Showing papers in "IEEE Journal of Quantum Electronics in 2020"

MEMS-Enabled Silicon Photonic Integrated Devices and Circuits

Abstract: Photonic integrated circuits have seen a dramatic increase in complexity over the past decades. This development has been spurred by recent applications in datacenter communications and enabled by the availability of standardized mature technology platforms. Mechanical movement of wave-guiding structures at the micro- and nanoscale provides unique opportunities to further enhance functionality and to reduce power consumption in photonic integrated circuits. We here demonstrate integration of MEMS-enabled components in a simplified silicon photonics process based on IMEC's Standard iSiPP50G Silicon Photonics Platform and a custom release process.

Efficient Mode Multiplexer for Few-Mode Fibers Using Integrated Silicon-on-Insulator Waveguide Grating Coupler

Abstract: We propose a novel and highly efficient multimode waveguide grating coupler which can simultaneously launch four channels including two polarizations of the linear polarized (LP) modes, LP 01 and LP 11 of a step-index few-mode fiber (FMF). The waveguide grating coupler on the silicon-on-insulator (SOI) platform is based on a subwavelength structure which was optimized using the genetic optimization approach with 2-dimensional finite-difference time-domain (2-D FDTD) simulations combined with the second - order effective medium theory (EMT). Simulations predicted the coupling efficiencies to be -4.3 dB for LP 01 mode and -5.0 dB for the LP 11 mode. The design was fabricated in a multi-project wafer (MPW) run for silicon photonics. Coupling efficiency of -4.9 dB and -6.1 dB was experimentally demonstrated for LP 01 mode and LP 11 mode, respectively. The proposed mode multiplexer is entirely passive and suitable for future applications with FMFs in the space-division-multiplexing (SDM) networks.

Q-Switched Fiber Laser at 1.5 \mu m Region Using Ti3AlC2 MAX Phase-Based Saturable Absorber

Abstract: A Ti 3 AlC 2 MAX phase-based saturable absorber (SA) is successfully demonstrated to induce passive Q-switching in an erbium-doped fiber laser (EDFL) at the 1.5 μm region. The Ti 3 AlC 2 -PVA film is fabricated using the solution casting method and incorporated into the laser cavity which uses a 0.89 m long erbium doped fiber as the gain medium. Stable and self-starting Q-switched laser pulses are observed above a threshold pump power of 87.81 mW at a central wavelength of 1567.4 nm. The repetition rate is observed to increase from 24.07 kHz to 46.3 kHz, while the corresponding pulse width decreases from 5.0 μs to 0.99 μs over a pump power range of 108.9 mW to 244.5 mW. At the maximum pump power of 244.5 mW, the highest pulse energy of 102.7 nJ and the maximum output power of 4.75 mW are obtained. These findings demonstrated the feasibility of the Ti 3 AlC 2 MAX phase as an SA material with significant promise for photonic applications. This is also, to the best knowledge of the authors, the first report of a Ti 3 AlC 2 MAX phase-based SA for inducing passive Q-switching in an EDFL.

InP Membrane on Silicon (IMOS) Photonics

Abstract: InP membranes have appeared in the last decade as a viable integrated photonics platform, suitable for adding photonic functions to silicon electronics. It combines the strengths of silicon photonics (high index contrasts and therefore small footprint devices) with those of generic InP-platforms (monolithic integration of active and passive devices). A range of functionalities has been developed on this platform, which goes by the name of Indium phosphide membrane on silicon (IMOS). Competitive performances have been demonstrated for lasers, fast detectors, waveguides, filters, couplers, modulators, and more. Here, we provide an overview of IMOS and describe recent developments regarding technology and devices. This includes record low propagation losses, plasmonic waveguides, a variety of laser structures, and improved wavelength demuliplexers. These developments demonstrate that IMOS has potential to deliver photonic integrated circuits to a wide variety of application fields, e.g. telecom, datacom, sensing, terahertz, and many others.

