Cavity enhancement of resonant frequencies in semiconductor lasers subject to optical injection

Evaluation of Performance Enhancement of Optical Multi-Level Modulation Based on Direct Modulation of Optically Injection-Locked Semiconductor Lasers

The performance of optical M-level (multi-level) amplitude shift keying (ASK) modulation is improved by directly using modulated optically injection-locked (OIL) semiconductor lasers. The direct modulation performance of free-running and OIL semiconductor lasers is evaluated and compared theoretically based on coupled-rate equation. We have found that OIL semiconductor lasers can significantly improve the modulation performance in terms of the signal eye opening and Q-factor. Additionally, we found that the Q-factor increases even more in the negative frequency detuning range due to its dependence on the locking parameters.

Simple frequency-tunable optoelectronic oscillator using integrated multi-section distributed feedback semiconductor laser

A novel approach to realizing an optoelectronic oscillator (OEO) based on an integrated multi-section (IMS) distributed feedback (DFB) laser is proposed and experimentally demonstrated. Our scheme adopts the method of direct modulation and a built-in microwave photonic filter (MPF), making the structure simpler and more flexible than an external modulator and electrical bandpass filter (EBPF). The IMS-DFB laser, which can overcome the drawbacks of using discrete lasers, is the key device in the scheme. Further, the two DFB sections, which are fabricated by Reconstruction Equivalent Chirp (REC) technique, are injected mutually. The SSB phase noise of the generated signal at the frequency of 20.3 GHz is -115.3 dBc/Hz@10kHz and -92.9 dBc/Hz@1kHz. The sidemode suppression ratio (SMSR) is 60.94 dB, which is a 40 dB improvement over a single loop. Furthermore, we demonstrate that the phase noise improves about 8 dB at the frequency offset of 1 kHz, when employing 13 km and 5.4 km fibers as the dual loop. The simple and compact structure, which consists of an IMS-DFB laser with high wavelength controlling accuracy and low process requirement, is a promising development for OEO integration.