Optical frequency comb and picosecond pulse generation based on a directly modulated microcavity laser

Optical frequency comb generation based on spectral broadening of a self-injection locked directly modulated microcavity laser

A coherent optical frequency comb (OFC) with suppressed linewidth is demonstrated based on the spectral broadening of a directly modulated semiconductor microcavity laser with self-injection locking. Due to the high electro-optical response, the directly modulated microcavity laser provides a 10-GHz-spaced seeding OFC with 9 comb teeth in a 10 dB flatness window. Besides, an optical feedback fiber loop with two sub-loops is introduced to reduce the linewidth of the microlaser and suppress the undesired longitudinal modes. Self-injection locking is realized at the feedback power of 72 µW, and the laser linewidth is narrowed from 10 MHz to 14.5 kHz. Moreover, spectral broadening and pulse compression are used to broaden the optical spectrum and compress the pulse width, which results in an OFC with 36 comb lines in a 10 dB power deviation and a 1.8 ps optical pulse. Owing to the high coherence of the directly modulated OFC, all comb lines feature narrow linewidths in the range of 14.5∼18.2 kHz.

Optical Bistability in a Tunable Gourd-Shaped Silicon Ring Resonator

In this study, a tunable gourd-shaped ring resonator is demonstrated to generate optical bistability. The system consists of two sub-rings for a gourd shape configuration with a U-shaped wave guiding pathway. The transfer matrix method and FDTD simulation are used to acquire the spectral characteristics of the system. For the fabricated device, the spectra profile and extinction ratio can be effectively tuned by the microheater above the U-shaped waveguide, which matches with the theoretical results. Due to the gourd structure of the resonator, the light waves in two rings can be cross-coupled with each other, and the optical bistability could come out effectively with the change in the input optical power around 6 mW. The presented optical bistability devices have great application potential in optical information processing such as optical storage, switch and logic operation.