On-chip optical architectures that enable angle-resolved spectroscopy are essential for advancing photonic platforms towards low-volume, scalable, and cryo-compatible devices. Here, we introduce spatially resolved momentum-space imaging using arrays of 3D-printed microlenses directly integrated onto semiconductor optical microcavities. Each microlens functions as an independent optical element with a high numerical aperture (approx. 0.95), enabling parallel back focal plane imaging across, in our implementation, 64 distinct locations. This approach eliminates the need for bulky microscope objectives while maintaining broad wavevector access, even under cryogenic conditions. We demonstrate its versatility across various cavity systems, including dielectric planar resonators, GaAs-based polariton microcavities, and CdTe platforms supporting nonequilibrium Bose-Einstein condensation of exciton-polaritons. The microlenses not only enhance collection efficiency but also enable tightly focused excitation, yielding an order of magnitude reduction in condensation thresholds compared with conventional setups. Our results establish 3D-printed microlens arrays as a compact, versatile, integrated platform for next-generation angle-resolved spectroscopy in nanophotonics and quantum materials.

Depending on environmental conditions, lightweight soft robots can exhibit various modes of locomotion that are difficult to model. As a result, optimizing their performance is complex, especially in small-scale systems characterized by low Reynolds numbers, when multiple aero- and hydrodynamical processes influence their movement. In this work, we study underwater swimmer locomotion by applying experimental results as the fitness function in two evolutionary algorithms: particle swarm optimization and genetic algorithm. Since soft, light-powered robots with different characteristics (phenotypes) can be fabricated quickly, they provide a great platform for optimisation experiments, using physical robots competing to improve swimming speed over consecutive generations. Interestingly, just like in natural evolution, unexpected gene combinations led to surprisingly good results, including several hundred percent increase in speed or the discovery of a self-oscillating underwater locomotion mode.

Prototype optical microscopes, built to pursue developments in advanced imaging techniques, need specific optomechanical constructions: preferably with high flexibility in the elements arrangement, easy access to the optical paths, straightforward integration with external optical subsystems - light sources and detectors - as well as good mechanical stability. Typically they are either built around an adapted commercial microscope body or as a home-built setup, based on standard optomechanical elements, and neither solution delivers the desired characteristics. We developed a series of versatile platforms for prototyping optical microscopes in various configurations that use folding mirror(s) to maintain the optical paths horizontal throughout most of the setup, thus enabling the use of standard optical components in the excitation and detection paths and, last but not least, increasing the laser safety of the optical system.

We discuss new ideas for developing fiber light sources for nonlinear imaging. We demonstrate high-power SC-based laser tunable within fingerprint region, as well as new methods of tuning FWM sidebands.

We present a stimulated Raman scattering (SRS) microscope integrated with a novel fiber-based light source. Our light source provides two synchronized pulse trains with 100 mW average power each, independently tunable in the range of 913 to 930 nm and 1024 to 1034 nm, respectively, thus enabling SRS measurements across the 990 to 1300 cm-1 spectral range with a spectral resolution of 15 cm-1. We demonstrate the SRS imaging of leukemic cells recorded in a few seconds. Our system may find potential application in biomedicine, in particular, helping to accelerate the diagnostics and follow-up treatment of leukemia patients.

Data set for all the experiments included in the main part of the text and in the supplementary information, together with the Mathematica notebook including all the theoretical and numerical calculations.

Despite spectacular progress in microfluidics, small-scale liquid manipulation, with few exceptions, is still driven by external pumps and controlled by large-scale valves, increasing cost and size and limiting complexity. By contrast, optofluidics uses light to power, control and monitor liquid manipulation, potentially allowing for small, self-contained microfluidic devices. Here we demonstrate a soft light-propelled actuator made of liquid crystal gel that pumps microlitre volumes of water. The strip of actuating material serves as both a pump and a channel leading to an extremely simple microfluidic architecture that is both powered and controlled by light. The performance of the pump is well explained by a simple theoretical model in which the light-induced bending of the actuator competes with the liquid's surface tension. The theory highlights that effective pumping requires a threshold light intensity and strip width. The proposed system explores the benefits of shifting the complexity of microfluidic systems from the fabricated device to spatio-temporal control over stimulating light patterns.

