Visible dual-wavelength light generation in optical superlattice Er : LiNbO3 through upconversion and quasi-phase-matched frequency doubling

Optical superlattice Er:LiNbO3 was fabricated by inducing a periodic ferroelectric domain structure into the crystal during the growing process. Because of the combination of the nonlinear optical properties of LiNbO3 and the spectral properties of Er3+, the crystal can simultaneously emit the second harmonic light through quasi-phase matching and the green light through upconversion at room temperature. Pumped by infrared diode lasers, violet-and-green and blue-and-green light generation was demonstrated in two samples. The detailed absorption spectrum and emission spectrum of upconversion were measured. The possible physical mechanism was discussed.