Showing papers in "IEEE Journal of Selected Topics in Quantum Electronics in 2018"
TL;DR: An overview of the most recent developments and improvements to the low-loss TriPleX Si3N4 waveguide technology is presented in this article, which can be combined to design complex functional circuits, but more important are manufactured in a single monolithic flow to create a compact photonic integrated circuit.
Abstract: An overview of the most recent developments and improvements to the low-loss TriPleX Si3N4 waveguide technology is presented in this paper The TriPleX platform provides a suite of waveguide geometries (box, double stripe, symmetric single stripe, and asymmetric double stripe) that can be combined to design complex functional circuits, but more important are manufactured in a single monolithic process flow to create a compact photonic integrated circuit All functionalities of the integrated circuit are constructed using standard basic building blocks, namely straight and bent waveguides, splitters/combiners and couplers, spot size converters, and phase tuning elements The basic functionalities that have been realized are: ring resonators and Mach–Zehnder interferometer filters, tunable delay elements, and waveguide switches Combination of these basic functionalities evolves into more complex functions such as higher order filters, beamforming networks, and fully programmable architectures Introduction of the active InP chip platform in a combination with the TriPleX will introduce light generation, modulation, and detection to the low-loss platform This hybrid integration strategy enables fabrication of tunable lasers, fully integrated filters, and optical beamforming networks
278 citations
TL;DR: In this article, the authors provide an overview of the main achievements that have been obtained to date, and highlight the strong potential of optical microcombs for RF photonics applications, and discuss some of the open challenges and limitations that need to be addressed for practical applications.
Abstract: Over the past decade, optical frequency combs generated by high-Q microresonators, or optical microcombs, which feature compact device footprints, low power consumption, and high repetition rates in broad optical bandwidths, have led to a revolution in a wide range of fields including metrology, telecommunications, radio frequency (RF) photonics, spectroscopy, sensing, and quantum optics. Among these, an application that has attracted great interest is the use of optical microcombs for RF photonics, where they offer enhanced functionalities as well as reduced size and power consumption over other approaches. This paper reviews the recent advances in this emerging field. We provide an overview of the main achievements that have been obtained to date, and highlight the strong potential of optical microcombs for RF photonics applications. We also discuss some of the open challenges and limitations that need to be addressed for practical applications.
261 citations
TL;DR: In this article, the authors summarize recent experimental results on transition-metal (TM)-doped II-VI chalcogenides providing access to the 1.8-6-μm spectral range with a high (>60%) efficiency, multi-Watt-level [140 W in continuous wave (CW)] output powers, tunability of >1000 nm, short-pulse (<16 F) multiWatt oscillation, and multi-Joule output energies in free running and gain-switched regimes.
Abstract: Enabling broad tunability, high peak and average power, ultrashort pulse duration, and all known modes of laser operation—transition-metal (TM)-doped II–VI chalcogenides are the materials of choice for direct lasing in the mid-IR. The host materials feature broad infrared transparency, high thermal conductivity, low phonon cutoff, low optical losses, and are available as either single crystals or polycrystalline ceramics. Doped with TM ions, these media exhibit a four-level energy structure, the absence of excited state absorption, as well as broad absorption and emission bands. Doped single-crystals of high optical quality are difficult to grow; however, the advent of postgrowth diffusion doped ceramics has resulted in significant progress in laser development. Here, we summarize recent experimental laser results on Cr and Fe doped II–VI chalcogenides providing access to the 1.8–6 μm spectral range with a high (>60%) efficiency, multi-Watt-level [140 W in continuous wave (CW)] output powers, tunability of >1000 nm, short-pulse (<16 fs) multi-Watt oscillation, and multi-Joule output energies in free running and gain-switched regimes. We also review recent results on hybrid fiber-bulk (Er-fiber/Er:YAG, Tm-fiber: Ho:YAG/YLF) systems combining high efficiency of CW fiber lasers with high pulse energies of bulk materials and serving as pump sources of gain-switched Cr:II-VI lasers.
