GaSe1−xSx and GaSe1−xTex thick crystals for broadband terahertz pulses generation

We demonstrate the possibility of broadband THz pulse generation in mixed GaSe1−xSx and GaSe1−xTex crystals. The ordinary and extraordinary refractive indices of the crystals have been measured by the terahertz time-domain spectroscopy method, those values strongly influence the efficiency of THz generation process. The high birefringence and transparency of pure GaSe and mixed crystals allow optical rectification of femtosecond laser pulses in the several millimeters thick crystal using the еее interaction process (with two pumping waves and generated THz wave all having extraordinary polarization in the crystal).