A tunable laser having a laser material capable of being tuned such as an ganic dye, tuning means including an intra-cavity semiconductor element to which an electric field can be applied, and an angle sensitive filter or reflector such as a diffraction grating.

A Q-switch for a laser having a resonant cavity including an output coupler, a gain medium and a retro-reflecting mirror is mounted in the resonant cavity between the gain medium and the retro-reflecting mirror. The Q-switch comprises a polarizer and a phase retarding element (such as a Pockels cell) which includes a birefringent substrate for inducing a controllable phase retardation in the cavity mode in response to an applied electric field. A tiltable mount supports the phase retarding element so that the lasing axis lies essentially in a plane of the crystallographic axis 45.degree. from the direction of polarization, and lies at an adjustable angle relative to the crystallographic axis. A control circuit supplies an applied electric field within the substrate having a first magnitude in a first state and a second magnitude in a seocnd state. In the first state, the phase retarding element induces 90.degree. rotation in a round trip for the cavity mode. In the second state, the phase retarding element induces effectively no rotation (0.degree. or 180.degree.) for the cavity mode. Therefore, the resonant cavity achieves a high extinction ratio by proper adjustment of the adjustable angle.

An electronically tuned, optically pumped, transition metal based, solid-state laser is disclosed. Tuning is achieved by using resonant reflecting means comprising an output mirror, a mirror located between the output mirror and the source of laser light, a polarizer located in the light path between the two mirrors, and an electronically tuned, voltage controlled, variable, liquid crystal waveplate for receiving light passing through the polarizer. The components of the resonant reflecting means are selected to have a longitudinal mode that is anti-resonant with the optical cavity of the laser.

A tunable laser using surface acoustic waves in the sides of a piezoelect prism to provide two reflective diffraction gratings for tuning the resonant cavity.

A multi-color, multi-pulse laser target designator is disclosed in which the target is illuminated with pulses of preselected colors and interpulse spacings so as to uniquely identify the target. Inter-pulse spacing may be varied down to an arbitarily small spacing by virtue of the use of pulses of differing colors, thereby increasing countermeasure resistance due to the difficulty of a target detecting and duplicating inter-pulse spacing. Pulse elongation is provided in one embodiment to provide prolonged illumination of the target so as to permit increased homing accuracy for optically guided weapons.