Single-plane and multiplane quantitative phase imaging by self-reference on-axis holography with a phase-shifting method

Author(s):

Hai, Nathaniel & Rosen, Joseph

Abstract:

“A new quantitative phase imaging approach is proposed based on self-reference holography. Three on-axis interferograms with different values of the phase filter are superposed. The superposition yields a more accurate phase map of the wavefront emerging from the object, compared with standard off-axis interferometry. Reduced temporal noise levels in the measured phase map and efficient phase recovery process for optically thin and thick transmissive phase objects highlight the applicability of the suggested framework for various fields ranging from metrology to bio-imaging. Qualitative phase imaging is also done online without altering the optical configuration. Qualitative phase detections of multiple planes of interest are converted to quantitative phase maps of the multiplane scene by a rapid phase contrast-based phase retrieval algorithm, from a single camera exposure and with no moving parts in the system.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 15; Pages 24210; 2021
DOI: 10.1364/oe.431529

Giant Helical Dichroism of Single Chiral Nanostructures with Photonic Orbital Angular Momentum

Author(s):

Ni, Jincheng; Liu, Shunli; Hu, Guangwei; Hu, Yanlei; Lao, Zhaoxin; Li, Jiawen; Zhang, Qing; Wu, Dong; Dong, Shaohua; Chu, Jiaru & Qiu, Cheng-Wei

Abstract:

“Optical activity, demonstrating the chiral light-matter interaction, has attracted tremendous attention in both fundamental theoretical research and advanced applications of high-efficiency enantioselective sensing and next-generation chiroptical spectroscopic techniques. However, conventional chiroptical responses are normally limited in large assemblies of chiral materials by circularly polarized light, exhibiting extremely weak chiroptical signals in a single chiral nanostructure. Here, we demonstrate that an alternative chiral freedom of light—orbital angular momentum—can be utilized for generating strong helical dichroism in single chiral nanostructures. The helical dichroism by monochromatic vortex beams can unambiguously distinguish the intrinsic chirality of nanostructures, in an excellent agreement with theoretical predictions. The single planar-chiral nanostructure can exhibit giant helical dichroism of ∼20% at the visible wavelength. The vortex-dependent helical dichroism, expanding to single nanostructures and two-dimensional space, has implications for high-efficiency chiroptical detection of planar-chiral nanostructures in chiral optics and nanophotonic systems.”

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Publication: ACS Nano
Issue/Year: ACS Nano, Volume 15; Number 2; Pages 2893-2900; 2021
DOI: 10.1021/acsnano.0c08941

Depth-of-field engineering in coded aperture imaging

Author(s):

Rai, Mani Ratnam & Rosen, Joseph

Abstract:

“Extending the depth-of-field (DOF) of an optical imaging system without effecting the other imaging properties has been an important topic of research for a long time. In this work, we propose a new general technique of engineering the DOF of an imaging system beyond just a simple extension of the DOF. Engineering the DOF means in this study that the inherent DOF can be extended to one, or to several, separated different intervals of DOF, with controlled start and end points. Practically, because of the DOF engineering, entire objects in certain separated different input subvolumes are imaged with the same sharpness as if these objects are all in focus. Furthermore, the images from different subvolumes can be laterally shifted, each subvolume in a different shift, relative to their positions in the object space. By doing so, mutual hiding of images can be avoided. The proposed technique is introduced into a system of coded aperture imaging. In other words, the light from the object space is modulated by a coded aperture and recorded into the computer in which the desired image is reconstructed from the recorded pattern. The DOF engineering is done by designing the coded aperture composed of three diffractive elements. One element is a quadratic phase function dictating the start point of the in-focus axial interval and the second element is a quartic phase function which dictates the end point of this interval. Quasi-random coded phase mask is the third element, which enables the digital reconstruction. Multiplexing several sets of diffractive elements, each with different set of phase coefficients, can yield various axial reconstruction curves. The entire diffractive elements are displayed on a spatial light modulator such that real-time DOF engineering is enabled according to the user needs in the course of the observation. Experimental verifications of the proposed system with several examples of DOF engineering are presented, where the entire imaging of the observed scene is done by single camera shot.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 2; Pages 1634; 2021
DOI: 10.1364/oe.412744

Partial aperture imaging system based on sparse point spread holograms and nonlinear cross-correlations

