Tunable dye laser with thin birefringent filter for improved tuning

An improved dye laser having a birefringent tuning filter comprised of one or more birefringent plates wherein each plate is oriented at Brewster's angle to the resonant light beam and is an integer multiple of the thickness of the thickness of the first plate characterized by the fact that the thickness of the first plate is chosen using a new tuning relationship so that a single order tuning curve covers a tuning range of interest. This single tuning curve is almost linear throughout the tuning range and has a tuning angle at the center of the range of approximately five degrees. Also, the tuning curve has a slope throughout the tuning range which provides sensitivity of selected wavelength to tuning angle which is neither too great nor too small. A further refinement in the structure is a non-birefringent polarizing plate at Brewster's angle which increases the losses imposed upon light passing therethrough which is polarized at other than Brewster's angle. These losses extinguish the laser when turning anomalies occur near the ends of the tuning range where the wavelength and polarization suddenly jump to different values.