The generation of terahertz (THz) radiation using a ZnGeP2 (ZGP) large-aperture photoconductive antenna (PCA) was demonstrated. The semiconductors were excited above and below the bandgap (400 and 800 nm) by a femtosecond Ti:sapphire laser. The THz pulse waveform generated by the ZGP antenna was measured using a time-domain spectroscopy technique. The antenna’s THz pulse energy dependence on the optical pump energy was measured, and saturation fluence and carrier mobility were estimated. The ZGP and a chemical vapor deposited ZnSe-based PCA were compared.
Volumetric defects in ZnGeP2 single crystal have been visualized by using the digital holography camera. Type, geometrical sizes and positioning of founded defects were determined. Based on this information researching zones were chosen on the test ZnGeP2 plate. Measurements of absorption coefficient and refractive index in THz range were carried out. It is shown that in the frequency range 0,3-1 THz the difference of absorption coefficients reaches the value Δα = 0.2 cm-1 between “clear” zones and zones with volumetric defects. In same time, maximum difference by refractive index is about Δnmax = 0,0015.
Conditions for the formation of THz radiation in ZnGeP2 single crystals when generating a difference frequency are considered. It is shown that effective THz radiation requires two-frequency laser pumping sources with a generation pulse duration of < 1 ns. It is proposed to use IR radiation as such a source dual-wavelength optical parametric oscillator based on the KTP singlecrystal with pumping by Nd:YAG lasers with active Q-switching with simultaneous synchronization mode.
In this paper presented a series of experiments determine the spectral characteristics of random lasing in lasers with agglomerated nanoparticles metals and dielectrics. The data allowed us to establish that, in the active heterogeneous environment, there are various gain effects of lasing the impact of which is determined nanoparticles concentration.