Author(s):

Bulbul, Angika & Rosen, Joseph

Abstract:

“Partial aperture imaging system (PAIS) is a recently developed concept in which the traditional disc-shaped aperture is replaced by an aperture with a much smaller area and yet its imaging capabilities are comparable to the full aperture systems. Recently PAIS was demonstrated as an indirect incoherent digital three-dimensional imaging technique. Later it was successfully implemented in the study of the synthetic marginal aperture with revolving telescopes (SMART) to provide superresolution with subaperture area that was less than one percent of the area of the full synthetic disc-shaped aperture. In the study of SMART, the concept of PAIS was tested by placing eight coded phase reflectors along the boundary of the full synthetic aperture. In the current study, various improvements of PAIS are tested and its performance is compared with the other equivalent systems. Among the structural changes, we test ring-shaped eight coded phase subapertures with the same area as of the previous circular subapertures, distributed along the boundary of the full disc-shaped aperture. Another change in the current system is the use of coded phase mask with a point response of a sparse dot pattern. The third change is in the reconstruction process in which a nonlinear correlation with optimal parameters is implemented. With the improved image quality, the modified-PAIS can save weight and cost of imaging devices in general and of space telescopes in particular. Experimental results with reflective objects show that the concept of coded aperture extends the limits of classical imaging”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-77912-3

Distinguishing intrinsic photon correlations from external noise with frequency-resolved homodyne detection

Author(s):

Lüders, Carolin & Assmann, Marc

Abstract:

“In this work, we apply homodyne detection to investigate the frequency-resolved photon statistics of a cw light field emitted by a driven-dissipative semiconductor system in real time. We demonstrate that studying the frequency dependence of the photon number noise allows us to distinguish intrinsic noise properties of the emitter from external noise sources such as mechanical noise while maintaining a sub-picosecond temporal resolution. We further show that performing postselection on the recorded data opens up the possibility to study rare events in the dynamics of the emitter. By doing so, we demonstrate that in rare instances, additional external noise may actually result in reduced photon number noise in the emission”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-79686-0

Gigantic vortical differential scattering as a monochromatic probe for multiscale chiral structures

Author(s):

Ni, Jincheng; Liu, Shunli; Wu, Dong; Lao, Zhaoxin; Wang, Zhongyu; Huang, Kun; Ji, Shengyun; Li, Jiawen; Huang, Zhixiang; Xiong, Qihua; Hu, Yanlei; Chu, Jiaru & Qiu, Cheng-Wei

Abstract:

“Spin angular momentum of light is vital to investigate enantiomers characterized by circular dichroism (CD), widely adopted in biology, chemistry, and material science. However, to discriminate chiral materials with multiscale features, CD spectroscopy normally requires wavelength-swept laser sources as well as wavelength-specific optical accessories. Here, we experimentally demonstrate an orbital-angular-momentum-assisted approach to yield chiroptical signals with monochromatic light. The gigantic vortical differential scattering (VDS) of ∼120% is achieved on intrinsically chiral microstructures fabricated by femtosecond laser. The VDS measurements can robustly generate chiroptical properties on microstructures with varying geometric features (e.g., diameters and helical pitches) and detect chiral molecules with high sensitivity. This VDS scheme lays a paradigm-shift pavement toward efficiently chiroptical discrimination of multiscale chiral structures with photonic orbital angular momentum. It simplifies and complements the conventional CD spectroscopy, opening possibilities for measuring weak optical chirality, especially on mesoscale chiral architectures and macromolecules.”

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Publication: Proceedings of the National Academy of Sciences
Issue/Year: Proceedings of the National Academy of Sciences, Volume 118; Number 2; Pages e2020055118; 2020
DOI: 10.1073/pnas.2020055118

Flexible measurement of high-order optical orbital angular momentum with a variable cylindrical lens pair

Author(s):

Jianneng Lu, Chongyang Cao, Zhuqing Zhu and Bing Gu

Abstract:

“We present a method to measure the high-order optical orbital angular momentum (OAM) with a variable cylindrical lens pair. The optical system consists of two cylindrical lenses with the opposite focal length. It produces a rotating position—spatial frequency transformation of phase modulation by changing the angle between the two cylindrical lenses. With this feature, the method can flexibly measure the OAM states of the vortex beams with different beam waists. The OAM states are determined by the number and direction of dark stripes of the diffraction pattern. The measurements of the topological charge and the radial index of Laguerre–Gaussian mode are demonstrated. As a compact high-order OAM measuring device, the variable cylindrical lens pair may find potential applications in optical communication.
This work was funded by the National Natural Science Foundation of China (Nos. 11774055 and 61875093), the Natural Science Foundation of Jiangsu Province of China (No. BK20181384) and the Natural Science Foundation of Tianjin of China (No. 19JCYBJC16500).”

