Maskless lithography for versatile and low cost fabrication of polymer based micro optical structures

Author(s):

Muhammad Shaukat Khan, Roland lachmayer, and Bernhard Roth

Abstract:

“For applications in optical communication, sensing or information projection in automotive lighting, polymer based optical devices are of keen interest. Optical structures such as waveguides and gratings are basic blocks for these devices. We report on a simple, versatile, and yet low-cost fabrication method suited for both binary and multilevel diffractive microstructures as well as multimode optical waveguides in polymers. The fabrication of the diffractive structures, i.e. gratings, with two and multiple levels, is achieved by using a maskless optical lithography system employing a spatial light modulator. With the same system, waveguide cladding structures are realized by stitching of multiple single exposure patterns. For replication of these structures on polymer, e.g. polymethyl methacrylate (PMMA), a lab-made hot embossing machine is used. We then employ UV curable material and doctor blading to realize the waveguide cores. The created diffractive and waveguide structures are characterized in terms of diffraction efficiency and optical propagation loss, respectively, showing good optical quality and performance. With our fabrication system we have demonstrated a diffraction efficiency of 71% for multilevel grating structure and a propagation loss for stitched waveguides of 2.07 dB/cm at a wavelength of 638 nm. These basic elements will be employed to realize entire optical measurement systems for applications in sensing and integrated photonics in the next step.”

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Publication: OSA Continuum
Issue/Year: OSA Continuum, Volume 3; Number 10; Pages 2808; 2020
DOI: 10.1364/osac.400056

Foveated near-eye display using computational holography

Author(s):

Cem, Ali; Hedili, M. Kivanc; Ulusoy, Erdem & Urey, Hakan

Abstract:

“Holographic display is the only technology that can offer true 3D with all the required depth cues. Holographic head-worn displays (HWD) can provide continuous depth planes with the correct stereoscopic disparity for a comfortable 3D experience. Existing HWD approaches have small field-of-view (FOV) and small exit pupil size, which are limited by the spatial light modulator (SLM). Conventional holographic HWDs are limited to about 20° × 11° FOV using a 4 K SLM panel and have fixed FOV. We present a new optical architecture that can overcome those limitations and substantially extend the FOV supported by the SLM. Our architecture, which does not contain any moving parts, automatically follows the gaze of the viewer’s pupil. Moreover, it mimics human vision by providing varying resolution across the FOV resulting in better utilization of the available space-bandwidth product of the SLM. We propose a system that can provide 28° × 28° instantaneous FOV within an extended FOV (the field of view that is covered by steering the instantaneous FOV in space) of 60° × 40° using a 4 K SLM, effectively providing a total enhancement of > 3 × in instantaneous FOV area, > 10 × in extended FOV area and the space-bandwidth product. We demonstrated 20° × 20° instantaneous FOV and 40° × 20° extended FOV in the experiments.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 10; Number 1; 2020
DOI: 10.1038/s41598-020-71986-9

New standard glass DOEs available

HOLOEYE introduces 5 new of off-the-shelf standard glass diffractive optical elements. These stock elements are made of Fused Silica glass by etching, or are replicated using Acrylate polymers on Soda Lime glass substrates. Both versions feature an anti-reflective (AR) coating on the plain side of the glass substrate. (more…)

New versions of SLM SDK for MatLab, LabVIEW, Octave and ANSI C (Windows)

SLM SDK IconUpdated versions of the HOLOEYE Spatial Light Modulator Display SDK for MatLab, LabVIEW, Octave and ANSI C (Windows versions) are now available. Updates are available trough our download website at https://customers.holoeye.com.

The main new features are transform functionalities for scaling and shifting of the image, reposition and changing focus and functions to add Zernike polynomials. (more…)

Light-triggered switching of liposome surface charge directs delivery of membrane impermeable payloads in vivo

Author(s):

Arias-Alpizar, Gabriela; Kong, Li; Vlieg, Redmar C.; Rabe, Alexander; Papadopoulou, Panagiota; Meijer, Michael S.; Bonnet, Sylvestre; Vogel, Stefan; van Noort, John; Kros, Alexander & Campbell, Frederick

Abstract:

“Surface charge plays a fundamental role in determining the fate of a nanoparticle, and any encapsulated contents, in vivo. Herein, we describe, and visualise in real time, light-triggered switching of liposome surface charge, from neutral to cationic, in situ and in vivo (embryonic zebrafish). Prior to light activation, intravenously administered liposomes, composed of just two lipid reagents, freely circulate and successfully evade innate immune cells present in the fish. Upon in situ irradiation and surface charge switching, however, liposomes rapidly adsorb to, and are taken up by, endothelial cells and/or are phagocytosed by blood resident macrophages. Coupling complete external control of nanoparticle targeting together with the intracellular delivery of encapsulated (and membrane impermeable) cargos, these compositionally simple liposomes are proof that advanced nanoparticle function in vivo does not require increased design complexity but rather a thorough understanding of the fundamental nano-bio interactions involved.”

