Continuously Tunable Ultra Broadband Terahertz Generation Implemented with 1.2 μm NIR Pumping of GaSe

Abstract

  This paper presents the characteristics of 1.2 μm-laser pumped wide frequency tunable terahertz (THz) light source based on difference frequency generation (DFG) with an excitation of phonon-polariton in gallium selenide (GaSe) crystal. The pump and signal lasers are 1.2 μm Cr: Forsterite lasers as a novel frequency. The frequency can be tuned by changing wavelength of signal laser and incidence angle to GaSe crystal. The collinear phase matching conditions of generating terahertz wave in this system are shown. The tuning range of the THz-wave frequency covers from 0.3 THz to 4.8 THz (type oee phase matching) and 8.3 THz to 10.2 THz (type eoo phase matching). The maximum conversion ratio is ~10⁻⁶ (J⁻¹), which is about 3 orders in magnitude larger than that of gallium phosphide (GaP) crystal.