Alignment-free dispersion measurement with interfering biphotons

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 dispersionlength 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.Chromatic dispersion is an important physical property that affects the propagation of optical pulses in photonic systems; in linear systems it is used for pulse shaping [1], while in nonlinear systems it plays an important role in soliton propagation, and affects the efficiency of many nonlinear interactions [2]. Dispersion characterization is then crucial for designing optimized photonic devices. Significant effort has been expended in past decades on extracting the chromatic dispersion of materials using classical light sources. Techniques such as time-of-flight [3], and modulation phase shift [4] were introduced to measure the dispersion of components with large dispersion-length products. Components with small dispersion-length products were characterized with temporal [5], and spectral [6] white-light interferometry (WLI), with the latter proving to be the more robust method against environmental noise [7].

Nonlinear Mach–Zehnder interferometer with ultrabroadband squeezed light

“…However, lowering losses and improving the quality of the aperiodic poling will provide an ultrabroadband phase measurement at a precision surpassing that of the interferometry with classical light. A similar recent experiment (16) reported a phase measurement in a band of 80 nm but in the low-gain regime, where at most one photon pair is produced for each pair of conjugated frequencies.…”

“…The aim of this article is to consider a nonlinear interferometer consisting of two aperiodically poled crystals placed into a common pump and generating broadband twin beams through high-gain PDC. The long-term motivation for considering this configuration is twofold: (i) measuring the broadband squeezing, produced by the first crystal (14), to determine the frequency band available for quantum operations, and (ii) measuring the phase shift introduced by a sample between the crystals in a wide band of frequencies (15,16). Our short-term objectives are building an analytic model of such an interferometer and observing the interference fringes as well as their displacement caused by the sample.…”

Biphoton shaping with cascaded entangled-photon sources

“…The biphotons generated in the cascade structure are sent to a dispersive medium (20 km of Corning SMF-28), which maps their wavelengths onto the arrival time at the single photon detectors 57 . After time-tagged detection with single photon detectors, the spectrum of the biphotons can be recovered by translating the time delays into wavelength 46,57 . The minimum resolution of our spectrometer depends primarily on the timing jitter of the single photon detectors 46 .…”

“…On the other hand, the spontaneous regime of these interferometers has also been studied both theoretically 28,[35][36][37] , and experimentally [38][39][40][41] to investigate more abstract concepts such as "induced coherence" effect 38,[42][43] . These studies have since found their applications in measuring absorption 44 , refractive index 45 , and dispersion 46 of linear media.…”

Broadband fiber-based entangled photon-pair source at telecom O-band

“…Operating near the zero-dispersion wavelength of silica fiber, the time-correlated and polarization entangled biphotons generated in this source are expected to be robust against chromatic dispersion and polarization mode dispersion in long-distance quantum fiber communication [32][33][34]. Through further development, we anticipate that the source can be used in quantum applications such as wavelength-multiplexed quantum communication [19,35,36] and high precision quantum sensing [4,5,7,[37][38][39].…”