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Optical Science Laboratory

Quantum Optical Physics Research Group

Dr. Hideki Gotoh
Group Leader
Dr. Hideki Gotoh

For realizing a new generation of optical devices that will bring about a revolution in optical information/transmission technology, we propose new device operating principles to overcome current limits. We study coherent control of excitonic and spin states in low dimensional structures, as well as the technology to manipulate optical field for fully control the laser-matter interaction.


The carrier-envelope offset (CEO) is a carrier-envelope phase (CEP) slip between adjacent pulses in a mode-locked laser. Recent progress in the mode-locked laser techniques has made it possible to lock the CEO. The CEO-locked mode-locked laser derivers frequency comb containing various frequency components in the hundreds of terahertz region which are regularly spaced. The CEO-locked frequency comb can be used as an "optical frequency ruler." Optical frequency measurement is one of applications of the "ruler". Lasers for applications, such as precision spectroscopy and telecommunications, should be small and have a high repetition rate. From this point of view, we need to achieve CEO locking with a small and high-repetition rate device with low pulse energy. For such purpose, we employed a tellurite photonic crystal fiber for supercontinuum generation with low pulse energy, and a periodically poled lithium niobate ridge waveguide for efficient second harmonic generation. As a result, we could demonstrate a CEO-locked frequency comb at the telecommunications wavelengths with a 230 pJ fiber coupling pulse energy, which, to the best of our knowledge, is the lowest fiber coupling pulse energy ever achieved.

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