Electrically controlled second harmonic generation of circular polarization in a single LiNbO3 optical superlattice

We demonstrate theoretically that a linearly polarized fundamental frequency wave (FW) can be effectively converted into a circularly polarized frequency doubling one in a single LiNbO3 optical supperlattice (OSL) by applying an appropriate electric field. The numerical results show that at 30°C, for a single OSL with a 91.235 V/mm applied electric field, a 100 MW/cm2 and 1064 nm laser beam can be converted into a right-handed circularly polarized (RHCP) light at 10 mm or a left-handed circularly polarized (LHCP) light at 25.747 mm. The quasi-periodic domain optimized process for minimizing the applied electric field can be obtained by changing the structural parameter, e.g., the positive or negative domain length of the OSL. It is also found that the generation of the second harmonic (SH) circularly polarized light (CPL) is insensitive to the fabrication errors of domains of the OSL; moreover, the bandwidth of conversion efficiency from the e-polarized FW to SH CPL is about 0.062 nm corresponding to a 60.85 ps FW pulse.