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Ge1-xSnx photodetectors (PDs) have emerged as a new type of mid-infrared (MIR) CMOS-compatible PDs for a wide range of applications. Here we present a comprehensive theoretical study to evaluate the achievable performance of Ge1-xSnx p-i-n homojunction PDs with strain-free and defect-free Ge1-xSnx active layer for the purpose of demonstrating its potential in advancing the MIR detection technology. Starting from the Sn-composition-dependent band structures, the theoretical model calculates optical absorption, responsivity, dark current density, and detectivity. The results show that the optical responsivity can be enhanced with the Sn incorporation due to the improved optical absorption and the large mobilities and diffusion lengths of the photo-generated electrons and holes. The dark current density, however, increases with the increasing Sn composition. Our model suggests that not only the photodetection range of the Ge1-xSnx PDs can be extended to the MIR region but their detectivity at room temperature can be competitive with the existing MIR technology, and in some cases better than some commercial PDs operating at lower temperatures. This study establishes the ultimate performance that can be potentially achieved with the Ge1-xSnx MIR technology with the maturity of its material development in due time in addition to its much anticipated CMOS-compatible advantages.

Non-Hermitian photonics has attracted increasing attention especially for sensing applications. Two coupled optical systems, designed to work at the “exceptional point”, exhibit a strong spectral response to perturbations. Due to the enhanced sensitivity of exceptional points, they have been usually suggested as perfect candidates for high resolution sensing. The drawback of these configurations is their undesired sensitivity also to external fluctuations and noise that could eliminate the advantages of exceptional points. Recently, the concept of exceptional surface has been proposed to overcome this problem. In particular, coupling two counterpropagating modes in the same structure prevents differential noise in distinct cavities from affecting the exceptional-point condition. In this work we present a new configuration based on exceptional surfaces to design an optical accelerometer. The strong spectral response guaranteed by exceptional surfaces is used here to demonstrate the enhancement of the sensitivity of a Bragg grating-based optical accelerometer, reaching a value of 3 nm/g at 0.5 g.

Silicon-based electronic-photonic integrated circuits, which are compatible with state-of-the-art complementary metal-oxide-semiconductor processes, offer promising opportunities for on-chip mid-infrared photonic systems. However, the lack of efficient mid-infrared optical modulators on silicon hinders the utilization of such systems. Here, we demonstrate the Franz-Keldysh effect in GeSn alloys and achieve mid-infrared electro-absorption optical modulation using GeSn heterostructures on silicon. Our experimental and theoretical results verify that the direct bandgap energy of GeSn can be widely tuned by varying the Sn content, thereby realizing wavelength-tunable optical modulation in the mid-infrared range with a figure-of-merit greater than 1.5 and a broadband operating range greater than 140 nm. In contrast to conventional silicon-photonic modulators based on the plasma dispersion effect, our GeSn heterostructure demonstrates practical and effective Franz-Keldysh mid-infrared optical modulation on silicon, helping to unlock the potential of electronic-photonic integrated circuits in a wide range of applications. Silicon-based electronic-photonic integrated circuits are promising for various applications, but their mid-infrared optical modulation is elusive. Here, tunable mid-infrared electro-absorption modulation, with broadband operation range >140 nm, is achieved in GeSn alloys on Si by controlling the Sn content.

The past two decades have witnessed the stagnation of the clock speed of microprocessors followed by the recent faltering of Moore’s law as nanofabrication technology approaches its unavoidable physical limit. Vigorous efforts from various research areas have been made to develop power-efficient and ultrafast computing machines in this post-Moore’s law era. With its unique capacity to integrate complex electro-optic circuits on a single chip, integrated photonics has revolutionized the interconnects and has shown its striking potential in optical computing. Here, we propose an electronic-photonic computing architecture for a wavelength division multiplexing-based electronic-photonic arithmetic logic unit, which disentangles the exponential relationship between power and clock rate, leading to an enhancement in computation speed and power efficiency as compared to the state-of-the-art transistors-based circuits. We experimentally demonstrate its practicality by implementing a 4-bit arithmetic logic unit consisting of 8 high-speed microdisk modulators and operating at 20 GHz. This approach paves the way to future power-saving and high-speed electronic-photonic computing circuits., Integrated photonics allows integration of complex optical circuits on a single chip. Here, the authors propose a wavelength division multiplexing based electronic-photonic arithmetic logic unit for computing at high speeds and with improved power consumption to help with the physical limits of Moore’s law.

