A microchip-sized laser stabilizer could be inexpensively mass-produced and integrated into existing laser systems, allowing them to transfer data as fast as much larger and more expensive lasers.
With streaming movies and UltraHD television taking more and more bandwidth, there is a race to deliver data into people's homes as quickly as possible. Light-based fiber optic connections promise far faster data rates than standard electricity-based coaxial cables, so making laser sources smaller, cheaper and more stable is a high priority for engineers. Stability is particularly important because, rather than simply representing bits by whether the laser is on or off, information could also be encoded in the light wave's harder-to-control frequency or phase. Additional layers of data can multiply a laser's transfer speed, but mass-market lasers aren't stable enough to carry a signal through the noise in those properties. Engineers at the University of Pennsylvania have now developed a silicon microchip that can significantly reduce the noise of low-cost lasers, enabling them to use the laser's phase to transmit data. This microchip measures the noise in the laser's phase in the form of an electrical current, then suppresses the noise by injecting that current back to the laser in a feedback loop. This method, known as the Pound-Drever-Hall (PDH) technique, is a mainstay of laser stabilization, but has thus far only been implemented as benchtop-sized systems.
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