Bradley Snyder

Bio: Bradley Snyder is an academic researcher from Tyndall National Institute. The author has contributed to research in topics: Silicon photonics & Waveguide (optics). The author has an hindex of 7, co-authored 10 publications receiving 236 citations.

Packaging Process for Grating-Coupled Silicon Photonic Waveguides Using Angle-Polished Fibers

Abstract: A novel process for fiber-packaging submicrometer silicon waveguides is presented. The process uses fibers polished at an angle to reflect light between a horizontal core and the slightly off-vertical input and output path of a grating coupler. The necessity for a reflective coating on the fiber facet is overcome through the use of total internal reflection and a novel technique of epoxy distribution based on capillary action. Simulations of alignment tolerance are presented, along with measurements confirming the applicability of passive alignment. A peak coupling efficiency within 0.2 dB of the theoretical maximum for the grating coupler is achieved.

Hybrid Integration of the Wavelength-Tunable Laser With a Silicon Photonic Integrated Circuit

Abstract: A technology for hybridly integrating a discrete edge-emitting laser with a submicrometer silicon-on-insulator waveguide is presented. This technology is based on a ceramic microoptical bench which is compatible with high-speed electrical direct modulation. The use of passive- and self-alignment techniques is demonstrated to be suitable for assembling the microoptical bench with the laser die and optical components. The placement tolerance of less than 1 dB loss over a 4 μm range during the final integration with the waveguide is suited to a passive alignment process as well, thus permitting wafer-scale assembly and mass manufacture. The integration of both a Fabry-Perot laser and a two-section electrically tunable multiwavelength laser was performed. An excess insertion loss of only 3.36 dB was measured, which combined with state-of-the-art grating couplers promises a coupling efficiency from laser to waveguide of better than 40%.

Ge/Si heterojunction photodiodes fabricated by low temperature wafer bonding.

Abstract: We report on the photoresponse of an asymmetrically doped p(-)-Ge/n(+)-Si heterojunction photodiode fabricated by wafer bonding. Responsivities in excess of 1 A/W at 1.55 μm are measured with a 5.4 μm thick Ge layer under surface-normal illumination. Capacitance-voltage measurements show that the interfacial band structure is dependent on both temperature and light level, moving from depletion of holes at -50 °C to accumulation at 20 °C. Interface traps filled by photo-generated and thermally-generated carriers are shown to play a crucial role. Their filling alters the potential barrier height at the interface leading to increased flow of dark current and the above unity responsivity.

Demonstration of a Photonic Integrated Mode Coupler With MDM and WDM Transmission

Abstract: In this letter, 3.072-Tb/s (six spatial and polarization modes × 4 wavelength-division multiplexing (WDM) ×128-Gb/s 16QAM) transmission over 30 km of few-mode fiber (FMF) is demonstrated employing a photonic integrated mode coupler based on silicon-on-insulator (SoI) technology. A 2-D top coupling solution with five small vertical grating couplers is proposed for coupling between an SoI chip and an FMF, guiding LP01 and LP11 modes. Push-pull and center launch configurations for exciting LP11 and LP01 modes, respectively, through mode-profile matching are analyzed and implemented on the SoI chip.

Planar fiber packaging method for silicon photonic integrated circuits

Abstract: A novel method for fiber packaging silicon waveguides is presented. The process uses angled fibers and capillary action of UV-cure epoxy. The technique is suited to passive alignment and can be scaled for fiber arrays.

Silicon Photonics Design: From Devices to Systems

Abstract: Part I. Silicon Photonics - Introduction: 1. Fabless Silicon Photonics: 1.1 Introduction 1.2 Silicon photonics - the next fabless semiconductor industry 1.3 Applications 1.4 Technical challenges and the state of the art 1.5 Opportunities 2. Modelling and Design Approaches: 2.1 Optical Waveguide Mode Solver 2.2 Wave Propagation 2.3 Optoelectronic models 2.4 Microwave Modelling 2.5 Thermal Modelling 2.6 Photonic Circuit Modelling 2.7 Physical Layout 2.8 Software Tools Integration Part II. Silicon Photonics - Passive Components: 3. Optical Materials and Waveguides: 3.1 Silicon-on-Insulator 3.2 Waveguides 3.3 Bent waveguides 3.4 Code Listings 3.5 Problems 4. Fundamental Building Blocks: 4.1 Directional couplers 4.2 Y-Branch 4.3 Mach-Zehnder Interferometer 4.4 Ring resonators 4.5 Waveguide Bragg Grating Filters 4.6 Code Listings 4.7 Problems 5. Optical I/O: 5.1 The challenge of optical coupling to silicon photonic chips 5.2 Grating Coupler 5.3 Edge Coupler 5.4 Polarization 5.5 Code Listings 5.6 Problems Part III. Silicon Photonics - Active Components: 6. Modulators: 6.1 Plasma Dispersion E 6.2 PN Junction Phase Shifter 6.3 Micro-ring Modulators 6.4 Forward-biased PIN Junction 6.5 Active Tuning 6.6 Thermo-Optic Switch 6.7 Code Listings 6.8 Problems 7. Detectors: 7.1 Performance Parameters 7.2 Fabrication 7.3 Types of detectors 7.4 Design Considerations 7.5 Detector modelling 7.5.2 Electronic Simulations 7.6 Code Listings 7.7 Problems 8. Lasers: 8.1 External Lasers 8.2 Laser Modelling 8.3 Co-Packaging 8.4 Hybrid Silicon Lasers 8.5 Monolithic Lasers 8.6 Alternative Light Sources 8.7 Problems Part IV. Silicon Photonics - System Design: 9. Photonic Circuit Modelling: 9.1 Need for photonic circuit modelling 9.2 Components for System Design 9.3 Compact Models 9.4 Directional Coupler - Compact Model 9.5 Ring Modulator - Circuit Model 9.6 Grating Coupler - S Parameters 9.7 Code Listings 10. Tools and Techniques: 10.1 Process Design Kit (PDK) 10.2 Mask Layout 11. Fabrication: 11.1 Fabrication Non-Uniformity 11.2 Problems 12. Testing and Packaging: 12.1 Electrical and Optical Interfacing 12.2 Automated Optical Probe Stations 12.3 Design for Test 13. Silicon Photonic System Example: 13.1 Wavelength Division Multiplexed Transmitter.

