Spectral Phase Control of Interfering Chirped Pulses for High-Energy Narrowband Terahertz Generation

TL;DR

This paper introduces a novel spectral phase tuning technique that significantly enhances narrowband terahertz generation efficiency, achieving record energy levels and enabling advanced applications like electron accelerators.

Contribution

The paper reveals how high-order spectral phase limits DFG efficiency and demonstrates a new method to overcome this, resulting in a 13-fold efficiency increase and record terahertz pulse energy.

Findings

13-fold increase in conversion efficiency

Record terahertz pulse energy of 0.6 mJ

Over an order of magnitude improvement over previous methods

Abstract

Highly-efficient optical generation of narrowband terahertz (THz) radiation enables unexplored technologies and sciences from compact electron acceleration to charge manipulation in solids. State-of-the-art conversion efficiencies are currently achieved using difference-frequency generation (DFG) driven by temporal beating of chirped pulses but remain, however, far lower than desired or predicted. Here we show that high-order spectral phase fundamentally limits the efficiency of narrowband DFG using chirped-pulse beating and resolve this limitation by introducing a novel technique based on tuning the relative spectral phase of the pulses. For optical terahertz generation, we demonstrate a 13-fold enhancement in conversion efficiency for 1%-bandwidth, 0.361 THz pulses, yielding a record energy of 0.6 mJ and exceeding previous optically-generated energies by over an order of magnitude. Our results prove the feasibility of millijoule-scale applications like terahertz-based electron accelerators and light sources and solve the long-standing problem of temporal irregularities in the pulse trains generated by interfering chirped pulses.