Cherenkov phase-matched terahertz wave generation using ridge-type waveguide

We present efficient terahertz (THz)-wave generation from waveguide propagation using Cherenkov-type radiation with non-linear optical (NLO) crystal. This approach presented the following advantages: 1) many crystals can be used as THz-wave emitters; 2) It is not necessary to satisfy the phase matching condition inside crystal. and 3) THz wave generation is not suppressed by the absorption in the crystal. We demonstrated THz generation using a ridge-type LiNbO₃ waveguide with a thickness of 3.8 μm. We obtained THz-wave generation with an ideal temporal half-cycle pulse and a wide tuning range, which is applied to reflection tomography imaging.