Geometric phase and wave-particle duality of the photon

The concepts of geometric phase and wave-particle duality are interlinked to several fundamental phenomena in quantum physics, but their mutual relationship still forms an uncharted open problem. Here we address this question by studying the geometric phase of a photon in double-slit interference. We especially discover a general complementarity relation for the photon that connects the geometric phase it exhibits in the observation plane and the which-path information it encases at the two slits. The relation can be seen as quantifying wave-particle duality of the photon via the geometric phase, thus corroborating a foundational link between two ubiquitous notions in quantum physics research

Measurement of spatial coherence of light

The most frequently used experimental techniques for measuring the spatial coherence properties of classical light fields in the space–frequency and space–time domains are reviewed and compared, with some attention to polarization effects. In addition to Young’s classical two-pinhole experiment and several of its variations, we discuss methods that allow the determination of spatial coherence at higher data acquisition rates and also permit the characterization of lower-intensity light fields. These advantages are offered, in particular, by interferometric schemes that employ only beam splitters and reflective elements, and thereby also facilitate spatial coherence measurements of broadband fields.Peer reviewe

Single-shot measurement of overall degree of spectral coherence : Bulk-generated supercontinuum case

Spectral and temporal correlations determine the majority of pulse properties, and a high degree of coherence is needed for minimizing the pulse length. However, there is no simple way to quantify these correlations experimentally, and nonlinear methods are often required. In this paper, we confirm an earlier proposed experiment [Koivurova, Opt. Lett. 44, 522 (2019)]0146-959210.1364/OL.44.000522 that can accurately estimate the spectral degree of coherence of arbitrary nonstationary fields. The method is entirely linear and can retrieve the quasicoherent contribution of the spectral correlation function. In particular, the method can be used to measure the overall degree of spectral coherence in a single-shot manner. We first establish the theoretical framework behind the method and experimentally test it for a bulk-generated supercontinuum. Our experimental results are in good agreement with the theory and confirm our earlier numerical findings [Halder, Photon. Res. 7, 1345 (2019)]2327-912510.1364/PRJ.7.001345. Moreover, the results yield insight into supercontinuum generation in bulk material.acceptedVersionPeer reviewe

Partially coherent beam generation with metasurfaces

An optical system for the generation of partially coherent beams with genuine cross-spectral density functions from spatially modulated globally incoherent sources is presented. The spatial intensity modulation of the incoherent source is achieved by quasi-planar metasurfaces based on spatial-frequency modulation of binary Bragg surface-relief diffraction gratings. Two types of beams are demonstrated experimentally: (i) azimuthally periodic, radially quasi-periodic beams and (ii) rotationally symmetric Bessel-correlated beams with annular far-zone radiation patterns.Peer reviewe

Generation of pulse trains with nonconventional temporal correlation properties

We apply time dependent spectral phase modulation to generate pulse trains that are spectrally and temporally partially coherent in an ensemble averaged sense. We consider, in particular, quadratic spectral phase modulation of Gaussian pulses, and demonstrate two particular types of nonuniformly correlated pulse trains. The controlled partial temporal coherence of the nonstationary fields is generated using a pulse compressor and experimentally verified with frequency resolved optical gating (FROG). We show that the correlation characteristics of such pulse trains can be retrieved directly from the FROG spectrograms provided one has certain a priori knowledge of the pulse train. Our results open a pathway for experimental confirmation of several correlation induced effects in the temporal domain.acceptedVersionPeer reviewe

Disruption of FDPS/Rac1 Axis Radiosensitizes Pancreatic Ductal Adenocarcinoma by Attenuating DNA Damage Response and Immunosuppressive Signalling

