Tantalum pentoxide (Ta2O5) is a promising material for both linear and nonlinear integrated optical device fabrication due to its high refractive index, low absorption over a wide wavelength range, high nonlinear refractive index, large value of chi 3 and high optical damage threshold. In particular Ta2O5 rib and ridge waveguides provide an interesting platform for solid state Laser applications. Waveguide surface roughness and sidewall slope profile can induce significant scattering loss reducing the efficiency of the device. Optimization of these parameters is key to obtain ultimate performance of the final device. In this paper, we present a method and photolithographic mask layout suitable to allow easy measurement of optical propagation loss for planar rib or ridge waveguides. The procedure is equivalent to the standard ‘cut- back’ method, but one that does not requiring devices to be cleaved and polished multiple times. The mask incorporates a set of narrow nano-wire waveguides coupled by tapered waveguide sections to wide input /output guides. The lengths of the central nano-wire section are determined precisely by the lithographic mask. The layout is designed to allow losses of each sub-component such as taper sections and input waveguides to be removed from the measurement, giving accurate measurement of loss in the central nanowire section of the guide. Optical loss measurements are presented for Ta2O5 nanowire rib waveguides. Loss was found to be dependent on lengths and widths of nanowire waveguide sections. Measured propagation losses for the rib waveguides are found to be just slightly higher than loss of a Ta2O5 slab waveguide as measured by a commercial Metricon system, validating the low loss nanowire waveguide fabrication processes.
In this paper we describe an experimental measurement procedure and automated system for analysis of angle dependent
dispersion associated with dielectric photonic crystals or surface Plasmon polariton dispersion associated with
nanostructured metallo-dielectric surfaces. This fully automated system utilizes a broadband spectroscopic reflectometry
method to acquire polarization resolved data. Angular dispersion is mapped by illuminating a sample with a white light
laser ranging from 450nm to 1800nm. A movable fiber probe then collects the reflected signal. Dips in reflectivity then
correspond to partially coupled Bloch modes. The measurement system was applied to the investigation of Plasmon
dispersion of periodic arrays of metal coated square pyramids SERS sensors. Comparisons are then made to
computational simulations derived using RSOFT DiffractMOD based on Rigorous Coupled Wave Analysis (RCWA). Measured experimental dispersion patterns are found to closely match simulation in the exact frame of wavelength
(400nm to 900nm).
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