Terahertz generation in plasmas using two-color laser pulses

Journal Article · Mon Feb 15 00:00:00 EST 2010 · Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print)

DOI:https://doi.org/10.1103/PHYSREVE.81.026407· OSTI ID:21344713

Penano, Joseph; Sprangle, Phillip; Gordon, Daniel ^[1]; Hafizi, Bahman ^[2]; Serafim, Philip ^[3]

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1. Naval Research Laboratory, Plasma Physics Division, Washington, DC 20375 (United States)
2. Icarus Research, Inc., Bethesda, Maryland (United States)
3. Northeastern University, Boston, Massachusetts (United States)

We analyze the generation of terahertz radiation when an intense, short laser pulse is mixed with its frequency-doubled counterpart in plasma. The nonlinear coupling of the fundamental and the frequency-doubled laser pulses in plasma is shown to be characterized by a third order susceptibility which has a time dependence characteristic of the laser pulse durations. The terahertz generation process depends on the relative polarizations of the lasers and the terahertz frequency is omegaapprox1/tau{sub L}, where tau{sub L} is the laser pulse duration. Since the laser pulse duration is typically in the picosecond or subpicosecond regime the resulting radiation is in the terahertz or multiterahertz regime. To obtain the third order susceptibility we solve the plasma fluid equations correct to third order in the laser fields, including both the relativistic and ponderomotive force terms. The relativistic and ponderomotive contributions to the susceptibility nearly cancel in the absence of electron collisions. Therefore, in this terahertz generation mechanism collisional effects play a critical role. Consistent with recent experimental observations, our model shows that (1) the terahertz field amplitude is proportional to I{sub 1}sq root(I{sub 2}), where I{sub 1} and I{sub 2} are the intensities of the fundamental and second harmonic laser pulses, respectively, (2) the terahertz emission is maximized when the polarization of the laser beams and the terahertz are aligned, (3) for typical experimental parameters, the emitted terahertz field amplitude is on the order of tens of kilovolts/cm with duration comparable to that of the drive laser pulses, and (4) the direction of terahertz emission depends sensitively on experimental parameters.

• OSTI ID: 21344713
• Journal Information: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics (Print), Vol. 81, Issue 2; Other Information: DOI: 10.1103/PhysRevE.81.026407; (c) 2010 The American Physical Society; ISSN 1539-3755
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ELECTRON COLLISIONS
LASER RADIATION
LASERS
NONLINEAR PROBLEMS
PLASMA
PLASMA FLUID EQUATIONS
POLARIZATION
PONDEROMOTIVE FORCE
PULSES
RELATIVISTIC RANGE
TIME DEPENDENCE
BOLTZMANN-VLASOV EQUATION
COLLISIONS
DIFFERENTIAL EQUATIONS
ELECTROMAGNETIC RADIATION
ENERGY RANGE
EQUATIONS
PARTIAL DIFFERENTIAL EQUATIONS
RADIATIONS