The recent rapid progress in integrated photonics has catalyzed the development of integrated optical computing in this post-Moore's law era. Electronic-photonic digital computing, as a new paradigm to achieve high-speed and power-efficient computation, has begun to attract attention. In this paper, we systematically investigate the optical sequential logic and pipelining in electronic-photonic computing, which together offer a solution to potential problems in latency and power budget as the size of electronic-photonic computing circuits scales up considerably to achieve much more complex functions. Pipelining and sequential logic open up the possibility of high-speed very-large-scale electronic-photonic digital computing.

Photonic qubits can represent an ideal choice in quantum information science since photons travel at the speed of light and interact weakly with the environment over long distances. In this context...

The GeSn detector offers high-performance Si-based infrared photodetectors with complementary metal-oxide-semiconductor (CMOS) technique compatibility. In this work, we report a comprehensive study...

We report an investigation on the photo-response from a GeSn-based photodetector using a tunable laser with a range of incident light power. An exponential increase in photocurrent and an exponential decay of responsivity with increase in incident optical power intensity were observed at higher optical power range. Time-resolved measurement provided evidence that indicated monomolecular and bimolecular recombination mechanisms for the photo-generated carriers for different incident optical power intensities. This investigation establishes the appropriate range of optical power intensity for GeSn-based photodetector operation.

We report normal-incidence planar GeSn resonant-cavity-enhanced photodetectors (RCE-PDs) with a lateral p - i - n homojunction configuration on a silicon-on-insulator (SOI) platform for short-wave infrared (SWIR) integrated photonics. The buried oxide of the SOI platform and the deposited S i O 2 layer serve as the bottom and top reflectors, respectively, creating a vertical cavity for enhancing the optical responsivity. The planar p - i - n diode structure is favorable for complementary-metal-oxide-semiconductor-compatible, large-scale integration. With the bandgap reduction enabled by the 4.2% Sn incorporation into the GeSn active layer, the photodetection range extends to 1960 nm. The promising results demonstrate that the developed planar GeSn RCE-PDs are potential candidates for SWIR integrated photonics.

The maturity of integrated photonics enables many applications including high-performance computing. Digital photonic computing always considers resonator-based modulators as the key active components due to their compactness as compared to broad-spectrum Mach-Zehnder interferometers (MZIs). In this paper, we investigate the dual-nanobeam (NB) based MZI 2 × 2 switches with much smaller footprint for realizing electro-optical logic circuits. New logic gates and scalable circuits assisted by multiplexing techniques are proposed. Results show that the NB MZI is another promising candidate for electronic-photonic digital computing.

This theoretical simulation paper presents designs and projected performance of ∼1550-nm silicon-on-insulator (SOI) and ∼2000-nm Ge-on-Si-on-nitride and Ge-on-nitride 2×2 optical crossbar switches based upon a three-waveguide coupler in which the central waveguide is a nanobeam actuated by the thermo-optical (TO) effect. A TO heater stripe is located atop the central nanobeam. To implement accurate and realistic designs, the 3D finite difference time domain approach was employed. The metrics of crossbar switching, insertion loss (IL) and crosstalk (CT) were evaluated for choices of 3-waveguide structure parameters and TO-induced index changes. The predicted ILs and CTs were excellent, enabling the designed devices to be considered as fundamental building blocks in wavelength-division-multiplexed cross-connect (WXC) applications. Proposed here are compact, nonblocking space-and-wavelength routing switches to be constructed in a monolithic, industry-standard SOI chip (and in Ge-on-SON and GON chips). Specifics are given for realizing 16 × 16 × Mλ WXCs as well as reconfigurable, multi-resonant, programmable hexagonal and diamond meshes.

This theoretical modeling and simulation paper presents designs and projected performance of non-volatile broadband on-chip 1 × 2 and 2 × 2 electro-optical switches operating in the telecommunication C-band and based on the silicon-on-insulator technological platform. These optical switches consist of an asymmetric two-waveguide directional coupler and a symmetric three-waveguide directional coupler, in which the optical phase change material Ge[subscript 2]Sb[subscript 2]Se[subscript 4]Te[subscript 1] (GSST) is the top cladding layer for one of the silicon strip waveguides. Reversible crossbar switching is attained by the amorphous (Am) to crystalline (Cr) and Cr-to-Am phase transitions in the GSST induced by heating the GSST in contact with an indium tin oxide (ITO) microstrip through Joule heating. We examined device performance in terms of mid-band insertion loss (IL), crosstalk (CT), and 0.3-dB IL bandwidth (BW). The 2 × 2 results were IL = -0.018 dB, CT < 31.3 dB, and BW = 58 nm for the coupling length Lc of 15.4 μm, and IL = 0.046 dB, CT < 38.1 dB, and BW = 70 nm for the coupling length Lc of 17.4 μm. Simulations of the 1 × 2 devices at 16.7-μm Lc revealed that IL = 0.083 dB and CT < 12.8 dB along with an expanded BW of 95 nm. Thermal simulations showed that a 5-V pulse train applied to 10[superscript 19]-cm[superscript -3] doped ITO would produce crystallization; however, the process of amorphization required a 24-V pulse of 2.9-μs duration to raise the GSST temperature above the melting temperature of 900 K., DARPA (Grant D18AP00070)

