Designing High-Power, Octave Spanning Entangled Photon Sources for Quantum Spectroscopy

TL;DR

This paper presents a novel high-flux, octave-spanning entangled photon source using a lithium tantalate platform, enabling advanced quantum spectroscopy with improved resolution and measurement capabilities.

Contribution

The authors develop a periodically poled, chirped lithium tantalate device that generates high-flux, broadband entangled photons suitable for quantum spectroscopy applications.

Findings

Achieved a photon flux of near microwatts at 10^{-7} efficiency.

Measured coherence times of 245 fs and 62 fs for different bandwidths.

Demonstrated broadband Hong-Ou-Mandel interference with full photon cone collection.

Abstract

Entangled photon spectroscopy is a nascent field that has important implications for measurement and imaging across chemical, biology, and materials fields. Entangled photon spectroscopy potentially offers improved spatial and temporal-frequency resolutions, increased cross sections for multiphoton and nonlinear measurements, and new abilities in inducing or measuring quantum correlations. A critical step in enabling entangled photon spectroscopies is the creation of high-flux entangled sources that can use conventional detectors, as well as provide redundancy for the losses in realistic samples. Here, we report a periodically poled, chirped, lithium tantalate platform that generates entangled photon pairs with a $10^{-7}$ efficiency. For a near watt level diode laser, this results in a near $\mu$W-level flux. The single photon per mode limit that is necessary to maintain non-classical photon behavior is still satisfied by distributing this power over up to an octave-spanning bandwidth. The spectral-temporal photon correlations are observed via a Michelson-type interferometer that measures the broadband Hong-Ou-Mandel two-photon interference. A coherence time of 245 fs for a 10 nm bandwidth in the collinear case and a 62 fs for a 125 nm bandwidth in the non-collinear case is measured using a CW pump laser, and, essentially, collecting the full photon cone. We outline in detail the numerical methods used for designing and tailoring the entangled photons source, such as changing center wavelength or bandwidth, with the ultimate aim of increasing the availability of high-flux UV-Vis entangled photon sources in the optical spectroscopy community.