From Scaling Disparities to Integrated Parallelism: A Decathlon for a Decade

Abstract: Based on a variety of long-term network traffic data from different geographies and applications, in addition to long-term scaling trends of key information and communication technologies, we identify fundamental scaling disparities between the technologies used to generate and process data and those used to transport data. These disparities could lead to the data transport network falling behind its required capabilities by a factor of approximately 4 every five years. By 2024, we predict the need for 10-Tb/s optical interfaces working in 1-Pb/s optical transport systems. To satisfy these needs, multiplexing in both wavelength and space in the form of a wavelength-division multiplexing × space-division multiplexing matrix will be required. We estimate the characteristics of such systems and outline their target specifications, which reveals the need for very significant research progress in multiple areas, from system and network architectures to digital signal processing to integrated arrayed device designs, in order to avoid an optical network capacity crunch.

In situ 3D nanoprinting of free-form coupling elements for hybrid photonic integration

Abstract: Hybrid photonic integration combines complementary advantages of different material platforms, offering superior performance and flexibility compared with monolithic approaches. This applies in particular to multi-chip concepts, where components can be individually optimized and tested. The assembly of such systems, however, requires expensive high-precision alignment and adaptation of optical mode profiles. We show that these challenges can be overcome by in situ printing of facet-attached beam-shaping elements. Our approach allows precise adaptation of vastly dissimilar mode profiles and permits alignment tolerances compatible with cost-efficient passive assembly techniques. We demonstrate a selection of beam-shaping elements at chip and fibre facets, achieving coupling efficiencies of up to 88% between edge-emitting lasers and single-mode fibres. We also realize printed free-form mirrors that simultaneously adapt beam shape and propagation direction, and we explore multi-lens systems for beam expansion. The concept paves the way to automated assembly of photonic multi-chip systems with unprecedented performance and versatility. By exploiting two-photon laser lithography for in situ printing of facet-attached beam-shaping elements, hybrid photonic integration can now be realized, opening opportunities for the automated assembly of photonic multi-chip systems with unprecedented performance and versatility.

Silicon photonic integration in telecommunications

Abstract: Silicon photonics is the guiding of light in a planar arrangement of silicon-based materials to perform various functions. We focus here on the use of silicon photonics to create transmitters and receivers for fiber-optic telecommunications. As the need to squeeze more transmission into a given bandwidth, a given footprint, and a given cost increases, silicon photonics makes more and more economic sense.

Ultrafast and sensitive photodetector based on a PtSe2/silicon nanowire array heterojunction with a multiband spectral response from 200 to 1550 nm

Abstract: The newly discovered Group-10 transition metal dichalcogenides (TMDs) like PtSe2 have promising applications in high-performance microelectronic and optoelectronic devices due to their high carrier mobilities, widely tunable bandages and ultrastabilities. However, the optoelectronic performance of broadband PtSe2 photodetectors integrated with silicon remains undiscovered. Here, we report the successful preparation of large-scale, uniform and vertically grown PtSe2 films by simple selenization method for the design of a PtSe2/Si nanowire array heterostructure, which exhibited a very good photoresponsivity of 12.65 A/W, a high specific detectivity of 2.5 × 1013 Jones at −5 V and fast rise/fall times of 10.1/19.5 μs at 10 kHz without degradation while being capable of responding to high frequencies of up to 120 kHz. Our work has demonstrated the compatibility of PtSe2 with the existing silicon technology and ultrabroad band detection ranging from deep ultraviolet to optical telecommunication wavelengths, which can largely cover the limitations of silicon detectors. Further investigation of the device revealed pronounced photovoltaic behavior at 0 V, making it capable of operating as a self-powered photodetector. Overall, this representative PtSe2/Si nanowire array-based photodetector offers great potential for applications in next-generation optoelectronic and electronic devices. Aligning ultra-thin semiconductors with silicon nanowires enables high-speed sensing of an unusually broad range of ultraviolet, visible, and infrared light frequencies. The shapes of silicon nanowires enable quicker and more effective light detection than conventional thin films, but their spectral response still falls outside the parameters needed for various applications, including optical telecommunication. Researchers led by Di Wu from China’s Zhengzhou University and Yuen Hong Tsang at Hong Kong Polytechnic University turned to the broadband absorption of graphene-like platinum selenide (PtSe2) films to extend the light sensitivity. To parallel the geometry of nanowires, the team used precision deposition techniques to grow 2D PtSe2 films into vertically-oriented layers, some tens of nanometers thick. Direct transfer of the PtSe2 film onto a large-scale nanowire array produced a microsecond-fast device sensitive to multiple optical bands. Platinum diselenide (PtSe2) is a newly discovered Group-10 transition metal dichalcogenide (TMD) which has unique electronic properties, in particular a semimetal-to-semiconductor transition. In this work, we have demonstrated the proposed vertically standing layered structure PtSe2 nanofilms based on hybrid heterojunction with high overall performance was realized for broadband light photodetection ranging from 200 nm to 1550 nm. The high-performance broadband photodetector will open up a new pathway for the development of next-generation two dimensional Group-10 materials based optoelectronic devices.