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Publication: Nature Communications
Issue/Year: Nature Communications, Volume 11; Number 1; 2020
DOI: 10.1038/s41467-020-17360-9

Direct comparison of anti-diffracting optical pin beams and abruptly autofocusing beams

Author(s):

Denghui Li, Domenico Bongiovanni, Michael Goutsoulas, Shiqi Xia, Ze Zhang, Yi Hu, Daohong Song, Roberto Morandotti, Nikolaos K. Efremidis, and Zhigang Chen

Abstract:

“We propose and demonstrate a generalized class of anti-diffracting optical pin-like beams (OPBs). Such beams exhibit autofocusing dynamics while morphing into a Bessel-like shape during long-distance propagation, where the size of their main lobe can be tuned by an exponent’s parameter. In particular, their amplitude envelope can be engineered to preserve the pin-like peak intensity pattern. In both theory and experiment, the OPBs are directly compared with radially symmetric abruptly autofocusing beams (AABs) under the same conditions. Furthermore, enhanced transmission and robustness of the OPBs are observed while traversing a scattering colloidal suspension, as compared to both AABs and conventional Bessel beams.”

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Publication: OSA Continuum
Issue/Year: Vol. 3, Issue 6, pp. 1525-1535 (2020)
DOI: 10.1364/OSAC.391878

Hologram generation via Hilbert transform

Author(s):

Tomoyoshi Shimobaba, Takashi Kakue, Yota Yamamoto, Ikuo Hoshi, Harutaka Shiomi, Takashi Nishitsuji, Naoki Takada, and Tomoyoshi Ito

Abstract:

“We propose an indirect method for generating a complex hologram and phase-only hologram from an amplitude hologram using the Hilbert transform. The Hilbert transform generates an imaginary part of complex amplitude from only an amplitude hologram, resulting in the reduction of the total computational complexity of complex and phase-only holograms. More importantly, the proposed method can reduce the hardware resources of dedicated hologram processors.”

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Publication: OSA Continuum
Issue/Year: Vol. 3, Issue 6, pp. 1498-1503 (2020)
DOI: 10.1364/OSAC.395003

Deep neural networks in single-shot ptychography

Author(s):

Omri Wengrowicz, Or Peleg, Tom Zahavy, Barry Loevsky, and Oren Cohen

Abstract:

“We develop and explore a deep learning based single-shot ptychography reconstruction method. We show that a deep neural network, trained using only experimental data and without any model of the system, leads to reconstructions of natural real-valued images with higher spatial resolution and better resistance to systematic noise than common iterative algorithms.”

Link to Publications Page

Publication: Optics Express
Issue/Year: Vol. 28, Issue 12, pp. 17511-17520
DOI: 10.1364/OE.393961

WISHED: Wavefront imaging sensor with high resolution and depth ranging

Author(s):

Yicheng Wu, Fengqiang Li, Florian Willomitzer, Ashok Veeraraghavan, Oliver Cossairt

Abstract:

“Phase-retrieval based wavefront sensors have been shown to reconstruct the complex field from an object with a high spatial resolution. Although the reconstructed complex field encodes the depth information of the object, it is impractical to be used as a depth sensor for macroscopic objects, since the unambiguous depth imaging range is limited by the optical wavelength. To improve the depth range of imaging and handle depth discontinuities, we propose a novel three-dimensional sensor by leveraging wavelength diversity and wavefront sensing. Complex fields at two optical wavelengths are recorded, and a synthetic wavelength can be generated by correlating those wavefronts. The proposed system achieves high lateral and depth resolutions. Our experimental prototype shows an unambiguous range of more than 1,000 x larger compared with the optical wavelengths, while the depth precision is up to 9µm for smooth objects and up to 69µm for rough objects. We experimentally demonstrate 3D reconstructions for transparent, translucent, and opaque objects with smooth and rough surfaces.”

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Publication: 2020 IEEE International Conference on Computational Photography (ICCP)
DOI: 10.1109/ICCP48838.2020.9105280
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