177 citations
TL;DR: A framework for understanding the underlying models, and a neuron-like processing device—an excitable laser—that has many favorable properties for integration with emerging photonic integrated circuit platforms are provided.
Abstract: This paper reviews some recent progress in the field of neuromorphic photonics, with a particular focus on scalability. We provide a framework for understanding the underlying models, and demonstrate a neuron-like processing device—an excitable laser—that has many favorable properties for integration with emerging photonic integrated circuit platforms. On a systems level, we compare several proposed interconnection frameworks that allow for fully tunable networks of photonic neurons.
174 citations
TL;DR: It can be concluded that generic integration on InP is maturing fast and with the current developments and infrastructure it is the technology of choice for low cost, densely integrated PICs, ready for high-volume manufacturing.
Abstract: The standardization of photonic integration processes for InP has led to versatile and easily accessible generic integration platforms. The generic integration platforms enable the realization of a broad range of applications and lead to a dramatic cost reduction in the development costs of photonic integrated circuits (PICs). This paper addresses the SMART Photonics generic integration platform developments. The integration technology based on butt joint active-passive epitaxy is shown to achieve a platform without compromising the performance of the different components. The individual components or building blocks are described. A process design kit is established with a comprehensive dataset of simulation and layout information for the building blocks. Latest results on process development and optimization are demonstrated. A big step forward is achieved by applying high-resolution ArF lithography, which leads to increased performance for AWGs and a large increase in reproducibility and yield. The generic nature of the platform is demonstrated by analyzing a number of commercial multiproject wafer runs. It is clear that a large variety of applications is addressed with more than 200 designs from industry as well as academia. A number of examples of PICs are displayed to support this. Finally, the design flow is explained, with focus on layout-aware schematic-driven design flow that is required for complex circuits. It can be concluded that generic integration on InP is maturing fast and with the current developments and infrastructure it is the technology of choice for low cost, densely integrated PICs, ready for high-volume manufacturing.
150 citations
TL;DR: A new numerical solution method for the system of equations that describes nonlinear multimode propagation, the generalized multimode nonlinear Schrödinger equation is demonstrated, which features a significant parallel computing speed-up on modern graphical processing units, translating to orders-of-magnitude speed- up over the conventionally-used split-step Fourier method.
Abstract: Building on the scientific understanding and technological infrastructure of single-mode fibers, multimode fibers are being explored as a means of adding new degrees of freedom to optical technologies such as telecommunications, fiber lasers, imaging, and measurement. Here, starting from a baseline of single-mode nonlinear fiber optics, we introduce the growing topic of multimode nonlinear fiber optics. We demonstrate a new numerical solution method for the system of equations that describes nonlinear multimode propagation, the generalized multimode nonlinear Schrodinger equation. This numerical solver is freely available, implemented in MATLAB and includes a number of multimode fiber analysis tools. It features a significant parallel computing speed-up on modern graphical processing units, translating to orders-of-magnitude speed-up over the conventionally-used split-step Fourier method. We demonstrate its use with several examples in graded- and step-index multimode fibers. Finally, we discuss several key open directions and questions, whose answers could have significant scientific and technological impact.
141 citations
TL;DR: In this article, a film-type ReS2-PVA saturable absorber is fabricated to realize Q-switching and mode locking of erbium-doped fiber lasers.
Abstract: Transition metal dichalcogenides, a family of two-dimensional material with unusual electronic, optical, mechanical, and electrochemical properties, have received much research attention in recent years. Here we demonstrate that, another type of few-layer transition metal dichalcogenides, rhenium disulfide (ReS2) nanosheets display saturable absorption property at 1.55 μm. By incorporating the ReS2 nanosheets with the polyvinyl alcohol (PVA), a film-type ReS2-PVA saturable absorber is fabricated to realize Q-switching and mode locking of erbium-doped fiber lasers. The repetition rate of the Q-switched laser pulses varies from 12.6 to 19 KHz while the duration changes from 23 to 5.496 μs by tuning the pump from 45 to 120 mW. By optimizing the polarization state, the mode-locked operation is also obtained, emitting a train of pulses centered at 1558.6 nm with the duration of 1.6 ps and the fundamental repetition rate of 5.48 MHz. It is demonstrated that ReS2 nanosheets have the similar saturable absorption property as that of MoS2 and WS2, and may find potential applications in pulsed laser, optical modulators, and sensors.
