Renjie Zhou

Chinese University of Hong Kong | CUHK · Department of Biomedical Engineering

Prof. Gabriel “Gabi” Popescu was a faculty member and the director of the Quantitative Light Imaging (QLI) Laboratory at the University of Illinois at Urbana-Champaign. He was a pioneer in quantitative phase imaging (QPI), having developed several common-path QPI methods at MIT and Illinois, and promoted the applications of QPI across different dom...

Quantitative phase imaging (QPI), propelled by advancements in digital holography and computational imaging, has revolutionized the ability to retrieve phase delays with high precision. Over the past two decades, the field has seen tremendous growth, contributing to numerous applications in biomedicine and material metrology, including live cell mo...

For more than 60 years, it has been widely accepted that the irradiance of the incoming light plays the most critical role in the etching effect of the photoelectrochemical (PEC) etching process, which is built upon the underlying physics that photo-generated charge carriers catalyze the dissolution of n-type semiconductors. However, in this paper,...

Optical computing systems provide high-speed and low-energy data processing but face deficiencies in computationally demanding training and simulation-to-reality gaps. We propose a gradient-based model-free optimization (G-MFO) method based on a Monte Carlo gradient estimation algorithm for computationally efficient in situ training of optical comp...

Laser spectroscopy offers a significant tool for revealing specific molecular details with the desired accuracy and sensitivity. However, it poses challenges to maintain high sensitivity when targeting a micro‐region. Here, a dual‐enhanced photothermal approach is presented using a high‐finesse fiber Fabry–Pérot (F–P) cavity, tailored for highly se...

JOSA A Editor-in-Chief Olga Korotkova, Deputy Editor Markus Testorf, and the members of the 2023 Emerging Researcher Best Paper Prize Committee announce the recipient of the 2023 prize for the best paper published by an emerging researcher in the Journal.

Optical diffraction tomography (ODT) is a label-free 3D light microscopy technique that utilizes refractive index (RI) distributions as a source of image contrast. In ODT, a sequence of 2D holograms is acquired to reconstruct a 3D RI map of a semi-transparent object by using an inverse scattering model. In recent developments, through using spatial...

The Compact Morpho‐Molecular Microscopy (CM 3 ) is proposed and demonstrated for multi‐functional imaging and characterization of living cells and material structures by simultaneously offering quantitative phase imaging (QPI), dispersion characterization, and fluorescence imaging. The compactness and stability of CM 3 are realized by propagating l...

Phase recovery (PR) refers to calculating the phase of the light field from its intensity measurements. As exemplified from quantitative phase imaging and coherent diffraction imaging to adaptive optics, PR is essential for reconstructing the refractive index distribution or topography of an object and correcting the aberration of an imaging system...

In single-molecule localization microscopy (SMLM) experiments, achieving precise localization results hinges on obtaining the authentic point spread function (PSF) influenced by system-induced and sample-induced aberrations. Here, we introduce VISPR (Vectorial in-situ PSF retrieval), a method employing the vector PSF model and the principles of max...

Imaging three-dimensional, subcellular structures with high axial resolution has always been the core purpose of fluorescence microscopy. However, trade-offs exist between axial resolution and other important technical indicators such as temporal resolution, optical power density, and imaging process complexity. In this paper, we report a new imagi...

Resolving three-dimensional morphological features in thick specimens remains a significant challenge for label-free imaging. We report a new speckle diffraction tomography (SDT) approach that can image thick biological specimens with ~500 nm lateral resolution and ~1 μm axial resolution in a reflection geometry. In SDT, multiple-scattering backgro...

Phase recovery (PR) refers to calculating the phase of the light field from its intensity measurements. As exemplified from quantitative phase imaging and coherent diffraction imaging to adaptive optics, PR is essential for reconstructing the refractive index distribution or topography of an object and correcting the aberration of an imaging system...

Soft-and-hard hybrid structures are ubiquitous in biological systems and have inspired the design of man-made mechanical devices, actuators, and robots. The realization of these structures, however, has been challenging at microscale, where material integration and actuation become exceedingly less practical. Here, through simple colloidal assembly...

The mammalian brain, with its complexity and intricacy, poses significant challenges for researchers aiming to understand its inner workings. Optical multilayer interference tomography (OMLIT) is a novel, promising imaging technique that enables the mapping and reconstruction of mesoscale all-cell brain atlases and is seamlessly compatible with tap...

Currently available deformability cytometry, combining microfluidics with the bright‐field high‐speed imaging system, has allowed label‐free mechanical characterizations of cells at a rate of hundreds of cells per second. However, the poor contrast between the signal and background under bright‐field imaging, especially for abnormal cells or cells...

