Terahertz-wave Generation Using Periodically Poled Near-stoichiometric Lithium Niobate Optical Waveguide

Project: Research

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The excellent electro-optic, acousto-optic, and nonlinear optical properties of congruent ([Li]/[Nb]~0.945) lithium niobate (LiNbO3or LN) optical waveguides have led to the development of high functionality devices and optical integrated circuits. However, serious photorefractive damage in both visible and near infrared wavelength regions limits the applications of these devices. Recently, we have developed a novel fabrication process based on diffusion process and vapor transport equilibration (VTE) treatment, and realized near-stoichiometric (NS, [Li]/[Nb]>0.98) titanium (Ti) diffused LN (Ti:LN) and Ti diffused magnesium oxide (MgO) doped LN (Ti:Mg:LN) waveguides. The NS waveguide exhibits similar bulk NS material properties and has a number of advantages over congruent material. Most importantly, the NS Ti:Mg:LN waveguide exhibits lower photorefractive damage susceptibility, enabling the device to operate in the visible and near infrared wavelength region.In this proposal, terahertz (THz) generator based on a new class of nonlinear integrated optical device using NS Ti:Mg:LN waveguide will be fabricated, confirming and demonstrating the practical applications of NS LN device and THz technology. The device to be fabricated is a quasi-phase-matched (QPM) difference frequency generator (DFG) utilizing periodically poled NS Ti:Mg:LN strip waveguide. The DFG uses a commercially available high-power 780nm wavelength laser diode as the pump source, and an external cavity laser with 1500-1558nm output wavelength range as the signal source. The device functions simultaneously as two coherent radiation sources, generating tunable, narrowband near-infrared (NIR) waves and THz waves. The periodically poled NS Ti:Mg:LN strip waveguide device combines a number of merits, such as 1) negligible photorefractive damage to the 780 nm wavelength pump light, 2) high pump light intensity is possible leading to strong nonlinearity in the waveguide structure, 3) low coercive electric field strength, 4) low MgO doping concentration requirement, hence superior material homogeneity and highquality ferroelectric micro-domain, 5) NS material exhibits higher nonlinear optical coefficient d33, and 6) high DFG conversion efficiency due to the collinear phase matching feature of the strip waveguide structure and long interaction length.THz radiation is the electromagnetic wave in the frequency interval from 0.3 to 10 THz (1 mm-30μm wavelength), and is a very attractive spectral region for a variety of advanced applications. Unfortunately there is a lack of appropriate sources and progress has been held up. THz science and technology is currently the hot spot and frontier in scientific research, and has great potential for material characterization, spectroscopy, communication, imaging and tomography, nondestructive, and biomedical applications.


Project number9042055
Grant typeGRF
Effective start/end date1/01/1527/06/18

    Research areas

  • Terahertz Generation,Lithium Niobate Device,Integrated Optics,Nonlinear Optical Device,