Understanding Terahertz Spectroscopy
March 15, 2025
Terahertz spectroscopy is a powerful technique that allows us to probe material properties in the frequency range between microwave and infrared radiation. This spectral region, often referred to as the "terahertz gap," has historically been difficult to access but provides unique insights into molecular dynamics and material properties.
In my research, I've been particularly interested in using Terahertz-Time Domain Spectroscopy (THz-TDS) to study polymers like PVDF-PANI composites. One of the key advantages of THz-TDS is its ability to directly measure both amplitude and phase of the electric field, allowing us to extract complex refractive indices without requiring Kramers-Kronig analysis.
The complex refractive index can be expressed as:
\[ \tilde{n}(\omega) = n(\omega) + i\kappa(\omega) \]
where \(n(\omega)\) is the real part representing the refractive index, and \(\kappa(\omega)\) is the imaginary part related to the absorption coefficient \(\alpha(\omega)\) by:
\[ \alpha(\omega) = \frac{2\omega\kappa(\omega)}{c} \]
When analyzing THz-TDS data, we typically calculate the transmission function, which is the ratio of the sample spectrum to the reference spectrum:
\[ T(\omega) = \frac{E_{sample}(\omega)}{E_{reference}(\omega)} = \frac{4\tilde{n}}{(1+\tilde{n})^2} \exp\left[ i\frac{\omega d}{c}(1-\tilde{n}) \right] \]
where \(d\) is the sample thickness and \(c\) is the speed of light.
Further analysis and results will be coming soon. Stay tuned for more updates on this exciting research!
