A simple method for the Kramers-Kronig analysis of reflectance spectra measured with diamond anvil cell

TL;DR

This paper presents a simplified method for Kramers-Kronig analysis of reflectance spectra obtained with diamond anvil cells, accounting for the diamond's refractive index to accurately derive optical constants.

Contribution

It introduces a straightforward approach using standard KK transform with cutoff and extrapolation, avoiding complex spectral fitting or modifications.

Findings

Enables accurate optical constant extraction from high-pressure reflectance data

Simplifies KK analysis for diamond anvil cell measurements

Provides a practical alternative to existing complex methods

Abstract

When the optical reflectance spectrum of a sample under high pressure is studied with a diamond anvil cell, it is measured at a sample/diamond interface. Due to the large refractive index of diamond, the resulting reflectance Rd(w) may substantially differ from that measured in vacuum. To obtain optical constants from Rd(w), therefore, the usual Kramers-Kronig (KK) transform cannot be straightforwardly applied, and either a spectral fitting or a modified KK transform has been used. Here we describe an alternative method to perform KK analysis on Rd(w). This method relies on the usual KK transform with an appropriate cutoff and extrapolation to Rd(w), and may offer a simpler approach to obtain infrared conductivity from measured Rd(w).