Shift of the emission frequency of a cw dye laser due to changes in pump intensity

Theoretical estimates are given of the shift of the emission frequency due to a change in the pumping rate resulting from a change in the optical thickness of the active medium because of the temperature effects ($\lesssim$50 MHz/W) and because of the optical pressure (55 MHz/W). Experimental observations indicate a shift of $\sim$100 MHz/W when the pump power is increased from the threshold value to 12 W. It is shown that the pump laser amplitude has to be stabilized if a narrow emission line from a dye laser is desired.