A segmented RCS data measurement and processing method was proposed. Attenuation elements were introduced to improve the measurable signal range of the measurement system, and the accuracy was improved by segmented calibration of data. Based on this method, the warhead model was measured in a large dynamic range up to 63 dB. A compact-field radar cross section (RCS) measurement system applicable in the high-frequency terahertz range was built based on a seed-injected terahertz parametric generator (ips-TPG). The reliability of the system was verified by taking smooth stainless-steel spheres as the standard calibration objects and the RCS measurement of common target was performed at a high frequency point at 5 THz. The error between the measured and theoretical results was less than 4 dB.
A compact and flexible dual-wavelength eye-safe intracavity optical parametric oscillator (IOPO) configuration driven by a coaxially end pumped laser was proposed. Two fundamental waves were provided by a coaxially end pumped Qswitched dual-wavelength laser with combined two laser crystals, and the OPO cavity was placed inside the laser cavity for efficient conversion. Theoretical simulations showed that the power ratio for each signal wave, as well as the time interval between two pulses at different wavelengths, were both tunable by tuning the pump focusing depth or pump wavelength. Experimental results were performed with combined laser crystals (Nd:YAG and a-cut Nd:YLF) and a nonlinear crystal (KTA), demonstrating coincident conclusions. The maximum OPO output power was 724 mW (388 mW at 1506 nm and 336 mW at 1535 nm) with the LD pump power of 10 W at 6 kHz, corresponding to the opticaloptical conversion efficiency of 7.24%. As there was no gain competition between two fundamental waves, stable signal output could be obtained. Moreover, various wavelength pairs can be generated by using different laser crystal combinations. It is believed that this is a promising method for simultaneously generating dual-wavelength eye-safe lasers pulses.
Theoretical simulations were carried out to evaluate the properties of terahertz (THz) generation in β-BaTeMo2O9 (βBTM) crystal by stimulated polariton scattering (SPS) process. The effects of different polariton modes on THz generation were analyzed, from which we determined the optimal crystal design and polarizations of the coupled waves. The dispersion and absorption characteristics of these vibration modes were also given based on the first-principle calculation and correlation Raman spectrum. Finally, the angle phase matching property and THz-wave gain were calculated. Simulation results showed that β-BTM is a kind of potential material for high-power tunable THz generation.
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