An AIGaAs laser transmitter has been developed that dichroically combines six single-mode 830 nm laser diodes in a 100 A total band-pass. Single-mode operation of each diode is necessitated by the 20 A diode-to-diode channel spacing. An external etalon is utilized for each laser diode to maintain single-mode operation (greater than 25 dB side mode suppression) in the presence of wideband modulation [1000 mega-pulses per second (Mpps)]. A universal header accommodates diodes from various manufacturers and includes an impedance-matching net-work as well as a thermistor and heater for diode closed-loop temperature control. Diffraction-limited optics are used to maximize the combined beam far-field irradiance for free-space applications. A 218 urad output beam with less than 1.05:1 ellipticity was measured for the combined output.
Robert J. Smith,
William L. Casey,
David L. Begley,
"Wideband Laser Diode Transmitter For Free-Space Communication," Optical Engineering 27(4), 274344 (1 April 1988). https://doi.org/10.1117/12.7976679