BACKGROUND: Radiation therapy (RT) has a suboptimal effect in patients with pancreatic ductal adenocarcinoma (PDAC) due to intrinsic and acquired radioresistance (RR). Comprehensive bioinformatics and microarray analysis revealed that cholesterol biosynthesis (CBS) is involved in the RR of PDAC. We now tested the inhibition of the CBS pathway enzyme, farnesyl diphosphate synthase (FDPS), by zoledronic acid (Zol) to enhance radiation and activate immune cells. METHODS: We investigated the role of FDPS in PDAC RR using the following methods: in vitro cell-based assay, immunohistochemistry, immunofluorescence, immunoblot, cell-based cholesterol assay, RNA sequencing, tumouroids (KPC-murine and PDAC patient-derived), orthotopic models, and PDAC patient\u27s clinical study. FINDINGS: FDPS overexpression in PDAC tissues and cells (P \u3c 0.01 and P \u3c 0.05) is associated with poor RT response and survival (P = 0.024). CRISPR/Cas9 and pharmacological inhibition (Zol) of FDPS in human and mouse syngeneic PDAC cells in conjunction with RT conferred higher PDAC radiosensitivity in vitro (P \u3c 0.05, P \u3c 0.01, and P \u3c 0.001) and in vivo (P \u3c 0.05). Interestingly, murine (P = 0.01) and human (P = 0.0159) tumouroids treated with Zol+RT showed a significant growth reduction. Mechanistically, RNA-Seq analysis of the PDAC xenografts and patients-PBMCs revealed that Zol exerts radiosensitization by affecting Rac1 and Rho prenylation, thereby modulating DNA damage and radiation response signalling along with improved systemic immune cells activation. An ongoing phase I/II trial (NCT03073785) showed improved failure-free survival (FFS), enhanced immune cell activation, and decreased microenvironment-related genes upon Zol+RT treatment. INTERPRETATION: Our findings suggest that FDPS is a novel radiosensitization target for PDAC therapy. This study also provides a rationale to utilize Zol as a potential radiosensitizer and as an immunomodulator in PDAC and other cancers. FUNDING: National Institutes of Health (P50, P01, and R01)

Propagation of Bessel-correlated specular and antispecular beams

We address the specular properties of Bessel-correlated fields, generated by illuminating a tilted rotating plane-parallel glass plate with a coherent Gaussian beam and passing the output beam though a mirror-based wavefront folding interferometer. This device allows us to produce beams whose specular properties are preserved in propagation. In the far zone, the specular nature of these partially coherent fields is shown to produce intensity-profile oscillations in the sub-diffraction-limit scale. The analytical results at various propagation distances are verified experimentally by using another wavefront-folding interferometer for coherence measurements.publishedVersionPeer reviewe

Mirror-based scanning wavefront-folding interferometer for coherence measurements

We demonstrate a modification to the traditional prism-based wavefront-folding interferometer that allows the measurement of spatial and temporal coherence, free of distortions and diffraction caused by the prism corners. In our modified system, the two prisms of the conventional system are replaced with six mirrors. The whole system is mounted on a linear XY-translation stage, with an additional linear stage in the horizontal arm. This system enables rapid and exact measurement of the full four-dimensional degree of coherence, even for relatively weak signals. The capabilities of our system are demonstrated by measuring the spatial coherence of two inhomogeneous and non-Schell model light sources with distinct characteristics.Peer reviewe

Polarization dependent beaming properties of a plasmonic lattice laser

Funding Information: The work was funded by the Academy of Finland (Projects 322002, 308393, 310511). The work is part of the Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN), decisions 320166 and 320165. Publisher Copyright: © 2021 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft.We study beaming properties of laser light produced by a plasmonic lattice overlaid with organic fluorescent molecules. The crossover from spontaneous emission regime to stimulated emission regime is observed in response to increasing pump fluence. This transition is accompanied by a strong reduction of beam divergence and emission linewidth due to increased degree of spatial and temporal coherence, respectively. The feedback for the lasing signal is shown to be mainly one-dimensional due to the dipolar nature of the surface lattice resonance. Consequently, the beaming properties along x and y directions are drastically different. From the measurements, we obtain the M 2 value along both principal directions of the square lattice as a function of the pump fluence. Our work provides the first detailed analysis of the beam quality in plasmonic lattice lasers and reveals the underlying physical origin of the observed strong polarization dependent asymmetry of the lasing signal.Peer reviewe