140 citations
TL;DR: Key advances which enabled the InP photonic integrated circuit (PIC) and the subsequent progression of InP PICs to fully integrated multichannel DWDM system-on-chip (SOC) PIC’s are described.
Abstract: Key advances which enabled the InP photonic integrated circuit (PIC) and the subsequent progression of InP PICs to fully integrated multichannel DWDM system-on-chip (SOC) PICs are described. Furthermore, the current state-of-the-art commercial multichannel SOC PICs are reviewed as well as key trends and technologies for the future of InP-based PICs in optical communications.
117 citations
TL;DR: The state-of-the-art of these compact modulators, with a focus on fabrication, design, and high-speed performance is reviewed in this paper, where guidelines for design optimization and key performance metrics of these important integrated photonic devices are presented.
Abstract: Lithium niobate (LN), spurred by its success for fiber-optic communications, has remained the material of choice for high-performance electrooptic (EO) modulators. The past decade has seen a surge in efforts aimed at miniaturizing LN EO modulators with higher order modulation formats, data centers, and optical interconnect applications in mind. The state-of-the-art of these compact modulators, with a focus on fabrication, design, and high-speed performance is reviewed. Guidelines for design optimization and key performance metrics of these important integrated photonic devices are presented. Furthermore, an outlook on the road toward commercial viability, along with potential novel applications is provided.
117 citations
TL;DR: In this paper, the photonic Damascene process was used for fabrication of high-confinement and low-loss silicon nitride waveguides with high attenuation of 5.5 dB/m.
Abstract: We report on fabrication of high-confinement and low loss silicon nitride ( $\text{Si}_{3}\text{N}_{4}$ ) waveguides using the photonic Damascene process. This process scheme represents a novel fabrication approach enabling reliable, wafer-scale fabrication of high-confinement optical waveguides. A reflow step of the silica preform reduces sidewall scattering to values not attainable with conventional etching, and reduces losses and backscattering significantly, resulting in a waveguide attenuation of 5.5 dB/m. We discuss the critical aspects of the process in detail and demonstrate the fabrication of high stress $\text{Si}_{3}\text{N}_{4}$ waveguides with unprecedentedly large dimensions ( $\text{1.75}\,\mu \text{m} \times \text{1.425}\,\mu \text{m}$ ) providing high-confinement at midinfrared wavelengths. A device characterization strategy allowing for systematic extraction of statistically relevant loss values is discussed and reveals the effects of the sidewall smoothing.
116 citations
TL;DR: The new horizon opened by the recently developed SFS is reviewed, and a kilowatt-level high power SFS based on a tandem pumping technique will be demonstrated for the first time, and the first hundred-watt level linearly polarized random fiber laser is presented.
Abstract: Thanks to the unique properties such as spatially coherent, broadband emission spectrum, and high temporal stability, superfluorescent fiber source (SFS) has shown tremendous potential in wide applications of sensing, imaging, spectroscopy, and material processing. The fast development of active fiber and pump diode provides unprecedented opportunity for the performance scaling of SFS. In this paper, the new horizon opened by the recently developed SFS will be reviewed. First, the output power scaling of SFS with different architectures will be summarized, and a kilowatt-level high power SFS based on a tandem pumping technique will be demonstrated for the first time. Second, spectrum manipulation of SFS, including coverage extending and spectrum shaping, will be introduced in detail. What is more, the spectrum evolution of narrowband SFS in power scaling will be numerically modeled and evaluated. Third, several novel applications of SFS, including midinfrared laser generation, nonlinear effect suppression, sensing, and imaging, will be given, indicating the versatile performance of SFS compared with traditional fiber laser oscillators. Based on the new developed SFS, we will present the first hundred-watt level linearly polarized random fiber laser. In the last section, future endeavors on SFS will be presented.
