Second harmonic microscopy of poled x-cut thin film lithium niobate: Understanding the contrast mechanism

Abstract

Thin film lithium niobate is of great recent interest and an understanding of periodically poled thin-films is crucial for both fundamental physics and device developments. Second-harmonic (SH) microscopy allows for the non-invasive visualization and analysis of ferroelectric domain structures and walls. While the technique is well understood in bulk lithium niobate, SH microscopy in thin films is largely influenced by interfacial reflections and resonant enhancements, which depend on film thicknesses and the substrate materials. We present a comprehensive analysis of SH microscopy in x-cut lithium niobate thin films, based on a full three dimensional focus calculations, and accounting for interface reflections. We show that the dominant signal in back-reflection originates from a co-propagating phase-matched process observed through reflections, rather than direct detection of the counter-propagating signal as in bulk samples. We can explain the observation of domain structures in the thin film geometry, and in particular, we show that the SH signal from thin poled films allows to unambiguously distinguish areas, which are completely or only partly inverted in depth.

References in corpus (10)

• Ultrahigh-efficiency second-harmonic generation in nanophotonic PPLN waveguides
• Hybrid Silicon Photonic-Lithium Niobate Electro-Optic Mach-Zehnder Modulator Beyond 100 GHz Bandwidth
• Ultra-low loss integrated visible photonics using thin-film lithium niobate
• Conduction of topologically-protected charged ferroelectric domain walls
• Phenomenological theory of a single domain wall in uniaxial trigonal ferroelectrics: lithium niobate and lithium tantalate
• Structural Domain Walls in Polar Hexagonal Manganites
• Highly efficient frequency conversion with bandwidth compression of quantum light
• Quantum frequency conversion of memory-compatible single photons from 606 nm to the telecom C-band
• Toolbox for the design of $LiNb{O}_3$-based passive and active integrated quantum circuits
• Quantum frequency conversion of quantum memory compatible photons to telecommunication wavelengths

Cited by in corpus (11)

• Integrated photonics on thin-film lithium niobate
• Entangled photon-pair generation in periodically-poled thin-film lithium niobate waveguides
• Intense optical parametric amplification in dispersion engineered nanophotonic lithium niobate waveguides
• Ultra-low-power second-order nonlinear optics on a chip
• Tunable and efficient ultraviolet generation in nanophotonic lithium niobate
• Highly efficient visible and near-IR photon pair generation with thin-film lithium niobate
• Quantifying the Coherent Interaction Length of Second-Harmonic Microscopy in Lithium Niobate Confined Nanostructures
• Probing Ferroelectric Phase Transitions in Barium Titanate Single Crystals via $in-situ$ Second Harmonic Generation Microscopy
• In-situ SHG microscopy investigation of the domain-wall-conductivity enhancement procedure in lithium niobate
• Multi-scale second harmonic generation microscopy of ferroelectric domains in x-cut thin-film lithium niobate
• On-Chip Generation of Co-Polarized and Spectrally Separable Photon Pairs