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Publication: Applied Physics Letters
Issue/Year: Appl. Phys. Lett. Volume:116 (2020)
DOI: 10.1063/5.0002756

High-resolution imaging system with an annular aperture of coded phase masks for endoscopic applications

Author(s):

Nitin Dubey, Joseph Rosen, and Israel Gannot

Abstract:

“Partial aperture imaging is a combination of two different techniques; coded aperture imaging and imaging through an aperture that is only a part of the complete disk, commonly used as the aperture of most imaging systems. In the present study, the partial aperture is a ring where the imaging through this aperture resolves small details of the observed scene similarly to the full disk aperture with the same diameter. However, unlike the full aperture, the annular aperture enables using the inner area of the ring for other applications. In this study, we consider the implementation of this special aperture in medical imaging instruments, such as endoscopes, for imaging internal cavities in general and of the human body in particular. By using this annular aperture, it is possible to transfer through the internal open circle of the ring other elements such as surgical tools, fibers and illumination devices. In the proposed configuration, light originated from a source point passes through an annular coded aperture and creates a sparse, randomly distributed, intensity dot pattern on the camera plane. A combination of the dot patterns, each one recorded only once, is used as the point spread hologram of the imaging system. The image is reconstructed digitally by cross correlation between the object intensity response and the point spread hologram.”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 10, pp. 15122-15137
DOI: 10.1364/OE.391713

Three-dimensional laser damage positioning by a deep-learning method

Author(s):

Zhan Li and Lu Han and Xiaoping Ouyang and Pan Zhang and Yajing Guo and Dean Liu and Jianqiang Zhu

Abstract:

“A holographic and deep learning-based method is presented for three-dimensional
laser damage location. The axial damage position is obtained by numerically focusing the
diffraction ring into the conjugate position. A neural network Diffraction-Net is proposed to
distinguish the diffraction ring from different surfaces and positions and obtain the lateral position.
Diffraction-Net, which is completely trained by simulative data, can distinguish the diffraction
rings with an overlap rate greater than 61% which is the best of results reported. In experiments,
the proposed method first achieves the damage pointing on each surface of cascade slabs using
diffraction rings, and the smallest inspect damage size is 8μm. A high precision result with the
lateral positioning error less than 38.5μm and axial positioning error less than 2.85mm illustrates
the practicability for locating the damage sites at online damage inspection.”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 7, pp. 10165-10178
DOI: 10.1364/OE.387987

Retrieving the optical transmission matrix of a multimode fiber using the extended Kalman filter

Author(s):

Guoqiang Huang and Daixuan Wu and Jiawei Luo and Yin Huang and Yuecheng Shen

Abstract:

” Characterizing the transmission matrix (TM) of a multimode fiber (MMF) benefits many fiber-based applications and allows in-depth studies on the physical properties. For example, by modulating the incident field, the knowledge of the TM allows one to synthesize
any optical field at the distill end of the MMF. However, the extraction of optical fields usually requires holographic measurements with interferometry, which complicates the system design and introduces additional noise. In this work, we developed an efficient method to retrieve the TM of the MMF in a referenceless optical system. With pure intensity measurements, this method uses the extended Kalman filter (EKF) to recursively search for the optimum solution. To facilitate the computational process, a modified speckle-correlation scatter matrix (MSSM) is constructed as a low-fidelity initial estimation. This method, termed EKF-MSSM, only requires 4N intensity measurements to precisely solve for N unknown complex variables in the TM. Experimentally, we successfully retrieved the TM of the MMF with high precision, which allows optical focusing with the enhancement (>70%) close to the theoretical value. We anticipate that this method will serve as a useful tool for studying physical properties of the MMFs and potentially open new possibilities in a variety of applications in fiber optics.”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 7, pp. 9487-9500
DOI: 10.1364/OE.389133