Semiconductor lasers with weak optical injection: a laser as a low-signal detector

Summary form only given. The main idea of optical injection is to give a reference to the injected laser from another laser. The injected laser can become slaved onto the master and frequency-locking occurs following the injected intensity and the frequency difference between both lasers. Phase locking is a different phenomenon which manifests itself in the locking of the linewidth of the slaved laser onto that of the master. The topics of this communication is to describe the power spectral density of the injected laser when the injected power is decreased to very low level (/spl sim/picowatt) with a central frequency identical for both lasers but each of them having very different linewidths. The study follows from an interpretation of the laser as a filter and amplifier as recently given.