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Non-invasive optical imaging techniques are essential diagnostic tools in many fields. Although various recent methods have been proposed to utilize and control light in multiple scattering media, non-invasive optical imaging through and inside scattering layers across a large field of view remains elusive due to the physical limits set by the optical memory effect, especially without wavefront shaping techniques. Here, we demonstrate an approach that enables non-invasive fluorescence imaging behind scattering layers with field-of-views extending well beyond the optical memory effect. The method consists in demixing the speckle patterns emitted by a fluorescent object under variable unknown random illumination, using matrix factorization and a novel fingerprint-based reconstruction. Experimental validation shows the efficiency and robustness of the method with various fluorescent samples, covering a field of view up to three times the optical memory effect range. Our non-invasive imaging technique is simple, neither requires a spatial light modulator nor a guide star, and can be generalized to a wide range of incoherent contrast mechanisms and illumination schemes. The authors demonstrate non-invasive fluorescence imaging behind scattering layers beyond the optical memory effect. They achieve this by demixing speckle patterns emitted by a fluorescent object under variable unknown random illumination, using matrix factorization and a fingerprint-based reconstruction.

Coherent Anti-Stokes Raman Scattering (CARS) has found critical applications across various fields, including high-speed chemical imaging, material science, and biomedical diagnostics. However, the inherent coherent nature of CARS poses challenges for quantitative chemical imaging due to the loss of spectral phase information. Accessing such information would enable faster chemical imaging speed through computational methods. Here, we develop a robust reference-less interferometric broadband pump/probe CARS to retrieve the vibrational spectral phase. We transfer the computational phase retrieval concept from quantitative spatial phase imaging to frequency-domain spectroscopy. We then unlock and demonstrate the concept of supervised compressive CARS microspectroscopy, enabling artifact-less high-speed quantitative chemical imaging. A vibrational spectral phase retrieval approach to broadband CARS spectroscopy is presented, therefore enabling supervised compressive CARS microspectroscopy for artifact-free, high-speed quantitative chemical imaging.

Three-dimensional (3D) high-resolution imaging is essential in microscopy, yet light scattering poses significant challenges in achieving it. Here, we present an approach to holographic imaging of spatially incoherent objects through scattering media, utilizing a virtual medium that replicates the scattering effects of the actual medium. This medium is constructed by retrieving mutually incoherent fields from the object and exploiting the spatial correlations between them. By numerically propagating the incoherent fields through the virtual medium, we non-invasively compensate for scattering, achieving accurate 3D reconstructions of hidden objects. Experimental validation with fluorescent and synthetic incoherent objects confirms the effectiveness of this approach, opening new possibilities for advanced 3D high-resolution microscopy in scattering environments. A computational imaging method is introduced that reconstructs three-dimensional structures of incoherently emitting objects through scattering media by retrieving scattered fields and compensating distortion, enabling accurate imaging in complex environments.

Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid–liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl–LiTFSI–water) and HCl–LiTFSI–water, prototypical salt–salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 μm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt–salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries.

Transition metal oxides are state-of-the-art materials for catalysing the oxygen evolution reaction (OER), whose slow kinetics currently limit the efficiency of water electrolysis. However, microscale physicochemical heterogeneity between particles, dynamic reactions both in the bulk and at the surface, and an interplay between particle reactivity and electrolyte makes probing the OER challenging. Here, we overcome these limitations by applying state-of-the-art compressive Raman imaging to uncover concurrent bias-dependent pathways for the OER in a dense, crystalline electrocatalyst, α-Li 2 IrO 3 . By spatially and temporally tracking changes in stretching modes we follow catalytic activation and charge accumulation following ion exchange under various electrolytes and cycling conditions, comparing our observations with other crystalline catalysts (IrO 2 , LiCoO 2 ). We demonstrate that at low overpotentials the reaction between water and the oxidized catalyst surface is compensated by bulk ion exchange, as usually only found for amorphous, electrolyte permeable, catalysts. At high overpotentials the charge is compensated by surface redox active sites, as in other crystalline catalysts such as IrO 2 . Hence, our work reveals charge compensation can extend beyond the surface in crystalline catalysts. More generally, the results highlight the power of compressive Raman imaging for chemically specific tracking of microscale reaction dynamics in catalysts, battery materials, or memristors. Advancing the oxygen evolution reaction understanding requires probing catalysts’ microscale dynamics in operando but is highly challenging. Here, authors use compressive Raman imaging to unravel the charge compensation pathways in a crystalline oxygen evolution catalyst, α-Li 2 IrO 3 .