TL;DR: In this paper, the authors present a brief overview of the various leading platforms for photonic integration and consider the possibility of a photonic integrated circuit platform utilizing epitaxially grown III-V material on silicon without the need for wafer bonding, or an externally coupled laser.
Abstract: We present a brief overview of the various leading platforms for photonic integration. Subsequently, we consider the possibility of a photonic integrated circuit platform utilizing epitaxially grown III–V material on silicon—without the need for wafer bonding, or an externally coupled laser. Finally, a techno-economic analysis contrasting the aforementioned platforms will be presented.
TL;DR: In this paper, a back-illuminated three-dimensional stacked single-photon avalanche diode (SPAD) was implemented in 45-nm CMOS technology for the first time.
Abstract: We present a high-performance back-illuminated three-dimensional stacked single-photon avalanche diode (SPAD), which is implemented in 45-nm CMOS technology for the first time. The SPAD is based on a P+/Deep N-well junction with a circular shape, for which N-well is intentionally excluded to achieve a wide depletion region, thus enabling lower tunneling noise and better timing jitter as well as a higher photon detection efficiency and a wider spectrum. In order to prevent premature edge breakdown, a P-type guard ring is formed at the edge of the junction, and it is optimized to achieve a wider photon-sensitive area. In addition, metal-1 is used as a light reflector to improve the detection efficiency further in backside illumination. With the optimized 3-D stacked 45-nm CMOS technology for back-illuminated image sensors, the proposed SPAD achieves a dark count rate of 55.4 cps/μm2 and a photon detection probability of 31.8% at 600 nm and over 5% in the 420–920 nm wavelength range. The jitter is 107.7 ps full width at half-maximum with negligible exponential diffusion tail at 2.5 V excess bias voltage at room temperature. To the best of our knowledge, these are the best results ever reported for any back-illuminated 3-D stacked SPAD technologies.
TL;DR: In this article, the design and characterization of single-photon avalanche diodes (SPADs) fabricated in a 0.16 μ m BCD (Bipolar-CMOS-DMOS) technology is reported.
Abstract: CMOS single-photon avalanche diodes (SPADs) have recently become an emerging imaging technology for applications requiring high sensitivity and high frame-rate in the visible and near-infrared range. However, a higher photon detection efficiency (PDE), particularly in the 700–950 nm range, is highly desirable for many growing markets, such as eye-safe three-dimensional imaging (LIDAR). In this paper, we report the design and characterization of SPADs fabricated in a 0.16 μ m BCD (Bipolar-CMOS-DMOS) technology. The overall detection performance is among the best reported in the literature: 1) PDE of 60% at 500 nm wavelength and still 12% at 800 nm; 2) very low dark count rate of μ m2 (in counts per second per unit area); 3) < 1% afterpulsing probability with 50 ns dead-time; and 4) temporal response with 30 ps full width at half-maximum and less than 50 ps diffusion tail time constant.
TL;DR: In this paper, the authors presented a comprehensive theoretical study of mode instability with a universal model for the first time, which includes quantitative study on the various influence factors and mitigation methods and properly combining the mitigation methods, an approach to achieve beyond 10-kW diode pumped fiber laser with near diffraction limited beam quality has been proposed.
Abstract: We present comprehensive theoretical study of mode instability with a universal model for the first time, which includes quantitative study on the various influence factors and mitigation methods. With large numerical results, the influence of various fiber and system parameters has been studied to summarize mitigation methods. The mode instability threshold behavior of multiwavelength pumping configurations has been studied for the first time, and the influence of pump wavelength shifting in the tandem pumping technique and amplitude modulation have also been given for the first time. The mitigation methods are discussed with review of the latest development in experimental results. The drawbacks and possible overcome measures are also discussed. By properly combining the mitigation methods, an approach to achieve beyond 10-kW diode pumped fiber laser with near diffraction limited beam quality has been proposed, which provides a creative way to overcome the mode instability limitation on diode pumped fiber lasers, and demonstrates the effectiveness of the mitigation methods.
