How to measure laser chirp rate at single-emitter excitation energies

TL;DR

The paper introduces a straightforward, low-power method for measuring laser chirp rate and group delay dispersion at energies suitable for quantum photonics, avoiding nonlinear processes used in traditional techniques.

Contribution

It presents a novel wavelength-to-time mapping approach using single-photon detection for linear dispersion measurement at ultralow power levels.

Findings

Accurately measures GDD at single-photon power levels.

Provides a linear wavelength-time relationship for dispersion analysis.

Applicable to quantum photonics and ultralow-power optical systems.

Abstract

We present a simple and direct method for measuring laser chirp rate, i.e., group delay dispersion (GDD) of ultrashort laser pulses at power levels compatible with single-quantum-emitter excitation. Traditional pulse characterization techniques rely on nonlinear optical processes that require high peak powers, making them unsuitable for the attojoule-to-femtojoule regime relevant to quantum photonics. Our approach utilizes a wavelength-to-time mapping method in which the arrival times of spectrally filtered components of a broadband pulse are recorded using a superconducting nanowire single-photon detector and correlated via a high-resolution time-tagging system. The resulting linear relationship between wavelength and arrival time directly yields the dispersion parameter and, subsequently, the GDD. Beyond single-emitter excitation, this technique can be applied in areas such as single-photon spectroscopy, ultralow-power optical communications, and time-domain quantum control, where linear and non-destructive dispersion characterization is essential.