A Fabry-Perot etalon is mounted within the optical cavity of a laser for selecting the wavelength of the output radiation of that laser from a plurality of discrete wavelengths closely distributed about a nominal wavelength. The etalon includes a pair of closely spaced prisms mounted along the optical axis of the laser cavity with the laser beam passing therethrough. Each of the prisms has a first surface facing outwardly of the etalon and inclined at a slight angle to a normal to the optical axis, and each prism includes a second surface opticaly adjacent and spaced from the second surface of the other prism, each such second surface being inclined relative to its respective first surface.
An etalon for use in lasers, particularly CW dye lasers, comprises a pair of plates, 10,11 respectively mounted at the ends of a tube 12 with the distal faces 10a, 11a of the plates parallel and the chamber 13 formed within the tube 12 between plates 10,11 is substantially completely filled with a fluid 20 whose refractive index matches that of the plates 10,11 and means 25 are provided for causing extension and contraction of the axial spacing of the plates 10,11. In one embodiment the tube 12 is made of piezoelectric material and the means 25 provides an electrical drive signal to the piezoelectric material. In another embodiment the tube 12 has piezoelectric portions and other portions made of a rigid material. In a further embodiment the tube has portions made of a rigid material which are separated by an elastomer 39 and the means 25 includes a pump 26 which is in fluid communication with the chamber 13. The plates 10 and 11 may be mounted directly on the ends of the tube 12 but more conveniently are mounted on adjustable holders 16, 16a, 17 and 17a.
Producing high efficiency laser wave mixing and laser harmonic generation laser beams by reconstruction of fundamental and second harmonic laser beams from a frequency doubling crystal by use of a pair of optical wedges. The optical wedges are positioned with their angled surfaces facing each other with substantially 180 degrees of relative rotation and separated at a predetermined distance. The two spaced apart laser beams enter the first optical wedge from the frequency doubling crystal and the two beams converge after exit the first wedge. The converged laser beams enter the second wedge and exit therefrom, forming a coaxially overlapping single beam which is to be used for high efficiency generation of a higher order harmonic laser beam.
A pulse laser system utilized for communication transmits a modulated pulsed laser beam having a precise wavelength to match a receiver. An etalon is positioned in the resonant cavity of the laser and is adjustable to tune the laser. A continuous wave reference beam is provided and is compared with the laser output beam and if the wavelength's bear other than a predetermined relationship with respect to one another, a control signal is generated to adjust the etalon in the laser resonant cavity. In one embodiment another etalon is placed in the reference beam path as well as the laser beam path with the transmitted beams being detected in order to derive normalized proportionality factors relating to each beam so that a comparison of the proportionality factors may be made and utilized for control purposes.
An improved telescope is disclosed in which an adjusting member for adjusting the reticule can be fitted on an optical axis thereof. The improved telescope has a reticule disposed at an ocular side in a lens-barrel and including a cross line for collimation; a reticule holding member including a front surface parallel to the reticule surface and a rear surface having at its periphery an inclined portion inclining with respect to the cross line surface and disposed within the lens-barrel for holding the reticule; a reticule holding member fitting portion disposed within the lens-barrel and receiving the reticule holding member by abutting against its front surface of the reticule holding member; and an adjusting member abutted against the inclined portion of the rear surface of the reticule holding member from the ocular side toward the optical axis direction to move the reticule holding member in order to adjust the cross line to the optical axis.
An actively stabilized laser is disclosed which includes a temperature tunable etalon in the laser cavity for single frequency operation. The operation of the laser is actively monitored to detect variations induced by changes in the length of the resonator. These changes tend to cause the frequency of the selected longitudinal mode to shift so that it is no longer aligned with the peak of the transmission curve of the etalon. When this misalignment occurs, operation deteriorates. By monitoring laser performance, the misalignment can be detected and the temperature of the etalon can be changed to realign its transmission peak to the selected mode. In the preferred embodiments, either the laser output power or the current supplied to the laser is monitored. This approach substantially reduces mode hopping.