TL;DR: In this paper, the authors present numerical results on the performance of a swirl-topology photonic reservoir integrated on a silicon chip for a classical nonlinear Boolean task (the delayed XOR task) for various designs of the reservoir in terms of lengths of the waveguides between consecutive nodes, and various injection parameters (injected power and optical detuning).
Abstract: We present in our work numerical results on the performance of a $\mathbf {4 \times 4}$ swirl-topology photonic reservoir integrated on a silicon chip. Nonlinear microring resonators are used as nodes. We analyze the performance of such a reservoir on a classical nonlinear Boolean task (the delayed XOR task) for: various designs of the reservoir in terms of lengths of the waveguides between consecutive nodes, and various injection parameters (injected power and optical detuning). From this analysis, we find that this kind of reservoir can perform–for a large variety of parameters–the delayed XOR task at 20 Gb/s with bit error rates lower than $\mathbf {10^{-3}}$ and an averaged injection power lower than 2.5 mW.
TL;DR: The recent, in particular since 2012, progress and findings obtained out of current academic and industry research activities for InP-PICs are discussed, with major emphasis on the high-performance and complex PICs that have been reported by the scientific community in this time period.
Abstract: Similar to the area of microelectronics, InPbased photonic integrated circuits (PICs) in the optical domain as a counterpart are also seeing a clear exponential development. This rapid progress can be defined by a number of active/passive components monolithically integrated on a single chip. Given the probability of achieving low-cost, compact, robust, and energy-efficient complex photonic systems, there have been significant achievements made in realizing relatively complex InPPICs in recent years. The performance of these complex PICs is reaching a stage that can enable a whole new class of applications beyond telecom and datacom. A great deal of effort from both academia and industry has made the significant advances of this technology possible. This development has resulted in a positive and profound impact in many areas including sensing, medical diagnostics, metrology, and consumer photonics. This review paper will mainly discuss the recent, in particular since 2012, progress and findings obtained out of current academic and industry research activities for InP-PICs. Major emphasis will be given to the high-performance and complex PICs that have been reported by the scientific community in this time period. A prospect for further development of this photonic integration in InP-platforms is also briefly described.
TL;DR: In this paper, the state of the art in the research field of this kind of the laser-active fibers is discussed and the fabrication and spectroscopic properties of the Bi-doped high-germania-core fibers are described.
Abstract: The light sources operating in the spectral range 1600–1800 nm are of great interest because of a number of potential scientific and practical applications. This stimulates a search for effective laser media for this wavelength region. Recent progress in the studying of bismuth (Bi)-doped fibers is related to the development of Bi-doped high-germania-core fibers for the mentioned wavelength region. This paper is concerned with the current state of the art in the research field of this kind of the laser-active fibers. The fabrication and spectroscopic properties of the Bi-doped high-germania-core fibers are described. The photo-induced bleaching and recovery stimulated by thermal treatment of luminescent centers in these fibers are presented. The review also includes the description of the basic parameters of the optical devices (continuous wave (CW) and pulsed lasers, amplifiers, superluminescent sources) developed using Bi-doped high-germania-core fibers.
Journal Article•
TL;DR: In this article, the authors discuss different types of photodetectors and ways in which plasmonics can be applied to them and discuss the main physical principles behind their operation.
Abstract: Plasmonic photodetectors are attracting the attention of the photonics community. Plasmonics is attractive because metallic structures have the ability to confine light by coupling an electromagnetic wave to charged carrier oscillations at the surface of the metal. The wavelength of such oscillations can be much smaller than the corresponding light wavelength in vacuum. This enables the light-matter interaction on a deep subwavelength scale, which in turn allows for more compact and potentially higher speed devices. In this review, we discuss different types of photodetectors and ways in which plasmonics can be applied to them. We elucidate several plasmonic photodetector concepts/schemes and discuss the main physical principles behind their operation. Finally, we reflect on the characteristics of an “ideal” photodetector and propose a device that might be the perfect plasmonic detector.
TL;DR: In this paper, a monolithic integrated optical phase lock loop (OPLL) was proposed for coherent detection using photonic integration technology and the first OPLL was created using foundry fabricated photonic integrated circuits and off-the-shelf electronic components.