Lasing from direct bandgap group-IV GeSn alloys has opened a new venue for the development of Si-based monolithic laser. In this work, we demonstrate optically pumped GeSn lasers based on both ridge and planar waveguide structures. The near room temperature operation at 270 K was achieved with optically pumped edge-emitting devices. Moreover, due to the reduced side-wall surface recombination and improved thermal management, the 100 μm wide ridge waveguide laser features a lower lasing threshold compared to other devices. The advance reported in this work, enabled by the material growth via an industry standard chemical vapor deposition reactor and low-cost commercially available precursors, is a major step forward toward Si-based mid-infrared sources for photonics integration.

This theoretical modeling and simulation the design and projected performance of an on-chip detector of trace gases using photonic matched filters, with operation in the 3–5-μm mid-infrared range. The thermo-optically tuned multi-Sagnac loop Mach–Zehnder interferometer (MZI), based on the germanium-on-silicon nitride technological platform, has been adopted to detect the signature of gases with regularly spaced and narrow absorption lines. The MZI arms are comprised of an N -cascaded connection of Sagnac loop reflectors, each pair separated by a waveguide whose length is designed according to the line spacing of the gas under detection. Detection of one or two gas absorption bands using one filter band is achieved at the Drop port of an MZI filter having on each arm the apodized Hamming Bragg waveguide grating. We performed parametric analysis on the GON platform to find the design rules for the waveguide gas cell and the Hamming or multi-Sagnac filters targeted at CH4 or CO2 or N2O or SO2 or CO. The analysis predicted good sensor performance.

This theoretical modeling-and-simulation paper presents designs and projected performance of ∼1550-nm silicon-on-insulator beamsteering of a microwave phased array antenna by the use of true time delays. The tunable on-chip optical delay line is a cascade connection of waveguide Bragg grating resonators (WBGRs) separated by a piece of straight waveguide. The notch in the reflectivity spectrum is translated along the wavelength axis by means of a low-power TO heater stripe atop the grating, inducing a time delay that depends upon the line position of the WBGR affected by TO switching. The filter resonator is a new in-guide array of identical Bragg structures, each one comprising N closely coupled phase-shifted Bragg-grating resonators. The length of each grating cavity in an N group is chosen according to the Butterworth filter technique to provide one resonant spectral profile with 40 GHz optical bandwidth. Finally, we examined the performances of the beamformer system operating in the X and Ku bands, respectively. The investigation demonstrated that steering angles up to 48° are feasible by assuming a minimum steering angle of 8° and a minimum WBGR spacing of about 354 and 236 μ m for X and Ku bands, respectively.

We present Stimulated Brillouin Scattering (SBS) process in AlGaN integrated photonic waveguides. The wide bandgap of this III-Nitride material platform allows operating at visible wavelengths enabling large Stokes shifts. For this study, we employ a multiphysics approach that includes electric-photoelastic, magnetic-photoelastic, material interface displacement effects, and for optimal waveguide dimensions to find the Brillouin-active acoustic modes involved in the SBS process. The SBS power gain and the Stokes frequency shift are investigated for both backward and forward scattering processes, and it is shown that stokes shift larger than 50 GHz with high gain are achievable. Moreover, a parametric analysis is presented in order to demonstrate the possibility of realizing Brillouin lasers operating at blue wavelengths.

We propose and analyze three Si-based room-temperature strip-guided &ldquo, manufacturable&rdquo, integrated quantum photonic chem/bio sensor chips operating at wavelengths of 1550 nm, 1330 nm, and 640 nm, respectively. We propose design rules that will achieve super-sensitivity (above the classical limit) by means of mixing between states of coherent light and single-mode squeezed-light. The silicon-on-insulator (SOI), silicon-on-sapphire (SOS), and silicon nitride-on-SiO2-on Si (SiN) platforms have been investigated. Each chip is comprised of photonic building blocks: a race-track resonator, a pump filter, an integrated Mach-Zehnder interferometric chem/bio sensor, and a photonic circuit to perform parity measurements, where our homodyne measurement circuit avoids the use of single-photon-counting detectors and utilizes instead conventional photodetectors. A combination of super-sensitivity with super-resolution is predicted for all three platforms to be used for chem/bio sensing applications.