Abstract: An optical system for a particle beam device such as an electron microscope, e-beam device or FIB device, including a particle beam column having an optical axis along which a beam of particles is projected and an apertured plate positioned in the column having an aperture which is coaxial with the optical axis, the plate being moveable in a direction which is parallel to the optical axis.

Abstract: A method of making an optically coupled semiconductor laser having cleaved facing end walls and precise alignment and spacing. An indium coated face of a semiconductor laser diode bar is placed on an indium coated support. A knife edge cleaves the bar into two closely spaced and aligned semiconductor diode laser bodies and concurrently cold bonds them to the support. The knife edge is used without deleteriously affecting their bonding to the support.

Abstract: A significantly more stable ohmic contact for a lead-salt semiconductor surface, especially for use in infrared lasers. The contact has layers of platinum, palladium or nickel alternating with gold, and then covered with indium. An Au-Pd-Au-In contact is used on lead-sulfide-selenide, lead-tin-selenide, and lead-tin-telluride of high tin content. A Pt-Au-Pt-Sn contact is preferred for lead-tin-telluride of low tin content. Lower contact resistance is attained if P type lead-tin-selenide and lead-tin-telluride surfaces are previously doped with oxygen, and the initial metal layer is applied in a manner that does not remove it.

Abstract: A semiconductor diode laser tunable within a range of over 200 wave numbers. Increased tuning range of a lead-salt laser, from about 30 to over 200 wave numbers, is attained by providing an increasing majority carrier concentration in the laser crystal within the laser cavity in the direction extending away from the contiguous PN junction contiguous the laser cavity.

Abstract: A higher power infrared Pb.sub.1-x Sn.sub.x Te diode laser that is tunable at this high output power at all wavelengths from 6.5 - 32 microns, particularly 6.5 - 9 microns. The diode laser has a P-type laser cavity with a degenerate carrier concentration. A low carrier concentration N-type region is adjacent the P-type region. The N-type region has unique characteristics inherent to a cadmium diffusion from an external source at a temperature of about 350.degree. - 500.degree. C. The cadmium diffusion N-type region forms a flat PN junction with the P-type laser cavity. Dislocation density in the monocrystal forming the completed laser body, even after the cadmium diffusion, is not noticeably higher than in the monocrystal from which the laser is made. A method of forming such a laser, using a short time, low temperature cadmium diffusion process, is claimed.