Hybrid Silicon-Fiber Tunable Multiwavelength Laser With Switchable Frequency Spacing

Agile optical systems and elastic optical networks demand for flexible, high-performance laser sources. We demonstrate a hybrid silicon-fiber laser that can be largely tuned in wavelength, switched in frequency spacing and easily switched between multi- and single-wavelength operations. Single-mode laser with a fiber-coupled output power of 6 to 8 dBm was measured across the spectral range of 1545 to 1560 nm. No significant sign of power limitation from nonlinear absorption or free carrier generation in silicon was found. It is thus expected that a higher output can be obtained by improving the gain saturation performances as well as the fiber-to-chip coupling efficiency. For multiwavelength operation, we have achieved a frequency spacing switchable between 56 GHz, 75 GHz, and 225 GHz. For both the multi- and single-wavelength operations, a linewidth of less than 20 kHz was measured. All the tuning mechanisms have been realized on the silicon chip, providing a scalable solution for tunable fiber lasers with minimized cost and integration complexity.