“How would you build a robot, the size of a bacteria, powered by light, that would swim towards the light source, escape from it, or could be controlled by means of different light colors, intensities or polarizations?” This was the question that Professor Diederik Wiersma asked PW on a sunny spring day in 2012, when they first met at LENS—the European Laboratory of Nonlinear Spectroscopy—in Sesto Fiorentino, just outside Florence in northern Italy. It was not just a vague question, as Prof. Wiersma, then the LENS director and leader of one of its research groups, already had an idea (and an ERC grant) about how to actually make such micro-robots, using a class of light-responsive oriented polymers, liquid crystal elastomers (LCEs), combined with the most advanced fabrication technique—two-photon 3D laser photolithography. Indeed, over the next few years, the LCE technology, successfully married with the so-called direct laser writing at LENS, resulted in a 60 micrometer long walker developed in Prof. Wiersma’s group (as, surprisingly, walking at that stage proved to be easier than swimming). After completing his post-doc at LENS, PW returned to his home Faculty of Physics at the University of Warsaw, and started experimenting with LCE, both in micrometer and millimeter scales, in his newly established Photonic Nanostructure Facility. This paper is a review of how the ideas of using light-powered soft actuators in micromechanics and micro-robotics have been evolving in Warsaw over the last decade and what the outcomes have been so far.

Laboratory procedures are often considered so unique that automating them is not economically justified – time and resources invested in designing, building and calibrating the machines are unlikely to pay off. This is particularly true if cheap labour force (technicians or students) is available. Yet, with increasing availability and dropping prices of many off-the-shelf components such as motorised stages, grippers, light sources (LEDs and lasers), detectors (high resolution, fast cameras), as well as user-friendly programmable microprocessors, many of the repeatable tasks may soon be within reach of either custom-built or universal lab robots. Building on our previous work on fabrication, characterization and applications of light-responsive liquid crystal elastomers (LCEs) in micro-robotics and micro-mechanics, in this paper we present a robotic workstation that can make LCE films with arbitrary molecular orientation. Based on a commercial 3D printer, the RoboLEC (Robot for LCE fabrication) performs precision component handling, structured light illumination, liquid dispensing and UV-triggered polymerization, within a four-hour-long procedure. Thus fabricated films with patterned molecular orientation are compared to the same, but handmade, structures.

Linear displacement is used for positioning and scanning, e.g., in robotics at different scales or in scientific instrumentation. Most linear motors are either powered by rotary drives or are driven directly by pressure, electromagnetic forces or a shape change in a medium, such as piezoelectrics or shape-memory materials. Here, we present a centimeter-scale light-powered linear inchworm motor, driven by two liquid crystal elastomer (LCE) accordion-like actuators. The rubbing overwriting technique was used to fabricate the LCE actuators, made of elastomer film with patterned alignment. In the linear motor, a scanned green laser beam induces a sequence of travelling deformations in a pair of actuators that move a gripper, which couples to a shaft via friction moving it with an average speed in the order of millimeters per second. The prototype linear motor demonstrates how LCE light-driven actuators with a limited stroke can be used to drive more complex mechanisms, where large displacements can be achieved, defined only by the technical constrains (the shaft length in our case), and not by the limited strain of the material. Inchworm motors driven by LCE actuators may be scaled down to sub-millimeter size and can be used in applications where remote control and power supply with light, either delivered in free space beams or via fibers, is an advantage.

Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool-a microbarbell-is used in two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four different trapping configurations provided different ways of sensing the torque and gave consistent results. The value of torque was determined by confronting the experimental results with numerical and analytical models.

The photomechanical response of liquid crystal polymer networks (LCNs) can be used to directly convert light energy into different forms of mechanical energy. In this study, we demonstrate how a traveling deformation, induced in a liquid crystal polymer ring by a spatially modulated laser beam, can be used to drive the ring (the rotor) to rotate around a stationary element (the stator), thus forming a light-powered micromotor. The photomechanical response of the polymer film is modeled numerically, different LCN molecular configurations are studied, and the performance of a 5.5 mm diameter motor is characterized.

In light science and applications, equally important roles are played by efficient light emitters/detectors and by the optical elements responsible for light extraction and delivery. The latter should be simple, cost effective, broadband, versatile and compatible with other components of widely desired micro-optical systems. Ideally, they should also operate without high-numerical-aperture optics. Here, we demonstrate that all these requirements can be met with elliptical microlenses 3D printed on top of light emitters. Importantly, the microlenses we propose readily form the collected light into an ultra-low divergence beam (half-angle divergence below 1°) perfectly suited for ultra-long-working-distance optical measurements (600 mm with a 1-inch collection lens), which are not accessible to date with other spectroscopic techniques. Our microlenses can be fabricated on a wide variety of samples, including semiconductor quantum dots and fragile van der Waals heterostructures made of novel two-dimensional materials, such as monolayer and few-layer transition metal dichalcogenides.

