Accurate Measurement of the Optical Constants n and k for a Series of 57 Inorganic and Organic Liquids for Optical Modeling and Detection

Abstract

For optical modeling and other purposes, we have created a library of 57 liquids for which we have measured the complex optical constants n and k. These liquids vary in their nature, ranging in properties that include chemical structure, optical band strength, volatility, and viscosity. By obtaining the optical constants, one can model most optical phenomena in media and at interfaces including reflection, refraction, and dispersion. Based on the works of others, we have developed improved protocols using multiple path lengths to determine the optical constants n/k for dozens of liquids, including inorganic, organic, and organophosphorus compounds. Detailed descriptions of the measurement and data reduction protocols are discussed; agreement of the derived optical constant n and k values with literature values are presented. We also present results using the n/k values as applied to an optical modeling scenario whereby the derived data are presented and tested for models of 1 µm and 100 µm layers for dimethyl methylphosphonate (DMMP) on both metal (aluminum) and dielectric (soda lime glass) substrates to show substantial differences between the reflected signal from highly reflective substrates and less-reflective substrates.

Infrared Optical Constants from Pressed Pellets of Powders: I. Improved n and k Values of (NH4)2SO4 from Single-Angle Reflectance

“…Both the real, n (ṽ∼), and imaginary, k (ṽ∼), components of the complex index of refraction, n^ = n + i k , are vital input parameters for modeling the reflectance, refraction, absorption, and emissivity of a material 1–6 and thus serve as valuable reference data. A common method of determining n and k of solid materials is to measure the change in amplitude of light reflected from a material as a function of frequency, R(ṽ∼), over a broad wavelength range, and then apply the Kramers–Kronig transform (KKT) to derive the optical constants.…”

An Approach to Ring Resonator Biosensing Assisted by Dielectrophoresis: Design, Simulation and Fabrication

“…The red peaks are attributed to the reference ring and the blue to the sensor ring. ( b ) The resonance peak shift of the ring resonators exposed to MeOH (n = 1.3118), [ 51 ] H 2 O (n = 1.3164), EtOH (n = 1.3503), and isopropanol (n = 1.3661) normalized to the peak position in air (n = 1.003). [ 52 ] ( c ) Nyquist and Bode plot representing the impedance measurement of NaCl aqueous solutions, as performed with the coplanar electrode configuration.…”

A free spectroscopic databank of optical constants for use in optics education and modeling: complex refractive index data n and k from 1.0 to 25 μm

“…The experimental methods use to derive the liquids n(ν) and k(ν) optical constants data were largely derived by Bertie and colleagues 7,14-16 and improvements to these methods have been described by Myers et al [18][19] While the basic experimental procedure involves making a series of simple liquids transmission measurements, attention to detail is required at every step in order to obtain quantitative values for k (and in turn for n).…”

“…Currently the optical constants for 57 liquid species spanning a diverse set of organic, inorganic and organophosphorous compounds are available on the NIST website at https://webbook.nist.gov/chemistry/silmarils-liquids-n-k/. 18,24 For this set of compounds, n and k values are available from 7,800 to 400 cm -1 at 2 cm -1 resolution. An additional 70 liquids have been measured using the MIR-NIR dual method to extend data out to 10,000 cm -1 .…”

“…In this paper we discuss the methods of using quantitative absorbance data of liquid and solid samples so as to derive the complex infrared optical components. The optical constants of a growing number of liquids and solids are freely available for download from the NIST website 18,24,25 for spectral modeling and other educational purposes.…”