Development of Collagen-IV Sensor Using Optical Fiber-Based Mach-Zehnder Interferometer Structure

Abstract: This study presents a label-free and efficient method for the diagnosis of collagen-IV by using an optical fiber-based Mach-Zehnder interferometer (MZI) structure The structure of MZI is fabricated by splicing a 23 cm long segment of single-mode fiber (SMF) between two ~ 45 cm strands of multi-mode fibers (MMF) Owing to the mismatch of core diameters, cladding of SMF guides the light SMF’s cladding is partially etched by using 40% hydrofluoric (HF) acid so that a part of propagating energy is released that can interplay with the surroundings The etched region is immobilized with ~ 10 nm size of gold nanoparticles (AuNPs) and ~ 50 nm size of copper oxide nanoparticles (CuO-NPs) to initiate the influence of localized surface plasmon resonance (LSPR) phenomenon For a comparative study, two different probes are developed and analyzed In one probe, CuO NPs are immobilized over the etched part of SMF and named as CuO-NPs probe In other probe, a monolayer of AuNPs is sandwiched between fiber surface and CuO-NPs and termed as AuNPs/CuO-NPs probe The characterization of NPs and developed sensor probe are performed using UV-Vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and energy distribution spectroscopy (EDS) The sensor probes are made very specific towards collagen-IV by functionalizing them with collagenase enzyme obtained from Clostridium histolyticum A wide range of Collagen-IV solutions of concentrations from 2 $\mu \text{g}$ /ml to 40 $\mu \text{g}$ /ml are sensed through the collagenase functionalized probe The specificity of the probes are analyzed by sensing other biomolecules present in the human body

Comprehensive Study on Chip-Integrated Germanium Pin Photodetectors for Energy-Efficient Silicon Interconnects

Abstract: Optical interconnects are promising alternatives to copper-based wirings in on-chip communications. Recent advances in integrated group-IV nanophotonics should address a range of challenges related with speed, energy consumption, and cost. Monolithically integrated germanium pin photodetectors on silicon-on-insulator (SOI) waveguides are indispensable devices in this buoyant research field. Here, we comprehensively investigate the opto-electrical properties of hetero-structured pin photodetectors. All photodetectors were fabricated on top of 200-mm SOI substrates using industrial-scale semiconductor manufacturing processes. Under a low-bias voltage supply of 1 V, pin photodetectors exhibit dark-currents from 5 nA to 100 nA, dark current densities from 0.404 A/cm 2 to 0.808 A/cm 2 , responsivities in a range of 0.17 A/W to 1.16 A/W, and cut-off frequencies from 7 GHz to 35 GHz, respectively. Such achievements make them promising for use in power-efficient optical links operating at 40 Gbps, with a device energy dissipation of only few fJ per bit.

A Multifunctional Polarization Converter Base on the Solid-State Plasma Metasurface

Abstract: A novel multifunctional polarization converter (PC) based on the solid-state plasma (SSP) is proposed, which can switch two functions and adjust the working band. By energizing different parts of SSP resonators, the presented PC can accomplish three different operating states. In the state 1, this PC can operate in 6.12-9.50 GHz and the relative bandwidth (RB) is 43.3%, which can achieve the aim of the linear-to-circular polarization conversion (LCPC). In the state 2, the cross-polarization conversion (CPC) can be achieved in 4.62-8.34 GHz (the RB is 57.4%). Besides, in the state 3, such a PC can be implemented within a 7.92-10.34 GHz working band of CPC (the RB is 26.5%). All in all, the proposed PC can realize the function switchover between LCPC and CPC, and the operating bands of the CPC can be shifted flexibly between the states 2 and 3. The proposed PC has great potential values in antennas, imaging systems, electromagnetic devices and so on.

Integral Equation Analysis of Terahertz Backscattering From Circular Dielectric Rod With Partial Graphene Cover

Abstract: We study how the backward scattering cross-section (BSCS) of a microsize dielectric rod illuminated by an H-polarized plane wave can be efficiently manipulated using a partial graphene cover and associated plasmon resonances. Our treatment is based on the hyper-singular boundary integral equation, discretized with a Nystrom-type algorithm, which has a mathematically grounded convergence. We compute the BSCS and the extinction cross-section (ECS) in the sub-THz and THz ranges with controlled accuracy and demonstrate that BSCS can be both enhanced and reduced due to the graphene strip.

