Frequency locking by injection in dye lasers: Analysis of the CW and delta pulse regimes

Experimental studies of frequency locking by injection are performed using a nanosecond and a microsecond pulse duration dye laser. Either of these two lasers can be used as the master oscillator, and the experimental conditions then lead to two different injection regimes defined as the CW and the delta pulse regime. In both regimes, the locking efficiency, which is measured as a function of the injected flux of the injected wavelength and of the time delay between the two pulses, reaches a value close to unity when the injected flux present in the forced oscillator cavity is at least equal to 10 W · cm^-2. An analytical relation is derived to explain the experimental results. The use of the injection locking technique to probe the progressive narrowing of tuned dye lasers and to monitor the occurrence of the laser threshold is emphasized.