This PDF file contains the front matter associated with SPIE Proceedings Volume 9752, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

This paper focuses on latest progress in experimental and theoretical studies on silicon-based carrier-depletion PNjunction phase shifters in terms of high modulation efficiency for energy-efficient photonic networks of high transmission capacity. Modulation efficiency of rib-waveguide phase shifters having various PN-junction configuration are characterized with respect to DC figure of merit defined for phase shifters using carrier-plasma dispersion as the physical principle of refractive-index modulation. In addition, RF drive voltage required for 10-Gb/s on-off keying is characterized for rib-waveguide phase shifters including lateral and vertical PN-junction configurations.

Small-footprint, low-power devices that can modulate optical signals at THz speeds would transform next-generation onchip photonics. We describe a hybrid silicon–vanadium dioxide (Si-VO₂) electro-optic ring resonator modulator as a candidate platform for achieving this performance benchmark. Vanadium dioxide (VO₂) is a strongly correlated material exhibiting a semiconductor-to-metal transition (SMT) accompanied by large changes in electrical and optical properties. While VO₂ can be switched optically on a sub-picosecond time scale, the ultimate electrical switching speed remains to be determined. In a 5 μm radius Si-VO₂ ring resonator, we achieve 1.5 dB modulation in response to a 10 ns square voltage pulse of 2.5 V. In the steady state regime, we report a modulation depth of 10 dB. The larger modulation depth at longer timescales is attributed to a Joule heating contribution. Experimental results, corroborated by FDTD simulations, reveal the relationship between the portion of a VO₂ patch undergoing the SMT and the resulting effects on the Si-VO₂ device performance. This work indicates that with further reduction of VO₂ patch sizes and increase in resonator Q factor, there is promise for the Si-VO₂ ring resonator electro-optic modulator as a competitive option for on-chip photonics technology.

In this work we reported the efficiency and loss performance of a depletion silicon rib phase shifter, with an overlayer of 220 nm, rib width of 500 nm, and etch depth of 125 nm. We identified a range of doping concentrations that allow the phase shifter to operate at <6 V and <5 dB loss. Junction placement variances are done with doping concentrations in this range. The study suggested that with reduced p dopant concentration (2×10¹⁷ cm^-3), both loss and phase performance will improve by 32% and 20% respectively when p region > n region, compared to central junction.

We report a novel bi-layer photonic crystal slab (PCS) Fano modulator via a coupled double-layer Si nanomembrane (SiNM) capacitor like structure. Surface normal incident light intensity modulation near 1500nm was achieved by carrier accumulation induced resonance spectral shifting. Device performance simulation suggests the opportunity for high speed modulation exceeding GHz with 20μm × 20μm device size.

Two types of silicon dual-ring resonator-based high-speed optical modulators are proposed. With two microring resonators cascaded either in series or in parallel, the transmission spectrum evolves from a deep notch to a sharp peak with the resonators operating in a push-pull manner. The frequency chirp of the modulated signals can be highly suppressed by choosing a proper working wavelength.

The short-wave infrared wavelength range (2-3 μm) is attractive for applications in gas sensing and next-generation communication systems. Photodetectors and wavelength (de)multiplexers are key components that have to be developed for these systems. In this contribution, we report the integration of InGaAs/GaAsSb type-II quantum well photodetectors and spectrometers on the silicon photonics platform. In this photodetector epitaxial layer stack, the absorbing active region consists of 6 periods of W-shaped quantum wells, which can also be used to realize lasers. The efficient coupling between silicon waveguides and quantum well photodetectors is realized by tapered III-V waveguides. The photodetectors have a very low dark current of 12 nA at -0.5 V bias at room temperature. The devices show a responsivity of 1.2 A/W at 2.32 μm wavelength, and higher than 0.5A/W over the 2.2-2.4 μm wavelength range. On the silicon-on-insulator platform we also demonstrate high performance short-wave infrared spectrometers. 8-channel spectrometers in the 2.3-2.4 μm range with a resolution of 5nm and 1.4nm are demonstrated, showing a cross-talk below -25 dB and an insertion loss lower than 3 dB.

