Abstract
Nonlinear interferometers with correlated photons hold promise to advance optical characterization and metrology techniques by improving their performance and affordability. These interferometers offer subshot noise phase sensitivity and enable measurements in detection-challenging regions using inexpensive and efficient components. The sensitivity of nonlinear interferometers, defined by the ability to measure small shifts of interference fringes, can be significantly enhanced by using multiple nonlinear elements, or crystal superlattices. However, to date, experiments with more than two nonlinear elements have not been realized, thus hindering the potential of nonlinear interferometers. Here, we build a nonlinear interferometer with up to five nonlinear elements, referred to as superlattices, in a highly stable and versatile configuration. We study the modification of the interference pattern for different configurations of the superlattices and perform a proof-of-concept gas sensing experiment with enhanced sensitivity. Our approach offers a viable path towards broader adoption of nonlinear interferometers with correlated photons for imaging, interferometry, and spectroscopy.
Highlights
Optical characterization and metrology techniques benefit from using correlated photons, in studies of light-sensitive and fragile biological and chemical samples[1,2]
Two-photon interference effects have formed the basis for dispersion-free optical coherence tomography[5,6,7], microscopy with enhanced phase contrast[8,9], and noiserobust spectroscopy of nanostructures[10] to name a few
The crystals are pumped by a coherent laser, and each crystal produces signal (s) and idler (i) photons via spontaneous parametric down-conversion (SPDC)
Summary
Optical characterization and metrology techniques benefit from using correlated photons, in studies of light-sensitive and fragile biological and chemical samples[1,2]. A nonlinear interferometer is composed of two nonlinear elements, which produce pairs of correlated photons (signal and idler) under coherent excitation. The signal (in the visible range) and idler (in the IR range) photons are mixed in the interferometric setup, and as long as one cannot distinguish which nonlinear element produced the photons, interference fringes are observed. The interference pattern of signal photons depends on the phases and IR range can be inferred from the interference pattern of signal photons in the visible range. This technique addresses practical challenges of generation and detection of IR light since the sample response is obtained using accessible components for visible light
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