A topologically optimized photonic cavity with an integrated lateral p-i-n structure-based silicon (Si) photodetector has been fabricated. The silicon-based cavity allows for the integration of Photodetectors (PDs) in CMOS technology, bypassing challenges associated with adding other materials. The goal of the topological optimization is to maximize the rate of two-photon absorption in silicon, while maintaining small dimensions. The fabricated device was characterized, obtaining a resonant wavelength at 1543 nm with a Q-factor of 6315 and a responsivity of 0.21 mA/W while maintaining a low dark current.
In this communication, we report on the design, fabrication and testing of silicon-nitride-in-insulator (SiNOI) nonlinear photonic circuits for comb generation in silicon photonics and optoelectronics. The low two-photon absorption when compared with crystalline silicon makes the SiNOI an attractive platform for frequency comb generation. Kerr combs have been recently used in terabit per second coherent communications demos. Such devices can overcome the intrinsic limitations of nowadays silicon photonics notably concerning the heterogenous integration of III-V on SOI lasers for both datacom and telecom applications. By using monolithically-integrated SiN-based Kerr frequency combs, the generation of tens or even hundreds of new optical frequencies can be obtained in dispersion tailored waveguides and resonators, thus providing an all-optical alternative to the heterointegration of hundreds of standalone III-V on Si lasers. However, in all the previous SiNOI-based frequency combs, the silicon nitride film is annealed under long and high temperature which made the cointegration with silicon based optoelectronics elusive. The annealing steps used in common SiN fabrication processes are not only incompatible with the front-end of line complementary metal-oxidesemiconductor processes, but also costly and long and thus an important cost factor in non-CMOS compatible processes. In our work, we present the fabrication and testing of an annealing-free and crack-free SiNOI. Notably, a 800-nmspanning (1300-2100 nm) frequency comb is generated using 740-nm-thick silicon nitride featuring full compatibility with silicon photonics integrated circuits. This work constitutes a new, decisive step toward time-stable power-efficient Kerr-based broadband sources featuring full process compatibility with Si photonic integrated circuits (Si-PICs) on CMOS-lines.
The combination of nonlinear and integrated photonics enables applications in telecommunication, metrology, spectroscopy, and quantum information science. Pioneer works in silicon-on-insulator (SOI) has shown huge potentials of integrated nonlinear photonics. However, silicon suffers two-photon absorption (TPA) in the telecom wavelengths around 1550 nm, which hampers its practical applications. To get a superior nonlinear performance, an ideal integrated waveguide platform should combine a high material nonlinearity, low material absorption (linear and nonlinear), a strong light confinement, and a mature fabrication technology. Aluminum gallium arsenide (AlGaAs) was identified as a promising candidate for nonlinear applications since 1994. It offers a large transparency window, a high refractive index (n≈3.3), a nonlinear index (n2) on the order of 10-17 m2W−1, and the ability to engineer the material bandgap to mitigate TPA. In spite of the high intrinsic nonlinearity, conventional deep-etched AlGaAs waveguides exhibit low effective nonlinearity due to the vertical low-index contrast. To take full advantage of the high intrinsic linear and nonlinear index of AlGaAs material, we reconstructed the conventional AlGaAs waveguide into a high index contrast layout that has been realized in the AlGaAs-on-insulator (AlGaAsOI) platform. We have demonstrated low loss waveguides with an ultra-high nonlinear coefficient and high Q microresonators in such a platform. Owing to the high confinement waveguide layout and state-of-the-art nanolithography techniques, the dispersion properties of the AlGaAsOI waveguide can be tailored efficiently and accurately by altering the waveguide shape or dimension, which enables various applications in signal processing and generation, which will be reviewed in this paper.
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