Scaling up the energy of THz pulses created by optical rectification

Department of Experimental Physics, University of Pécs, Fuenfkirchen, Baranya, Hungary
Optics Express (Impact Factor: 3.49). 08/2005; 13(15):5762-8. DOI: 10.1364/OPEX.13.005762
Source: PubMed


The possibility for up-scaling the energy of sub-ps THz pulses generated by tilted pulse front excitation is demonstrated. Using 150-fs-long 500 muJ optical pump pulses at 800 nm up to 240 nJ THz pulse energy has been achieved. For a 1.2 mm2 pump spot area, the energy conversion efficiency of pump energy to THz pulse energy had a maximum of 5 x 10-4 at 300 muJ pump pulse energy. The corresponding photon conversion efficiency amounts to 10 %. For comparison, the maximum attainable THz pulse energy was limited to 3.1 nJ if a line focusing excitation geometry was utilized. This limit was reached at 32 muJ pump energy. For the latter configuration the THz energy dropped for larger pump energies. The tilted pulse front excitation allows further up-scaling of the THz pulse energy by using a larger pump spot size and still stronger pump pulses.

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    • "Blanchard et al [9] obtained 1.5 µJ THz pulses using a large-aperture ZnTe crystal directly pumped by a Ti: sapphire amplifier at 100 Hz. Fülöp et al [10] made use of the tilted pulse front pump (TPFP) technique [7] [8] [11] to generate 125 µJ high-energy THz pulses from a LiNbO 3 crystal pumped by 1 1612-2011/13/125404+05$33.00 c a Ti: sapphire amplifier at 10 Hz. However, the utilization of these high-energy broadband THz sources is limited due to the large scale and complex operation of the femtosecond amplification systems, and the low repetition rate. "
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    • "A way to solve the problem of propagation velocity mismatch and increase the interaction length is to use tilted pulse front excitation. A conversion efficiency of 5 × 10 −4 and a THz average power of 240 µW was reported in [15] using bulk lithium niobate pumped by optical pulses from a 1 kHz Ti:Sapphire oscillator–regenerative amplifier system with 500 mW of average power. Another approach to increase the efficiency of OR is to use quasi-phase-matched (QPM) nonlinear materials, as was first demonstrated with periodically poled lithium niobate (PPLN) [13], [20]. "
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    • "For high-dielectric materials, which offer attractive electro-optic coefficients and other parameters, velocity matching cannot be achieved collinearly. For such a situation, tilting of the pump pulse front has been proposed [5], and applied [6] to reach velocity matching in LiNbO 3. Very recently, this method generated THz pulses with 240 nJ of energy [7]. "
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