Silicon-on-insulator (SOI) technology has been a promising platform for photonic applications. However, the high index-contrast between silicon and the top cladding (SiO₂ or air) of the SOI waveguides makes the modal birefringence hard to control. Consequently, SOI based photonics integrated circuits (PICs) are in general highly polarization-sensitive, making polarization management important. In this paper, a polarization rotator (PR) design on the 220 nm SOI platform is demonstrated through numerical simulations and experiments. The demonstrated PR design is based on asymmetrical periodic loaded waveguide structures. The demonstrated design features compact device footprint and can be fabricated by CMOS compatible process. In addition, no special cladding is required to break the vertical symmetry of the waveguide. The design has shown promising performance over the C-band wavelengths (1530 nm-1565 nm) by simulations. However, the fabrication requirements are stringent for the design, thus the performance of the fabricated devices are limited by the current fabrication technology.

The experimental demonstration of fundamental direct bandgap, group IV GeSn alloys has constituted an important step towards realization of the last missing ingredient for electronic-photonic integrated circuits, i.e. the efficient group IV laser source. In this contribution, we present electroluminescence studies of reduced-pressure CVD grown, direct bandgap GeSn light emitting diodes (LEDs) with Sn contents up to 11 at.%. Besides homojunction GeSn LEDs, complex heterojunction structures, such as GeSn/Ge multi quantum wells (MQWs) have been studied. Structural and compositional investigations confirm high crystalline quality, abrupt interfaces and tailored strain of the grown structures. While also being suitable for light absorption applications, all devices show light emission in a narrow short-wave infrared (SWIR) range. Temperature dependent electroluminescence (EL) clearly indicates a fundamentally direct bandgap in the 11 at.% Sn sample, with room temperature emission at around 0.55 eV (2.25 µm). We have, however, identified some limitations of the GeSn/Ge MQW approach regarding emission efficiency, which can be overcome by introducing SiGeSn ternary alloys as quantum confinement barriers.

Silicon photonics, due to its compatibility with the CMOS platform and unprecedented integration capability, has become the preferred solution for the implementation of next generation optical interconnects. However, current Si photonics require on-chip integration of several materials, including III-V for lasing, doped silicon for modulation and Ge for detection. The very different requirements of these materials result in complex fabrication processes that offset the cost-effectiveness of the Si photonics approach. We are developing an alternative route towards the integration of optoelectronic devices in Si photonic, relying on the use of single wall carbon nanotubes (SWNTs). SWNTs can be considered as a Si compatible material able to emit, modulate and detect near-infrared light. Hence, they hold a unique potential to implement all active devices in the Si photonics platform. In addition, solution processed SWNTs can be integrated on Si using spin-coating techniques, obviating the need of complex epitaxial growth or chip bonding approaches. Here, we report on our recent progress in the coupling of SWNTs light emission into optical resonators implemented on the silicon-on-insulator (SOI) platform.

Micromachined infrared sources are enabling component for interferometric and spectroscopic sensors. Their compact size and low cost transform bulky instruments to the sensor scale, which is needed for a wide range of applications in the conventional and unconventional environments. The silicon micromachined sources should be engineered to have good emissivity across a large wavelength range because the intrinsic emissivity of silicon is low. This optimization was reported in literature by either the deposition of black metal at the surface of an emitter or the use of deep phonic crystal cavities, which complicates the fabrication technology and results in sharp dip lines in the spectral emissivity, respectively. In this work we report a micromachined infrared radiation source based on a heater on the top of black silicon structure for the first time in the literature, up to the authors’ knowledge. The temperature of the device is characterized versus the applied voltage and the radiated spectrum is captured in the 1300 nm to 2500 nm spectral range; limited by the spectrum analysis instrument. The reported source opens the doors for completely integrated MEMS spectral sensors onchip.

Currently, one of the main challenges in the field of silicon photonics is the fabrication of efficient laser sources compatible with the microelectronic fabrication technology. An alternative to the complexity of integration of group III-V laser compounds is advancing from high tensile strains applied to germanium leading to improved emission properties by transforming the material from an indirect to a direct bandgap semiconductor. Theory predicts this transformation occurs at around 4.7% uniaxial tensile strain or 2.0% bi-axial tensile strain. Here, we report on ultrahigh strains obtained by amplifying the residual strain from novel optical Germanium-On-Insulator (GeOI) substrates fabricated by Smart Cut^TM technology and patterned with micro-bridges and micro-crosses. The high crystalline quality of the GeOI layers dramatically declined the mechanical failure limits when liberating the Ge microbridges. Record level Raman shift of 8.1 cm-1 for biaxial (micro-crosses) and 8.7 cm^-1 for uniaxial stress (micro-bridges) were reached by carefully designing the geometry of the micro-structures. The photoluminescence (PL) evolution is compared to theoretical calculations based on the tight-binding model revealing a detailed understanding of the influence of strain on the germanium optical properties.

