A Laser History of Lincoln Laboratory, Part 1

The MIT Lincoln Laboratory has been the site of numerous discoveries and has yielded some incredibly important technologies — among them, lasers. In the fall of 1962, the laboratory demonstrated a gallium arsenide (GaAs) laser, which was worked on concurrently by groups at General Electric and IBM. The credit for the laser has been the subject of debate, though Nick Holonyak Jr. is credited for the first visible-wavelength GaAs laser. According to Lincoln Laboratory, the use of the lasers evolved from the laboratory’s research into GaAs for use in high-speed electronic devices, which led to the discovery that GaAs diodes were efficient light emitters.

In 1969, the laboratory began its high-energy laser program to understand the propagation of high-energy lasers in the atmosphere. The lab’s ballistic range was converted to a laser measurement facility, and later measurements were taken at a contractor facility in Florida. The laboratory was the first to arrive at a theoretical understanding of the nonlinear atmospheric propagation of high-energy laser beams, a phenomenon referred to as thermal blooming.

1972 saw the investigation of high-power range-Doppler laser radar for space-object monitoring and identification. Soon after, the laboratory developed specifications for a high-power CO₂ laser radar capable of imaging unenhanced satellite targets in low Earth orbit at slant ranges out to approximately 1000 km, with down-range and cross-range resolutions of less than 30 cm.

In the mid-’70s the laboratory demonstrated a 10.6-μm CO₂ gas-dynamic laser, which at the time was the most powerful laser in the country, with a cooled 52-channel deformable mirror, the first to be used with a high-power laser. The beam was expanded to 1.2 m and propagated over a 2-km horizontal path to an instrumented vehicle that ran on a stretch of railroad track. The experiment enabled researchers to produce the first thermal-blooming compensation with a high-energy laser.

The lab resumed its research into high-power laser radar in 1985 with the Optical Discrimination Technology Program. The project was tasked with developing laser radars capable of discriminating a large number of targets in the midcourse trajectory phase. One approach envisioned multiple space-based bistatic systems that could rapidly sample many targets scattered over a large field of regard. The concept required large apertures, about 2 m in diameter, that could be steered between targets spaced as much as 3° apart.