A gain-boosted terahertz-wave parametric generator (TPG) in high frequency tuning range based on MgO-doped nearstoichiometric LiNbO3 (MgO:SLN) crystal has been demonstrated with 1064 nm nanosecond pulsed laser pumping. The pulse-seed is provided by nanosecond singly resonant near-degenerated KTP optical parametric oscillator with the wavelength range of 1068.08 nm to 1084.76 nm. The terahertz tuning range of 0.97 THz to 4.07 THz was achieved. The maximum THz wave output signal was 4285mV at 1.82 THz under the pump energy of 180 mJ and pulse-seed energy of 20.2 mJ. During the frequency range of 1.25 THz to 3.43 THz, the THz output energies were larger than 2000mV. Compared with the maximum THz output energy, the THz energy attenuation factors of 0.55 dB, 1.71 dB and 3.31 dB were realized in pulse-seeded TPG at 2.5 THz, 3.0THz and 3.5THz, respectively. The significantly increasing of THz gain in high frequency range (<2.5 THz) was achieved.
Recently, terahertz (THz) computed tomography (CT) has emerged as a possible effective technique for 3D structural information detection. However, THz-CT is difficult to be applied to high refractive index object, due to the severe refraction phenomenon occurred during the acquisition of raw data. We propose a novel experimental procedure to solve this problem. Including the use of a sink filled with liquid whose refractive index is close to the sample, and a correction algorithm to eliminate the noise of liquid. The proposed method is applied to the high-density polyethylene samples of different shapes.