Researchers in UCSD’s engineering department are taking lasers to new lows, demonstrating a micron-scale laser measuring less than one-thousandth of a millimeter per side. And while sub-wavelength lasers have been demonstrated in the past, the UCSD team did it without cryogenically cooling their gear to extremely low temperatures; their tiny laser pulses away at room temperature, making it the smallest laser to do so and paving the way for practical commercial use.
Sub-wavelength lasers are incredibly small, measuring one micron or less in all dimensions. The light that comes out of them has a wavelength of 1.4 microns, meaning the device itself is smaller than the light it emits. To provide some perspective, imagine a three-inch semiconductor wafer; you could pack a full 4 billion of these nanolasers onto that chip.
Generally, lasers operating at such small dimensions and wavelengths require extremely low-temperature environments, but the UCSD team was able to shrink their lasers down by encasing the core of each device in a silica and aluminum housing. The aluminum serves as a barrier between lasers so they don’t interfere with one another, as well as a means to dissipate heat. As a result, they can be packed into very tight arrays.
So what might one do with 4 billion lasers packed on a silicon wafer? In theory, such small lasers could be used in dense arrays in optical interconnecting devices, which is why it’s so crucial that they can operate at room temperature. From a scientific standpoint, such sub-wavelength lasers could be integrated into devices that image in the far-infrared neighborhood of the spectrum.
The lead UCSD researcher thinks commercial applications are still a couple of years out, but in meantime the team is pressing on. As part of DARPA’s Nanoscale Architectures for Coherent Hyper-Optic Sources (NACHOS) program, they’ve got deadlines to meet. By the time the five-year program is up in 2012, they expect to have upgraded from an optical pump to electrical pumping and demonstrate nanolasers that can fire continuously as well as in pulse mode.