Hall initially thought that the semiconductor green laser pointer was a “long shot” because the LEDs were very inefficient at the time. At the same time, he was skeptical, because lasers that had been confirmed two years ago and already existed needed “exquisite mirrors”. In the summer of 1962, Hall stated that he was quite shocked by the more efficient gallium arsenide light-emitting diodes developed by the Massachusetts Institute of Technology.
He later stated that he was fortunate to pass some high-quality GaAs materials and used his experience as an amateur astronomer to develop a method to polish the edges of GaAs chips to form a cavity. Hall’s successful demonstration was based on a design where the radiation bounces back and forth across the interface, rather than a vertical bounce. He modestly stated that no one had “proposed the idea before.”
“In fact, Hall’s design is essentially a lucky coincidence that the semiconductor material forming the waveguide also has the property of limiting bipolar carriers at the same time. Otherwise, semiconductor green laser pointers would not be possible. By using dissimilar semiconductors Materials that can form slab waveguides so that photons and carriers overlap. These preliminary demonstrations at General Electric are a major breakthrough.