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OCIS codes: (190.7110) Ultrafast nonlinear optics; (160.4890) Organic
materials; (050.1590) Chirping; (120.5050) Phase measurement
Abstract:
We report on the generation of high-energy (1.9 μJ) farinfrared pulses tunable between 4 and 18 THz frequency. Emphasis is placed on tunability and on minimizing the bandwidth of these pulses to less than 1 THz, as achieved by difference-frequency mixing of two linearly chirped near-infrared pulses in the organic nonlinear crystal DSTMS. As the two near-infrared pulses are derived from amplification of the same white light continuum their carrier envelope phase fluctuations are mutually correlated, and hence the difference-frequency THz field exhibits absolute phase stability. This source opens up new possibilities for the control of condensed matter and chemical systems by selective excitation of low-energy modes in a frequency range that has to date been difficult to access.