High Speed Mid-Wave Infrared Uni-Traveling Carrier Photodetector

Abstract: A mid-wave infrared (MWIR) frequency comb is expected to dramatically improve the precision and sensitivity of molecular spectroscopy. For high resolution applications, a high speed MWIR photodetector is one of the key components, however, commercially available high speed MWIR photodetectors only have sub-GHz bandwidth currently. In this paper, we demonstrate, for the first time to our knowledge, a high speed mid-wave infrared (MWIR) uni-traveling carrier photodetector based on InAs/GaSb type-II superlattice (T2SL) at room temperature. The device exhibits a cutoff wavelength of $5.6~\mu \text{m}$ and a 3dB bandwidth of 6.58 GHz for a $20~\mu \text{m}$ diameter device at 300 K. These promising results show that the device has potential to be utilized in high speed applications such as frequency comb spectroscopy, free space communication and others. The limitations on the high frequency performance of the photodetectors are also discussed.

Ultrafast UV AlGaN Metal–Semiconductor–Metal Photodetector With a Response Time Below 25 ps

Abstract: Aluminum-gallium-nitride photodetectors were successfully fabricated with micrometer-scale metal–semiconductor–metal structures and tested with ultrafast, UV laser pulses. The measurements were done with single-shot oscilloscopes. Pulse-broadening effects caused by the measurement system were systematically evaluated and reduced to resolve the intrinsic response time of the detector. The best-performing devices showed a response time of below 25 ps and dark currents below 20 pA. The devices showed linear response with the bias voltage and the laser energy.

Silicon Photonics High-Order Distributed Feedback Resonators Filters

Abstract: High-order distributed feedback resonators realized in silicon-on-insulator technology for the implementation of high-performance integrated optical filters are reported. This approach combines design simplicity and flexibility in a compact footprint with filter transfer functions featuring a flat-top response, large out-of-band rejection of more than 40 dB, ultra-steep roll-off up to 1000 dB/nm, and unprecedented stopband-to-passband ratios up to 600 for high-index-contrast technology. Active control of the coupled cavities through local micro heaters is employed for optimizing the filter response and passband tuning. Exemplary implementations of a box-like transfer function filter with a bandwidth of 25 GHz and of a narrow linewidth 2 GHz filter realized with 6 th - and 3 rd -order filter designs, respectively, are presented.

Rate Equation Modeling of Interband Cascade Lasers on Modulation and Noise Dynamics

Abstract: This work presents a rate equation model for interband cascade lasers, which is used for investigating modulation dynamics and optical noise properties. Through standard small-signal analysis of the rate equations, we analytically derive the resonance frequency, the damping factor, the relative intensity noise (RIN), and the frequency noise (FN) of the interband cascade lasers. It is shown that more cascading stages are beneficial for reaching a broad modulation bandwidth at a low pump current. On the other hand, fewer cascading stages are favorable to achieve low-RIN and low-FN (or narrow-linewidth) laser emission.

GeSe Evanescent Field Saturable Absorber for Mode-Locking in a Thulium/Holmium Fiber Laser

Abstract: A mode-locked Thulium-Holmium doped fiber laser (THDFL) with a Germanium Selenide (GeSe) saturable absorber (SA) is demonstrated for operation in the 2.0 μm wavelength region. The SA device is fabricated by drop-casting the GeSe onto an arc-shaped fiber which is then incorporated into the THDFL to induce mode-locked pulses. Stable mode-locking is attained at 1908.78 nm, with pulse duration of 1.67 ps and output power of 2.74 mW at a maximum pump power of 476 mW. The results of this work show that the GeSe can be a viable alternative for ultrafast photonics applications in the 2.0 μm. region.

