Nearly Single-Cycle Terahertz Pulse Generation in Aperiodically Poled Lithium Niobate

In the present work, an opportunity of nearly single-cycle THz pulse generation in aperiodically poled lithium niobate (APPLN) crystal is studied. A radiating antenna model is used to simulate the THz generation from chirped APPLN crystal pumped by a sequence of femtosecond laser pulses with chirped delays (<i>m</i> = 1, 2, 3 &#8230;) between adjacent pulses. It is shown that by appropriately choosing &#916;<i>t_m</i>, it is possible to obtain temporal overlap of all THz pulses generated from positive (or negative) domains. This results in the formation of a nearly single-cycle THz pulse if the chirp rate of domain length <i>&#948;</i> in the crystal is sufficiently large. In the opposite case, a few cycle THz pulses are generated with the number of the cycles depending on <i>&#948;.</i> The closed-form expression for the THz pulse form is obtained. The peak THz electric field strength of 0.3 MV/cm is predicted for APPLN crystal pumped by a sequence of laser pulses with peak intensities of the separate pulse in the sequence of about 20 GW/cm². By focusing the THz beam and increasing the pump power, the field strength can reach values in the order of few MV/cm.

Abstract licence: CC BY

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