Shaping light deep inside complex media such as biological tissue is critical to many research fields. Although the coherent control of scattered light via wavefront shaping has led to substantial advances in addressing this challenge, controlling light over extended or multiple targets without physical access to the inside of a medium remains elusive. Here we present a phase conjugation method for spatially incoherent light, which enables non-invasive light control based on incoherent emission from multiple target positions. Our method characterizes the scattering responses of hidden sources by retrieving mutually incoherent scattered fields from speckle patterns. By time-reversing scattered fluorescence with digital phase conjugation, we experimentally demonstrate focusing of light on individual and multiple targets. We also demonstrate maximum energy delivery to an extended target through a scattering medium by exploiting transmission eigenchannels. This paves the way to control light propagation in complex media using incoherent contrasts mechanisms.The non-invasive control of light based on incoherent emission from multiple target positions can be achieved by retrieving mutually incoherent scattered fields from speckle patterns, and then time-reversing scattered fluorescence with digital phase conjugation.

Understanding (de)lithiation heterogeneities in battery materials is key to ensure optimal electrochemical performance. However, this remains challenging due to the three-dimensional morphology of electrode particles, the involvement of both solid- and liquid-phase reactants and a range of relevant timescales (seconds to hours). Here we overcome this problem and demonstrate the use of confocal microscopy for the simultaneous three-dimensional operando measurement of lithium-ion dynamics in individual agglomerate particles, and the electrolyte in batteries. We examine two technologically important cathode materials: Li x CoO 2 and Li x Ni 0.8 Mn 0.1 Co 0.1 O 2 . The surface-to-core transport velocity of Li-phase fronts and volume changes are captured as a function of cycling rate. Additionally, we visualize heterogeneities in the bulk and at agglomerate surfaces during cycling, and image microscopic liquid electrolyte concentration gradients. We discover that surface-limited reactions and intra-agglomerate competing rates control (de)lithiation and structural heterogeneities in agglomerate-based electrodes. Importantly, the conditions under which optical imaging can be performed inside the complex environments of battery electrodes are outlined. Confocal optical microscopy is used to visualize—at high speed—solid (particle volume changes and phase-front velocities) and liquid electrolyte (concentration polarization gradients) dynamics inside operating batteries.

The last decade has seen the development of a wide set of tools, such as wavefront shaping, computational or fundamental methods, that allow us to understand and control light propagation in a complex medium, such as biological tissues or multimode fibers. A vibrant and diverse community is now working in this field, which has revolutionized the prospect of diffraction-limited imaging at depth in tissues. This roadmap highlights several key aspects of this fast developing field, and some of the challenges and opportunities ahead.

In recent years, rapid developments in imaging concepts and computational methods have given rise to a new generation of imaging technologies based on chaos. These chaos-inspired imaging technologies (CI 2 -Tech) consist of two directions: non-invasive and invasive. Non-invasive imaging, a much older research direction with a goal of imaging through scattering layers, has reached faster, smarter, and sharper imaging capabilities in recent years. The invasive imaging direction is based on exploiting the chaos to achieve imaging characteristics and increase dimensionalities beyond the limits of conventional imagers. In this roadmap, the current and future challenges in invasive and non-invasive imaging technologies are presented.

The intricate nature of the brain necessitates the application of advanced probing techniques to comprehensively study and understand its working mechanisms. Neurophotonics offers minimally invasive methods to probe the brain using optics at cellular and even molecular levels. However, multiple challenges persist, especially concerning imaging depth, field of view, speed, and biocompatibility. A major hindrance to solving these challenges in optics is the scattering nature of the brain. This perspective highlights the potential of complex media optics, a specialized area of study focused on light propagation in materials with intricate heterogeneous optical properties, in advancing and improving neuronal readouts for structural imaging and optical recordings of neuronal activity. Key strategies include wavefront shaping techniques and computational imaging and sensing techniques that exploit scattering properties for enhanced performance. We discuss the potential merger of the two fields as well as potential challenges and perspectives toward longer term in vivo applications.