Real-Time 2.5-Gb/s Correlated Random Bit Generation Using Synchronized Chaos Induced by a Common Laser With Dispersive Feedback

Abstract: We experimentally demonstrate high-speed correlated random bit generation in real time using synchronized chaotic lasers commonly driven by a laser with dispersive feedback. The dispersive feedback from a chirped fiber Bragg grating induces frequency-dependent feedback delay and thus no longer causes time-delay signature, and resultantly ensures the signal randomness and security of chaotic laser. Driven by the time-delay signature-free chaotic signal, the two response lasers are routed into chaotic states and establish a synchronization with correlation beyond 0.97 while they maintain a low correlation level with the drive signal. Through quantizing the synchronized laser chaos with a one-bit differential comparator, real-time 2.5-Gb/s correlated random bits with verified randomness are experimentally obtained with a bit error ratio of 0.07. Combining with a robust sampling method, the BER could be further decreased to 1×10 -4 corresponding to an effective generation rate of 1.7 Gb/s. Bit error analysis indicates that the bit error ratio between the responses is lower than that between the drive and responses over a wide parameter region due to the synchronization superiority of the responses over the drive.

High Absorption Contrast Quantum Confined Stark Effect in Ultra-Thin Ge/SiGe Quantum Well Stacks Grown on Si

Abstract: We report on the performance of the quantum confined Stark effect (QCSE) in ultra-thin (~350 nm) Ge/SiGe quantum well stacks grown on Si. We demonstrate an absorption contrast $\Delta \alpha /\alpha $ of 2.1 at 1 Vpp swing in QCSE stacks grown on ultra-thin (100 nm) strain relaxed GeSi buffer layers on 300 mm Si wafers. Such ultra-thin QCSE stacks will enable future integration of highly efficient QCSE electro-absorption modulators with low optical coupling loss to passive Si waveguides in a sub-micron silicon photonics platform.

Performance Improvement of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes With Step-Like Quantum Barriers

Abstract: AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) still confront many challenges, which is partially limited by the poor carrier injection in the active region. Although incorporating a high Al-composition quantum barrier (QB) may boost carrier confinement capability, it will aggravate the quantum confined Stark effect (QCSE) and thus deteriorate the optical performance. In this article, a DUV LED structure with step-like QBs has been proposed and carefully investigated. This unique QB structure suppresses the electron overflow into the p-side of the device and benefits the hole injection efficiency simultaneously, thereby promoting the radiative recombination rate in the active region. As a result, the internal quantum efficiency (IQE) and light output power (LOP) of the DUV LED with step-like QBs are significantly improved with an enhancement factor of 40% under 60 mA current injection. Therefore, our step-like QB design provides a feasible approach to the enhancement of the optical performance of DUV LEDs.

The High-Performance Imaging Verification of Si:P Blocked Impurity Band Detector for Very-Long-Wave-Infrared Spectral Range

Abstract: Very-long-wave-infrared (VLWIR) photodetectors have attracted great attention from scientists worldwide in the ground and space-based detections, imaging and early warning. However, the application of VLWIR photodetectors on earth is limited by the difficulty of establishing a high spatial-resolution fine imaging system with high-performance detector and large size optical lens. In this work, the VLWIR Si-based blocked-impurity-band (BIB) detector is fabricated and its high-performance imaging system is constructed. The CVD growth progress is optimized by enhancing the doping concentration of absorption layer, and shortening the transition length between blocking and absorption layers. At the temperature of 4.2K, the blackbody responsivity of Si-based BIB detector reaches 20.78A/W and the Noise Equivalent Power is $8.7\times 10^{-16}\text{W}$ /Hz1/2 at 2.6V. Based on the high performance Si-based BIB detector, an imaging verifying system is set up to detect different room-temperature objects. Its spatial and temperature resolution reaches $250~\mu \text{m}$ and 10mK, respectively. Our results indicate that with suitable optical imaging system, the BIB detector is more effective than the infrared detector of commercial thermal infrared imager in detecting room temperature or low temperature objects like metal. Our work is helpful for the further research on the large scale array integrated BIB imaging and detection system used on earth for explosives detection, biological nondestructive detection as well as security check.

