A Littrow prism is cut so that light enters at the Brewster angle, undergoes dispersion, strikes the rear face at normal incidence, and reflects back through the same front face. This double-pass geometry doubles the dispersion for a given footprint while keeping the input and output beams collinear. It is heavily used in tunable laser cavities to select specific wavelengths without altering the beam pointing.
We need to tune the dye laser, so swap out the end mirror for a Littrow prism on a rotation mount.
Related terms
Resonator
The arrangement of mirrors that sends light back and forth through the gain medium to build up laser oscillation.
Linewidth
The spectral width of a single-frequency laser's output, usually given in Hz, kHz or MHz at half maximum.
Chromatic dispersion
The change of refractive index with wavelength, which separates colors in prisms and spreads pulses in time.