Jinyang Liang

Single-shot fringe projection profilometry (SS-FPP) has been extensively applied to the study of rapid three-dimensional (3D) dynamics in physics, engineering, and biology. Despite these advancements, the imaging capability of time-resolved SS-FPP is still limited by the flexibility and speed of both pattern projection and image acquisition, as well as by the duration of the observation time window. Here, we overcome these constraints by developing chromatically band-limited illumination profilometry (C-BLIP). On the illumination side, C-BLIP projects programmable grayscale fringes at ultrahigh speed by synergizing a digital micromirror device with a user-selectable encoding region of interest and a custom-designed projection lens for chromatically band-limited illumination with incoherent light sources. On the detection side, C-BLIP acquires spatially multiplexed color fringe images, followed by 3D image reconstruction. Using C-BLIP, we demonstrated color 3D imaging of a turbofan blade-projectile collision at 25 thousand frames per second (kfps), as well as intensity 3D imaging of maple samara’s fall aerodynamics at 75 kfps and ultrasound encryption/recovery at 150 kfps. These results highlight C-BLIP’s promise for continuous-streaming, ultrahigh-speed 3D metrology in industrial inspection, bionics, and data security.

A multi-dimensional spatiotemporal projection-based ultrafast compressed imaging technique is proposed. By incorporating a multi-angle projection module via time-wavelength mapping and two-dimensional diffraction, omnidirectional spatial frequencies of the transient event are captured to eliminate spatial anisotropy and achieve ultrafast imaging with high spatiotemporal resolutions.

This JOSA B feature issue showcases cutting-edge research by participants of the 2025 Photonics North conference held in Ottawa, Canada, in May 2025. This inaugural Photonics North feature issue comprises 31 articles from researchers in Canada and abroad that cover a broad scope of optics and photonics, including quantum light–matter interaction, biophotonics, advanced imaging and sensing, green photonics and energy, high power laser technology, ultrafast optics, nonlinear optics, nanophotonics, plasmonics, semiconductor photonics, photonic materials, photonics and artificial intelligence, as well as photonic theory, design, and simulations. This introduction provides a brief history of the Photonics North conference and an overview of the articles in this feature issue.

Compressed streak imaging (CSI) is a computational imaging strategy that can acquire video at over 150 trillion frames per second. Despite this achievement, CSI faces challenges in detecting subtle intensity fluctuations in slow-moving, continuously illuminated objects. This limitation, largely attributable to high streak compression and motion blur, has curtailed the broader adoption of CSI in cellular fluorescence microscopy. To address these issues and expand the utility of CSI, we developed a two-axis CSI (TACSI) method that results in significant improvements to the reconstructed video fidelity. TACSI introduces a second scanning axis, which shuttles a conjugate image of the object with respect to the coded aperture (CA). The moving image decreases the localized spatiotemporal mixing and produces a “flash and shutter” phenomenon that reduces CA motion blur, overcoming the limitations of current CSI technologies. This approach is supported by an analytical model describing the TACSI compression ratio, along with simulated and empirical measurements. We demonstrate TACSI’s ability to measure rapid variations in cell membrane potentials, previously unattainable with conventional CSI. This method has broad implications for high-speed photography, including visualization of action potentials, muscle contractions, and enzymatic reactions that occur on microsecond and faster timescales using fluorescence microscopy.

Real-time dynamic imaging of microbubbles is crucial for understanding their microscale biophysical interactions and advancing ultrasound therapy. Despite progress in time-resolved optical imaging, existing techniques still face trade-offs between acquisition speed, spatial resolution, affordability, and system complexity. Here, we introduce compressed optical-streaking dark-field ultrahigh-speed microscopy (COSDUM), a compact imaging platform that synergistically combines compressed sensing, streak imaging, dark-field microscopy, and deep learning. COSDUM compressively records megahertz acoustic microbubble dynamics over a wide field of view in a snapshot and reconstructs spatially resolved dynamics using a convolutional neural network-based algorithm. Using COSDUM, we captured stable cavitation, nonlinear oscillations, post-excitation free oscillations, and inertial collapse across microbubbles whose radii range from 0.5 to 2.1 μm. Applying COSDUM to microbubble-cell interaction in whole blood, we observed, for the first time, interplay between vibrating microbubbles and blood cells, including microbubble-driven platelet dynamics and highly asymmetric microbubble deformation and conformation around an adjacent red blood cell.

