During the past decade, the development of intense few-cycle mid-infrared (mid-IR, λ<5 µm) laser sources has made significant progress, which has opened many opportunities for infrared nonlinear optics, high-harmonic generation and pump-probe experiments in the “molecular fingerprint” region. However, even longer carrier wavelength (~10 µm) are needed in many applications. It is one of the current challenges to generate high-energy, ultra-short long-wavelength IR pulses (LWIR), beyond the capability of existing methods including optical parametric amplifiers, high pressure carbon-dioxide lasers, difference frequency generation, and four-wave mixing, etc. In this work, we propose a new scheme that utilizes asymmetric self-phase modulation in a tailored plasma density structure to generate multi-millijoule energy, single-cycle LWIR pulses tunable in the spectral range of 5-14 μm. We experimentally demonstrate this novel scheme for the first time. An intense single-cycle IR pulse with a central wavelength of 9.4 µm and energy of 3.4 mJ is generated using a ~580 mJ, 36 fs, 810 nm drive laser. Furthermore, the tunability of the IR wavelength in the range of 3-19 µm is also demonstrated through simple adjustment of the plasma structure.
|Working group||Secondary radiation generation & applications|