Nanosecond nonlinear Čerenkov conical beams generation by intracavity sum frequency mixing in KTiOAsO4 crystal

Nanosecond Čerenkov-type conical beam at 628 nm is obtained by intracavity sum frequency mixing (SFM) of 1064 and 1534 nm in KTiOAsO(4) (KTA) crystal. The 1534 nm signal generated by the KTA optical parametric oscillation (OPO), respectively, interacts with the orthogonally polarized 1064 nm radiations by the nonlinear Čerenkov SFM, emitting two red rings with cone angles of 11.4° and 16.0°, respectively. Multidomain structure observed in the KTA crystal can account for the corresponding phenomenon. The KTA crystal simultaneously serves as OPO medium and Čerenkov radiation emitter in this experiment, indicating that it is a promising multifunctional nonlinear crystal material. Furthermore, the naturally grown crystal combined with intracavity Čerenkov-type configuration will provide a simple and compact approach, opening a door for the wide application of nonlinear Čerenkov radiation sources due to its cost-effectiveness.