Multiple-plane image formation by Walsh zone plates

Author(s):

Federico Machado, Vicente Ferrando, Fernando Giménez, Walter D. Furlan, and Juan A. Monsoriu

Abstract:

“A radial Walsh filter is a phase binary diffractive optical element characterized by a set of concentric rings that take the phase values 0 or π, corresponding to the values + 1 or −1 of a given radial Walsh function. Therefore, a Walsh filter can be re-interpreted as an aperiodic multifocal zone plate, capable to produce images of multiple planes simultaneously in a single output plane of an image forming system. In this paper, we experimentally demonstrate for the first time the focusing capabilities of these structures. Additionally, we report the first achievement of images of multiple-plane objects in a single image plane with these aperiodic diffractive lenses.”

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Publication: Optics Express

Issue/Year/DOI: Optics Express Volume 26, Issue 16
DOI: 10.1364/OE.26.021210

Wide-field in situ multiplexed Raman imaging with superresolution

Author(s):

Houkai Chen and Xiaojing Wu and Yuquan Zhang and Yong Yang and Changjun Min and Siwei Zhu and Xiaocong Yuan and Qiaoliang Bao and Jing Bu

Abstract:

“Because of the fingerprint-like specificity of its characteristic spectrogram, Raman spectral imaging has been applied widely in various research areas. Using a combination of structured illumination with the surfaceenhanced Raman scattering (SERS) technique, wide-field Raman imaging is developed with a significant improvement in spatial resolution. As a result of the relatively narrow Raman characteristic peaks, optically encoded SERS nanoparticles can be used to perform multiplexed imaging. The results show excellent superresolution wide-field multiplexed imaging performance. The developed technique has extraordinary potential for applications in biological imaging and other related fields.”

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Publication: Photonics Research
Issue/Year/DOI: Photonics Research Volume 6, Issue 6 pp. 530-534
DOI: 10.1364/PRJ.6.000530

Experimental demonstration of tunable refractometer based on orbital angular momentum of longitudinally structured light

Author(s):

Dorrah, Ahmed H and Zamboni-Rached, Michel and Mojahedi, Mo

Abstract:

“The index of refraction plays a decisive role in the design and classification of optical materials and devices; therefore, its proper and accurate determination is essential. In most refractive index (RI) sensing schemes, however, there is a trade-off between providing high-resolution measurements and covering a wide range of RIs. We propose and experimentally demonstrate a novel mechanism for sensing the index of refraction of a medium by utilizing the orbital angular momentum (OAM) of structured light. Using a superposition of co-propagating monochromatic higher order Bessel beams with equally spaced longitudinal wavenumbers, in a comb-like setting, we generate nondiffracting rotating light structures in which the orientation of the beam’s intensity profile is sensitive to the RI of the medium (here, a fluid). In principle, the sensitivity of this scheme can exceed ∼ 2700°/RIU with a resolution of ∼ 10-5 RI unit (RIU). Furthermore, we show how the unbounded degrees of freedom associated with OAM can be deployed to offer a wide
dynamic range by generating structured light that evolves into different patterns based on the change in RI. The rotating light structures are generated by a programmable spatial light modulator (SLM). This provides dynamic control over the sensitivity, which
can be tuned to perform coarse or fine measurements of the RI in real time. This, in turn, allows high sensitivity and resolution to be achieved simultaneously over a very wide dynamic range, which is a typical trade-off in all RI sensing schemes. We thus envision that this method will open new directions in refractometry and remote sensing.”

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Publication: Light: Science \& Applications

Issue/Year/DOI: Light: Science & Applications accepted article preview 18 May 2018
DOI: 10.1038/s41377-018-0034-9

Single camera shot interferenceless coded aperture correlation holography

Author(s):

Mani Ratnam Rai and A. Vijayakumar and Joseph Rosen

Abstract:

“We propose a new scheme for recording an incoherent digital hologram by a single camera shot. The method is based on a motionless, interferenceless, coded aperture correlation holography for 3D imaging. Two random-like coded phase masks (CPMs) are synthesized using the Gerchberg–Saxton algorithm with two different initial random phase profiles. The two CPMs are displayed side by side and used as the system aperture. Light from a pinhole is introduced into the system, and two impulse responses are recorded corresponding to the two CPMs. The two impulse responses are subtracted, and the resulting intensity profile is used as a reconstructing hologram. A library of reconstructing holograms is created corresponding to all possible axial locations. Following the above training stage, an object is placed within the axial limits of the library, and the intensity patterns of a single shot, corresponding to the same two CPMs, are recorded under identical conditions to generate the object hologram. The image of the object at any plane is reconstructed by a cross-correlation between the object hologram and the corresponding reconstructing hologram from the library.”

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Publication: Optics Letters

Issue/Year/DOI: Optics Letters Vol. 42, Issue 19, pp. 3992-3995 (2017)

DOI: 10.1364/OL.42.003992

 

Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer.

Author(s):

Duan, Hong-Guang and Prokhorenko, Valentyn I. and Cogdell, Richard J. and Ashraf, Khuram and Stevens, Amy L. and Thorwart, Michael and Miller, R. J. Dwayne

Abstract:

“We have revisited the 2D spectroscopy of the excitation energy transfer in the Fenna-Matthews-Olson (FMO) protein. Based on 2D spectroscopic signatures, the energy transfer dynamics in the FMO protein has been argued to be supported by long-lived electronic quantum coherence on timescales up to 1.5 ps. In contrast, our analysis, based on experimental data and confirmed by theoretical calculations, shows that the electronic decoherence occurs within 60 fs, in agreement with typical dephasing times in systems under these conditions. Given the relatively well-defined structure of the FMO protein, and comparative couplings between chlorophylls to other photosynthetic systems, the observed extremely fast decoherence should be viewed as general, bringing to question any significant quantum coherent transport contributions to photosynthesis.”

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Publication: Proceedings of the National Academy of Sciences of the United States of America

Issue/Year/DOI:
DOI: 10.1073/pnas.1702261114