A gallium-arsenide laser facsimile printer

We summarize the development of a high-resolution facsimile printing system in which miniature archival images are machined in metal film by a pulsed, focused, scanning laser beam The film is designed to machine at optical energies within the pulse-power capabilities of GaAs semiconductor lasers. The images are instantly available, as machined, for rear-projection viewing in a compact desk-top printer. Frames of 8 × 10 mm area containing 3.3 × 10⁵ pixels and demonstrating up to seven distinguishable gray levels have been written in 12 seconds. Extensive data on hole machining in partially oxidized, low-melting-temperature, metal films are marshalled to show that single-layer films are inhospitable media for facsimile machining with GaAs lasers. We describe a two-layer film consisting of about 600Å of bismuth followed by approximately 650Å of selenium evaporated onto a low-surface-energy substrate. This selenium thickness is antireflective at the laser wavelength, and the composition is nearly stoichiometric for Bi2Se3. A strongly exothermic reaction occurs when molten bismuth and selenium mix in the irradiated area. We present data illustrating the machining performance of this film with a thick-cavity, GaAlAs, double-heterostructure laser providing 300 mW of peak power at 3-percent duty factor and 0.1-μs pulse duration and give examples of the image quality obtained in raster-scanned, hole-array machining. Studies of film adhesion, scratch resistance, and shelf life are summarized. Several diffraction-limited optical systems for acquiring, deflecting, and focusing the GaAs beam onto the film, cylindrically corrected for astigmatism and ellipticity, are described, and several laser properties which affect image machining abversely are characterized.