Terahertz waveform synthesis from integrated lithium niobate circuits

TL;DR

This paper demonstrates the use of integrated thin-film lithium niobate circuits to synthesize customizable terahertz waveforms with broad bandwidth and precise control, overcoming previous limitations of bulk crystal systems.

Contribution

It introduces a novel integrated circuit approach for THz waveform synthesis, enabling flexible, broadband, and coherent THz emission with low pump energy.

Findings

Broadband THz emission up to 680 GHz achieved

On-chip control of phase, amplitude, and coherence demonstrated

Low pump energy requirement below 100 pJ

Abstract

Bridging the "terahertz (THz) gap" relies upon synthesizing arbitrary waveforms in the THz domain enabling applications that require both narrow band sources for sensing and few-cycle drives for classical and quantum objects. However, realization of custom-tailored waveforms needed for these applications is currently hindered due to limited flexibility for optical rectification of femtosecond pulses in bulk crystals. Here, we experimentally demonstrate that thin-film lithium niobate (TFLN) circuits provide a versatile solution for such waveform synthesis through combining the merits of complex integrated architectures, low-loss distribution of pump pulses on-chip, and an efficient optical rectification. Our distributed pulse phase-matching scheme grants shaping the temporal, spectral, phase, amplitude, and farfield characteristics of the emitted THz field through designer on-chip components. This strictly circumvents prior limitations caused by the phase-delay mismatch in conventional systems and relaxes the requirement for cumbersome spectral pre-engineering of the pumping light. We provide a toolbox of basic blocks that produce broadband emission up to 680 GHz with adaptable phase and coherence properties by using near-infrared pump pulse energies below 100 pJ.