Development of Reliable and High Responsivity ZnO-Based UV-C Photodetector

Abstract: This work is focused on the development of reliable and high-performance ZnO based deep UV (UV-C) photodetectors. Herein, hydrothermally synthesized ZnO honeycomb nanostructures were utilized to develop a high sensitivity UV-C photodetector. A systematic analysis of the device performance and stability in deep UV (250 nm) radiations has been performed. The as-synthesized device has shown high sensitivity of 2.4 $\times \,\,10^{5}$ and responsivity of 597 A/W, at 20 V applied bias. Further, we have demonstrated that the coating of Pt nanoparticles over ZnO nanostructures could significantly improve not only the device stability but also the response speed and device endurance in deep UV radiations. The proposed device is a promising contender for future deep UV detector based optoelectronic products.

A General Relation Between Frequency Noise and Lineshape of Laser Light

Abstract: Lasers and especially semiconductor lasers (SCLs) are playing a major role in advanced technological and scientific tasks ranging from sensing, fundamental investigations in quantum optics and communications. The demand for ever-increasing accuracy and communication rates has driven these applications to employ phase modulation and coherent detection. The main laser attribute that comes into play is its coherence which is usually quantified by either the Schawlow-Townes (S-T) linewidth, the spectral width of the laser field, or the power spectral density (PSD) function of the laser frequency fluctuation. In this paper, we present a derivation of a general and direct relationship between these two coherence measures. We refer to the result as the Central Relation. The relation applies independently of the physical origin of the noise. Experiments are described which demonstrate the validity of the Central Relation and at the same time suggest new methods of controlling frequency noise at base band by optical filtering.

Optimum Operation of Radiation-Balanced Lasers

Abstract: The operation of radiation-balanced lasers (RBLs) is analyzed for practical considerations of cavity losses, optimum out-coupling, and radial distribution of pump and laser modes. We derive expressions for laser efficiency under arbitrary heat loads, discuss the limitations on high-power scaling imposed by thermal gradients in radiation-balanced disk geometries, and propose potential remedies. The effects of parasitic absorption of the pump and fluorescence are evaluated. The analysis is intended primarily for disk lasers but is also applicable to rod laser geometries.

Ultracompact 40-Channel Arrayed Waveguide Grating on Silicon Nitride Platform at 860 nm

Abstract: Arrayed waveguide gratings (AWG) have been widely used as wavelength multiplexers and demultiplexers in dense wavelength division multiplexing communications. In this letter, we describe a highly compact 40-channel AWG fabricated on the silicon nitride platform for operation with a center wavelength near 860 nm for use in spectral domain optical coherence tomography. The total footprint of the AWG is 910μm × 680μm. The transmission spectrum of the fabricated device was measured. The AWG had a channel spacing of 1.5 nm and optical spectral range of 60 nm, in accord with the design. The measured insertion loss was 1.3 dB for the central channels and 1.8 dB for the outmost channels. The inter-channel crosstalk varied from 17.2 dB to 19.7 dB for the central 20 channels.

Optical Noise of Dual-State Lasing Quantum Dot Lasers

Abstract: This paper theoretically investigates the optical noise characteristics of the simultaneous ground-state (GS) and excited-state (ES) lasing quantum dot lasers. The optical noise dynamics of both states are analysed through coupling the Langevin noise sources into a set of coupled rate equations. It is pointed out that the ES emission significantly changes the evolution scenario of the relative intensity noise, the frequency noise (spectral linewidth), and the linewidth broadening factor of the GS emission, as a function of the bias current. In the vicinity of the ES lasing threshold, the relative intensity noise and the frequency noise of the GS emission is lower than those of ES emission. However, the linewidth broadening factor of the GS emission is larger than the latter.

