Free-space spectro-temporal and spatio-temporal conversion for pulsed light

TL;DR

This paper introduces a novel apparatus that converts pulsed light into a spectro-temporal pulse train, enabling spectrum measurement with a single detector, featuring high efficiency, tunability, and fiber-free design.

Contribution

The authors present a fiber-free, tunable apparatus that converts pulsed light into a measurable pulse train, allowing efficient spectrum measurement with a single detector.

Findings

Achieved over 10% efficiency in near-infrared spectrum

Demonstrated measurement of joint spectrum of bi-photon source

Apparatus is fiber-free and tunable across wavelengths

Abstract

We present an apparatus that converts every pulse of a pulsed light source to a pulse train in which the intensities of the different pulses are samples of the spatial or temporal frequency spectrum of the original pulse. In this way, the spectrum of the incident light can be measured by following the temporal response of a single detector. The apparatus is based on multiple round-trips inside a 2f- cavity-like mirror arrangement in which the spectrum is spread on the back focal plane, where after each round-trip a small section of the spectrum is allowed to escape. The apparatus is fibre-free, offers easy wavelength range tunability, and a prototype built achieves over 10% average efficiency in the near infra red. We demonstrate the application of the prototype for the efficient measurement of the joint spectrum of a non-degenerate bi-photon source in which one of the photons is in the near infra red.