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3D polarization-dependent waveguide arrays in LiNbO3 crystal produced by femtosecond laser writing
摘要： Waveguide arrays are basic photonic elements in integrated optics. We propose a 3D hybrid-integrated waveguide array based on the femtosecond laser writing of lithium niobate (LiNbO3) crystals by engineering the layout of laser-induced tracks. The cross section of the structure is a cross-shaped geometry. The light propagation through this waveguide array shows polarization-dependent behaviors, which enables mode-coupling along either the vertical or the horizontal direction under excitation of linearly polarized light. This work opens new way to produce polarization-dependent optical devices in photonic systems by using femtosecond laser writing of LiNbO3.
关键词： Femtosecond laser writing,waveguide arrays,polarization-dependent devices,lithium niobate (LiNbO3)
更新于2025-09-19 17:13:59
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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) - Quadratic Solitons and their Interaction with Dispersive Waves in Lithium Niobate Nano-Waveguides
摘要： Lithium Niobate (LN) nano-waveguides combine the high nonlinearity and broadband transparency of LN with the sensitive tunability of geometric group velocity dispersion (GVD) and the strong field enhancement of subwavelength waveguides. Together these properties make the newly emerging LN nano-waveguides a compelling candidate for research into dynamics of quadratic temporal solitons, and frequency conversion processes driven by solitons interacting with dispersive waves. Emission of resonant radiation (RR) by temporal solitons due to cubic nonlinearity is known to be one of the key mechanism behind supercontinuum generation. Recent research into cubic solitons interacting with quadratic nonlinearities has found new mechanisms for tunable RR. In this work we analyse theoretically bright temporal quadratic solitons in LN nano-waveguides. Quadratic solitons consist of two co-propagating pulses at fundamental harmonic (FH) and second harmonic (SH) frequencies. The interaction between these two pulses mediated by a nonlinear material allows for the self-phase modulation crucial for soliton formation. Using the slowly varying envelope approximation the normalised fields of the FH, and SH, are described by the coupled nonlinear equations. Structures in which both harmonics experience the same sign of group velocity dispersion (GVD) are predicted to support quadratic solitons. Sub-picosecond solitons with peak powers below 100W can be excited in LN nano-waveguides. We analyse different regimes of RR emission due to non-constant GVD in FH and SH, as well as three wave mixing (TWM) radiation driven by soliton interaction with dispersive waves. Our simulations show RR in agreement with our theoretical predictions. These results suggest the possibility of temporal quadratic soliton excitation and novel mechanisms for RR relevant to frequency conversion and supercontinuum generation in LN nano-waveguides.
关键词： dispersive waves,frequency conversion,resonant radiation,nano-waveguides,supercontinuum generation,Lithium Niobate,quadratic solitons
更新于2025-09-16 10:30:52
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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) - Second-Harmonic Generation in Monolithic Lithium Niobate Metasurfaces
摘要： Second harmonic generation (SHG) in nonlinear metasurfaces has proven as a versatile tool for novel ultra-thin light sources with engineered spatial wavefronts. However, the availability of second-order nonlinear materials suitable for fabrication of such metasurfaces has so far been mainly limited to III-V semiconductors (e.g. GaAs, AlGaAs, GaP). Such systems have a limited transparency range and unusual off-diagonal second-order susceptibility tensors. These constraints have driven the search for new material platforms, including lithium niobate as one of the most promising nonlinear materials. Various approaches, such as plasmonic cavities [1], bottom-up techniques [2] and lithium niobate on insulator [3], have been recently explored, however with limited applicability. Here we propose a new design concept for second-order nonlinear metasurfaces on a monolithic substrate, which is not limited by the availability of thin crystalline films and can be applied to any non-centrosymmetric material. Our approach enables blue SHG from a monolithic lithium niobate metasurface with a conversion efficiency above 10?5 using 1 GW/cm2 pump intensity, opening new opportunities for practical designs of nonlinear metasurfaces.
关键词： second harmonic generation,monolithic substrate,Mie-type resonances,lithium niobate,nonlinear metasurfaces
更新于2025-09-16 10:30:52
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Determination of Electro-Optical Coefficients of Lithium Niobate Crystals
摘要： The electro-optical coefficients r22, rе of doped lithium niobate crystals were determined by the interference-polarization method, depending on the zinc concentration in the range 0.018-0.88 wt. %. The dependence of the electro-optical coefficient on the zinc concentration is nonlinear. The values r22, rе are determined.
