Apratim Majumder
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View article: Wavefront Coding for Accommodation-Invariant Near-Eye Displays
Wavefront Coding for Accommodation-Invariant Near-Eye Displays Open
We present a new computational near-eye display method that addresses the vergence-accommodation conflict problem in stereoscopic displays through accommodation-invariance. Our system integrates a refractive lens eyepiece with a novel wave…
View article: High-definition (HD) snapshot diffractive computational spectral imaging and inferencing
High-definition (HD) snapshot diffractive computational spectral imaging and inferencing Open
Capturing spatial and spectral information from a scene is challenging due to the seemingly orthogonal nature of these dimensions. Here, we introduce a compact high-definition snapshot diffractive spectral imaging system that employs a dif…
View article: Fresnel zone plate outperforms the metalens at high NA
Fresnel zone plate outperforms the metalens at high NA Open
Rigorous simulations challenge recent claims that metalenses outperform conventional diffractive lenses, such as fresnel zone plates (FZPs), in focusing efficiency at high numerical apertures (NAs). Across various lens diameters, FZPs exhi…
View article: Diffraction-free orbital angular momentum holography
Diffraction-free orbital angular momentum holography Open
Holography offers significant potential for applications in information storage, encryption, beam-shaping, all-optical artificial intelligence, and three-dimensional displays. However, conventional holograms suffer from rapid image diffrac…
View article: Dynamic spectral fluorescence microscopy via event-based & CMOS image-sensor fusion
Dynamic spectral fluorescence microscopy via event-based & CMOS image-sensor fusion Open
We present a widefield fluorescence microscope that integrates an event-based image sensor (EBIS) with a CMOS image sensor (CIS) for ultra-fast microscopy with spectral distinction capabilities. The EBIS achieves a temporal resolution of ∼…
View article: Dynamic Spectral fluorescence microscopy via Event-based & CMOS image-sensor fusion
Dynamic Spectral fluorescence microscopy via Event-based & CMOS image-sensor fusion Open
We present a widefield fluorescence microscope that integrates an event-based image sensor (EBIS) with a CMOS image sensor (CIS) for ultra-fast microscopy with spectral distinction capabilities. The EBIS achieves temporal resolution of $\s…
View article: High-resolution optical coherence tomography using a multi-level diffractive lens
High-resolution optical coherence tomography using a multi-level diffractive lens Open
We present a high-resolution optical coherence tomography (OCT) imaging system that utilizes a multi-level diffractive lens (MDL) to enhance lateral resolution. The system utilizes a polygon-based swept laser source with a center wavelengt…
View article: HD snapshot diffractive spectral imaging and inferencing
HD snapshot diffractive spectral imaging and inferencing Open
We present a novel high-definition (HD) snapshot diffractive spectral imaging system utilizing a diffractive filter array (DFA) to capture a single image that encodes both spatial and spectral information. This single diffractogram can be …
View article: FDTD-based Inverse Design enables f/0.27 flat Microlens Array for Integral Imaging
FDTD-based Inverse Design enables f/0.27 flat Microlens Array for Integral Imaging Open
We demonstrate a high-NA (0.88), ultra-low-f-number (f/0.2714), multi-wavelength (480nm, 550nm and 650nm) multilevel diffractive MicroLens Array (MLA) using inverse design. Each microlens in the array is close-packed with diameter of 70 μm…
View article: Refractive-type varifocal liquid-crystal Fresnel lenses for smart contacts
Refractive-type varifocal liquid-crystal Fresnel lenses for smart contacts Open
We demonstrate the implementation of a low-power, low-profile, varifocal liquid-crystal Fresnel lens stack suitable for tunable imaging in smart contact lenses. The lens stack consists of a high-order refractive-type liquid crystal Fresnel…
View article: Refractive-type Varifocal Liquid-crystal Fresnel lenses for smart contacts
Refractive-type Varifocal Liquid-crystal Fresnel lenses for smart contacts Open
We demonstrate the implementation of a low-power, low-profile, varifocal liquid-crystal Fresnel lens stack suitable for tunable imaging in smart contact lenses. The lens stack consists of a high-order refractive-type liquid crystal Fresnel…
View article: Circumventing size-bandwidth limits in imaging with flat lenses
Circumventing size-bandwidth limits in imaging with flat lenses Open
Recent theoretical work suggested upper bounds on the operating bandwidths of flat lenses. Here, we show how these bounds can be circumvented via a multi-level diffractive lens (MDL) of diameter = 100 mm, focal length = 200 mm, device thic…
View article: Broadband point-spread function engineering via a freeform diffractive microlens array
Broadband point-spread function engineering via a freeform diffractive microlens array Open
We utilized inverse design to engineer the point-spread function (PSF) of a low-f-number, freeform diffractive microlens in an array, so as to enable extended depth of focus (DOF). Each square microlens of side 69 µm and focal length 40 µm…
View article: Large-area, high-numerical-aperture multi-level diffractive lens via inverse design: reply
Large-area, high-numerical-aperture multi-level diffractive lens via inverse design: reply Open
We proposed the use of relative encircled power as a measure of focusing efficiency [ Optica 7 , 252 ( 2020 ) OPTIC 82334-2536 10.1364/OPTICA.388697 ]. The comment [ Optica 8 , 1009 ( 2021 ) OPTIC 82334-2536 10.1364/OPTICA.416017 ] has rai…