Abstract: An Optical Phase Lock Loop (OPLL) is a feedback control system that allows the phase stabilization of a laser to a reference laser with absolute but adjustable frequency offset Such phase and frequency locked optical oscillators are of great interest for sensing, spectroscopy, and optical communication applications, where coherent detection offers advantages of higher sensitivity and spectral efficiency than can be achieved with direct detection As explained in this paper, the fundamental difficulty in realising an OPLL is related to the limitations on loop bandwidth and propagation delay as a function of laser linewidth In particular, the relatively wide linewidth of semiconductor lasers requires short delay, which can only be achieved through shortening of the feedback path, which is greatly facilitated through photonic integration This paper reviews the advances in the development of semiconductor laser-based OPLLs and describes how improvements in performance have been enabled by improvements in photonic integration technology We also describe the first OPLL created using foundry fabricated photonic integrated circuits and off-the-shelf electronic components Stable locking has been achieved for offset frequencies between 4 and 12 GHz with a heterodyne phase noise below –100 dBc/Hz at 10 kHz offset This is the highest performance yet reported for a monolithically integrated OPLL and demonstrates the attractiveness of the foundry fabrication approach
TL;DR: In this paper, a 300mm silicon photonics platform for large-scale device integration was developed, leveraging 40nm complementary metal-oxide-semiconductor technology, which can enable manufacturing of high-speed, low-power optical interconnects.
Abstract: A 300-mm silicon photonics platform for large-scale device integration was developed, leveraging 40-nm complementary metal-oxide-semiconductor technology. Through fabrication using this technology platform, wire waveguides were obtained with low propagation losses for the C-band (0.4 dB/cm) and O-band (1.3 dB/cm). Several types of wavelength filters, including a coupled resonator optical waveguide (CROW), an arrayed waveguide grating, and a cascaded Mach–Zehnder interferometer, were also demonstrated, with low crosstalk and low insertion loss. A polarization rotator Bragg grating with multiple reflection peaks having polarization independence was also obtained. In terms of wafer-scale uniformity, a small standard deviation of 0.7 nm in resonant wavelength for the CROW was confirmed. A grating coupler also exhibited low wafer-scale variations in the maximum coupling efficiency and the diffraction wavelength in optical coupling with a single-mode fiber. Extraction of fabrication deviations for the waveguides was performed using the spectral variation of microring resonators and grating couplers. The extracted wafer-scale variations in waveguide width and height and grating depth well reproduced the results of physical measurements, with subnanometer-level accuracy. The developed technology can thus enable manufacturing of high-speed, low-power optical interconnects.
TL;DR: In this paper, the authors provide a unified perspective of the unique opportunities created by operating at high repetition rates together with efforts into the development of enabling laser technology, including new results on further scaling up the capabilities of the laser systems.
Abstract: Ultrafast lasers operating at high repetition rates, in particular the GHz range, enable new possibilities in laser-material processing, particularly accessing the recently demonstrated ablation-cooled regime. We provide a unified perspective of the unique opportunities created by operating at high repetition rates together with our efforts into the development of enabling laser technology, including new results on further scaling up the capabilities of the laser systems. In order to access GHz repetition rates and microjoule-level pulse energies without requiring kilowatts of average power, we implement burst-mode operation. Our results can be grouped into two distinct directions: low- and high-power systems. Pulsed pumping is employed in the later stages of low-power systems, which have low burst repetition rates to achieve high pulse energies, whereas the technique of doping management is developed for the continuously pumped power amplifier stage of high power systems. While most of the developments have been at 1- $\mu$ m wavelength range due to the relative maturity of the laser technology, we also report the development of Tm-fiber lasers around the 2- $\mu$ m region specifically for tissue processing and laser-surgery applications.
TL;DR: In this article, the spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements, with outputs ranging from 1908 to 2130 nm.