Impact of Self-heating and Elevated Temperature on Performance of Quantum Dot Microdisk Lasers

Abstract: We discuss the effect of self-heating on performance of injection microdisk lasers operating in continuous-wave (CW) regime at room and elevated temperature. A model is developed that allows one to obtain analytical expressions for the peak optical power limited by the thermal rollover effect, the corresponding injection current and excess temperature of the device. The model predicts, there exists the maximum temperature of microlaser operation in CW regime and the minimum mircrodisk diameter, at which CW lasing is possible. The model allows one to determine the dependence of the device characteristics on its diameter and the inherent parameters, such as thermal resistance, electrical resistance, non-radiative recombination and characteristic temperature of the threshold current. It is found that a rapid growth of the threshold current density with decreasing the diameter (which takes place even in the absence of the self-heating effect) is the main internal reason leading to the dependence of the temperature characteristics of the mirodisk laser on its size. In the calculations, we used a set of parameters extracted from experiments with InGaAs quantum dot microdisk lasers. The simulation results (in particular, the light-current curve and the dependence of the minimum microdisk diameter on ambient temperature) comply well with the measured dependences.

Ultrapure Green Light-Emitting Diodes Based on CdSe/CdS Core/Crown Nanoplatelets

Abstract: Colloidal nanoplatelets (NPLs) are a kind of two-dimensional nano-material with an atomically flat surface, leading to an ultra-narrow emission linewidth of 8~12 nm. In this article, we fabricated green light-emitting diodes (LEDs) based on CdSe/CdS core/crown NPLs. This device exhibited an electroluminescence (EL) at 521 nm with a full-width at half maximum (FWHM) of 15 nm and a maximum luminance of 4684 cd/m 2 . Such narrow EL FWHM indicates that the core/crown NPLs can achieve an ultrapure green LED with 124.7% of National Televison System Committee (NTSC), realizing a high color saturation and wide color gamut display.

A Monolithically Integrated Racetrack Colliding-Pulse Mode-Locked Laser With Pulse-Picking Modulator

Abstract: We present a novel photonic integrated circuit (PIC) that monolithically integrates a racetrack colliding-pulse mode-locked laser with a pulse-picking electro-absorption modulator and a semiconductor optical amplifier on Indium Phosphide. We present detailed characterization of this PIC that includes optical pulse characterization, phase noise and long term stability under passive and hybrid mode-locking conditions. Allan deviation measurements made on the optical pulse train from the PIC show a fractional frequency instability of $8\times 10 ^{-11}$ at 1 second and follow a 1/ $\tau $ trend. We also demonstrate repetition rate reduction from ~10 GHz to ~500 MHz with an extinction ratio of ~14.65 dB using an on-chip pulse-picking electro-absorption modulator.

4-dB Quadrature Squeezing With Fiber-Coupled PPLN Ridge Waveguide Module

Abstract: We have developed an optical parametric amplification module for quadrature squeezing with input and output ports coupled with optical fibers for both fundamental and second harmonic. The module consists of a periodically poled LiNbO 3 ridge waveguide fabricated with dry etching, dichroic beamsplitters, lenses and four optical fiber pigtales. The high durability of the waveguide and the good separation of squeezed light from a pump beam by the dichroic beamsplitter enable us to inject intense continuous-wave pump light with the power of over 300 mW. We perform −4.0±0.1 dB of noise reduction for a vacuum state at 1553.3 nm by using a fiber-optics-based measurement setup, which consists of a fiber-optic beamsplitter and a homemade fiber-receptacle balanced detector. The intrinsic loss of the squeezed vacuum in the module is estimated to be 25%. Excluding the extrinsic loss of the measuremental system, the squeezing level in the output fiber of the module is estimated to be −5.7±0.1 dB. A modularized alignment-free fiber-coupled quadrature squeezer could help to realize quantum information processing with fiber optics.

THz Waves Scattering by Finite Graphene Strip Grating Embedded Into Dielectric Slab

Abstract: We consider the scattering and absorption of plane H-polarized wave by finite number of graphene strips placed inside a dielectric slab, in the THz range. The problem is reduced to the singular integral equation. Here we obtain two types of singular integrals: Cauchy principal value integral and integral with poles. To eliminate the poles we present the regularization procedure. The theoretically guaranteed convergent Nystrom-type method is used for discretization. Results for the total scattering and absorption cross sections and the near field patterns are presented. We pay special attention to plasmon and gratingmode resonances, as well as excitation of eigenwaves of dielectric slab. These waves carry energy of the incident field along the dielectric slab. Dramatic growth in the power is observed at the grating-mode resonance frequencies.

