Abstract: A hermetically sealed injection laser package is made by first forming a sub-assembly of a monitoring photodiode (50) on a metal support member (53) and welding it to a heat sink (30) on which the laser (31) is mounted. The heat sink is secured inside the package housing (10) and then a further sub-assembly, comprising a plastics packaged optical fiber (60) hermetically sealed in a fiber support tube (61), is introduced through an aperture in one wall of the housing. Anchorage means (70) is laser beam welded to this tube and to the heat sink to secure the inner end in position for optimum optical coupling between the laser and the fiber.

Abstract: The aluminium-backed phosphor layer on the output window of conventional image intensifier tubes of the photoemissive/luminescent screen type can be seriously damaged by the extremely high energy density pulse of electrons resulting from exposure of the tube to very bright light (such as a shell flash). The invention prevents or minimises the damage by placing in between and in contact with the phospher layer and the aluminium layer a layer of material (for example, potassium silicate) whose thermal properties are such as to cause it to act as a heat sink and so absorb most, if not all, of the thermal energy released by the electron pulse.