Abstract: Thulium-doped fiber lasers (TDFLs) have had the second highest growth in average output power next to ytterbium-doped fiber lasers. This has been enabled by access to high power, high brightness ∼790-nm pump diodes in conjunction with the cross-relaxation process that improves laser efficiency. While numerous high power TDFLs have been recently demonstrated, a 1-kW result from 2010 remains the highest output power system reported to date. This paper reviews these systems and the concepts behind high power TDFLs. The spectroscopic properties of Tm3+ -doped silica are first detailed, revealing complex processes and large variations among published measurements. Notable multi-100 W TDFLs are then summarized, with outputs ranging from 1908 to 2130 nm. Another route for power scaling is to in-band pump with another TDFL to enable >90% efficiencies. Both 790- and 1900-nm pumped TDFL architectures are theoretically modeled based on currently available systems. Hindered by high background losses and available pump sources, achieving >4 kW like ytterbium-fiber systems will be a substantial challenge.
TL;DR: In this paper, the authors focus on the design of resonator-based circuits in the silicon nitride platform and the balancing of desired properties like quality factor, free spectral range, finesse, transmission shape with waveguide design, and footprint.
Abstract: Integrated optical resonators are key building blocks for an ever-increasing range of applications including optical communications, sensing, and navigation. A challenge to today's photonics integration is realizing circuits and functions that require ultralow loss waveguides on-chip while balancing the waveguide loss with device function and footprint. Incorporating Si3N4/SiO2 waveguides into a photonic circuit requires tradeoffs between waveguide loss, device footprint, and desired device specifications. In this paper, we focus on the design of resonator based circuits in the silicon nitride platform and the balancing of desired properties like quality factor ${\text{Q}}$ , free spectral range, finesse, transmission shape with waveguide design, and footprint. The design, fabrication, and characterization of two resonator-based circuit examples operating at 1550 nm are described in detail. The first design is a thin core, large mode-volume bus-coupled resonator, with a 2.72 GHz free spectral range and a measured intrinsic ${\text{Q}}$ of 60 million and loaded ${\text{Q}}$ on the order of 30 Million, representing the highest reported loaded ${\text{Q}}$ for a large mode volume resonator with a deposited upper cladding. The second circuit is a thicker core, smaller footprint, low loss flat passband third-order resonator filter with an ultrahigh extinction ratio of 80 dB tunable over 100% of the free spectral range and insertion loss under 1.3 dB.
TL;DR: In this paper, a review and discussion of the directly modulated semiconductor lasers and their applications to optical communications and microwave photonics is presented for the first time to the best of our knowledge.
Abstract: This paper presents a review and discussion of the directly modulated semiconductor lasers and their applications to optical communications and microwave photonics. A detailed and comprehensive demonstration of directly modulated semiconductor lasers from development history to specific techniques on measurement, analysis, and packaging is provided for the first time to the best of our knowledge. A few typical applications based on directly modulated lasers are also illustrated, such as optical fiber communications, free-space optical communications and microwave photonics. Future directions of research are also highlighted.
TL;DR: In this paper, a high-quality saturable absorber based on multilayered black phosphorus (BP) nanosheet film deposited on a CaF2 substrate was successfully fabricated and employed.
Abstract: Efficient continuous wave (CW) and passively Q-switched Ho3+,Pr3+:LiLuF 4 (Ho,Pr:LLF) laser operating at 2.95 μ m were realized using a 1150-nm Raman fiber laser as the pump source. A CW output power as high as 1.15 W, which we believe to be the highest one ever achieved from Ho 3+-doped bulk laser emission around 3 μ m, corresponds to an optical-to-optical conversion efficiency of 14.5% and a slope efficiency of 15.5%, respectively. A high-quality saturable absorber (SA) based on multilayered black phosphorus (BP) nanosheet film deposited on a CaF2 substrate was successfully fabricated and employed. Under the absorbed pump power of 7.36 W, the shortest pulse width of 194.3 ns was obtained, which is the shortest among the two-dimensional materials as SA around 3 μ m. The results not only indicated that Ho,Pr:LLF crystal would be a promising mid-infrared (MIR) gain medium for obtaining high power output, but verified that the multilayered BP is a promising optical modulator for generating short pulses in MIR spectral range.