We present the performance of 4-channel × 25 Gb/s all-silicon photonic receivers based on hybrid-integrated vertical Ge-on-bulk-silicon photodetectors with 65nm bulk CMOS front-end circuits, characterized over 100 Gb/s. The sensitivity of a single-channel Ge photoreceiver module at a BER = 10^-12 was measured -11 dBm at 25 Gb/s, whereas, the measured sensitivity of a 4-ch Ge photoreceiver was -10.06 ~ -10.9 dBm for 25Gb/s operation of each channel, and further improvement is in progress. For comparison, we will also present the performance of a 4-ch × 25 Gb/s photoreceiver module, where commercial InP HBT-based front-end circuits is used, characterized up to 100 Gb/s.

In this work a novel photonic sampled and electronically quantized analog-to-digital converter (ADC) system is introduced. High overall sampling rate and relaxed analog bandwidth requirements for photodetectors and electronic quantizers are attained by multichannel architecture. The proposed scheme, with a dedicated electro-optic modulator for each of the channels, is much simpler and has a perspective to outreach the performance of a similar time- wavelength demultiplexed photonic ADC. Absolute optical power isolation between the channels completely eliminates the issue of channel crosstalk, resulting in increased power efficiency of the system. Owing to small number of wavelength demultiplexers less wavelength alignment is required, which reduces the complexity of both photonic and electronic subsystems. Due to the significance of having compact, on-chip photonic ADCs, the analysis of integration of proposed system on a silicon platform is performed. The availability of high performance devices in various Si platforms, such as low loss Si waveguides, microring resonator filters, modulators, photodetectors, necessary for building the system, proves that the photonic ADC is well suited for integration on a silicon chip. For integrated version of proposed architecture Si microring resonator modulators are suitable. They are compact, and can have shorter total length of diode phase shifters as compared to Mach-Zehnder modulators, used in time-wavelength demultiplexed photonic ADCs. To achieve large modulation depth and lower nonlinear distortions, the choice of optimum optical bandwidth of microring modulator is analyzed. Finally, the nonlinearity analysis of ring modulators is performed and the influence of nonlinearities on the ADC performance is discussed.

We report our recent progress on high-throughput 16×16 silicon non-blocking optical switches based on Mach- Zehnder interferometers (MZIs) and dual-ring assisted MZIs (DR-MZIs). TiN microheaters and p-i-n diodes are both integrated in each switch element for thermo-optic phase error correction and GHz-speed electro-optic switching, respectively. The MZI switch exhibits a broad optical bandwidth and low crosstalk. The DR-MZI switch exhibits low electrical switching power but with a narrower optical bandwidth. The two types of switches are designed to have a chip size of 12.1 mm × 4.6 mm mainly restricted by the chip package requirement. The DR-MZI chip can potentially have a smaller footprint due to its much more compact switch element, suitable for high-density on-chip optical data exchange.

Low energy operation is a must for using silicon photonic system to replace the conventional electrical interconnection systems. Three energy-saving approaches in silicon photonics are highlighted in this paper: low driving voltage for Mach-Zehnder modulator (MZM), negative chirp compensation for MZM-based long-haul transmission, and athermal filter for wavelength division multiplexing (WDM). These methods serve to reduce energy consumption of modulation and WDM, and are thus valuable to the development of future communication systems.

In this work, interferometric silicon chips with monolithically-integrated light-emitting devices coupled to co-integrated monomodal waveguides shaped as Young interferometers through mainstream silicon technology, are presented. Although the light sources are broad-band emitters, Young interferometry is possible through filtering. Chips with arrays of ten multiplexed interferometers have been employed for the label-free determination of pesticides in drinking water currently achieving detection limits in the ng/ml range.

This submission presents results on the frequency response of silicon resonant detectors, suitable for operation at wavelengths around 1550nm. The resonant structures are made sensitive to sub-bandgap light via the introduction of lattice defect states. An instability in operation is associated with the generation of free carriers within the resonant structure, producing a transient shift in the resonance wavelength. This manifests as a bit-pattern dependence for the detector, limiting the bandwidth of operation.

