Compact narrow-linewidth optical negative feedback laser with Si optical filter

Abstract

A compact narrow-linewidth semiconductor laser is demonstrated by hybridly integrating an optical filter constructed from Si waveguides with a single-mode semiconductor laser, whose spectral linewidth is narrowed through optical negative feedback. We design the optimum structure of a reflective ring filter for an optical negative feedback laser, and a narrow spectral linewidth of 160 kHz is realized by the hybridly integrated laser source whose effective device length is less than 1.5 mm.

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

“…The dimensions of the fabricated Si ring filter are the same as the one explained in the previous section. The characteristics of the filter are almost the same as the previous one [30] as predicted from the numerical analysis mentioned above. Fig.…”

“…The waveguide at the right of the ring waveguide is attached in order to monitor the condition of the butt joint between the single-mode semiconductor laser and the Si ring filter. The finesse of the Si ring filter is estimated to be 13.9, which is the same as the filter in the previous report [30]. The maximum conversion efficiency from frequency change to electrical field reflection coefficient of the filter is estimated to be 1:02 Â 10 À10 Hz −1 .…”

“…In the optical negative feedback laser, the optical filter does not constitute the laser cavity, so the laser is free from the issue of frequency noise increase. By using a ring optical filter with a Si optical waveguide, a compact optical negative feedback laser with the spectral linewidth of 160 kHz has been achieved [30]. The value of the reduced spectral linewidth, however, is limited by the small phase margin of the negative feedback system.…”

“…The total round trip waveguide length (feedback loop length) is reduced to L FBL $ 828 µm, which corresponds to the feedback loop delay time of FBL $ 9:9 ps. The value can be reduced to almost half the value of the previous Si ring filter (L FBL $ 1226 µm and FBL $ 18:8 ps) [30]. The radius of the ring waveguide is set to 220 µm and the free spectral range of the filter is 50 GHz.…”

Nonlinear Optical SiC:C Microring for an ASK-to-PSK Gate and NOT + XOR Logic beyond 10 Gbit/s

“…Owing to the mature technology of silicon-based semiconductor processing, the silicon photonic devices with the high modulation speed, low consumption, or broad linewidth have been developed over decades for next-generation optical interconnect communication. − For future integrated circuits, the optical waveguide that handles high data rates with low power consumption is the alternative to replace the electric cable with a finite bandwidth-length product. For long-distance communication, the silicon photonic platforms also play important roles in breakthrough advantages beyond 50 Gbit/s per channel. − Versatile fundamental integrated on-chip devices including optical switches, − modulators, − filters, − and detectors − have been demonstrated for future development. Most works used the electrical-to-optical mechanism to achieve high-speed modulation.…”