Generation of UV-Vis correlated photon pairs using PP-LaBGeO₅

The second-harmonic generation (SHG) and spontaneous parametric down-conversion (SPDC) output of a periodically poled bulk LBGO crystal was measured. The SHG efficiency was measured to be (3.52 ± 0.04) × 10^-3 %/W. The SPDC output was temporally characterized by a Hanbury-Brown-Twiss (HBT) interferometer; a maximum coincidence-to-accidental ratio (CAR) of 244 and pair generation rate (PGR) of (1.45 ± 0.47) × 10⁶ pairs s^-1 mW^-1 were measured. An EMICCD spectrometer was used to measure the spectral characteristics of the PP-LBGO source. Of the four gratings tested, one operational grating (poling period = 2.10 µm) of the PP-LBGO device produced a temperature-tunable spectrum of entangled photon pairs centered at 532 nm, with signal and idler photons being tunable from 507 to 556 nm, respectively. The work paves the way for future wave-guided entangled-photon sources reaching UV wavelengths using periodic poling.