关键词： conoscopic figures,electro-optic coefficient,electro-optical effect,lithium niobate crystal
更新于2025-09-16 10:30:52
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[IEEE 2019 10th International Conference on Computing, Communication and Networking Technologies (ICCCNT) - Kanpur, India (2019.7.6-2019.7.8)] 2019 10th International Conference on Computing, Communication and Networking Technologies (ICCCNT) - Electro-Optical Design and Modeling of Convolutional Code Encoder
摘要： Error detection using electro-optical methods has evolved as a new research domain in the recent years. They have proved to be more reliable than the conventional electronic methods. The presented paper describes the design and analysis of an electro-optical convolutional code encoder. The convolutional code has been long in use for the efficient detection of errors. The design has been proposed using Lithium Niobate based Mach-Zehnder Interferometer. The code bits are generated by modulo-2 addition of the input data in different patterns by the use of shift register and XOR gate. The design has successfully been tested using the beam propagation method. The calculated extinction ratio (24.82 dB), insertion loss (0.11 dB) and contrast ratio (23.26 dB) are meeting the desired values for the better performance of the device.
关键词： Mach Zehnder Interferometer,Convolution code,Lithium Niobate,Parity,Electro-optic
更新于2025-09-16 10:30:52
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Good-Quality and High-Efficiency Dicing for Thick LiNbO3 Wafers Using Picosecond Laser Pulses
摘要： Lithium niobate (LiNbO3) has become popular with applications in electronics and communication industries due to its excellent electro-optical and nonlinear properties. This paper presents the influence of laser power, repetition frequency, number of subpulses, depth of each pass, and scanning velocity in picosecond laser dicing on multiple characteristics of LiNbO3 using the Taguchi method. By means of analysis of variance and analysis of relations between the characteristics, the optimal ps-laser-dicing parameter is obtained with good quality and high efficiency, which is applied to LiNbO3 products. The result indicates that picosecond laser dicing provides an alternative to machine thick LiNbO3 wafers with narrow kerf width, micro chipping, smooth surface, and high productivity.
关键词： thick lithium niobate,picosecond laser,LiNbO3 wafers,laser dicing,dicing quality optimization
更新于2025-09-16 10:30:52
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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) - Periodic Poling with Short Period for Thin Film Lithium Niobate Waveguides
摘要： Lithium niobate (LN) is a favourable material for many applications, especially in integrated optics, due to its excellent electro-optic, acousto-optic, and nonlinear optic properties. One promising application of LN is second-harmonic generation (SHG). For enhancing the efficiency of SHG, phase matching between the interacting waves is needed, which is often realized by employing quasi-phase matching (QPM). QPM is typically realized by periodic poling of LN, i.e. the periodic flipping of the crystal orientation. The needed period is determined by the wavelengths as well as by the wave vectors of the fundamental- and the second-harmonic waves (FW and SH, respectively). For the case of backward SHG with a fundamental wavelength of 1.55 μm, where the SH wave travels in the opposite direction to the FW, typically sub-micrometer periods of the poled LN are required. Here, we demonstrate the realization of short-period QPM structures in LN-on-insulator (LNOI) thin-film substrates with a thickness of 600 nm. We aim to fabricate periodically poled LNOI (PPLNOI) waveguides with a periodicity as small as 1 μm, facilitating efficient nonlinear interaction due to the strong mode confinement.
关键词： periodic poling,second-harmonic generation,integrated optics,Lithium niobate,quasi-phase matching
更新于2025-09-12 10:27:22
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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) - Second-Harmonic Generation in Lithium Niobate Metasurfaces
摘要： Lithium niobate (LN), a birefringent crystal, is an attractive material for nonlinear photonics due to its wide transparency range and high second-order nonlinearity. Among other applications, it has been used for fabrication of fast optical modulators and nonlinear frequency converters. However, almost all implementations to date were using bulk LN crystals or waveguides. Although isolated Mie-type nanoresonators in lithium niobate have been shown very recently [1], functional metasurfaces based on densely packed arrangements of such nanoresonators have not yet been demonstrated. In order to close this gap, we have designed, fabricated and experimentally investigated a nonlinear metasurface consisting of an array of nanocubes featuring Mie-type resonances.
关键词： metasurfaces,nonlinear photonics,Mie-type resonances,second-harmonic generation,Lithium niobate
更新于2025-09-12 10:27:22
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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