Highly reflective Er-doped ZnO thin-film coating for application in a UV optical ring resonator

Abstract

We achieved doping-induced optical variation in Erbium-doped ZnO (EZO) that may prove to be a promising material for use in optical ring resonators. EZO thin-film samples were deposited on n-type Si substrate via the sol-gel spin-coating technique followed by annealing in air at 500 °C. The doping-induced morphological variations of the deposited thin film were characterized using x-ray diffraction, ellipsometry, scanning electron microscopy and energy dispersive x-ray spectroscopy. Further, in order to establish the suitability of EZO for optical applications, detailed optical analysis was performed that exhibited that 1 mol% Er-doped ZnO may prove to be suitable material. Finally, a ring resonator design has been proposed using 1 mol% EZO thin film. The proposed structure was simulated using the MODE tool by Lumerical solutions. The Eigenmode Solver has been used to simulate and calculate the effective refractive index, group velocity, propagation constant β, dispersion and bending losses for a wavelength region of 200 nm to 900 nm. Simplified expressions for the free spectral range, full-width at half-maximum and quality factor have been derived and validated by the simulated data for the proposed ring resonator.

Ytterbium doped ZnO nanolaminated planar waveguide for ring resonator applications

“…At longer wavelengths, this negative shift causes the dispersion to approach zero. [30] 7.5 -1600 Silicon [31] 0.9 0.713 760 EZO [25] 7.8 -400 Polymer [32] 2.07 -300 YZO [present work] 1.2 0.713 3600…”

“…The energy band gap of YZO thin films increases with increase in concentration of Yb in ZnO as shown in figure 5(b). It is possible that the change in E g with differing Yb concentrations is attributable to defects introduced by Yb ion [25]. The variation of refractive index with wavelength is shown in figure 5(c).…”

“…The relation between FSR with wavelength is given by equation (10) [23] FSR = λ 2 2πRη eff (10) where, λ is resonance wavelength, R is the radius, and η eff is the effective refractive index of the waveguide. The equation for resonance wavelength and η eff is derived mathematically in authors previous work [25]. The value of resonance wavelength is 310 nm and η eff is 3.45.…”

Design and analysis of visible photonics resonators coated with CuO thin film

“…Here n=1 is a positive integer, and the lattice constraints a, b, c and g are premeditated from equation (5), which is specific for a monoclinic structure [23] ( )…”

“…The basic principle of operation of optical microcavities involves the confinement of light by making use of repetitive resonant circulation. Unlike conventional optical structures, which make use of mirrors to confine light, optical microcavities rely on dielectric coatings or optical band gap systems to achieve total internal reflection and thereby the confinement of light [4,5]. The application and appeal of optical microcavities have brought forth a new generation of on-chip optical devices [6].…”