City of Light: The Story of Fiber Optics

150 CITY OF LIGHT
Figure 12-1: The first semiconductor laser was a simple cube of gallium arsenide
(GaAs), half p-type and half n-type.
and back in Schenectady he rounded up a crew of other scientists to try some
experiments. 6 In short order, they made gallium arsenide chips with edges
polished to act as the mirrors needed to generate a laser beam. When they
fired powerful electrical pulses through the chips, they emitted light at a narrow
range of wavelengths, a sign of laser action. The whole process took just
two and a half months. 7 It was a scientific tour de force.
Hall was good, but three other labs were hot on his heels. A team from
IBM came in a close second with a slightly different variation, although no
one from the lab had attended the New Hampshire meeting. 8 Nick Holonyak,
Jr., returned from the New Hampshire meeting to try making lasers from
gallium arsenide phosphide at GE’s Syracuse lab but didn’t succeed until he
tried Hall’s approach of polishing the crystals. 9 The Lincoln Lab group, distracted
by other projects, wound up a close but frustrating fourth. 10
That remarkably close finish—achieved in the shadow of the Cuban missile
crisis—seemed to herald good things for semiconductor lasers, but there the
technology stalled. The developers of communication systems wanted lasers
that generated steady beams and operated for long periods at room temperature.
The lasers made by Hall and the others only fired intermittent pulses
and didn’t last long even when cooled to liquid nitrogen temperature, �321�F
or �196�C. Progress from there was painfully slow. By the end of 1964, the
best semiconductor laser could fire a single pulse at room temperature when
25 amperes—more current than a standard household refrigerator draws—
flowed through an area of 0.02 square millimeter for 50 billionths of a second.
Then it had to cool before firing again. 11