Walk-off Compensated 266-nm Generation with Two β-BaB2O4 Crystals

Highly efficient deep ultraviolet generation by sum-frequency mixing in a BBO crystal pair

“…The value of the walk-off angle in our case is 3.675 AE . Although in WOC arrangement the effective length of the crystal is doubled, the experimental value of the enhancement factor obtained in BBO crystal in our experiment as well as the reported value of Droz et al [11] are less than its theoretically expected value of 4.0 and also less than the value reported in KTP for SHG [9,10]. One of the reasons for this may be that, due to the large value of the birefringence of BBO, the angular bandwidth is quite small compared to that of KTP which reduces the conversion efficiency even for small misalignments in phase-matching angle.…”

“…Although theoretically in the configuration C an enhancement by a factor of 4 relative to configuration A is expected, we could achieve only half the value. Droz et al [11] reported the walk-off compensated fourth harmonic generation (266 nm) of Nd : YAG radiation in BBO crystal and they also achieved similar enhancement in the conversion efficiency in the WOC arrangement over the single crystal. For the calculation of conversion efficiency (η) for THG we have used the relation η E 3 Ô´E 1 E 2 µ.…”

“…The phase-matching direction was in the XZ plane and the SHG process was o · e o, with the walk-off angle of 2.5 AE . Droz et al [11] reported the generation of 266 nm radiation with two BBO crystals in WOC arrangement and obtained only an increase by a factor 2.0 in the WOC arrangement over the single crystal case. The value of the walk-off angle in their case was 4.879 AE .…”

“…Thus the birefringent walk-off limits the effective interaction length and hence limits the conversion efficiency of birefringently phase-matched NLO processes. To overcome the deleterious effect of such walk-off, several authors [8][9][10][11] use a pair of crystals in walk-off compensated arrangements. In this configuration, the optic axis directions of the two crystals are kept in alternating directions.…”

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

“…To this end, the spatial walk-off is compensated in an YVO 4 plate (having the walk-off angle above 6°). This solution is much more robust than the scheme based on inverted nonlinear crystals 8 , where the two crystals have to be independently tilted. The temporal walk-off is compensated with a birefringent plate – a calcite crystal in our case.…”