In this work we present novel and detailed dispersion the modal analysis of (SOS) strip waveguide in the mid-IR region. The effect of the various design parameters on each mode has been illustrated and carefully studied. The analysis has been extended to cover the fundamental and higher order TE and TM modes over the entire range of operation of this waveguides. The finite element method (FEM) and finite difference method have been both utilized to double verify the analysis. This dispersion analysis has been also utilized to propose novel functional devices in the MIR such as such as mode converter, switches, modulators and TE/TM-pass polarizer design based on the birefringence between the TE and TM mode.

In order to protect optoelectronic and mechanical properties of atomically thin layered materials (ATLMs) fabricated over SiO₂/Si substrates, a secondary oxide or nitride layer can be capped over. However, such protective capping might decrease ATLMs’ visibility dramatically. Similar to the early studies conducted for graphene, we numerically determine optimum thicknesses both for capping and underlying oxide layers for strongest visibility of monolayer MoS₂, MoSe₂, WS₂, and WSe₂ in different regions of visible spectrum. We find that the capping layer should not be thicker than 60 nm. Furthermore the optimum capping layer thickness value can be calculated as a function of underlying oxide thickness, and vice versa.

We propose an athermal Mach-Zehnder interferometer (MZI) with a subwavelength grating waveguide implemented in one of the arms to increase its fabrication error tolerance. The design is demonstrated with a CMOS compatible fabrication. In this work we will discuss the design principles of the subwavelength grating, loss mechanism, fabrication procedure and experimental results obtained. The fabricated devices have a temperature sensitivity of less than 10 pm/K over a spectral range from 1.5μm to 1.64μm. Also, the fabricated devices have a stable performance within the aforementioned specifications even with fabrication linewidth variations from -20 nm to 40 nm.

We present the characterization of Silicon-on-insulator (SOI) photonic-crystal based 2D grating-couplers (2D-GCs) fabricated by CEA-Leti in the frame of the FP7 Fabulous project, which is dedicated to the realization of devices and systems for low-cost and high-performance passives-optical-networks. On the analyzed samples different test structures are present, including 2D-GC connected to another 2D-GC by different waveguides (in a Mach-Zehnder like configuration), and 2D-GC connected to two separate 2D-GCs, so as to allow a complete assessment of different parameters. Measurements were carried out using a tunable laser source operating in the extended telecom bandwidth and a fiber-based polarization controlling system at the input of device-under-test. The measured data yielded an overall fiber-to-fiber loss of 7.5 dB for the structure composed by an input 2D-GC connected to two identical 2D-GCs. This value was obtained at the peak wavelength of the grating, and the 3-dB bandwidth of the 2D-GC was assessed to be 43 nm. Assuming that the waveguide losses are negligible, so as to make a worst-case analysis, the coupling efficiency of the single 2D-GC results to be equal to -3.75 dB, constituting, to the best of our knowledge, the lowest value ever reported for a fully CMOS compatible 2D-GC. It is worth noting that both the obtained values are in good agreement with those expected by the numerical simulations performed using full 3D analysis by Lumerical FDTD-solutions.

One of the biggest challenges of silicon photonics is the efficient coupling of light between the sub-micron SiP waveguides and a standard optical fiber (SMF-28). We recently proposed a novel approach based on a spot-size converter (SSC) that fulfills this need. The SSC integrates a tapered silicon waveguide and a superimposed structure made of a plurality of rods of high index material, disposed in an array-like configuration and embedded in a cladding of lower index material. This superimposed structure defines a waveguide designed to provide an efficient adiabatic transfer, through evanescent coupling, to a 220 nm thick Si waveguide tapered down to a narrow tip on one side, while providing a large mode overlap to the optical fiber on the other side. An initial demonstration was made using a SSC fabricated with post-processing steps. Great coupling to a SMF-28 fiber with a loss of 0.6 dB was obtained for TEpolarized light at 1550 nm with minimum wavelength dependence. In this paper, SSCs designed for operation at 1310 and 1550 nm for TE/TM polarizations and entirely fabricated in a CMOS fab are presented.

