Broadband THz emission of long pulses from photomixing process with optical chirped pulses

TL;DR

This paper introduces a novel method for generating long, broadband terahertz pulses using oppositely chirped optical pulses in photomixing, advancing THz technology for applications like ranging.

Contribution

The paper proposes a new technique combining two long optical pulses with opposite chirps to produce broadband, long-duration THz pulses, enhancing photomixer capabilities.

Findings

Generated 12 ps-long THz pulse with 1 THz bandwidth

Achieved a frequency ramp of 90 GHz/ps in THz spectrum

Demonstrated potential for improved THz ranging applications

Abstract

Terahertz (THz) generation via photomixing on photoconductive antenna using twin delayed chirped pulses provides a long THz pulse with a narrow bandwidth. To generate a long pulse with broad bandwidth, we propose a new method that combines two long optical pulses with opposite chirps. The pulses exhibit temporal distributions of their instantaneous frequencies with opposite slopes. As a result, interaction between the beat frequency evolving over time and a photoconductor produces a broad THz spectrum with temporal variations. In our experimental setup, we generate a 12 ps-long pulse with a 1 THz bandwidth spectrum, featuring a frequency ramp of 90 GHz/ps, resembling a chirped THz pulse. This approach signifies a major advancement toward integrating photomixer technology, particularly in THz ranging applications.