Widely-tunable, narrow-linewidth III-V/silicon hybrid external-cavity laser for coherent communication

Abstract

We demonstrate a III-V/silicon hybrid external cavity laser with a tuning range larger than 60 nm at the C-band on a silicon-on-insulator platform. A III-V semiconductor gain chip is hybridized into the silicon chip by edge-coupling the silicon chip through a SiN spot size converter. The demonstrated packaging method requires only passive alignment and is thus suitable for high-volume production. The laser has a largest output power of 11 mW with a maximum wall-plug efficiency of 4.2%, tunability of 60 nm (more than covering the C-band), and a side-mode suppression ratio of 55 dB (>46 dB across the C-band). The lowest measured linewidth is 37 kHz (<80 kHz across the C-band), which is the narrowest linewidth using a silicon-based external cavity. In addition, we successfully demonstrate all silicon-photonics-based transmission of 34 Gbaud (272 Gb/s) dual-polarization 16-QAM using our integrated laser and silicon photonic coherent transceiver. The results show no additional penalty compared to commercially available narrow linewidth tunable lasers. To the best of our knowledge, this is the first experimental demonstration of a complete silicon photonic based coherent link. This is also the first experimental demonstration of >250 Gb/s coherent optical transmission using a silicon micro-ring-based tunable laser.

High-power sub-kHz linewidth lasers fully integrated on silicon

“…This hybrid approach is attractive because it allows for the gain chip and external cavity to be separately optimized. This starts with the material selection, and external cavities based on planar lightwave circuits (PLC) [15], low-loss silicon nitride [16,17], and silicon [18,19] have been demonstrated. The drawback regarding these assembled hybrid semiconductor lasers is their limited scalability, because each laser must be individually assembled.…”

Compact silicon photonic hybrid ring external cavity (SHREC)/InGaSb-AlGaAsSb wavelength-tunable laser diode operating from 1881-1947 nm

“…Thus far, impressive work on SHREC wavelength-tunable laser diodes have been achieved near the C-band [41][42][43][44][45][46]; examples include wide tuning range [42], increased power and operating temperature [44], large side-mode suppression ratio (SMSR) [45] and shifting of tuning range from C-to L-band [46]. However, there seems to be lesser development around the 2 µm waveband [47,48].…”

Electro-Optic Tuning of a Monolithically Integrated Widely Tuneable InP Laser With Free-Running and Stabilized Operation

“…Lasers with even lower intrinsic linewidths have been demonstrated using heterogeneous and hybrid integration of InP with silicon (bonded) and silicon nitrite (butt-coupled). In [21][22][23][24], lasers with intrinsic linewidth from tens of kHz down to sub-kHz have been reported. The reduction of linewidth in these examples is achieved through high quality factor resonators realized with very low loss waveguides.…”