For decades, the semiconductor industry has been steadily shrinking transistor sizes to fit more performance into a single silicon-based integrated chip. This technology has become the driving force for advances in education, transportation, and health, among others. However, transistor sizes are quickly approaching their physical limits (channel lengths are now only a few silicon atoms in length), and Moore's law will likely soon be brought to a stand-still despite many unique attempts to keep it going (FinFETs, high-k dielectrics, etc.). This technology must then be pushed further by exploring (almost) entirely new methodologies. Given the explosive growth of optical-based long-haul telecommunications, we look to apply the use of high-speed optics as a substitute to the digital model; where slow, lossy, and noisy metal interconnections act as a major bottleneck to performance. We combine the (nonlinear) optical Kerr effect with a single add-drop microring resonator to perform the fundamental AND-XOR logical operations of a half adder, by all-optical means. This process is also applied to subtraction, higher-order addition, and the realization of an all-optical arithmetic logic unit (ALU). The rings use hydrogenated amorphous silicon as a material with superior nonlinear properties to crystalline silicon, while still maintaining CMOS-compatibility and the many benefits that come with it (low cost, ease of fabrication, etc.). Our method allows for multi-gigabit-per-second data rates while maintaining simplicity and spatial minimalism in design for high-capacity manufacturing potential.

In this paper we report the physical micromanipulation of standard InP telecommunications laser die in a liquid medium by means of optoelectronic tweezers. Optoelectronic tweezers have been shown to use much less optical power than optical tweezers, they do not require a coherent light source to function and the creation of multiple traps is straightforward. These properties make the technique a very good candidate for the massive parallel micromanipulation of optoelectronic components for assembly on a photonic platform. We discuss the positional and orientation accuracy of the optoelectronic tweezers in relation to the alignment requirements for low-loss coupling between the light sources and the other components in a photonic platform. Our experiments indicate that the accuracy is better than 2 μm and 2° for translations and rotations, respectively.

Multimode Interferometers (MMIs) are an attractive alternative to directional couplers, ensuring more relaxed tolerances to fabrication errors and broader operation bandwidth. The drawback is that only a limited discrete set of splitting ratios is achievable with MMIs of constant cross section. This issue clearly limits their use in flat-top interferometric filters, which design requires, in general, free choice of the splitting ratios. Here we show for the first time that it is possible to design 4-stage flat-top interferometers using only standard MMIs with 50:50 and 85:15 splitting ratios. The design approach is based on the representation of the system on the Bloch sphere. Flat-top interleavers with different free spectral ranges have been designed and fabricated on the silicon photonics platform of VTT, based on 3 μm thick rib and strip waveguides. Two different layouts have been explored: one where all components are collinear and a more compact one which elements have been folded in a spiral shape. All interleavers have been designed for TE polarization, and they work in a wavelength range comparable with the 100 nm bandwidth of the MMI splitters. Even though fabrication imperfections and non-ideal behaviour of both waveguide bends and MMIs led to reduced extinction compared to simulations, most devices show in-band extinction exceeding 15 dB. The in-band losses of the most central channels did not exceed 1.5 dB compared to the reference straight waveguide. The designed interleavers can be employed in cascaded configurations to achieve broadband and fabrication tolerant flat-top wavelength (de)multiplexers.

The development of compact, low power, silicon photonics CMOS compatible components for all-optical signal processing represents a key step towards the development of fully functional platforms for next generation all-optical communication networks. The wavelength conversion functionality at key nodes is highly desirable to achieve transparent interoperability and wavelength routing allowing efficient management of network resources operated with high speed, phase encoded signals. All optical wavelength conversion has already been demonstrated in Si-based devices, mainly utilizing the strong Kerr effect that silicon exhibits at telecommunication wavelengths. Unfortunately, Two Photon Absorption (TPA) and Free Carrier (FC) effects strongly limit their performance, even at moderate power levels, making them unsuitable for practical nonlinear applications. Amorphous silicon has recently emerged as a viable alternative to crystalline silicon (c-Si), showing both an enhanced Kerr as well as a reduced TPA coefficient at telecom wavelengths, with respect to its c-Si counterpart. Here we present an ultra-low power wavelength converter based on a passive, CMOS compatible, 1-mm long amorphous silicon waveguide operated at a maximum pump power level of only 70 mW. We demonstrate TPA-free Four Wave Mixing (FWM)-based wavelength conversion of Binary Phase Shift Keyed (BPSK) and Quadrature Phase Shift Keyed (QPSK) signals at 20 Gbit/s with <1 dB power penalty at BER = 10^-5.

