An experimental investigation of the detection of optical laser radiation in a magnetized transparent ferromagnet, at room temperature was made. As a source of electromagnetic radiation in the optical region we used Spectra-Physics Mai-Tai femtosecond laser with a wavelength tuning range from 710 nm to 950 nm. The laser radiation was linearly polarized, and the peak power was about 300 kW. For the detection of laser pulses a monocrystalline ferromagnet YIG was used, which is partially transparent in the laser tuning region. It is established that the detection is due to the nonlinearity of the static magnetization curve. To determine the dependence of the degree of correlation between the magnetization curve and the amplitude of the detected signal, on the external magnetic field, the detection process was modeled in Matlab. The comparison shows that the results of measurements and simulations correlate well with each other, and the magnitude and sign of the detected signal correspond to the curves of static magnetization.
A new scheme for generating high-energy terahertz (THz) pulses by optical rectification of tilted pulse front (TPF) femtosecond laser pulses in ZnTe crystal is proposed and analyzed. The TPF laser pulses are originated due to propagation through a multistep phase mask (MSPM) attached to the entrance surface of the nonlinear crystal. Similar to the case of contacting optical grating the necessity of the imaging optics is avoided. In addition, introduction of large amounts of angular dispersion is also eliminated. The operation principle is based on the fact that the MSPM splits a single input beam into many smaller time-delayed “beamlets”, which together form a discretely TPF in the nonlinear crystal. The dimensions of the mask’s steps required for high-energy THz-pulse generation in ZnTe and widely used lithium niobate (LN) crystals are calculated. The optimal number of steps is estimated taking into account individual beamlet’s spatial broadening and problems related to the mask fabrication. The THz field in no pump depletion approximation is analytically calculated using radiating antenna model. The analysis shows that application of ZnTe crystal allows obtaining higher THz-pulse energy than that of LN crystal, especially when long-wavelength pump sources are used. The proposed method is a promising way to develop high-energy, monolithic, and alignment-free THzpulse source.