Jock Bovington

Demonstration of 12.2% wall plug efficiency in uncooled single mode external-cavity tunable Si/III-V hybrid laser

A Si/III-V hybrid laser has been a highly sought after device for energy-efficient and cost-effective high-speed silicon photonics communication. We present a high wall-plug efficiency external-cavity hybrid laser created by integrating an independently optimized SOI ring reflector and a III-V gain chip. In our demonstration, the uncooled integrated laser achieved a waveguide-coupled wall-plug efficiency of 12.2% at room temperature with an optical output power of ~10 mW. The laser operated single-mode near 1550 nm with a linewidth of 0.22 pm. This is a tunable light source with 8 nm wavelength tuning range. A proof-of-concept laser wavelength stabilization technique has also been demonstrated. Using a simple feedback loop, we achieved mode-hop-free operation in a packaged external-cavity hybrid laser as bias current was varied by 60mA.

Error-free operation of a polarization-insensitive 4λ x 25 Gbps silicon photonic WDM receiver with closed-loop thermal stabilization of Si microrings

We report the first closed-loop operation of a 100 Gbps polarization-insensitive, 4-channel wavelength-tracking WDM receiver in silicon photonics platform. Error-free operation is achieved with input polarization scrambling over input wavelength change of 4.5 nm using efficient thermal tuning of Si microring demux, corresponding to greater than 60°C fluctuation in temperature.

III-V/Si Hybrid Laser Arrays Using Back End of the Line (BEOL) Integration

Creating arrays of efficient optical sources to enable dense integration of silicon photonic transceivers with silicon very large-scale integration circuits remains a challenge. We review manufacturing strategies and challenges for back-end-of-line integration of tunable, external-cavity lasers using edge-coupled and surface-normal-coupled integration approaches showing that such laser arrays can be manufactured with a fab-less model. We demonstrate, for the first time, hybrid laser arrays using both integration approaches highlighting performance and design differences. We also discuss challenges and opportunities for each method and present experimental techniques to reduce alignment tolerance and improve laser stability and mode control.

Efficient, tunable flip-chip-integrated III-V/Si hybrid external-cavity laser array

We demonstrate a surface-normal coupled tunable hybrid silicon laser array for the first time using passively-aligned, high-accuracy flip chip bonding. A 2x6 III-V reflective semiconductor optical amplifier (RSOA) array with integrated total internal reflection mirrors is bonded to a CMOS SOI chip with grating couplers and silicon ring reflectors to form a tunable hybrid external-cavity laser array. Waveguide-coupled wall plug efficiency (wcWPE) of 2% and output power of 3 mW has been achieved for all 12 lasers. We further improved the performance by reducing the thickness of metal/dielectric stacks and achieved 10mW output power and 5% wcWPE with the same integration techniques. This non-invasive, one-step back end of the line (BEOL) integration approach provides a promising solution to high density laser sources for future large-scale photonic integrated circuits.

A Process-Tolerant Ring Modulator Based on Multi-Mode Waveguides

We present a novel 3.3-μm radius ring modulator design with dramatically reduced resonance wavelength variations. By implementing a multi-mode waveguide design for the ring waveguides, phase errors from processing non-idealities in waveguide width and etching depth are significantly reduced. Measured resonance wavelengths from four 200-mm wafers fabricated in a commercial 130-nm CMOS foundry showed a total of ~5-nm peak-to-peak variation, which is only about 1/6 of the free spectral range of the ring design. With this tighter control over the absolute resonance positions, the tuning range and tuning power requirements of the ring modulators can be significantly reduced, which in turn enhances their functionality for applications in high density, energy-efficient high-performance computing systems.

A CMOS-compatible low back reflection grating coupler for on-chip laser sources integration

We demonstrate a low back reflection grating coupler on a SOI CMOS-compatible process designed for vertical integration of on-chip laser sources. It showed <;-26dB back reflection and 1.9dB coupling loss to a 4μm-diameter laser mode.

12.2% waveguide-coupled wall plug efficiency in single mode external-cavity tunable Si/III–V hybrid laser

We demonstrate an external-cavity Si/III-V hybrid laser with a waveguide-coupled wall-plug efficiency of 12.2% at room temperature. The laser operates single-mode in C-band with a linewidth of 0.22 pm and is capable of wavelength tuning.

III–V/Si Vernier-Ring Comb Lasers (VRCLs)

We present a novel reconfigurable comb laser design that enables channel sparing, and demonstrate its functionality in a III-V/Si external cavity configuration. The laser is comprised of a single shared tunable Si ring mirror Vernier-paired with an array of tunable channel ring filters each coupled to their respective reflective semiconductor optical amplifier. This comb laser is not only tunable, capable of shifting all comb lines together, but it is flexible, able to change the spacing of channels in the comb within a fixed grid defined by the ring mirror. This flexibility results in features not previously demonstrated in a comb, such as mixed channel spacing and channel sparing capability. This is a practical candidate for flexible, scalable wavelength division multiplexed links targeting the next generation of data centers for the cloud.

Si/III-V hybrid external-cavity laser stabilization using real-time micro-ring monitoring and feedback control

Stable mode-hop-free operation for a Si/III-V hybrid external-cavity laser was demonstrated during 320mA bias current sweep using a real-time ring monitoring, a fast feedback control loop, and a simple bang-bang control algorithm, by both tunable micro-ring filter and cavity phase section.

Alignment and integration of a hybrid, external-cavity InP-SOI laser

A 1550nm external-cavity hybrid III-V/SOI laser with a room-temperature threshold current of 18mA and output powers up to 4mW was demonstrated with a novel assembly technique. An edge-coupled 1×6 laser array was passively aligned with sub-micron positional tolerance.