Dye laser tuner

A laser including a lasing medium which lases over a relatively wide band of wavelengths,

• means effecting strong linear polarisation in one plane of the intracavity light beam,
• and means of tuning the output wavelength of the laser, said tuning means comprising a wedged plate made of birefringent material located to intercept the beam of intracavity light, said plate having its incident surface oriented with respect to the incident light beam such that within the plate at the point of incidence the projection onto the plane normal to the light beam path of the normal from the incident plate surface is at an angle .phi., substantially equal to an odd multiple of 45.degree., to the projection of the optic axis of the plate onto said plane and, the nominal plate thickness and the angle .gamma. between the light beam path within the plate and the optic axis of the plate are such that the free spectral range of the plate is greater than the bandwidth of lasing wavelengths, and at one wavelength within the lasing bandwidth the components of incident-light along the fast and slow axes of the birefringent material have a relative retardation equal to an integral multiple of 2.pi.,
• and a linear translator drivingly connected to the tuning means so that the thickness of the plate traversed by the intracavity beam of light may be varied without alteration of the angles .phi. and .gamma. whereby to effect tuning of the output wavelength of the laser within the lasing bandwidth.