High power,widely tunable femtosecond MgO:PPLN optical parametric oscillator

We demonstrate a high power,widely tunable femtosecond MgO-doped periodically poled lithium niobate(MgO:PPLN)optical parametric oscillator(OPO)at 151 MHz,pumped by a Kerr-lens mode-locked Yb:KGW laser.With a maximum pump power of 7 W,the OPO is capable of delivering as high as 2.2 W of the signal centered around 1500 nm with tunable signal spectrum ranges of 1377 nm-1730 nm at an extraction efficiency of 31.4%,which exhibits a long-term passive power stability better than 0.71%rms over 4 h.The maximum idler bandwidths of 185 nm at 3613 nm are obtained across the idler tuning ranges of 2539 nm-4191 nm.By compensating intracavity dispersion,the signal has the shortest pulse duration of 170 fs at 1428 nm.

Compact generation scheme of path–frequency hyperentangled photons using 2D periodical nonlinear photonic crystal

Hyperentanglement is a promising resource for achieving high capacity quantum communication.Here,we propose a compact scheme for the generation of path-frequency hyperentangled photon pairs via spontaneous parametric down-conversion(SPDC)processes,where six different paths and two different frequencies are covered.A two-dimensional periodicalχ^((2))nonlinear photonic crystal(NPC)is designed to satisfy type-Ⅰquasi-phase-matching conditions in the plane perpendicular to the incident pump beam,and a perfect phase match is achieved along the pump beam's direction to ensure high conversion efficiency,with theoretically estimated photon flux up to 2.068×10^(5) pairs·s^(-1)·mm^(-2).We theoretically calculate the joint-spectral amplitude(JSA)of the generated photon pair and perform Schmidt decomposition on it,where the resulting entropy S of entanglement and effective Schmidt rank K reach 3.2789 and 6.4675,respectively.Our hyperentangled photon source scheme could provide new avenues for high-dimensional quantum communication and high-speed quantum information processing.

Tunable Second Harmonic Generation with High Conversion Efficiency in Periodically Poled Lithium Niobate Channel Waveguide

The experiment on quasi-phase-matched second harmonic generation (SHG) in a channel waveguide was reported. The waveguide was made by annealed proton exchange in the periodically poled lithium niobate (PPLN) with the period of PPLN of 14.9 μm, which was designed for cascading wavelength conversion in dense wavelength division multiplexer optical communications. The measurement results of SHG conversion efficiency as a function of fundamental wavelength at room temperature fit well to sinc^2 shape. The peak of SHG conversion efficiency was 75%·W~ -1 ·cm~ -2 as well as reported. The relationship between the center fundamental wavelength and temperature shows that SHG can be effectively tuned by the temperature in PPLN waveguide.

Generation of tripartite Einstein-Podolsky-Rosen steering by cascaded nonlinear process

A scheme is proposed to generate genuine tripartite Einstein-Podolsky-Rosen(EPR)steering in cascaded nonlinear process of the fourth-harmonic generation.The second-harmonic is generated by the first double-frequency process in an optical superlattice.Then,the fourth-harmonic is produced by the second cascaded double-frequency process through quasi-phase-matching technique in the same optical superlattice.The genuine tripartite EPR steering among the pump,the second-harmonic,and the fourth-harmonic beams can be obtained by this cascaded nonlinear process according to a criterion for genuine multipartite quantum steering.The quantum steering properties are discussed by adjusting the parameters related to the cascaded nonlinear system.The present research provides a reference scheme and data for obtaining good multipartite EPR steering in experiment and can advance the applications of quantum steering in the quantum information processing.

Experimental investigation of nonlinear process based on cSHG/DFG in PPLN waveguide

Effects of second harmonic generation (SHG) and cascaded second harmonic generation/difference frequency generation(cSHG/DFG) based on the quasi-phase-matching (QPM) condition in periodically poled lithium niobate (PPLN) waveguide were investigated experimentally. SHG conversion efficiency of-13.6 dB and QPM bandwidth of 0.45 nm were achieved using a 16.1 dBm power of fundamental wave at 1550.4 nm. Using pulsed all-fiber passive mode locked laser and tunable continuous wave laser,cSHG/DFG effect utilized for optical sampling was observed. Conversion efficiencies were calculated, and 11.88 nm-wide QPM bandwidth was achieved through changing the wavelength of input signal. Conversion efficiency of cSHG/DFG effect increased linearly with the total injected power.