View article: Imaging from the visible to the longwave infrared wavelengths via an inverse-designed flat lens
Imaging from the visible to the longwave infrared wavelengths via an inverse-designed flat lens Open
It is generally assumed that correcting chromatic aberrations in imaging requires multiple optical elements. Here, we show that by allowing the phase in the image plane to be a free parameter, it is possible to correct chromatic variation …
View article: Ultra-compact integrated photonic devices enabled by machine learning and digital metamaterials
Ultra-compact integrated photonic devices enabled by machine learning and digital metamaterials Open
We demonstrate three ultra-compact integrated-photonics devices, which are designed via a machine-learning algorithm coupled with finite-difference time-domain (FDTD) modeling. By digitizing the design domain into “binary pixels,” these di…
View article: Supplementary document for Imaging from the visible to the longwave infrared wavelengths via an inverse-designed flat lens - 5267513.pdf
Supplementary document for Imaging from the visible to the longwave infrared wavelengths via an inverse-designed flat lens - 5267513.pdf Open
Supplementary information
View article: Supplementary document for Free-form broadband flat lenses for visible imaging - 5007442.pdf
Supplementary document for Free-form broadband flat lenses for visible imaging - 5007442.pdf Open
Supplementary Information
View article: Free-form broadband flat lenses for visible imaging
Free-form broadband flat lenses for visible imaging Open
The resolution of a conventional lens is governed by its numerical aperture (NA) while its light-concentration ability is governed by its f-number (f/#), both of which are dependent on the diameter and focal length of the lens. Hence, thes…
View article: Machine Learning enables Ultra-Compact Integrated Photonics through\n Silicon-Nanopattern Digital Metamaterials
Machine Learning enables Ultra-Compact Integrated Photonics through\n Silicon-Nanopattern Digital Metamaterials Open
In this work, we demonstrate three ultra-compact integrated-photonics devices, which are designed via a machine-learning algorithm coupled with finite-difference time-domain (FDTD) modeling. Through digitizing the design domain into "binar…
View article: Machine Learning enables Ultra-Compact Integrated Photonics through Silicon-Nanopattern Digital Metamaterials
Machine Learning enables Ultra-Compact Integrated Photonics through Silicon-Nanopattern Digital Metamaterials Open
In this work, we demonstrate three ultra-compact integrated-photonics devices, which are designed via a machine-learning algorithm coupled with finite-difference time-domain (FDTD) modeling. Through digitizing the design domain into "binar…
View article: Super-resolution imaging with an achromatic multi-level diffractive microlens array
Super-resolution imaging with an achromatic multi-level diffractive microlens array Open
Compound eyes found in insects provide intriguing sources of biological inspiration for miniaturized imaging systems. Inspired by such insect eye structures, we demonstrate an ultrathin arrayed camera enabled by a flat multi-level diffract…
View article: Large-area, high-numerical-aperture multi-level diffractive lens via inverse design: erratum
Large-area, high-numerical-aperture multi-level diffractive lens via inverse design: erratum Open
This erratum contains corrections to Optica 7 , 252 ( 2020 ). OPTIC8 2334-2536 10.1364/OPTICA.388697
View article: Inverse-designed achromatic flat lens enabling imaging across the visible and near-infrared with diameter <b>&gt;</b> 3 mm and NA <b>=</b> 0.3
Inverse-designed achromatic flat lens enabling imaging across the visible and near-infrared with diameter <b>></b> 3 mm and NA <b>=</b> 0.3 Open
It is generally thought that correcting chromatic aberrations in imaging requires multiple surfaces. Here, we show that by allowing the phase in the image plane of a flat lens to be a free parameter, it is possible to correct chromatic abe…
View article: Extreme-depth-of-focus imaging with a flat lens
Extreme-depth-of-focus imaging with a flat lens Open
A lens performs an approximately one-to-one mapping from the object to the image plane. This mapping in the image plane is maintained within a depth of field (or referred to as depth of focus, if the object is at infinity). This necessitat…
View article: Supplementary document for Extreme depth of focus imaging with a flat lens - 4431475.pdf
Supplementary document for Extreme depth of focus imaging with a flat lens - 4431475.pdf Open
Supplementary Information
View article: Diffractive flat lens enables Extreme Depth-of-focus Imaging
Diffractive flat lens enables Extreme Depth-of-focus Imaging Open
A lens performs an approximately one-to-one mapping from the object to the image planes. This mapping in the image plane is maintained within a depth of field (or referred to as depth of focus, if the object is at infinity). This necessita…
View article: Single flat lens enabling imaging in the short-wave infra-red (SWIR) band
Single flat lens enabling imaging in the short-wave infra-red (SWIR) band Open
We designed and fabricated a flat multi-level diffractive lens (MDL) that is achromatic in the SWIR band (875 nm to 1675 nm). The MDL had a focal length of 25 mm, aperture diameter of 8.93 mm, and thickness of only 2.6 µm. By pairing the M…
View article: Broadband lightweight flat lenses for long-wave infrared imaging
Broadband lightweight flat lenses for long-wave infrared imaging Open
Significance We demonstrate, with simulations corroborated by experiments, that broadband long-wave infrared (LWIR) imaging is possible with a single flat lens with a thickness of 10 μm and a weight that is over 100 times less than convent…