III-N/Si₃N₄ Integrated Photonics Platform for Blue Wavelengths

Abstract: In this paper, we report a low-loss photonic integrated circuits (PICs) platform at blue wavelengths of the visible spectral regime. Silicon nitride (SiN) is a popular passive waveguide material due to its fabrication flexibility, CMOS compatibility and spectral transparency in this wavelength regime. For active devices including lasers, gallium nitride (GaN) and its alloys are considered. Several basic building blocks for the development of a complete integrated platform, including blue diode lasers, in-plane- and out-of-plane light couplers, as well as on-and off-chip coupling between these active and passive components are theoretically investigated. The proposed in-plane and out-of-plane architectures operate through edge- and vertical grating couplers (VGCs), respectively. With edge-coupling, large mode-mismatch between the GaN laser diode and SiN waveguide is alleviated through nanotapers on both the active and passive sections and the calculated peak coupling efficiency is achieved to be 74% at a wavelength of 450 nm. We also separately designed efficient VGCs for coupling light from standard, commercial, off-the-shelf fibers to the SiN chip, and edge couplers for fiber-chip coupling, exhibiting coupling efficiencies of 51% and 83%, respectively. For robust on-chip light-coupling between active and passive circuit elements, with relaxed alignment tolerances, two approaches, i.e., flip-chip based hybrid integration and evanescent coupling based heterogeneous integration are studied. Calculated maximum coupling efficiencies of 40% (−4 dB) are achieved for both the hybrid and heterogeneous schemes. The theoretical work performed is an initial step towards demonstrating complex blue PICs which could offer a comprehensive range of photonic functionalities.

Impacts of Laboratory Vibrations and Laser Flicker Noise on Digital Holography

Abstract: In this paper, we experimentally demonstrate the impacts of laboratory vibrations and laser flicker noise on digital holography (DH) Specifically, we measure both the vibration efficiency and the coherence efficiency of our DH system at various focal-plane array integration times and path-length differences between the signal and reference These efficiencies, in practice, contribute to the overall mixing efficiency, which is a measure for how well the detected signal and reference interfere The results show that when the integration time is ≤1ms, the laboratory vibrations are negligible with a vibration efficiency of 100%; however, when the integration time equals 100 ms, the laboratory vibrations lead to a 94% vibration efficiency In addition, the results show that the effective coherence length of the master-oscillator (MO) laser increases by 280% when the integration time decreases from 100ms to 100 $\mu \text{s}$ To account for this outcome, we present a model of the coherence efficiency based on the frequency noise of the MO laser The model fit to the DH data then shows that the frequency of the MO laser is flicker-noise dominated As a result, decreasing the integration time improves the overall mixing efficiency because of high-pass filtering in both the vibration efficiency and the coherence efficiency Based on previous published efforts, these results have direct ties to the achievable signal-to-noise ratio of a DH system

Edge-Coupling of O-Band InP Etched-Facet Lasers to Polymer Waveguides on SOI by Micro-Transfer-Printing

Abstract: O-band InP etched facets lasers were heterogeneously integrated by micro-transfer-printing into a $1.54~\mu \text{m}$ deep recess created in the $3~\mu \text{m}$ thick oxide layer of a 220 nm SOI wafer. A $7\times 1.5\,\,\mu \text{m}^{2}$ cross-section, 2 mm long multimode polymer waveguide was aligned to the ridge post-integration by e-beam lithography with $ lateral misalignment and incorporated a tapered silicon waveguide. A 170 nm thick metal layer positioned at the bottom of the recess adjusts the vertical alignment of the laser and serves as a thermal via to sink the heat to the Si substrate. This strategy shows a roadmap for active polymer waveguide-based photonic integrated circuits.