Shaping the spectrum of terahertz photoconductive antenna by frequency-dependent impedance modulation

TL;DR

This paper presents a theoretical and experimental study on shaping terahertz pulse spectra in photoconductive antennas through frequency-dependent impedance modulation, enabling optimized THz generation for spectroscopy and imaging.

Contribution

It introduces a new theoretical model for THz pulse generation considering impedance effects and demonstrates its effectiveness through simulation and experimental validation.

Findings

Theoretical model accurately predicts THz spectra with impedance modulation.

Experimental results agree with simulations, confirming the model's validity.

Impedance modulation enables spectral shaping of THz pulses.

Abstract

In this paper, we report on an approach for shaping the spectra of THz pulse generation in photoconductive antennas (PCAs) by frequency-dependent impedance modulation. We introduce a theoretical model describing the THz pulse generation in PCAs and accounting for impedances of the photoconductor and of the antenna. In order to showcase an impact of frequency-dependent impedance modulation on the spectra of THz pulse generation, we applied this model to simulating broadband PCAs with log-spiral topology. Finally, we fabricated two different log-spiral PCAs and characterized them experimentally using the THz pulsed spectroscopy. The observed results demonstrate excellent agreement between the theoretical model and experiment, justifying a potential of shaping the spectra of THz pulse generation in PCA by modulation of frequency-dependent impedances. This approach makes possible optimizing the PCA performance and thus accommodating the needs of THz pulsed spectroscopy and imaging in fundamental and applied branches of THz science and technologies.