A system gain of 40 dB was realized with a semiconductor injection-laser oscillator operating into a neodymium-glass-fiber laser amplifier. InAsP ingots were grown by a modified Czochralski technique. The injection laser was fabricated from a mixed crystal of InAs0.17P0.83. This composition was chosen because laser emission occurs at 1.063 μ at liquid nitrogen temperatures. The p-n junction was obtained by zinc diffusion under phosphorus pressure. The method of fabricating contacts and the Fabry-Perot cavity is described, and optical and electrical characteristics of the devices are given. Coarse tuning of the lasing wavelength is based on . Fine tuning can be accomplished by temperature variation of the laser junction in accordance with Å/°K between 80- 140°K. The injection laser was optically mated to the samarium-clad neodymium-glass-fiber amplifier by microscope optics and a gimbal-mounted reflector. Design details of the optical amplifier are given in context with optimum low-noise-level operation. The peak optical amplifier wavelength can be varied over a 100- Å interval by appropriate choice of the host-glass composition. The injection-laser pulse was delayed until the spontaneous emission had reached its peak for a maximum observed gain of approximately .