Search

Birefringence, quantified as the maximum effective index difference of two orthogonally polarized modes, is one of the key characteristics of Lithium Niobate on Insulator (LNOI) waveguide devices. As LNOI optical properties strongly depend on the polarization of the propagating light beam, achieving the zero‐birefringence condition (ZBC) is highly desired. In this work, a rib LNOI waveguide is designed, and the influence of geometrical dimensions on the birefringence is characterized. From the result, the slab's height is found to be the dominant geometrical factor that significantly contributes to the birefringence, with an optimum slab's height found at 50 nm. For this optimized value, the influence of width and wavelength on birefringence are characterized. The analysis is extended to investigate the properties of group indices that can result in the temporal walk‐off phenomenon. This phenomenon can significantly impact the performance of single‐photon devices, as it can cause a polarization mismatch between the incident photon and the polarization properties of the medium, resulting in reduced efficiency of devices such as single‐photon detectors. In the analysis, the zero birefringence and walk‐off are achieved at narrow waveguide width, 푤 of 250 nm and wavelength, λ${\mathrm{\lambda }}$ = 1500 nm, which is within the telecommunication region band. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hand osteoarthritis is one of the most common forms of arthritis which impact millions of people worldwide. The disabling problem occurs when the protective cartilage on the boundaries of bones wear off over time. Currently, in order to identify hand osteoarthritis, special instruments namely X-ray scanning and MRI are used for the detection but it also has its limitations such as radiation exposure and can be quite costly. In this work, an optical metrology system based on digital fringe projection which comprises of an LCD projector, CCD camera and a personal computer has been developed to anticipate abnormal growth or deformation on the joints of the hand which are common symptoms of osteoarthritis. The main concept of this optical metrology system is to apply structured light as imaging source for surface change detection. The imaging source utilizes fringe patterns generated by C++ programming and is shifted by 3 phase shifts based on the 3 steps 2 shifts method. Phase wrapping technique and analysis were applied in order to detect the deformation of live subjects. The result has demonstrated a successful method of hand deformation detection based on the pixel tracking differences of a normal and deformed state.