Switching, Amplifying, and Chirping Diode Lasers with Current Pulses for High Bandwidth Quantum Technologies

TL;DR

This paper presents low-cost, high-speed diode laser devices for precise amplitude and phase control using current modulation, outperforming external modulators and enabling advanced quantum technology applications.

Contribution

It introduces novel diode laser switching, amplifying, and chirping devices that leverage amplifier saturation and direct current modulation for improved quantum optics performance.

Findings

Achieved ON:OFF ratios >10^6 with semiconductor optical amplifiers within 50 ns.

Produced 3 W optical pulses of few nanoseconds with high extinction ratio.

Implemented frequency chirping up to 300 MHz with a rate of 150 MHz/ns within 65 ns.

Abstract

A series of simple and low-cost devices for switching, amplifying, and chirping diode lasers based on current modulation are presented. Direct modulation of diode laser currents is rarely sufficient to establish precise amplitude and phase control over light, as its effects on these parameters are not independent. These devices overcome this limitation by exploiting amplifier saturation and dramatically outperform commonly used external modulators in key figures of merit for quantum technological applications. Semiconductor optical amplifiers operated on either rubidium D line are recast as intensity switches and shown to achieve ON:OFF ratios $>10^6$ in as little as 50 ns. Current is switched to a 795 nm wavelength (Rb D1) tapered amplifier to produce optical pulses of few nanosecond duration and peak powers of 3 W at a similar extinction ratio. Fast rf pulses are applied directly to a laser diode to shift its emission frequency by up to 300 MHz in either direction and at a maximum chirp rate of 150 MHz/ns. Finally, the latter components are combined, yielding a system that produces watt-level optical pulses with arbitrary frequency chirps in the given range and <2% residual intensity variation, all within 65 ns upon asynchronous demand. Such systems have broad application in atomic, molecular, and optical physics, and are of particular interest to fast experiments simultaneously requiring high power and low noise, for example quantum memory experiments with atomic vapors.