Improved intrinsic dynamic distortions in directly modulated semiconductor lasers by optical injection locking

Abstract

The effects of optical injection locking on the nonlinear distortions of directly modulated semiconductor distributed feedback (DFB) lasers are investigated experimentally. The second harmonic distortion (SHD) and third harmonic distortion (THD), as well as the third-order intermodulation distortion (IMD3), are measured as functions of modulation frequency for both the free-running and injection-locked lasers. Under strong injection locking with 08-dB injection ratio, the SHD and THD of the DFB laser have been suppressed by 15 dB from 2 to 4 GHz. Moreover, nearly 15-dB reduction in IMD3 has been observed from 1.4 to 3.0 GHz with the same injection conditions. We also found that the injection locking is not effective in reducing the low-frequency distortions.Index Terms-Detuning frequency, harmonic distortion, injection-locked semiconductor lasers, injection ratio, intermodulation distortion, resonant frequency, stable locking range.

Analysis of Spectral Characteristics of Semiconductor Lasers under Strong Optical Injection Locking for Tens of Giga Hz Signal Generation

“…2, SL output power is fixed at 2mW. If the gain suppression and the spontaneous emission terms are ignored, the range of Δƒ that allows locking can be determined as follows [5].…”