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Simultaneous generation of two THz waves with bulk LiNbO3 and four THz waves with PPLN by coupled optical parametric generation
摘要： We present a theoretical research concerning simultaneous generation of two terahertz (THz) waves with bulk LiNbO3 and four THz waves with periodically poled LiNbO3 (PPLN) by coupled optical parametric generation (COPG). First, we investigate collinear phase matching of COPG generating two orthogonally polarized THz waves with two types of phase matching of o = e ? e and o = e ? o with bulk LiNbO3. The two orthogonally polarized THz waves are generated from stimulated polariton scattering (SPS) with A1 and E symmetric transverse optical (TO) modes in bulk LiNbO3, respectively. Then, we ?nd that perturbations of phase mismatch for o = e ? e and o = e ? o can be compensated by a same grating vector of PPLN. As a result, four THz waves are simultaneously generated with a PPLN crystal and a pump laser. We calculate third-order nonlinear optical coef?cients of o = e ? o generating THz waves from E symmetric TO modes. The intensities of four THz waves are calculated by solving coupled-wave equations. The calculation results demonstrate that four THz waves with high intensities can be simultaneously realized by COPG with existing laser technology and crystal fabrication technology.
关键词： Stimulated polariton scattering,Coupled optical parametric generation,Periodically poled LiNbO3,Terahertz wave
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodically Poled MgO:LiNbO <sub/>3</sub> , MgO:LiTaO <sub/>3</sub> and KTiOPO <sub/>4</sub> Crystals for Laser Light Frequency Conversion
摘要： We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate (LN), lithium tantalate (LT) and potassium titanyl phosphate (KTP) based on the experimental study of the domain structure evolution by the complementary high-resolution domain visualization methods [1]. The crystals with tailored periodically poled domain structures (PPLN and PPLT) produced with nano-scale period reproducibility have been used for Second Harmonic Generation (SHG) and Optical Parametric Oscillation (OPO) based on quasi-phase-matched nonlinear optical wavelength conversion. The periodical poling techniques were based on the deep experimental and theoretical study of the mechanisms of domain growth and domain wall motion in these crystals. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field [2,3]. The kinetic maps allowed analyzing the spatial distribution of the wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls in KTP differed by their orientation. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. It was shown that the polarization reversal in KTP with artificial surface dielectric layer leads to formation and growth of the large number of narrow domain streamers oriented strictly along [010] direction with about ten times higher velocity (6-60 mm/s) than the domain walls (2-5.5 mm/s). Study of the static domain structures demonstrated that the streamers are formed by [100] and [010]-oriented domain walls. The streamer width was about 500 nm and the distance between the neighboring streamers – about 100 nm. The global domain kinetics during the poling process at elevated temperatures has been studied by in situ optical observation which allowed us to reveal the main characteristics of the poling process at elevated temperatures. It has been shown that the periodically poled area propagates from the edges to the middle of the electrode pattern. The interfering effect of essential increasing of the bulk conductivity during poling has been studied and several ways to overcome this problem have been proposed. The static domain images revealed by chemical etching were visualized by optical and scanning probe microscopy. The influence of the spatially nonuniform electric field on the domain kinetics has been studied for finite-size electrodes of various shapes. The key role of the field anomalies at the electrode corners, ends, and edges in the nucleation process has been revealed by computer simulations and confirmed experimentally. Essential acceleration of the switching at the boundaries of the electrode patterns (so called “pattern effect”) has been explained. The optimized design of the electrode pattern was based on experimental results and computer simulation. The fan-out periodical domain structures created in 3-mm-thick MgO:LN wafers allowed us to realize the widely tunable OPO generation with the signal wave from 2.5 to 4.5 μm using the 1.053 μm pump. The possibility of producing the elements with thickness up to 10 mm for high-power application has been discussed. The peridical domain struture with period of 40 μm was created in KTP single crystals for OPO generation at 2.4 μm using the 1.053 μm pump. The abilities and perspectives of producing the elements with submicron periods has been discussed. The optimized periodical poling techniques have been used for creation of ridge waveguides in periodically poled MgOLN single crystals. The high-index contrast of obtained multi-mode waveguides allowed tuning of the SHG wavelength from 510 to 570 nm using the 1.064 μm pump. The deep knowledge of the domain structure evolution at elevated temperatures and relaxation of the high bulk conductivity along the charged domain walls MgO:LN and MgO:LT allowed us to optimize the periodical poling technique and to produce high-fidelity domain patterns.
