Ptychographic ultrahigh-speed imaging

Unsupervised physics-informed deep learning-based reconstruction for time-resolved imaging by multiplexed ptychography

We explore numerically an unsupervised, physics-informed, deep learning-based reconstruction technique for time-resolved imaging by multiplexed ptychography. In our method, the untrained deep learning model replaces the iterative algorithm's update step, yielding superior reconstructions of multiple dynamic object frames compared to conventional methodologies. More precisely, we demonstrate improvements in image quality and resolution, while reducing sensitivity to the number of recorded frames, the mutual orthogonality of different probe modes, overlap between neighboring probe beams and the cutoff frequency of the ptychographic microscope - properties that are generally of paramount importance for ptychographic reconstruction algorithms.

Single-shot ptychographic imaging of non-repetitive ultrafast events

We demonstrate experimentally high-speed ptychographic imaging of non-repetitive complex-valued events. Three time-resolved complex-valued frames are reconstructed from data recorded in a single camera snapshot. The temporal resolution of the microscope is determined by delays between illuminating pulses. The ability to image amplitude and phase of nonrepetitive events with ultrafast temporal resolution will open new opportunities in science and technology.

Temporal and spectral multiplexing for EUV multibeam ptychography with a high harmonic light source

We demonstrate temporally multiplexed multibeam ptychography implemented for the first time in the EUV, by using a high harmonic based light source. This allows for simultaneous imaging of different sample areas, or of the same area at different times or incidence angles. Furthermore, we show that this technique is compatible with wavelength multiplexing for multibeam spectroscopic imaging, taking full advantage of the temporal and spectral characteristics of high harmonic light sources. This technique enables increased data throughput using a simple experimental implementation and with high photon efficiency.

Wavelength-multiplexed single-shot ptychography

We present the first experimental demonstration of wavelength-multiplexing in single-shot ptychography. Specifically, we experimentally reconstruct the complex transmission profile of a wavelength-independent and wavelength-dependent object simultaneously for 532 nm and 633 nm probing wavelengths. In addition, we discuss the advantages of a more general approach to detector segmentation in single-shot ptychography. A minimization to correct for uncertainties in a priori information that is required for single-shot geometries is presented along with a novel probe constraint. Furthermore, this technique is complementary to dual-wavelength interferometry without the need for an external reference. This work is enabling to imaging technologies and applications such as broadband single-shot ptychography, time-resolved imaging by multiplexed ptychography, real-time inspection for laser micro-machining, and plasma imaging.

Spatiospectral characterization of ultrafast pulse-beams by multiplexed broadband ptychography

Ultrafast pulse-beam characterization is critical for diverse scientific and industrial applications from micromachining to generating the highest intensity laser pulses. The four-dimensional structure of a pulse-beam, E~(x,y,z,ω), can be fully characterized by coupling spatiospectral metrology with spectral phase measurement. When temporal pulse dynamics are not of primary interest, spatiospectral characterization of a pulse-beam provides crucial information even without spectral phase. Here we demonstrate spatiospectral characterization of pulse-beams via multiplexed broadband ptychography. The complex spatial profiles of multiple spectral components, E~(x,y,ω), from modelocked Ti:sapphire and from extreme ultra-violet pulse-beams are reconstructed with minimum intervening optics and no refocusing. Critically, our technique does not require spectral filters, interferometers, or reference pulses.

Punching holes in light: recent progress in single-shot coded-aperture optical imaging

Single-shot coded-aperture optical imaging physically captures a code-aperture-modulated optical signal in one exposure and then recovers the scene via computational image reconstruction. Recent years have witnessed dazzling advances in various modalities in this hybrid imaging scheme in concomitant technical improvement and widespread applications in physical, chemical and biological sciences. This review comprehensively surveys state-of-the-art single-shot coded-aperture optical imaging. Based on the detected photon tags, this field is divided into six categories: planar imaging, depth imaging, light-field imaging, temporal imaging, spectral imaging, and polarization imaging. In each category, we start with a general description of the available techniques and design principles, then provide two representative examples of active-encoding and passive-encoding approaches, with a particular emphasis on their methodology and applications as well as their advantages and challenges. Finally, we envision prospects for further technical advancement in this field.

