Alignment-free dispersion measurement with interfering biphotons

TL;DR

This paper introduces a quantum, alignment-free fiber optic dispersion measurement method using a biphoton interferometer, enabling precise, multi-order dispersion analysis of short fibers without complex alignment.

Contribution

The paper presents a novel quantum interferometric technique that measures second- and third-order dispersion in fibers without alignment, utilizing broadband biphoton sources and a common-path setup.

Findings

Accurate dispersion measurements on small-dispersion fibers.

No need for beam alignment or phase stabilization.

First quantum optical measurement of third-order dispersion.

Abstract

Measuring the dispersion of photonic devices with small dispersion-length products is challenging due to the phase-sensitive, and alignment-intensive nature of conventional methods. In this letter, we demonstrate a quantum technique to extract the second-, and third-order chromatic dispersion of a short single-mode fiber using a fiber-based quantum nonlinear interferometer. The interferometer consists of two cascaded fiber-based biphoton sources, with each source acting as a nonlinear beamsplitter. A fiber under test is placed in between these two sources, and introduces a frequency-dependent phase that is imprinted upon the biphoton spectrum (interferogram) at the output of the interferometer. This interferogram contains within it the dispersion properties of the test fiber. Our technique has three novel features: (1) The broadband nature of the biphoton sources used in our setup allows accurate dispersion measurements on test devices with small dispersion-length products; (2) our all-fiber common-path interferometer requires no beam alignment or phase stabilization; (3) multiple phase-matching processes supported in our biphoton sources enables dispersion measurements at different wavelengths, which yields the third-order dispersion, achieved for the first time using a quantum optical technique.