AT&T Bell Laboratories scientists say that they have made and operated the world’s smallest semiconductor lasers. Seen through a scanning electron microscope, the lasers look like microscopic drawing pins with the head of each pin only 400 atoms thick (about one-thousandth the diameter of a human hair). They are attached to their semiconductor substrate by thin posts. At least 10,000 of the microscopic lasers, each about five microns in diameter, would fit on the head of a pin. Designed by Bell Labs Researcher Sam McCall, the lasers operate in what is called a whispering gallery mode, named after the sound effect noted in such cathedrals as St. Paul’s in London and St. Peter’s in Rome, where one can whisper along the wall and be heard all along the inside perimeter of the dome. Like whispers in these buildings, photons travel with low losses around the edge of the laser. The lasers may be used either as surface-emitting or side-emitting devices. Each semiconductor disk laser is made of one or more layers of indium gallium arsenide sandwiched between indium gallium arsenide phosphide.
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