Construction of a Compact, Fully Automatic non-linear Absorption Spectrometer to Measure the Two-Photon Absorption Coefficient

TL;DR

This paper presents a compact, fully automatic non-linear absorption spectrometer using an EFTL, integrating sphere, and femtosecond laser to measure two-photon absorption coefficients of semiconductors efficiently across a broad wavelength range.

Contribution

It introduces a novel, fully automated, and compact spectrometer design that simplifies measurement of two-photon absorption in semiconductors with high accuracy.

Findings

Accurately measured two-photon absorption coefficients of CdS and ZnSe.

Achieved measurements across 690-1040 nm with 5 nm resolution in under 30 minutes.

Results showed excellent agreement with theoretical dispersion models.

Abstract

Using an Electrically Focus Tunable Lens (EFTL), an integrating sphere and a tunable femtosecond-pulse laser (Mai Tai HP), we were able to measure the degenerate two-photon absorption coefficient (in transmission) of CdS and ZnSe in a long range of wavelengths (690-1040 nm), with a 5 nm resolution, in less than 30 minutes. We compared our results with theoretical approaches for the dispersion relations of the non-linear properties of semiconductors, and found excellent agreement with the experimental results. The system has no moving parts, is highly compact, and is fully automated.