Narrow Spectral Linewidth Silicon Photonic Wavelength Tunable Laser Diode for Digital Coherent Communication System

Si Photonics for Practical LiDAR Solutions

“…A narrow linewidth laser and wide band tunable laser may potentially be addressed by using a Si photonics high Q and tunable cavity chip. There has been ongoing research on this topic in the past decade [87][88][89] and some companies are currently bringing it to telecom applications. The schematic design and the experimental results of an early work of such Si photonics external cavity tunable laser are shown in Figure 9.…”

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

“…Modal transmittance difference (MTD), the extent of transmittance difference between the main and adjacent peak of the Vernier transmittance spectra, is an important index of single-mode stability, the higher the value, the greater the selectivity of the wavelength tunable Vernier cavity [41], facilitating lasing by mode competition, a feature that will not be possible in a single MRR filter configuration. While the MTD and maximum tunable range of the wavelength-tunable Vernier filter can be increased by decreasing the radius of the MRR [41], one will be limited by the diffraction limit. The MRR-bus waveguide coupling gap is another design parameter that affects the MTD; by increasing the coupling gap, the MTD will increase, but however, the drop efficiency of the tunable laser will decrease leading to a rise in threshold current.…”

“…5(a). The lasing output is collected from the output facet of the SOA via a lensed-fiber [41] (prevent possible reflection into the laser cavity) and connected to the optical spectrum analyzer (OSA, Yokogawa AQ6375) for measuring the lasing spectra or coupled directly into the aperture of the photodetector for laser power characterization taking into account laser divergence angles (on-chip output power). The III -V waveguide-lensed fiber coupling loss is 10 dB; the coupling loss is determined by comparing the difference in the two cases when laser output is coupled directly into the aperture of the photodetector and coupled via a lensed fiber connected to the photodetector.…”

“…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].…”

Performance improvement of optical negative feedback laser by reducing feedback loop length

“…Compact and narrow spectral linewidth semiconductor lasers are required for digital coherent optical transmission systems [1]. Many studies have been conducted to develop such lasers [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23], and almost all of them have focused on increasing the laser cavity quality factor (Qfactor) by lengthening the laser cavities via the addition of external cavities. As a result, the cavity sizes of these lasers become long.…”