Optimisation of sample thickness for THz-TDS measurements

TL;DR

This paper investigates the optimal sample thickness for transmission THz-TDS measurements, balancing signal-to-noise ratio and detectability to improve measurement accuracy.

Contribution

It introduces a method to determine the optimal sample thickness that minimizes variance in measured optical constants in THz-TDS.

Findings

Optimal thickness balances interaction and signal attenuation.

Too thick samples reduce SNR, too thin samples are nearly invisible.

The method minimizes variance in optical constant measurements.

Abstract

How thick should the sample be for a transmission THz-TDS measurement? Should the sample be as thick as possible? The answer is `no'. Although more thickness allows T-rays to interact more with bulk material, SNR rolls off with thickness due to signal attenuation. Then, should the sample be extremely thin? Again, the answer is `no'. A sample that is too thin renders itself nearly invisible to T-rays, in such a way that the system can hardly sense the difference between the sample and a free space path. So, where is the optimal boundary between `too thick' and `too thin'? The trade-off is analysed and revealed in this paper, where our approach is to find the optimal thickness that results in the minimal variance of measured optical constants.