The article comments on a new approach to information acquisition in hyperspectral imaging.
2023, 5(4): 040502
Structured illumination microscopy (SIM) has been widely applied in the superresolution imaging of subcellular dynamics in live cells. Higher spatial resolution is expected for the observation of finer structures. However, further increasing spatial resolution in SIM under the condition of strong background and noise levels remains challenging. Here, we report a method to achieve deep resolution enhancement of SIM by combining an untrained neural network with an alternating direction method of multipliers (ADMM) framework, i.e., ADMM-DRE-SIM. By exploiting the implicit image priors in the neural network and the Hessian prior in the ADMM framework associated with the optical transfer model of SIM, ADMM-DRE-SIM can further realize the spatial frequency extension without the requirement of training datasets. Moreover, an image degradation model containing the convolution with equivalent point spread function of SIM and additional background map is utilized to suppress the strong background while keeping the structure fidelity. Experimental results by imaging tubulins and actins show that ADMM-DRE-SIM can obtain the resolution enhancement by a factor of ∼1.6 compared to conventional SIM, evidencing the promising applications of ADMM-DRE-SIM in superresolution biomedical imaging.structured illumination microscopy superresolution imaging resolution enhancement untrained neural network
Advanced Photonics Nexus
2023, 2(4): 046005
This paper reports the fabrication of regular large-area laser-induced periodic surface structures (LIPSSs) in indium tin oxide (ITO) films via femtosecond laser direct writing focused by a cylindrical lens. The regular LIPSSs exhibited good properties as nanowires, with a resistivity almost equal to that of the initial ITO film. By changing the laser fluence, the nanowire resistances could be tuned from 15 to 73 kΩ/mm with a consistency of ±10%. Furthermore, the average transmittance of the ITO films with regular LIPSSs in the range of 1200–2000 nm was improved from 21% to 60%. The regular LIPSS is promising for transparent electrodes of nano-optoelectronic devices—particularly in the near-infrared band.transparent nanowires periodic surface nanostructures femtosecond laser direct writing ITO film anisotropic electrical conductivity
2023, 2(1): 220002
Various super-resolution microscopy techniques have been presented to explore fine structures of biological specimens. However, the super-resolution capability is often achieved at the expense of reducing imaging speed by either point scanning or multiframe computation. The contradiction between spatial resolution and imaging speed seriously hampers the observation of high-speed dynamics of fine structures. To overcome this contradiction, here we propose and demonstrate a temporal compressive super-resolution microscopy (TCSRM) technique. This technique is to merge an enhanced temporal compressive microscopy and a deep-learning-based super-resolution image reconstruction, where the enhanced temporal compressive microscopy is utilized to improve the imaging speed, and the deep-learning-based super-resolution image reconstruction is used to realize the resolution enhancement. The high-speed super-resolution imaging ability of TCSRM with a frame rate of 1200 frames per second (fps) and spatial resolution of 100 nm is experimentally demonstrated by capturing the flowing fluorescent beads in microfluidic chip. Given the outstanding imaging performance with high-speed super-resolution, TCSRM provides a desired tool for the studies of high-speed dynamical behaviors in fine structures, especially in the biomedical field.super-resolution microscopy high-speed imaging compressive sensing deep learning image reconstruction
2023, 5(2): 026003
Femtosecond laser ablation (FLA) has been playing a prominent role in precision fabrication of material because of its circumvention of thermal effect and extremely high spatial resolution. Molecular dynamics modeling, as a powerful tool to study the mechanism of femtosecond laser ablation, still lacks the connection between its simulation results and experimental observations at present. Here we combine a single-shot chirped spectral mapping ultrafast photography (CSMUP) technique in experiment and a three-dimensional two-temperature model-based molecular dynamics (3D TTM-MD) method in theory to jointly investigate the FLA process of bulky gold. Our experimental and simulated results show quite high consistency in time-resolved morphologic dynamics. According to the highly accurate simulations, the FLA process of gold at the high laser fluence is dominated by the phase explosion, which shows drastic vaporized cluster eruption and pressure dynamics, while the FLA process at the low laser fluence mainly results from the photomechanical spallation, which shows moderate temperature and pressure dynamics. This study reveals the ultrafast dynamics of gold with different ablation schemes, which has a guiding significance for the applications of FLA on various kinds of materials.
