When a filter is placed in front of a double slit illuminated by a primary source of finite extent, the theory of partial coherence predicts that in general the interference fringes do not acquire unit visibility even as the passband of the filter is made arbitrarily narrow. The effect of reducing the filter bandwidth is that the visibility of the fringes tends to the modulus of the spectral degree of coherence and that more interference fringes become visible. A systematic experimental verification of these theoretical predictions is lacking so far and is provided here from the use of a highly sensitive CCD camera.
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http://dx.doi.org/10.1364/ao.42.006239 | DOI Listing |
Sci Adv
January 2025
State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China.
Hong-Ou-Mandel (HOM) interference is the foundation of quantum optics to test the degree of indistinguishability of two incoming photons, playing a key role in quantum communication, sensing, and photonic quantum computing. Realizing high-visibility HOM interference with massively parallel optical channels is challenging due to the lack of available natural optical references for aligning independent arrayed laser pairs. Here, we demonstrate 50 parallel comb-teeth pairs of continuous-wave weak coherent photons HOM interference using two independently frequency post-aligned soliton microcombs (SMCs), achieving an average fringe visibility over 46%.
View Article and Find Full Text PDFCoherent lensless imaging usually suffers from coherent noise and twin-image artifacts. In the terahertz (THz) range, where wavelengths are 2 to 4 orders of magnitude longer than those in the visible spectrum, the coherent noise manifests primarily as parasitic interference fringes and edge diffraction, rather than speckle noise. In this work, to suppress the Fabry-Pérot (F-P) interference fringes, we propose a novel method, which involves the averaging over multiple diffraction patterns that are acquired at equal intervals within a sample's half-wavelength axial shift.
View Article and Find Full Text PDFThis paper introduces an interferometer for single-shot areal quantitative phase imaging at two wavelengths simultaneously, suitable for use with low coherence sources. It operates in reflection geometry with on-axis illumination, so that it can be conveniently applied to surface texture measurements. The system consists of two identical 4f systems forming the reference and sample arm.
View Article and Find Full Text PDFCoherence scanning interferometry (CSI) is a non-destructive method for measuring the microstructure surface topography, but it fails to retrieve the bottom topography because the detection light is blocked by the sidewalls of the high aspect ratio (HAR) samples. Our team has proposed CSI technology with the detection light transparent to the sample to measure the surface topography thus ensuring the numerical aperture of the detection light with high throughput. However, a dedicated optical path to monitor the aberrations caused by the modulation from the sample is necessary and a complex optical path is added for aberration correction, which inevitably increases the design complexity and component costs of the optical system.
View Article and Find Full Text PDFIn previous work, we introduced a structured illumination strategy using linear gratings to achieve sub-nanometer misalignment sensing, which significantly enhanced accuracy and sensitivity. However, the approach was limited to linear gratings, as maintaining consistent fringe patterns during interference and modulation is essential for precise alignment. To overcome this limitation, we propose qhat we believe to be a novel misalignment sensing method based on cascaded interference in polar coordinates, enabling the use of sub-wavelength circular gratings for sub-nanometer alignment.
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