Modern optical design and simulation software, while both powerful and feature-rich, requires significant training investment for effective use, even for simple optical design tasks. By contrast, software for two-dimensional (2D) non-sequential raytracing, while sufficient for many optical design tasks and popular for educational purposes, has remained without the benefit of mature computer-aided design (CAD) technologies that are now a key feature of software dedicated to three-dimensional (3D) optical design. To overcome this limitation, we introduce M-TRACE—an open source toolkit for non-sequential 2D raytracing with scripting-based customization and animation capabilities implemented in MATLAB. This toolkit allows users to specify optical designs using tools compatible with free-form 2D illustration via scalable vector graphics (SVG), analogous to the integration of 3D CAD technologies with enterprise optical design software. The intuitive and precise drawing features of SVG illustration software (e.g., Adobe Illustrator, Inkscape) allow for a straightforward means for the creation of system designs. We intend M-TRACE to complement the spectrum of available optical design software for research, development, and education, specifically targeting design cases requiring rich visualization and/or rapid exploration.

Efficiently and accurately mapping the temperature of human inner canthi is crucial for disease diagnostics and monitoring. The specific anatomical location of the inner canthi precludes temperature screening methods that are invasive, require tissue contact, and/or demand active illumination. Camera-based thermography, although capable of passive and non-contact temperature mapping, suffers from low efficiency in pixel allocation to the inner canthi as well as from measurement inaccuracies due to background blending and moderate pixel sensitivity. In response to these challenges, we develop single-pixel infrared imaging thermometry (SPIRIT). We design diagonally aggregated two-dimensional transmissive encoding masks using a cyclic S-matrix, which supports compressed data acquisition in a single scan and high image quality through non-iterative reconstruction. SPIRIT maps the temperature distribution of human inner canthi with a resolution of 0.3 °C, which enables human temperature mapping via single-pixel imaging. Using SPIRIT, we reveal sub-degree temperature differences induced by daily physical activities and the glasses-wearing habit. These findings shed light on SPIRIT’s contribution to improving evaluation criteria for public health, including COVID-19 febrile screening.

Single-shot, high-speed 2D optical imaging is essential for studying transient phenomena in various research fields. Among existing techniques, compressed optical-streaking ultra-high-speed photography (COSUP) uses a coded aperture and a galvanometer scanner to capture non-repeatable time-evolving events at the 1.5 million-frame-per-second level. However, the use of a randomly coded aperture complicates the reconstruction process and introduces artifacts in the recovered videos. In contrast, non-multiplexing coded apertures simplify the reconstruction algorithm, allowing the recovery of longer videos from a snapshot. In this work, we design a non-multiplexing coded aperture for COSUP by exploiting the properties of congruent sphere packing (SP), which enables uniform space-time sampling given by the synergy between the galvanometer linear scanning and the optimal SP encoding patterns. We also develop an implicit neural representation—which can be self-trained from a single measurement—to not only largely reduce the training time and eliminate the need for training datasets but also reconstruct far more ultra-high-speed frames from a single measurement. The advantages of this proposed encoding and reconstruction scheme are verified by simulations and experimental results in a COSUP system.

The near-infrared (NIR) emission of rare-earth doped nanoparticles (RENPs), known as downshifting luminescence, has been extensively investigated in diverse applications from information technology to biomedicine. In promoting brightness and enriching the functionalities of the downshifting luminescence of RENPs, numerous studies have exploited inert shell to protect rare-earth dopants from surface quenchers. However, internal concentration quenching remains an unsolved puzzle when using higher dopant concentrations of rare-earth ions in an attempt to obtain brighter emission. Following a plethora of research involving core-shell structures, the interface has shown to be controllable, ranging from a well-defined, abrupt boundary to an obscure one with cation intermixing. By utilizing this inter-mixed core-shell property for the first time, we design a new architecture to create a homogeneous double-layer core-shell interface to extend the active layer, allowing more luminescent centers without severe concentration quenching. By systematically deploying the crystallinity of the starting core, shell growth dynamics, and dopant concentrations, the downshifting luminescence intensity of new archictecture achieves a 12-fold enhancement surpassing the traditional core-shell structure. These results provide deeper insight into the potential benefits of the intermixed core-shell structure, offering an effective approach to tackling the internal concentration quenching effect for highly boosted NIR optical performance.