Hybrid integration of VCSELs onto silicon-on-insulator (SOI) substrates has emerged as an attractive approach for bridging the gap between cost-effective and energy-efficient directly modulated laser sources and silicon-based PICs by leveraging flip-chip (FC) bonding techniques and silicon grating couplers (GCs). In this context, silicon GCs, should comply with the process requirements imposed by the complimentary-metal-oxide-semiconductor manufacturing tools addressing in parallel the challenges originating from the perfectly vertical incidence. Firstly, fully etched GCs compatible with deep-ultraviolet lithography tools offering high coupling efficiencies are imperatively needed to maintain low fabrication cost. Secondly, GC's tolerance to VCSEL bonding misalignment errors is a prerequisite for practical deployment. Finally, a major challenge originating from the perfectly vertical coupling scheme is the minimization of the direct back-reflection to the VCSEL’s outgoing facet which may destabilize its operation. Motivated from the above challenges, we used numerical simulation tools to design an ultra-low loss, bidirectional VCSEL-to-SOI optical coupling scheme for either TE or TM polarization, based on low-cost fully etched GCs with a Si-layer of 340 nm without employing bottom reflectors or optimizing the buried-oxide layer. Comprehensive 2D Finite-Difference-Time- Domain simulations have been performed. The reported GC layout remains fully compatible with the back-end-of-line (BEOL) stack associated with the 3D integration technology exploiting all the inter-metal-dielectric (IMD) layers of the CMOS fab. Simulation results predicted for the first time in fully etched structures a coupling efficiency of as low as -0.87 dB at 1548 nm and -1.47 dB at 1560 nm with a minimum direct back-reflection of -27.4 dB and -14.2 dB for TE and TM polarization, respectively.

We design, fabricate and experimentally demonstrate a compact thermo-optic gate switch comprising a 3.78μm-long coupled L0-type photonic crystal microcavities on a silicon-on-insulator substrate. A nanohole is inserted in the center of each individual L0 photonic crystal microcavity. Coupling between identical microcavities gives rise to bonding and antibonding states of the coupled photonic molecules. The coupled photonic crystal microcavities are numerically simulated and experimentally verified with a 6nm-wide flat-bottom resonance in its transmission spectrum, which enables wider operational spectrum range than microring resonators. An integrated micro-heater is in direct contact with the silicon core to efficiently drive the device. The thermo-optic switch is measured with an optical extinction ratio of 20dB, an on-off switching power of 18.2mW, a therm-optic tuning efficiency of 0.63nm/mW, a rise time of 14.8μsec and a fall time of 18.5μsec. The measured on-chip loss on the transmission band is as low as 1dB.

We introduce a novel type of chiral spiral waveguide where the usual waveguide crossings are replaced by 100:0 Multimode Interferometers (MMIs), i.e. 2x2 splitters that couple all the input light in the cross output port. Despite the topological equivalence with the standard configuration, we show how resorting to long MMIs has non-trivial advantages in terms of footprint and propagation length. An accurate analytic model is also introduced to show the impact of nonidealities on the spiral performances, including propagation loss and cross-talk. We have designed and fabricated three chiral spirals on our platform, based on 3 μm thick silicon strip waveguides with 0.13 dB/cm propagation loss, and 1.58 mm long MMIs. The fabricated spirals have 7, 13 and 49 loops respectively, corresponding to the effective lengths 6.6 cm, 12.5 cm and 47.9 cm. The proposed model is successfully applied to the experimental results, highlighting MMI extinction ratio of about 16.5 dB and MMI loss of about 0.08 dB, that are much worse compared to the simulated 50 dB extinction and 0.01 dB loss. This imposes an upper limit to the number of rounds, because light takes shortcuts through the bar MMI ports. Nevertheless, the novel chiral spiral waveguides outperform what is achievable in mainstream silicon photonics platforms based on submicron waveguides in terms of length and propagation losses, and they are promising candidates for the realization of integrated gyroscopes. They can be significantly further improved by replacing the MMIs with adiabatic 100:0 splitters, ensuring lower cross-talk and broader bandwidth.

