# All-Optically Controlled Terahertz Modulation by Silicon-Grown CdSe/CdZnS Colloidal Quantum Wells

## TL;DR

This paper introduces a new terahertz modulator using CdSe/CdZnS quantum wells on silicon, offering high performance and low power requirements for future communication systems.

## Contribution

A novel all-optically controlled terahertz modulator using silicon-grown CdSe/CdZnS colloidal quantum wells is developed.

## Key findings

- The modulator achieves 87.6% modulation depth at 2 W/cm² power density.
- It operates across a broadband range of 0.25–1.4 THz.
- The device is suitable for terahertz communication and non-destructive testing.

## Abstract

The CdSe/CdZnS colloidal quantum wells, with their exceptionally high carrier mobility and ultrafast response characteristics, emerge as highly promising candidate material for high-performance active terahertz modulators—indispensable core components critical for next-generation communication technologies. A high-performance, cost-effective terahertz modulator was fabricated through spin-coating CdSe(4ML)/CdZnS nanosheets onto a silicon substrate. This all-optical device demonstrates broadband modulation capabilities (0.25–1.4 THz), achieving a remarkable modulation depth of 87.6% at a low power density of 2 W/cm2. Demonstrating pump-power-efficient terahertz modulation characteristics, this core–shell composite shows immediate applicability in terahertz communication systems and non-destructive testing equipment.