Measurement of submilliwatt, picosecond terahertz emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter based on a ZnSe crystal

Abstract

We measured the terahertz pulse emission from a femtosecond-laser-pumped solid-state dc to ac radiation converter using a 150fs Ti:sapphire laser pulse for dense plasma diagnostics. The laser-produced ionization front was directly modulated from a periodic electrostatic field to pulsed emission. The central frequency of the emission was measured to be 0.13THz having a bandwidth of 0.1THz and a peak power of 0.2mW. This emission source is suitable for use in various novel diagnostic techniques, such as dense plasma diagnostics.

Dc to ac field conversion due to leaky-wave excitation in a plasma slab behind an ionization front

“…Conversion of static electric fields by their interaction with moving ionization fronts has attracted considerable attention due to the possibilities of its use for the creation of frequency-tunable sources of electromagnetic radiation [1][2][3][4][5][6][7][8][9][10][11][12]. In the context of such a conversion, one-dimensional Doppler-like effects are often considered when waves interact with a transversely unlimited ionization front [1][2][3][4][5][6][7][13][14][15][16][17][18][19][20][21][22][23]. A spatially periodic electric field produced by a system of capacitors is usually considered a wave to be converted.…”

“…A spatially periodic electric field produced by a system of capacitors is usually considered a wave to be converted. Such sources, called dc to ac radiation converters, are proposed for the generation of microwave and terahertz radiation [1][2][3][4][5][6][7]. Another type of problem is related to the conversion of a uniform static electric field interacting with a transversely limited superluminal ionization front [8][9][10][11][12].…”

“…Available femtosecond laser systems are capable of securing the propagation of such fronts over sufficiently long distances and the formation of subsurface plasma over sufficiently large areas (tens of square centimeters) [24][25][26][27]. Photoconductive devices (including large-area ones) that use ultrafast ionization have been used for generation, detection, frequency conversion, phase shifting, and fast switching of terahertz or microwave radiation (see, e.g., [5][6][7][20][21][22][23][24][25][26][27][28][29][30][31]). Since the speed of propagation of ionization fronts is greater than the speed of light, fast leaky polarization waves are excited behind the front and radiate energy through the transverse plasma boundaries at an angle to the direction of front propagation.…”