Microwave emission by nonlinear crystals irradiated with a high-intensity, mode-locked laser

Abstract

We report on the experimental investigation of the efficiency of some nonlinear crystals to generate microwave (RF) radiation as a result of optical rectification (OR) when irradiated with intense pulse trains delivered by a mode-locked laser at 1064 nm. We have investigated lithium triborate (LBO), lithium niobate (LiNbO 3 ), zinc selenide (ZnSe), and also potassium titanyl orthophosphate (KTP) for comparison with previous measurements. The results are in good agreement with the theoretical predictions based on the form of the second-order nonlinear susceptibility tensor. For some crystals we investigated also the second harmonic generation (SHG) to cross check the theoretical model. We confirm the theoretical prediction that OR leads to the production of higher order RF harmonics that are overtones of the laser repetition rate.

Generation of microwave fields in cavities with laser-excited nonlinear media: competition between the second- and third-order optical nonlinearities

“…Although it is known that χ (2) must be zero in crystals possessing the inversion symmetry [15], this is true, as a matter of fact, in the idealized case of infinite ideal crystals, whereas real crystals of finite size do show the secondorder nonlinear effects, either due to the presence of some impurities/defects or due to the loss of the inversion symmetry in the regions nearby the surface [16][17][18][19][20]. The generation of microwave radiation in the cavity containing different nonlinear materials with high χ (2) coefficients, irradiated with intense infra-red pulse trains, was reported in [21,22]. Although this phenomenon can find various useful applications, it should be considered as a spurious effect in the DCE experiments, because the related mechanism can be considered as totally classical, i.e.…”