Rediscovering Spontaneous Light Emission: LEDs Could Replace Some Lasers

 

“Sometimes the great discoveries are looking right at us and waiting.”

Berkeley Lab researchers have developed a nano-sized optical antenna that can greatly enhance the spontaneous emission of light from atoms, molecules and semiconductor quantum dots. This advance opens the door to light-emitting diodes (LEDs) that can replace lasers for short-range optical communications, including optical interconnects for microchips, plus a host of other potential applications.

“Since the invention of the laser, spontaneous light emission has been looked down upon in favor of stimulated light emission,” says Eli Yablonovitch, an electrical engineer with Berkeley Lab’s Materials Sciences Division. “However, with the proper optical antenna, spontaneous emission can actually be faster than stimulated emission.”

Yablonovitch, who also holds a faculty appointment with the University of California (UC) Berkeley where he directs the NSF Center for Energy Efficient Electronics Science (E³S), and is a member of the Kavli Energy NanoSciences Institute at Berkeley (Kavli ENSI), led a team that used an external antenna made from gold to effectively boost the spontaneous light emission of a nanorod made from Indium Gallium Arsenide Phosphide (InGaAsP) by 115 times. This is approaching the 200-fold increase that is considered the landmark in speed difference between stimulated and spontaneous emissions. When a 200-fold increase is reached, spontaneous emission rates will exceed those of stimulated emissions.

“With optical antennas, we believe that spontaneous emission rate enhancements of better than 2,500 times are possible while still maintaining light emission efficiency greater than 50-percent,” Yablonovitch says. “Replacing wires on microchips with antenna -enhanced LEDs would allow for faster interconnectivity and greater computational power.”

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