Abstract

Optical injection in semiconductor lasers has been studied extensively and many effects of optical injection on the behaviour of the semiconductor lasers have been reported. Much of this work is, however, restricted to intramodal injection, where the frequency ω_inj of the master laser (ML) is close to the slave laser (SL) free-running frequency ω_o. The ML frequency must be tuned within a relatively narrow bandwidth of the SL frequency. This stringent requirement on matching the frequency of the ML and SL can be relaxed by using intermodal injection locking, in which the optical injection in the vicinity of a nonlasing longitudinal side mode. Goldberg et al.[1] measured the intermodal injection locking bandwidth. Schanne et al [2] demonstrated the existence of nearly degenerate four-wave mixing (NDFWM), where the SL side mode ω₁ became the dominant lasing mode and, the coexisting side mode ω₁ and the injected beam ω_inj gave rise to a strong NDFWM processes and generated a conjugate beam ω₂. In this paper, the dynamical behaviour of a semiconductor laser under intermodal injection locking is studied experimentally in some detail. We provide what we believe to be the first report of several new regimes in intermodal injection of semiconductor lasers. The most significant newly-identified regime is a side mode resonance regime. Here the side mode becomes the dominant lasing mode and, instead of injection locking occurring, the SL wavelength is switched from the free-running wavelength to the side mode wavelength. We also observed that NDFWM arises in the positive detuning regime (ΔΩ = ω_inj – ω₁′ > 0, where ω₁′ is side mode frequency under optical injection), as well as in the negative detuning regime (ΔΩ < 0). This is similar to the case of intramodal injection studied both experimentally and theoretically by Mogensen et al. [3], As the injection level is further increased NDFWM is observed for positive detunings only.

© 2000 IEEE