TL;DR: In this article, the state of the art and perspectives on emerging technologies based on integrated silicon photonic microresonators in the technology domains of intradatacenter optical interconnects, integrated nonlinear and quantum photonics, and lab-on-a-chip optical biosensing are reviewed.
Abstract: Silicon photonics is becoming the leading technology for photonic integrated circuits (PICs) due to large-scale integration, low cost, and high-volume productions enabled by complementary metal-oxide-semiconductor (CMOS) fabrication process. Thanks to various material and optical characteristics of crystalline silicon, the silicon-on-insulator platform has become the dominant material platform for silicon photonics. Meanwhile, monolithic or heterogeneous integration of other materials on silicon photonic chips, including the silicon nitride (SiN)-on-insulator platform and the III–V-on-silicon platform, are under rapid developments to enhance the functionalities of silicon photonics. Among the myriad of silicon photonic structures for passive and active components, integrated microresonators are promising for a broad range of applications due to their strong resonance field enhancement, narrowband wavelength selectivity, and compact footprints. In this paper, we review the state of the art and our perspectives on emerging technologies based on integrated silicon photonic microresonators in the technology domains of intradatacenter optical interconnects, integrated nonlinear and quantum photonics, and lab-on-a-chip optical biosensing. We specifically review recent progress and our original work in SOI microring-based crossbar switch fabrics; III–V-on-silicon microresonator lasers; silicon-based microresonator nonlinear and quantum sources; and SiN microresonator-based optical biosensors.
TL;DR: In this paper, an approach using an indium phosphide based membrane is reviewed, and a range of realized and proposed membrane devices are presented, and the prospects of this technique will be discussed.
Abstract: Integrating electronic and photonic functions has become a major issue in the last decade. This integration requires small photonic circuits that are compatible with CMOS processing. Here an approach using an indium phosphide based membrane is reviewed. The high index contrast, leading to micron-sized devices, the full set of photonic functions, including lasers, and the possibility to add these membranes to realized CMOS-circuits, make this an attractive option for hybrid integration. In this paper, the concepts and the required technologies are introduced. A range of realized and proposed membrane devices will be presented, and the prospects of this technique will be discussed.
IBM1
TL;DR: In this paper, a fiber-to-silicon-chip coupling loss of less than 3.5 dB across the O-band was shown for broadband and polarization-tolerant optical packaging of silicon photonics devices.
Abstract: Optically transparent polymer waveguides are employed for interfacing silicon photonics devices to fibers. The highly confined optical mode in the nanophotonic silicon waveguide is transferred to a fiber-matched polymer waveguide through adiabatic optical coupling by tapering the silicon waveguide. The polymer waveguides are either processed onto the silicon photonics wafer or bonded to individual chips. Fibers are interfaced to the polymer waveguides through butt-coupling. We show polarization and wavelength-tolerant fiber-to-chip coupling loss of less than 3.5 dB across the O-band. The polymer waveguide-to-silicon-chip alignment tolerance is 2 μ m for a loss increase of only 1 dB. Reflection losses are well below −45 dB and the scalability to large numbers of channels is demonstrated. These results open a path to broadband and polarization-tolerant optical packaging of silicon photonics devices for ultrahigh bandwidth applications employing wavelength division multiplexing across multiple channels as envisioned for future data-center interconnects.
TL;DR: In this article, a preliminary on-chip integration of GaN-based laser, modulator, and photodetector grown on Si is reported, where the modulator is integrated into the laser and shares the same InGaN quantum well active region with the laser.
Abstract: A preliminary on-chip integration of GaN-based laser, modulator, and photodetector grown on Si is reported. The modulator is integrated into the laser and shares the same InGaN quantum well active region with the laser and the photodetector. By varying the applied voltage to the modulator, the absorption of the modulator can be adjusted due to the changed band bending of the InGaN quantum well active region, and hence the threshold current and the light output power of the laser can be tuned. The photodetector can effectively detect the output power of the laser tuned by the applied voltage to the modulator, which opens up a new way for GaN-based on-chip photonic integration on Si.