Optical diffraction tomography (ODT) has gradually become a popular label-free imaging technique that offers diffraction-limited resolution by mapping an object's three-dimensional (3D) refractive index (RI) distribution. However, there is a lack of comprehensive quantitative image assessment metrics in ODT for studying how various experimental con...

Single-frame off-axis holographic reconstruction is promising for quantitative phase imaging. However, reconstruction accuracy and contrast are degraded by noise, frequency spectrum overlap of the interferogram, severe phase distortion, etc. In this work, we propose an iterative single-frame complex wave retrieval based on an explicit model of obje...

We propose a high-resolution label-free two-dimensional imaging method by introducing second-harmonic generation (SHG) and structured illumination in quantitative phase microscopy (QPM), termed S2QPM, which can achieve a fourfold lateral resolution improvement compared with normal incident illumination for noncentrosymmetric structures. Unlike trad...

Two-photon photopolymerization (TPP) has recently become a popular method for the fabrication of three-dimensional (3D) micro- and nanostructures. The reproduction fidelity of the designed micro- and nanostructures is influenced by experimental writing conditions, including laser power, exposure time, etc. To determine the appropriate writing param...

Single neural networks have achieved simultaneous phase retrieval with aberration compensation and phase unwrapping in off-axis Quantitative Phase Imaging (QPI). However, when designing the phase retrieval neural network architecture, the trade-off between computation latency and accuracy has been largely neglected. Here, we propose Neural Architec...

Two-photon photopolymerization (TPP) has recently become a popular method for the fabrication of three-dimensional (3D) micro- and nanostructures. The reproduction fidelity of the designed micro- and nanostructures is influenced by experimental writing conditions, including laser power, exposure time, etc. To determine the appropriate writing param...

The physical properties of two-dimensional (2D) materials may drastically vary with their thickness profiles. Current thickness profiling methods for 2D material (e.g., atomic force microscopy and ellipsometry) are limited in measurement throughput and accuracy. Here we present a novel high-speed and high-precision thickness profiling method, terme...

Liquid–liquid phase separation (LLPS) forms biomolecular condensates or coacervates in cells. Metabolic enzymes can form phase‐separated subcellular compartments that enrich enzymes, cofactors, and substrates. Herein, we report the construction of synthetic multienzyme condensates that catalyze the biosynthesis of a terpene, α‐farnesene, in the pro...

Liquid‐liquid phase separation (LLPS) forms biomolecular condensates or coacervates in cells. Metabolic enzymes can form phase‐separated subcellular compartments that enrich enzymes, co‐factors, and substrates. Here, we report the construction of synthetic multienzyme condensates that catalyze the biosynthesis of a terpene, a‐farnesene in the proka...

The growing demand for electronic devices, smart devices, and the Internet of Things constitutes the primary driving force for marching down the path of decreased critical dimension and increased circuit intricacy of integrated circuits. However, as sub-10 nm high-volume manufacturing is becoming the mainstream, there is greater awareness that defe...

Optical diffraction tomography (ODT) has emerged as a powerful label-free three-dimensional (3D) bioimaging techniques for observing living cells and thin tissue layers. We report a new reflection-mode ODT (rODT) method for imaging thick biological specimens with 500 nm lateral resolution and 1 {\mu}m axial resolution. In rODT, multiple scattering...

Three-dimensional structured illumination microscopy (3D-SIM) plays an essential role in biological volumetric imaging with the capabilities of improving lateral and axial resolution. However, the traditional linear 3D algorithm is sensitive to noise and generates artifacts, while the low temporal resolution hinders live-cell imaging. In this paper...

Three-dimensional (3D) image cytometers may significantly improve the cell analysis accuracy to facilitate biological discoveries and clinical diagnosis, but their development is curbed by the low imaging throughput. Here we report SIngle-frame LAbel-free Cell Tomography (SILACT) with diffraction-limited resolution and unprecedented imaging speed o...

We present an algorithm to correct aberrations in off-axis quantitative phase microscopy. The distortion is efficiently estimated by fitting a polynomial model to the wrapped phase iteratively. Robustness to noise and phase discontinuity is demonstrated.

We demonstrate a high-speed optical diffraction tomography method with an unprecedented three-dimensional imaging speed of over 10,000 volumes per second and diffraction-limited resolution and apply it for high-throughput cell analysis and additive manufacturing metrology.