2022, 2(1): 9754131
laser-induced periodic structures (LIPSs) formation mechanisms femtosecond pulse shaping pump-probe imaging structural color birefringent effects optical absorption photoluminescence
Over the past two decades, femtosecond laser-induced periodic structures (femtosecond-LIPSs) have become ubiquitous in a variety of materials, including metals, semiconductors, dielectrics, and polymers. Femtosecond-LIPSs have become a useful laser processing method, with broad prospects in adjusting material properties such as structural color, data storage, light absorption, and luminescence. This review discusses the formation mechanism of LIPSs, specifically the LIPS formation processes based on the pump-probe imaging method. The pulse shaping of a femtosecond laser in terms of the time/frequency, polarization, and spatial distribution is an efficient method for fabricating high-quality LIPSs. Various LIPS applications are also briefly introduced. The last part of this paper discusses the LIPS formation mechanism, as well as the high-efficiency and high-quality processing of LIPSs using shaped ultrafast lasers and their applications.
2022, 1(6): 220005
Inhomogeneity and low efficiency are two important factors that limit the application of laser-induced periodic surface structures (LIPSSs), especially on glass surfaces. In this study, two-beam interference (TBI) of femtosecond lasers was used to produce large-area straight LIPSSs on fused silica using cylindrical lenses. Compared with those produced using a single circular or cylindrical lens, the LIPSSs produced by TBI are much straighter and more regular. Depending on the laser fluence and scanning velocity, LIPSSs with grating-like or spaced LIPSSs are produced on the fused silica surface. Their structural colors are blue, green, and red, and only green and red, respectively. Grating-like LIPSS patterns oriented in different directions are obtained and exhibit bright and vivid colors, indicating potential applications in surface coloring and anti-counterfeiting logos.
2021, 4(12): 200036-1
Single-shot 2D optical imaging of transient scenes is indispensable for numerous areas of study. Among existing techniques, compressed optical-streaking ultrahigh-speed photography (COSUP) uses a cost-efficient design to endow ultrahigh frame rates with off-the-shelf CCD and CMOS cameras. Thus far, COSUP’s application scope is limited by the long processing time and unstable image quality in existing analytical-modeling-based video reconstruction. To overcome these problems, we have developed a snapshot-to-video autoencoder (S2V-AE)—which is a deep neural network that maps a compressively recorded 2D image to a movie. The S2V-AE preserves spatiotemporal coherence in reconstructed videos and presents a flexible structure to tolerate changes in input data. Implemented in compressed ultrahigh-speed imaging, the S2V-AE enables the development of single-shot machine-learning assisted real-time (SMART) COSUP, which features a reconstruction time of 60 ms and a large sequence depth of 100 frames. SMART-COSUP is applied to wide-field multiple-particle tracking at 20,000 frames per second. As a universal computational framework, the S2V-AE is readily adaptable to other modalities in high-dimensional compressed sensing. SMART-COSUP is also expected to find wide applications in applied and fundamental sciences.
2021, 9(12): 12002464
In ultrafast optical imaging, it is critical to obtain the spatial structure, temporal evolution, and spectral composition of the object with snapshots in order to better observe and understand unrepeatable or irreversible dynamic scenes. However, so far, there are no ultrafast optical imaging techniques that can simultaneously capture the spatial–temporal–spectral five-dimensional (5D) information of dynamic scenes. To break the limitation of the existing techniques in imaging dimensions, we develop a spectral-volumetric compressed ultrafast photography (SV-CUP) technique. In our SV-CUP, the spatial resolutions in the x, y and z directions are, respectively, 0.39, 0.35, and 3 mm with an 8.8 mm × 6.3 mm field of view, the temporal frame interval is 2 ps, and the spectral frame interval is 1.72 nm. To demonstrate the excellent performance of our SV-CUP in spatial–temporal–spectral 5D imaging, we successfully measure the spectrally resolved photoluminescent dynamics of a 3D mannequin coated with CdSe quantum dots. Our SV-CUP brings unprecedented detection capabilities to dynamic scenes, which has important application prospects in fundamental research and applied science.ultrafast optical imaging multi-dimensional imaging computational imaging compressed sensing image reconstruction
2021, 3(4): 045001