We present a dynamic model based on temporal coupled-mode theory to model microring resonators considering silicon nonlinearities. By taking into account the vectorial nature of the optical modes propagating in strongly confining silicon waveguides, we introduce effective areas for two-photon absorption (TPA) and free-carrier distribution in order to adapt the rate equation describing the generation of free-carriers due to TPA and Sorefs equations for silicon waveguides. The performance of optical systems utilizing microring resonators can be degraded due to its nonlinear response. In this paper, we investigate the impact of silicon nonlinearities in microring resonators on the effective number of bits (ENOB) in integrated photonic analog-to-converters (ADCs). This is done by analyzing the nonlinear response of a first-order microring drop filter to a modulated optical pulse train. The dependence of the nonlinear response of the microring resonator, embodied in the input pulse energy vs output pulse energy, and the maximum ENOB on various filter and input pulse train parameters is analyzed by varying the finesse, microring waveguide geometry, modulation index, and average pulse energy.

We have designed and numerically simulated a novel spot size converter for coupling standard single mode fibers with 10.4μm mode field diameter to 500nm × 220nm SOI waveguides. Simulations based on the eigenmode expansion method show a coupling loss of 0.4dB at 1550nm for the TE mode at perfect alignment. The alignment tolerance on the plane normal to the fiber axis is evaluated at ±2.2μm for ≤1dB excess loss, which is comparable to the alignment tolerance between two butt-coupled standard single mode fibers. The converter is based on a cross-like arrangement of SiO_xN_y waveguides immersed in a 12μm-thick SiO₂ cladding region deposited on top of the SOI chip. The waveguides are designed to collectively support a single degenerate mode for TE and TM polarizations. This guided mode features a large overlap to the LP01 mode of standard telecom fibers. Along the spot size converter length (450μm), the mode is first gradually confined in a single SiO_xN_y waveguide by tapering its width. Then, the mode is adiabatically coupled to a SOI waveguide underneath the structure through a SOI inverted taper. The shapes of SiO_xN_y and SOI tapers are optimized to minimize coupling loss and structure length, and to ensure adiabatic mode evolution along the structure, thus improving the design robustness to fabrication process errors. A tolerance analysis based on conservative microfabrication capabilities suggests that coupling loss penalty from fabrication errors can be maintained below 0.3dB. The proposed spot size converter is fully compliant to industry standard microfabrication processes available at INO.

High repetition-rate frequency combs with tunable repetition rate and carrier frequency are extensively used in areas like Optical communications, Microwave Photonics and Metrology. A common technique for their generation is strong phase modulation of a CW-laser. This is commonly implemented using Lithium-Niobate based modulators. With phase modulation alone, the combs have poor spectral flatness and significant number of missing lines. To overcome this, a complex cascade of multiple intensity and phase modulators are used. A comb generator on Silicon based on these principles is desirable to enable on-chip integration with other functionalities while reducing power consumption and footprint. In this work, we analyse frequency comb generation in carrier injection based Silicon modulators. We observe an interesting effect in these comb generators. Enhanced absorption accompanying carrier injection, an undesirable effect in data modulators, shapes the amplitude here to enable high quality combs from a single modulator. Thus, along with reduced power consumption to generate a specific number of lines, the complexity has also been significantly reduced. We use a drift-diffusion solver and mode solver (Silvaco TCAD) along with Soref-Bennett relations to calculate the variations in refractive indices and absorption of an optimized Silicon PIN – waveguide modulator driven by an unbiased high frequency (10 Ghz) voltage signal. Our simulations demonstrate that with a device length of 1 cm, a driving voltage of 2V and minor shaping with a passive ring-resonator filter, we obtain 37 lines with a flatness better than 5-dB across the band and power consumption an order of magnitude smaller than Lithium-Niobate modulators.

This paper demonstrates the experimental study of edge and top illuminated SiGe phototransistors (HPT) implemented using the existing industrial SiGe2RF Telefunken GmbH BiCMOS technology for opto-microwave (OM) applications using 850nm Multi-Mode Fibers (MMF). Its technology and structure are described. Two different optical window size HPTs with top illumination (5x5μm², 10x10μm²) and an edge illuminated HPTs having 5μm x5μm size are presented and compared. A two-step post fabrication process was used to create an optical access on the edge of the HPT for lateral illumination with a lensed MMF through simple polishing and dicing techniques. We perform Opto-microwave Scanning Near-field Optical Microscopy (OM-SNOM) analysis on edge and top illuminated HPTs in order to observe the fastest and the highest sensitive regions of the HPTs. This analysis also allows understanding the parasitic effect from the substrate, and thus draws a conclusion on the design aspect of SiGe/Si HPT. A low frequency OM responsivity of 0.45A/W and a cutoff frequency, f_-3dB, of 890MHz were measured for edge illuminated HPT. Compared to the top illuminated HPT of the same size, the edge illuminated HPT improves the f_-3dB by a factor of more than two and also improves the low frequency responsivity by a factor of more than four. These results demonstrate that a simple etched HPT is still enough to achieve performance improvements compared to the top illuminated HPT without requiring a complex coupling structure. Indeed, it also proves the potential of edge coupled SiGe HPT in the ultra-low-cost silicon based optoelectronics circuits with a new approach of the optical packaging and system integration to 850nm MMF.

