Scientists build the smallest optical frequency comb to-date
Optical frequency combs are laser sources whose spectrum consists of a series of discrete, equally spaced frequency lines that can be used for precise measurements. In the last two decades, they have become a major tool for applications such as precise distance measurement, spectroscopy, and telecommunications.
Most of the commercially available optical frequency comb sources based on mode-lock lasers are large and expensive, limiting their potential for use in large volumes and portable applications. Although chip-scale versions of optical frequency combs using microresonators were first demonstrated in 2007, a fully integrated form has been hindered by high material losses and complex excitation mechanisms.
Research teams led by Tobias J. Kippenberg at EPFL and Michael L. Gorodetsky at the Russian Quantum Center have now built an integrated soliton microcomb operating at a repetition rate of 88 GHz using a chip-scale indium phosphide laser diode and the silicon nitride (Si3N4) microresonator. At only 1 cm3 in size, the device is the smallest of its kind to-date.
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