of strong persistent photoconductivity in Pb_0.75Sn_0.25Te(In) under the action of monochromatic submillimeter radiation at wavelengths of 176 and 241 microns. The sample temperature was 4.2 K, the background radiation was completely screened out. The sample was initially in the semiinsulating state providing dark resistance of more than 100 GOhm. The responsivity of the photodetector is by several orders of magnitude higher than in the state of the art Ge(Ga). The red cut-off wavelength exceeds the upper limit of 220 microns observed so far for the quantum photodetectors in the uniaxially stressed Ge(Ga). It is possible that the photoconductivity spectrum of Pb_1-xSn_xTe(In)covers all the submillimeter wavelength range.

Rare earth activated 1-D photonic crystals were fabricated by rf-sputtering technique. The cavity is constituted by an Er³⁺-doped SiO₂ active layer inserted between two Bragg reflectors consisting of ten pairs of SiO₂/TiO₂ layers. SEM microscopy is employed to put in evidence the quality of the sample, the homogeneities of the layers thicknes and the good adhesion. NIR transmittance and variable angle reflectance spectra confirm that the presence of a stop-band from 1500 nm to 2000 nm with a cavity resonance centered at 1749 nm at 0° with a quality factor Q is about 890. The influence of the cavity on the ⁴I_13/2 → ⁴I_15/2 emission band of Er³⁺ ion is also demonstrated.

Two sets of c-Si solar cells varying in front side phosphorus doped emitters were produced by standard screen printing technique. The first group of samples 3121 was prepared by combination of standard washing and bath with and highly dilute HF before diffusion of n⁺-emitter. The second group of samples 3122 was treated only with standard washing. This paper brings the comparison of solar cell conversion efficiency and results from a noise spectroscopy and microplasma presence. As it was already shown in previous publications [1-3] noise spectral density reflects the quality of solar cells and thus it represents an alternative advanced cell diagnostic tool. Our results confirm this relationship and moreover bring the clear evidence for the maximum spectral noise voltage density being related with the emitter structure. The best results were reached for a group of solar cell with of samples 3122 was treated only with standard washing.