Balanced Air-Biased Detection of Terahertz Waveforms

TL;DR

This paper introduces a balanced air-biased coherent detection method for ultrabroadband terahertz waveforms, significantly improving detection speed, dynamic range, and signal-to-noise ratio without complex modulation or lock-in amplifiers.

Contribution

The paper presents a novel balanced detection scheme that enhances terahertz waveform measurement by simplifying setup and boosting performance compared to traditional air-biased detection.

Findings

Doubling the dynamic range

Quadrupling the signal-to-noise ratio

Enabling high-fidelity waveform acquisition in under a second

Abstract

A novel balanced air-biased coherent detection scheme for capturing ultrabroadband terahertz (THz) waveforms is implemented. The balanced detection scheme allows for coherent detection at the full repetition rate of the laser system without requiring bias modulation, signal generators, or lock-in amplifiers while doubling the dynamic range and quadrupling the signal-to-noise ratio compared to conventional air-biased coherent detection. These advantages are achieved by rotating the bias electrodes by 90{\deg} relative to the conventional scheme. With a 1 kHz driving laser, the scheme enables sub-second, high-fidelity waveform acquisition with a continuously moving delay stage, demonstrated by collecting 200 waveforms in 100 s. The balanced detection scheme paves the way for much faster and higher quality 2D ultrabroadband terahertz spectroscopy.