We propose a high-bandwidth complex wave retrieval algorithm from a single off-axis interferogram. A 40% improvement of allowed object wave bandwidth over standard approaches is demonstrated. Despite being iterative, our implementation is efficient.

Optical super-resolution microscopy can break the diffraction limit in far-field imaging to achieve nanoscopic resolution. Nowadays, super-resolution imaging based on saturated excitation exhibits great potentials in extracting high-frequency components. Current saturated absorption competition (SAC) method is based on spatio-temporally modulating...

Polarization light microscopes are powerful tools for probing molecular order and orientation in birefringent materials. While a number of polarization microscopy techniques are available to access steady-state properties of birefringent samples, quantitative measurements of the molecular orientation dynamics on the millisecond time scale have rema...

Understanding the complexity of animals' behaviors and intellect relies on decoding the underlying structure and wiring diagram of their brains. Various imaging techniques have been developed to tackle this challenge, yet they still have limitations in mapping all cells in a brain region at mesoscale level. Here we propose an optical multilayer int...

Leukocyte differential test is a widely performed clinical procedure for screening infectious diseases. Existing hematology analyzers require labor-intensive work and a panel of expensive reagents. Here we report an artificial-intelligence enabled reagent-free imaging hematology analyzer (AIRFIHA) modality that can accurately classify subpopulation...

Fourier ptychographic microscopy (FPM), as an emerging computational imaging method, has been applied to quantitative phase imaging with resolution bypassing the physical limit of the detection objective. Due to the weak illumination intensity and long image acquisition time, the achieved imaging speed in current FPM methods is still low, making th...

Close to half of the world population have smartphones, while a flagship smartphone today has been integrated with more than 20 smart components and sensors, making a smartphone a highly integrated platform that can potentially mimic the five senses of humans. Recent advancement in achieving high compactness, high performance computing, high flexib...

Quantitative Phase Imaging A reagent-free hematology analyzer is developed in article number 2000277 by Rishikesh Pandey, Renjie Zhou, and co-workers. The researchers employ a quantitative phase imaging in conjunction with a neural network to classify leukocytes. In the cover image, cells are illuminated by a laser and phase images are acquired by...

Polarization light microscopes are powerful tools for probing molecular order and orientation in birefringent materials. While a multitude of polarization light microscopy techniques are often used to access steady-state properties of birefringent samples, quantitative measurements of the molecular orientation dynamics on the millisecond time scale...

Leukocyte differential test is a widely carried out clinical procedure for screening infectious diseases. Existing hematology analyzers require labor‐intensive work and a panel of expensive reagents. Herein, an artificial‐intelligence‐enabled reagent‐free imaging hematology analyzer (AIRFIHA) modality is reported that can accurately classify subpop...

Phase sensitivity determines the lowest optical path length value that can be detected from the noise floor in quantitative phase microscopy (QPM). The temporal phase sensitivity is known to be limited by both photon shot noise and a variety of noise sources from electronic devices and environment. To beat the temporal phase sensitivity limit, we e...

We propose a single-shot 3D cell imaging method with unprecedented sub-millisecond temporal resolution and diffraction-limited spatial resolution. This method is based on an angle-multiplexed illumination interferometric imaging system and a deep-learning 3D image reconstruction model.

Non-interferometric quantitative phase imaging at 1 μm wavelength regime is demonstrated using transport-of-intensity equation-based phase retrieval algorithm and fiber laser. Amplitude and phase information of the complex field of the sample has been retrieved and presented.

For high-throughput single cell analysis with a high accuracy, it is vital to develop a high-speed three-dimensional (3D) imaging method. For this endeavor, we propose a single-shot 3D cell imaging method that can achieve diffraction-limited spatial resolution and sub-millisecond temporal resolution. This method is realized through training a deep...

Leukocyte differential test is a widely performed clinical procedure for screening infectious diseases. Existing hematology analyzers require labor-intensive work and a panel of expensive reagents. Here we report an artificial-intelligence enabled reagent-free imaging hematology analyzer (AIRFIHA) modality that can accurately classify subpopulation...

A new optical microscopy technique, termed high spatial and temporal resolution synthetic aperture phase microscopy (HISTR-SAPM), is proposed to improve the lateral resolution of wide-field coherent imaging. Under plane wave illumination, the resolution is increased by twofold to around 260 nm, while achieving millisecond-level temporal resolution....

Phase sensitivity determines the lowest optical path length (OPL) value that can be detected from the noise floor in a quantitative phase microscopy (QPM) system. The temporal phase sensitivity is known to be limited by both photon shot-noise and a variety of noise sources from electronic devices and environment. To beat temporal phase sensitivity...