Advancement of silicon photonics technology can offer a new dimension in data communications with un-precedent bandwidth. Increasing the integration level in the silicon photonics is required to develop compact high-performance chip-level optical interconnects for future systems. Especially, monolithic integration of light source on a silicon wafer is important for future silicon photonic integrated circuits, since realizing a compact on-chip light source on a silicon wafer is a serious issue which impedes practical implementation of the silicon photonic interconnects. At present, due to the lack of a practical light source based on Group IV elements, flip chip-bonded or packaged lasers based on III–V semiconductor are usually being used as external light sources, to feed silicon modulators on SOI wafers to complete a photonic transmitter, except the reported silicon hybrid lasers monolithic-integrated on SOI wafers. To overcome above problem, we have proposed a compact on-chip light source, the directly monolithic-integrated VCSEL on a bulk silicon wafer (VCSEL-on-Si), based on the transplanted epitaxial film by substrate lift-off process and following device-fabrication on the bulk Si wafer. This can offer practical low-power-consumption light sources integrated on a silicon wafer, which can provide a complete chip-level I/O set when combined with monolithic-integrated vertical-illumination Ge-on-Si photodetectors on the same silicon wafer. In this work, we report the characterization of direct-modulation VCSELs-on-Si for λ ~850 nm with CW optical output power > ~2 mW and the threshold current < ~3 mA, over 10 Gb/s operations. We also discuss about the thermal characteristics of the VCSELs-on-Si.

In this paper, we present a single microring resonator structure formed by incorporating a reflectivity-tunable loop mirror for the tuning of resonance spacing. Based on the optical mode-splitting in the resonator structure, spacing between two adjacent resonances can be tuned from zero to one whole free spectral range (FSR) by controlling the coupling strength between the two counter-propagating degenerate modes in the microring resonator. In experiment, by integrating metallic microheater, the resonance-spacing tuning over the whole FSR (1.17 nm) is achieved within 9.82 mW heating power dissipation. The device is expected to have potential applications in reconfigurable optical filtering and microwave photonics.

In the absence of suitable methods for integrating III-V materials into standard microelectronic fabrication processes, Si has been actively explored as an alternative light emitter for silicon photonics. Although several proposals on how to increase the internal quantum efficiency of interband above bandgap (λ ≤1μm) luminescence in this indirect bandgap material were successful and are becoming fruitful, the luminescence mode is not without pitfalls. These drawbacks are low emission power, temperature quenching, and the need for additional technological steps, like doping by emissive centers or fabrication of quantum-confined structures. Below, we describe an innovatively different approach for extracting light from Si at below-bandgap wavelengths (λ >>1μm) by making use of thermal emission from a bulk material. We also suggest several new optoelectronic devices operating in this unconventional mode.

The series JSIR350 sources are MEMS based infrared emitters. These IR sources are characterized by a high radiation output. Thus, they are excellent for NDIR gas analysis and are ideally suited for using with our pyro-electric or thermopile detectors. The MEMS chips used in Micro-Hybrid’s infrared emitters consist of nano-amorphous carbon (NAC). The MEMS chips are produced in the USA. All Micro-Hybrid Emitter are designed and specified to operate up to 850°C. The improvements we have made in the source's packaging enable us to provide IR sources with the best performance on the market. This new technology enables us to seal the housings of infrared radiation sources with soldered infrared filters or windows and thus cause the parts to be impenetrable to gases.

Micro-Hybrid provide various ways of adapting our MEMS based infrared emitter JSIR350 to customer specifications, like specific burn-in parameters/characteristic, different industrial standard housings, producible with customized cap, reflector or pin-out.