Research Output
The influence of crystal orientation variation towards the modal phase matching condition in Lithium Niobate on insulator waveguide
Phase matching in microstructured lithium niobate on insulator waveguides
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Publication
We systematically demonstrate the influence of crystal orientation towards the phase matching condition in Lithium Niobate on insulator waveguide structure. The phase matching condition is one of the important elements that required prior to the development of ultracompact photonic integrated circuit. This is achieved as the effective refractive indices of fundamental mode, TE00 at pump wavelength overlapped with the second order mode, TE20 of second harmonic wavelength. With a proper selection of crystal orientation, the perfect phase matching condition is achievable over a broader telecommunication wavelength, hence, improve the efficiency of the device. In this work, we examine the phase matching interaction over the x-, y- and z- cut LNOI crystal structure. From the numerical analysis, the significant variation of phase matching width over crystal orientation is demonstrated with x-cut LNOI shows a strong ability to achieve the modal phase matching at narrower width, allowing the realization of ultracompact waveguide fabrication. Interestingly, z-cut LNOI, offers a broader range of phase matching wavelength tunability which beneficial for the development of optical modulator. Eventually, the y-cut LNOI suit for the fabrication of the wavelength-independent optical devices such as surface acoustic waveguide.
Publication
The recent development of the Lithium Niobate on Insulator (LNOI) fabrication process has opened a bright future for integrating ultra-compact photonic circuits. Due to its excellent nonlinear properties, as a waveguide material, Lithium Niobate supports nonlinear optical processes including efficient sum frequency generation and second harmonic generation. To enhance these effects, precise control of mode confinement and modal phase matching is required. In this work, we engineer an LNOI waveguide to match the effective refractive indices of the fundamental mode, TE00 at the fundamental wavelength and second-order mode, TE20 at the second harmonic wavelength. As waveguide geometry plays an essential role, optimization of waveguide parameters is crucial for the design of high-performance, feasible devices. Here, we numerically engineer and characterize the influence of rib waveguide geometry parameters including etching depth, D , width, W and sidewall angle, θ on the phase matching condition. We find that the waveguide phase matching condition is most susceptible to variations in the sidewall angle. For the optimized parameter values of {D,θ}={450nm,10o} , the phase-matching wavelength tunability is achieved through the waveguide width control.