High positional freedom SOI subwavelength grating coupler (SWG) for 300 mm foundry fabrication.

We present an apodized, single etch-step, subwavelength grating (SWG) high positional freedom (HPF) grating coupler based on the 220 nm silicon-on-insulator (SOI) with 2µm BOX substrate. The grating coupler was designed for 1550 nm light with transverse electric (TE) polarization. It has a measured maximum coupling efficiency of -7.49 dB (17.8%) and a -1 dB/-3 dB bandwidth of ~14 nm/29.5 nm respectively. It was fabricated in a 300mm state of the art CMOS foundry. This work presents an SOI-based grating coupler with the highest-to the best of our knowledge- -1 dB single mode fiber lateral alignment of 21.4 µm × 10.1 µm.

Whispering gallery germanium-on-silicon photodetector.

We design and demonstrate, to the best of our knowledge, the first whispering gallery germanium-on-silicon photodetector with evanescent coupling from a silicon bus waveguide in a CMOS-compatible process. The small footprint (63.6 µm2), high responsivity (∼1.04 A/W at 1530 nm), low bias voltage (-1 V), low dark current (2.03 nA), and large optoelectric bandwidth (32.9 GHz) of the detector enable simultaneous wavelength filtering and power detection, ideal for handling large network data traffic. In addition, with the resonant nature of the detector, we also optimize the design to enable long-wavelength detection, achieving a separate device with a detection range of up to 1630 nm with a >0.45 A/W responsivity, making it an important building block for optical communication networks.

Monolithically-integrated distributed feedback laser compatible with CMOS processing.

An optically-pumped, integrated distributed feedback laser is demonstrated using a CMOS compatible process, where a record-low-temperature deposited gain medium enables integration with active devices such as modulators and detectors. A pump threshold of 24.9 mW and a slope efficiency of 1.3 % is demonstrated at the lasing wavelength of 1552.98 nm. The rare-earth-doped aluminum oxide, used as the gain medium in this laser, is deposited by a substrate-bias-assisted reactive sputtering process. This process yields optical quality films with 0.1 dB/cm background loss at the deposition temperature of 250 °C, and therefore is fully compatible as a back-end-of-line CMOS process. The aforementioned laser's performance is comparable to previous lasers having gain media fabricated at much higher temperatures (> 550 °C). This work marks a crucial step towards monolithic integration of amplifiers and lasers in silicon microphotonic systems.

Mode-evolution-based coupler for high saturation power Ge-on-Si photodetectors.

We propose a mode-evolution-based coupler for high saturation power germanium-on-silicon photodetectors. This coupler uniformly illuminates the intrinsic germanium region of the detector, decreasing saturation effects, such as carrier screening, observed at high input powers. We demonstrate 70% more photocurrent generation (9.1-15.5 mA) and more than 40 times higher opto-electrical bandwidth (0.7-31 GHz) than conventional butt-coupled detectors under high-power illumination. The high-power and high-speed performance of the device, combined with the compactness of the coupling method, will enable new applications for integrated silicon photonics systems.

C-band swept wavelength erbium-doped fiber laser with a high-Q tunable interior-ridge silicon microring cavity.

We demonstrate swept-wavelength operation of an erbium-doped fiber laser using a tunable silicon microring cavity. The microring cavity is designed to have 35 nm free spectral range, a high Q of 1.5 × 105, and low insertion loss of <0.05 dB. The resonance wavelength of the cavity is tuned efficiently (8.1µW/GHz) and rapidly (τr,f~2.2µs) using an embedded Si heater. The laser achieves single-mode continuous-wave emission over the C-band (1530 nm-to-1560 nm). A mean swept-wavelength rate of 22,600 nm/s or 3106 THz/s is demonstrated within 1532 nm-to-1542 nm wavelength range. Its linewidth is measured to be 16 kHz using loss-compensated circulating delayed self-heterodyne detection.

CMOS-compatible 75 mW erbium-doped distributed feedback laser.

On-chip, high-power, erbium-doped distributed feedback lasers are demonstrated in a CMOS-compatible fabrication flow. The laser cavities consist of silicon nitride waveguide and grating features, defined by wafer-scale immersion lithography and an erbium-doped aluminum oxide layer deposited as the final step in the fabrication process. The large mode size lasers demonstrate single-mode continuous wave operation with a maximum output power of 75 mW without any thermal damage. The laser output power does not saturate at high pump intensities and is, therefore, capable of delivering even higher on-chip signals if a stronger pump is utilized. The amplitude noise of the laser is investigated and the laser is shown to be stable and free from self-pulsing when the pump power is sufficiently above threshold.

Four-port integrated polarizing beam splitter.

In this Letter, we report on the first integrated four-port polarizing beam splitter. The device operates on the principle of mode evolution and was implemented in a silicon-on-insulator silicon photonics platform and fabricated on a 300 mm CMOS line using 193 nm optical immersion lithography. The adiabatic transition forming of the structure enabled over a 150 nm bandwidth from λ~1350 to λ~1500 nm, achieving a cross-talk level below -10 dB over the entire band.