Abstract
Ultrashort intense optical pulses in the mid-infrared (mid-IR) region are very important for broad applications ranging from super-resolution spectroscopy to attosecond X-ray pulse generation and particle acceleration. However, currently, it is still difficult to produce few-cycle mid-IR pulses of relativistic intensities using standard optical techniques. Here, we propose and numerically demonstrate a novel scheme to produce these mid-IR pulses based on laser-driven plasma optical modulation. In this scheme, a plasma wake is first excited by an intense drive laser pulse in an underdense plasma, and a signal laser pulse initially at the same wavelength (1 micron) as that of the drive laser is subsequently injected into the plasma wake. The signal pulse is converted to a relativistic multi-millijoule near-single-cycle mid-IR pulse with a central wavelength of ~5 microns via frequency-downshifting, where the energy conversion efficiency is as high as approximately 30% when the drive and signal laser pulses are both at a few tens of millijoules at the beginning. Our scheme can be realized with terawatt-class kHz laser systems, which may bring new opportunities in high-field physics and ultrafast science.
Highlights
Since the laser was invented in 19601, it has become a powerful and important tool for various applications in fundamental science, industry, medicine, and so on
Concept for mid-IR pulse generation Figure 1 shows a schematic of the relativistic few-cycle mid-IR pulse generation from a laser-driven plasma wake
An intense drive pulse propagates in an underdense plasma and creates a nonlinear plasma wake, which is composed of a few plasma bubbles moving at a phase velocity close to the group velocity of the laser pulse
Summary
Since the laser was invented in 19601, it has become a powerful and important tool for various applications in fundamental science, industry, medicine, and so on. The invention of the chirped pulse amplification technique[2] by Strickland and Mourou in 1985 dramatically boosted the intensity of laser pulses, usually at nearinfrared (near-IR) wavelengths, to an unprecedented level This revolutionary invention brought laser-matter interactions into the relativistic regime for the first time. It has produced the highest accelerating field and highest pressure on earth, which are comparable to those of energetic events in the universe, providing unprecedented opportunities for various scientific studies[3,4,5,6,7,8]. There is increasing interest in extending these laser pulses to other wavebands, such as the mid-IR range
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