Single-shot ptychography with highly tilted illuminations

A single-shot ptychographic iterative engine (PIE) using highly tilted illumination is proposed to realize accurate phase retrieval from a single frame of multiple and non-overlapping sub-diffraction patterns generated by a bunch of laser beams propagating at greater angles with respect to the optical axis. A non-paraxial reconstruction algorithm is developed to numerically propagate these highly tilted laser beams in back and forth iterative computations. Faster data acquisition and higher reconstruction quality are achieved in the proposed method by recording non-overlapping sub-diffraction patterns in a single frame and eliminating usual reconstruction errors arising from paraxial approximations.

Three-dimensional single-shot ptychography

Here we introduce three-dimensional single-shot ptychography (3DSSP). 3DSSP leverages an additional constraint unique to the single-shot geometry to deconvolve multiple 2D planes of a 3D object. Numeric simulations and analytic calculations demonstrate that 3DSSP reconstructs multiple planes in an extended 3D object with a minimum separation consistent with the depth of field for a conventional microscope. We experimentally demonstrate 3DSSP by reconstructing orthogonal hair strands axially separated by 5 mm. 3DSSP provides a pathway towards volumetric imaging of dynamically evolving systems on ultrafast timescales.

Deep neural networks in single-shot ptychography

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.

Experimental time-resolved imaging by multiplexed ptychography

A recently proposed technique introduced a time-resolved option of fast transient non-repetitive events to ptychographic microscopy. This technique, termed time-resolved imaging by multiplexed ptychography (TIMP), is based on algorithmic reconstruction of multiple frames from data recorded in a single camera acquisition of a single-shot ptychographic microscope. We demonstrate TIMP experimentally, reconstructing thirty-six frames of a dynamical complex-valued object from ptychographic data recorded in a single camera snapshot.

Multiplexed single-shot ptychography

We demonstrate experimentally multiplexed single-shot ptychography. Specifically, we present a polarization-resolved single-shot ptychographic microscope, where the orthogonally polarized amplitudes and phases of a polarization-sensitive object are reconstructed from ptychographic data recorded in a single camera exposure. Moreover, the amplitudes, phases, and polarization states of the probe beams are also recovered. That is, altogether we decipher eight images from single-shot ptychographic data. This work is an important step towards experimental demonstration of time-resolved imaging by multiplexed ptychography.

Single-shot aperture-scanning Fourier ptychography

Aperture-scanning Fourier ptychography [Opt. Express22, 13586 (2014)] is a promising non-interferometric wavefront measurement technique. It eliminates the thin-sample requirement in typical Fourier ptychography employing angle-varying illumination. However, as aperture-scanning Fourier ptychography is based on step-by-step scanning, it requires long data acquisition time and a high-stability optical system. In this paper, we propose a single-shot aperture-scanning Fourier ptychography method. In our method, multiple low-resolution images are collected in a single shot by inserting a Dammann grating at a certain distance before the aperture, and the images are subsequently converted to a high-resolution complex wavefront. Compared with scanning-based aperture-scanning Fourier ptychography, the total acquisition time of the proposed method is dramatically reduced. The feasibility of our proposed method is demonstrated by proof-of-concept experiments.

Single-shot ultrafast optical imaging

Single-shot ultrafast optical imaging can capture two-dimensional transient scenes in the optical spectral range at ≥100 million frames per second. This rapidly evolving field surpasses conventional pump-probe methods by possessing the real-time imaging capability, which is indispensable for recording non-repeatable and difficult-to-reproduce events and for understanding physical, chemical, and biological mechanisms. In this mini-review, we survey comprehensively the state-of-the-art single-shot ultrafast optical imaging. Based on the illumination requirement, we categorized the field into active-detection and passive-detection domains. Depending on the specific image acquisition and reconstruction strategies, these two categories are further divided into a total of six sub-categories. Under each sub-category, we describe operating principles, present representative cutting-edge techniques with a particular emphasis on their methodology and applications, and discuss their advantages and challenges. Finally, we envision prospects of technical advancement in this field.