Photon deceleration in plasma wakes generates single-cycle relativistic tunable infrared pulses

Abstract

Availability of relativistically intense, single-cycle, tunable infrared sources will open up new areas of relativistic nonlinear optics of plasmas, impulse IR spectroscopy and pump-probe experiments in the molecular fingerprint region. However, generation of such pulses is still a challenge by current methods. Recently, it has been proposed that time dependent refractive index associated with laser-produced nonlinear wakes in a suitably designed plasma density structure rapidly frequency down-converts photons. The longest wavelength photons slip backwards relative to the evolving laser pulse to form a single-cycle pulse within the nearly evacuated wake cavity. This process is called photon deceleration. Here, we demonstrate this scheme for generating high-power (~100 GW), near single-cycle, wavelength tunable (3-20 µm), infrared pulses using an 810 nm drive laser by tuning the density profile of the plasma. We also demonstrate that these pulses can be used to in-situ probe the transient and nonlinear wakes themselves.

Cascaded generation of isolated sub-10 attosecond half-cycle pulses

“…The normalized amplitude of the driving pulse is a 3 , where a t , E is the peak electric field of the pulse and c is the light speed in vacuum. With the developments of laser technologies, similar near-single-cycle laser pulses have been experimentally realized at nonrelativistic [20][21][22] and moderately relativistic intensities 23,24 . Relativistic one-cycle pulses are also promising to be obtained from plasma optic devices 25,26 .…”

Seed source for plasma compression in the long wavelength infrared

“…This dispersion relation gives the real part of the susceptibility over a broad spectral range. The nonlinear response of neutral air molecules is modeled as a constant nonlinear susceptibiltiy, χ (3) , which is varied by hand with pulse duration to approximate the effects of molecular rotations 18,19 . Photoionization is evaluated in the tunneling limit, using the Coulomb corrected quasiclassical PPT theory [23][24][25][26] , with an effective residual charge of Z = 0.53, ionization potential 12.1 eV, and gas density of 5.4 × 10 18 cm −3 .…”

“…Sources of long wavelength infrared (LWIR) radiation with terawatt peak power are currently limited to highly specialized CO 2 laser systems 1,2 . Recently, ∼ 100 gigawatt singlecycle pulses were obtained via down-conversion of near infrared ultra-short pulses in a relativistic plasma 3 . This paper is directed toward producing sub-picosecond, terawatt LWIR pulses, by means of backward Raman amplification (BRA) [4][5][6][7] .…”

Ultra-short pulse generation from mid-IR to THz range using plasma wakes and relativistic ionization fronts

“…Remarkable progress for generating such mid-IR/THz pulses has been made through various optical methods in nonlinear crystals or gases, such as optical parametric amplification (OPA) 16,17 , differencefrequency generation (DFG) [18][19][20][21] , optical rectification 22,23 , and two-color filamentation 24,25 . Recent numerical and experimental studies show that plasmas can also be utilized as nonlinear optical media to generate ultra-short mid-IR/THz pulses with high efficiency 26,27 . Unlike in traditional nonlinear crystals, there is no damage concerns for the power/intensity scala) Electronic mail: znie@ucla.edu ing in plasmas, which makes it possible to generate relativistically intense pulses in the mid-IR to THz spectral range.…”

“…II we briefly describe the first plasma technique that uses frequency downshifting (or photon deceleration) in a nonlinear plasma wake. We first summarize our particle-in-cell (PIC) simulations and experiments on generating multi-millijoule, single-cycle pulses in the 3-20 µm wavelength range with a specially prepared plasma density structure 26,27 . In Sec.…”