Abstract: Electrical apparatus comprises a number of modules (4) supplied with eletrical power by ducts (6) which convey cooling fluid between adjacent modules (4).

Abstract: A pulsed laser comprises a laser rod (6), and is pumped by diode array (3) selected such that with additional components (7, 9) only a maximum of two longitudinal modes are generated between mirror (1) and output coupler (2). By slow Q-switching Q-switch (9) hoped to get a single longitudinal mode output pulse. However if on the onset of the relaxation pulse mode beating is detected by detector (28), indicating that two longitudinal modes are present, then the optical path length of the resonator is changed by quarter of one wave length, by applying an electrical signal to a pulse length control means (10), such that one of the modes is suppressed prior to the Q-switch being fully opened. The output may be amplified by amplifier arrangement (24).

Abstract: An optical arrangement includes an infrared imaging system operating in conjunction with a first beam having wavelengths less than 15 microns, and a coherent infrared source generating a second beam having wavelengths shorter than the first beam wavelengths. Also provided is an objective lens arrangement including an objective lens having an aperture formed in one side of the objective lens. A partially reflective member is located between the objective lens arrangement, and the imaging system and infrared source. A T.V. camera is provided for receiving an image through the objective lens aperture. The first beam is directed to the imaging system from a region being imaged, and the second beam is directed from the infrared source to the region being imaged. The respective beams are directed to the partially reflective member so as to cause the respective beams to pass through the objective lens along substantially the same optical path as each other.

Abstract: An apparatus and method for depositing multiple layer, thin optical films onto a substrate and an optical filter made thereby. The apparatus includes a vacuum chamber; moving means for moving the substrate between regions of the vacuum chamber; material depositing means within each region for depositing a film of material on the substrate; a reactive substance source for introducing a reactive substance into each region so as to react with the material as it is deposited in that region; and control means for controlling the degree of such reaction in one region relative to the other, to obtain desired stoichiometry in the deposited materials.

Abstract: An optical modulator comprises a crystal (15) of material exhibiting the pyroelectric effect, and charge-dissipating means for dissipating any charge built up on the optical faces of the prism. The charge-dissipating means may comprise point electrodes (30) positioned adjacent to the optical faces (21) of the crystal and connected to an alternating-current high-voltage power supply (31). The electrodes produce charged ions which neutralize any charge on the optical faces of the crystal. The crystal may be used as the Q-switch in a laser.