No abstract

Future quantum information networks operated on telecom channels require qubit transfer between different wavelengths while preserving quantum coherence and entanglement. Qubit transfer is a nonlinear optical process, but currently the types of atoms used for quantum information processing and storage are limited by the narrow bandwidth of up-conversion available. Here we present the first experimental demonstration of broadband and high-efficiency quasi-phase matching second harmonic generation (SHG) in a chip-scale periodically poled lithium niobate thin film. We achieve large bandwidth of up to 2 THz for SHG by satisfying quasi-phase matching and group-velocity matching simultaneously. Furthermore, by changing film thickness, the central wavelength of quasiphase matching SHG bandwidth can be modulated from 2.70 µm to 1.44 µm. The reconfigurable quasi-phase matching lithium niobate thin film provides a significant on-chip integrated platform for photonics and quantum optics. OCIS Codes:(130.3730) Lithium niobate; (310.6845) Thin film devices and applications; (190.2620) harmonic generation and mixing; (190.4390) Nonlinear optics, integrated optics.

An efficient two-dimensional arbitrary harmonic wavefront shaping has been demonstrated in amplitude-type nonlinear photonic crystals, where the phase-matching condition is fulfilled through the birefringence and nonlinear Raman–Nath effects in longitudinal and transverse phase matching, respectively. The binary modulated nonlinear photonic crystal was fabricated by femtosecond laser micromachining based on binary computer-generated holograms. Three second-harmonic Hermite–Gaussian beams, H G 10 , H G 11 , and H G 12 , were achieved by pumping a nanosecond pulsed fundamental Gaussian beam, with the measured normalized conversion efficiency of 8.4 % W − 1 c m − 2 in the first diffraction order of the H G 11 structure. The amplitude-type nonlinear photonic crystal opens wide possibilities in the field of efficient harmonic beam shaping and mode conversion.

The computer-generated holography technique is a powerful tool for three-dimensional display, beam shaping, optical tweezers, ultrashort pulse laser parallel processing, and optical encryption. We have realized nonlinear holography in ferroelectric crystals by utilizing spatial light modulators in our previous works. Here, we demonstrate an improved method to realize second-harmonic (SH) holographic imaging through a monolithic lithium niobate crystal based on binary computer-generated holograms (CGHs). The CGH patterns were encoded with the detour phase method and fabricated by femtosecond laser micromachining. By the use of the birefringence phase-matching process in the longitudinal direction, bright nonlinear holograms can be obtained in the far-field. The realization of SH holography through monolithic crystal opens wide possibilities in the field of high power laser nonlinear holographic imaging.

Lithium tantalate (LT) is one of the most attractive optical nonlinear materials, as it possesses a high optical damage threshold and great UV transparency (0.28–5.5 µm). Recently, optical grade LT nanoscale film was developed. Here a high-quality-factor ( ∼ 10 5 ) LT microdisk resonator based on LT-on-insulator (LTOI) film is fabricated by utilizing focused ion beam (FIB) milling. 2 µW output second-harmonic waves are achieved in the LTOI microdisk at about 500 mW input power. Cascaded third-harmonic generation is also observed in the fabricated device. This work may pave the way for LTOI in integrated photonic chips.