Theoretical analysis of cascaded optical parametric oscillations generating tunable terahertz waves

Phonon-assisted nonlinear optical processes in ultrashort-pulse pumped optical parametric amplifiers

“…Recently, the topic of coherent interactions between electromagnetic radiation and the vibrational modes in the NLO crystals has been receiving a revived interest in light of the ongoing developments in terahertz parametric oscillators (TPOs) 5 6 7 8 9 10 11 12 and Raman lasers 13 14 . In this regard, KTP and its isomorphs such as potassium titanyl arsenate (KTiOAsO 4 , KTA), RbTiOPO 4 etc., represent a versatile group of NLO materials that possess relatively high 2 nd -order nonlinear coefficients 15 , wide spectral transparency window (~400–4500 nm for KTP; ~350–5000 nm for KTA) 16 17 , and relatively high damage thresholds (reaching 100’s of GW/cm 2 in femtosecond regime 16 ).…”

“…Moreover, one can also distinguish a group of NLO processes that involve the above-mentioned TO-phonon modes and that are inherently connected to the third-order optical nonlinearity χ (3) . These are represented primarily by: 1) the stimulated Raman scattering (SRS) and Raman lasing; 13 14 28 and 2) the stimulated phonon-polariton scattering (SPS) and generation of laser beams in the terahertz (THz) frequency range 7 9 10 12 29 .…”

Multiple-beam output of a surface-emitted terahertz-wave parametric oscillator by using a slab MgO:LiNbO_3 crystal

“…Terahertz-wave parametric oscillators (TPOs) have been demonstrated as efficient terahertz wave sources [1][2][3][4][5][6][7]. They have the advantages of room temperature operation, compactness, high peak power, ease of use, wide tunable range, and narrow linewidth [1,2,5] and have potential applications in spectroscopy, imaging, and direct studies of molecular vibrational and rotational states.…”

“…Nevertheless, in the conventional SE-TPOs [6,11,12], only the THz-wave radiation generated near the total reflection area of the pump and the Stokes beams can be emitted. Most energy generated at other interaction areas can never escape from the crystal.…”