关键词： domain structure evolution,MgO:LiTaO3,KTiOPO4,Second Harmonic Generation,Optical Parametric Oscillation,MgO:LiNbO3,Periodically Poled
更新于2025-09-23 15:19:57
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[IEEE 2019 Joint Conference of the IEEE International Frequency Control Symposium anEuropean Frequency and Time Forum (EFTF/IFC) - Orlando, FL, USA (2019.4.14-2019.4.18)] 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC) - Numerical Simulation on Periodically Poled Lithium Niobate Transducers on Rotated Cuts
摘要： Rotated cut Periodically Poled Structures (PPS) are a promising technology allowing to generate bulk acoustic waves from ferroelectric domains periodicity. In this work, evolution of frequency-period product and k2 is investigated in function of the substrate orientation. Numerical computation points out Periodically Poled Lithium Niobate (PPLN) transducers with k2 up to 15% as well as frequency-period factor up to 12600m.s-1. Experimental comparison with the numerical computation for a (YXl)/64° PPLN transducer shows a relative difference of the frequency-period product less than 5%.
关键词： Lithium Niobate,Periodically Poled Structures,Rotated cuts,Electro-acoustic transducers,Bulk Structure
更新于2025-09-19 17:13:59
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Characterization of Broadband Spontaneous Parametric Down-Conversion in Periodically Poled Materials
摘要： Spontaneous parametric down-conversion (SPDC) is one of the most important sources for entangled or correlated photon pairs, which are the foundation of the emerging fields of quantum-optical imaging and spectroscopy. Using periodically poled materials as an SPDC-source allows broad emission spectra in widely tunable wavelength ranges in an efficient and walk-off-free process. For applications that employ nonlinear interference setups [1,2], maximum interferometric contrast is only achieved when signal and idler modes are overlapped precisely in the second crystal. Thus, accurate knowledge of the spectral-angular characteristic of SPDC is crucial for designing such devices. In our work, we extend an analytic approach introduced by Byer and Harris [3] and develop an application- oriented model for the signal power density of broadband SPDC. For spectrally broad emission, non-collinear phasematching has to be described properly. Here, the finite pump diameter is taken into account by introducing an angular dependent effective interaction length. As an exemplary case, we calculate the angular characteristics, the spectral power density and the total signal power for SPDC in periodically poled lithium niobate pumped at 532 nm. For verification, we compare the calculations to experimental results obtained with a 2 cm long, 5 % MgO-doped lithium niobate crystal at 40 °C crystal temperature. The crystal contains 11 poling channels with periods ranging from 8.2 μm to 11.2 μm. It is pumped by a narrowband laser with 2 W power at 532 nm wavelength focused to a beam waist of 120 μm. Using the different poling periods, we cover a signal wavelength range of 613 nm to 750 nm, which corresponds to correlated idler wavelengths ranging from 4 μm to 1.8 μm. In figure 1a, the calculated spectral power density for different poling channels (solid lines) is compared to measured spectra. To account for the angular-dependent coupling efficiency to the spectrometer fiber input, each measured spectrum is scaled with a constant factor to the best fit with the calculated power density and thus only allows a qualitative comparison. The quantitative comparison of the calculated (solid lines) and measured (black dots) total signal power for the different channels as a function of the collinear (peak) signal wavelength in figure 1b) further verifies our calculations. The presented analytical model is easily applicable to a wide range of experimental configurations for SPDC in periodically-poled crystals, without the need for time-consuming numerical simulations. The exact knowledge of the spatial and spectral structure of SPDC emission allows predictions on design criteria for functionalized devices that employ SPDC as a photon pair source.
关键词： spectroscopy,periodically poled materials,SPDC,Spontaneous parametric down-conversion,quantum-optical imaging
更新于2025-09-16 10:30:52
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Proceedings of Meetings on Acoustics [Acoustical Society of America 172nd Meeting of the Acoustical Society of America - Honolulu, Hawaii (28 November – 2 December 2016)] - Distribution of point defects in phononic periodically poled lithium niobate
摘要： The concentration of point defects is investigated along the neighboring domains in a ZX-cut periodically poled lithium niobate (PPLN) plate. PPLN is a ferroelectric phononic crystal (FPC) in which the inversion of polarization occurs across the interdomain wall. The spectra of photoluminescence (PL) are recorded along the domain structure parallel to the x-axis, at room temperature. The PL spectra reveal a nonuniform distribution of defects along the PPLN. The striking result is that some defects have narrow extrema in PL-intensity right in the interdomain wall location. The spread in PL intensity from the average is higher in PPLN when compared to single crystal lithium niobate. Engineering application of these findings may be new non-destructive characterization method of ferroelectric phononic crystals.
关键词： photoluminescence,phononic periodically poled lithium niobate,point defects,ferroelectric phononic crystals
更新于2025-09-12 10:27:22