Suppression of the free-lasing background on injection of external monochromatic radiation into the resonator of a high-energy flashlamp-pumped dye laser

A method is proposed for raising the efficiency of frequency locking when an external narrow-band signal is injected into a laser. It is based on providing frequency and spatial filtering of the radiation in a nonlinear absorber (a spectral contrast enhancer) positioned inside the resonator of a dye laser. It is shown that this method can increase the efficiency of concentrating the laser output energy into a narrow 5-pm wide line to a value of 90%.