With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized smaller scales. One way towards miniaturization of robots involves remotely powered, light-driven soft mechanisms based on photo-responsive materials, such as liquid crystal elastomers (LCEs). While several simple devices have been demonstrated with contracting, bending, twisting, or other, more complex LCE actuators, only their simple behavior in response to light has been studied. Here we characterize the photo-mechanical response of a linear light-driven LCE actuator by measuring its response to laser beams with varying power, pulse duration, pulse energy, and the energy spatial distribution. Light absorption decrease in the actuator over time is also measured. These results are at the foundation of further development of soft, light-driven miniature mechanisms and micro-robots.

The ability to grip and handle small objects, from sub-millimeter electronic components to single-micrometer living cells, is vital for numerous ever-shrinking technologies. Mechanical grippers, powered by electric, pneumatic, hydraulic or piezoelectric servos, are well suited for the job at larger scales, but their complexity and need for force transmission prevent their miniaturization and remote control in tight spaces. Using liquid crystal elastomer microstructures that can change shape quickly and reversibly in response to light, a light-powered gripping tool-optical pliers-is built by growing two bending jaws on the tips of optical fibers. By delivering UV light to trigger polymerization via a micrometer-size fiber core, structures of similar size can be made without resorting to any microfabrication technology, such as laser photolithography. The tool is operated using visible light energy supplied through the fibers, with no force transmission. The elastomer growth technique readily offers micrometer-scale, remotely controlled functional structures with different modes of actuation as building blocks for the microtoolbox.

Safe interactions between humans and robots require the robotic arms and/or tools to recognize and react to the surrounding environment via pressure sensing. With small-scale surgical interventions in mind, we have developed a flexible skin with tens of pressure sensing elements, designed to cover a 5mm diameter tool. The prototype uses only biocompatible materials: soft silicones, carbon powder and metal wires. The material performance, sensing element design, manufacturing technology, and the readout electronics are described. Our prototype demonstrates the feasibility of using this technology in various intervention scenarios, from endoscopic navigation to tissue manipulation. We conclude by identifying research directions that maximise the potential of the proposed technology.

Just like nanometer-scale conductive paths in an electronic chip at some point end up connected to macroscopic wires of the printed circuit board, photonic integrated circuits often need light in/out coupling from/to external devices, such as light sources or detectors. In the optical domain, these connections are challenging due to the scale mismatch and alignment precision required. At the same time, there is more than 24,500 μm2 of space available on two cleaved single mode optical fiber tips. We demonstrate that this space can be used to fabricate compound photonic assembly - Photonic-chip-on-tip - directly integrated with the fibers. As an example, we present a simple setup consisting of in- and out-coupling prisms, tapered waveguide, and a whispering gallery micro-resonator, all made in a single process with two-photon laser photolithography. Temperature sensing is demonstrated as an example of application. This approach to photonic circuit design intrinsically addresses the problems of scale mismatch, fiber alignment, light coupling, and packaging.

Crawling by means of the traveling deformation of a soft body is a widespread mode of locomotion in nature-animals across scales, from microscopic nematodes to earthworms to gastropods, use it to move around challenging terrestrial environments. Snails, in particular, use mucus-a slippery, aqueous secretion-to enhance the interaction between their ventral foot and the contact surface. In this study, a millimeter-scale soft crawling robot is demonstrated that uses a similar mechanism to move efficiently in a variety of configurations: on horizontal, vertical, as well as upside-down surfaces; on smooth and rough surfaces; and through obstacles comparable in size to its dimensions. The traveling deformation of the robot soft body is generated via a local light-induced phase transition in a liquid crystal elastomer and resembles the pedal waves of terrestrial gastropods. This work offers a new approach to micro-engineering with smart materials as well as a tool to better understand this mode of locomotion in nature.

As the 3D quantitative phase imaging (QPI) methods mature, their further development calls for reliable tools and methods to characterize and compare their metrological parameters. We use refractive index engineering during two-photon laser photolithography to fabricate a life-scale phantom of a biological cell with internal structures that mimic optical and structural properties of mammalian cells. After verification with a number of reference techniques, the phantom is used to characterize the performance of a limited-angle holographic tomography microscope.

Dr. X.T. Liu, Ms. P. Q. Long, Prof. Z. G. Yi CAS Key Laboratory of Optoelectronic Materials Chemistry and Physics Fujian Institute of Research on the Structure of Matter Chinese Academy of Sciences Fuzhou 350002, China E-mail: zhiguo@fjirsm.ac.cn Dr. F.Q. Zhang, Prof. H. R. Zeng, Prof. Y. X. Li CAS Key Laboratory of Inorganic Functional Materials and Devices Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050, China E-mail: yxli@mail.sic.ac.cn Ms. T. Lu, Prof. Y. Liu, Prof. R.L.Withers Research School of Chemistry The Australian National University Canberra, ACT 2601, Australia. Prof. Z. G. Yi University of Chinese Academy of Sciences Beijing 100049, China