Measurement of the refractive index dispersion of As2Se3 bulk glass and thin films prior to and after laser irradiation and annealing using prism coupling in the near- and mid-infrared spectral range

Abstract

The prism coupling technique has been utilized to measure the refractive index in the near- and mid-IR spectral region of chalcogenide glasses in bulk and thin film form. A commercial system (Metricon model 2010) has been modified with additional laser sources, detectors, and a new GaP prism to allow the measurement of refractive index dispersion over the 1.5-10.6 μm range. The instrumental error was found to be ±0.001 refractive index units across the entire wavelength region examined. Measurements on thermally evaporated AMTIR2 thin films confirmed that (i) the film deposition process provides thin films with reduced index compared to that of the bulk glass used as a target, (ii) annealing of the films increases the refractive index of the film to the level of the bulk glass used as a target to create it, and (iii) it is possible to locally increase the refractive index of the chalcogenide glass using laser exposure at 632.8 nm.

Demonstration of high-Q mid-infrared chalcogenide glass-on-silicon resonators

“…We chose As 2 Se 3 over more commonly used sulfide ChGs given its high refractive index (n ∼ 2.66 the mid-IR) [15] and reduced phonon energy, which gives rise to a long wavelength absorption onset up to 14 μm. The devices were tested by fiber end fire coupling using a quantum cascade laser (QCL) at 5.2 μm mid-IR wavelength.…”

Compositional-tailoring of optical properties in IR transparent chalcogenide glasses for precision glass molding

“…Details of this system have been reported previously. 13,14 In this system, the plano-plano sample is held in physical contact with a Ge prism, and the prism-sample combination is rotated to determine the critical angle for each laser wavelength. The critical angle measurement is then used to directly determine the sample refractive index.…”

Determining the refractive index dispersion and thickness of hot-pressed chalcogenide thin films from an improved Swanepoel method

“…More importantly, it has until recently been difficult to apply some of these techniques to the MIR spectral region because of the paucity of suitable beam sources (Carlie et al 2011). Carlie et al (2011) modified a commercial system prism coupling system (Metricon model 2010) using additional laser sources, detectors, and a GaP prism in order to enable the measurement of refractive index dispersion at spot wavelengths over the 1.5-10.6 lm range and used it to determine the refractive index of As 2 Se 3 bulk glass and thin films across this wavelength region to an accuracy of ±0.001. Due to the high accuracy of the method the authors were able to compare the refractive indices of as-deposited and annealed As 2 Se 3 films with those of the parent bulk glasses.…”

“…Techniques commonly used for refractive index measurement include the modelling of transmission or reflection spectroscopic data (Swanepoel 1985;Marquez et al 1998), spectroscopic ellipsometry (Orava et al 2009;Wang et al 2017), prism coupling (Carlie et al 2011), grating coupling (Laniel et al 2003), and the measurement of the minimum deviation angle of light passing through a prism (Fang et al 2016). Several of these techniques require intensive sample preparation, are time consuming, and are costly to conduct.…”