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The ability to retrieve image data through hair-thin optical fibers promises to open up new applications in a range of fields, from biomedical imaging to industrial inspection. Unfortunately, small changes in mechanical deformation and temperature can completely scramble optical information, distorting any resulting images. Correction of these dynamic changes requires measurement of the fiber transmission matrix (TM) in situ immediately before imaging, which typically requires access to both the proximal and distal facets of the fiber simultaneously. As a result, TM calibration is not feasible during most realistic usage scenarios without compromising the thin form factor with bulky distal optics. Here, we introduce a new approach to determine the TM of multimode or multicore optical fibers in a reflection-mode configuration, without requiring access to the distal facet. We propose introducing a thin stack of structured metasurface reflectors at the distal facet of the fiber, to introduce wavelength-dependent, spatially heterogeneous reflectance profiles. We derive a first-order fiber model that compensates these wavelength-dependent changes in the fiber TM and show that, consequently, the reflected data at three wavelengths can be used to unambiguously reconstruct the full TM by an iterative optimization algorithm. Unlike previous approaches, our method does not require the fiber matrix to be unitary, making it applicable to physically realistic fiber systems that have non-negligible power loss. We demonstrate TM reconstruction and imaging first using simulated nonunitary fibers and noisy reflection matrices, then using larger experimentally measured TMs of a densely packed multicore fiber (MCF), and finally using experimentally measured multiwavelength TMs recorded from a step-index multimode fiber (MMF). Parallelization of multiwavelength in situ measurements could enable experimental characterization times comparable with state-of-the-art transmission-mode fiber TM experiments. Our findings pave the way for online TM calibration in situ in hair-thin optical fibers.

Understanding and improving the perceived quality of reconstructed images is key to developing computer-generated holography algorithms for high-fidelity holographic displays. However, current algorithms are typically optimized using mean squared error, which is widely criticized for its poor correlation with perceptual quality. In our work, we present a comprehensive analysis of employing contemporary image quality metrics (IQM) as loss functions in the hologram optimization process. Extensive objective and subjective assessment of experimentally reconstructed images reveal the relative performance of IQM losses for hologram optimization. Our results reveal that the perceived image quality improves considerably when the appropriate IQM loss function is used, highlighting the value of developing perceptually-motivated loss functions for hologram optimization.

Non-destructive, on-site screening methods capable of molecular analysis directly through commercial packaging remain a significant challenge for safety, security, and quality assurance. Here, we introduce an original non-invasive photonics approach based on Raman spectroscopy that combines wavefront shaping with wavelength modulation. The wavefront shaping acts to limit the signal contribution from the packaging, while wavelength modulation further suppresses fluorescence to enhance the method's sensitivity. As a result of this judicious combination, we are able to enhance the signal-to-noise ratio of the Raman scattering obtained through the packaging up to 12-fold. We demonstrate the capability of the system by quantifying methanol in bottled spirits. Our method achieves quantification of methanol through coloured spirit bottles with a limit of detection of 0.2% (v/v) methanol in 40% ethanol, well below the reported maximum tolerable methanol concentration of 2% (v/v). In contrast to previous approaches, this method remains robust across a diverse range of coloured glass bottles, validated by measurements on real spirit bottles and samples. More broadly, this geometry establishes a versatile Raman sensing platform for assessing authenticity, composition, and contaminants directly through packaging.

This work describes a novel approach to time-multiplexed holographic projection on binary phase devices. Unlike other time-multiplexed algorithms where each frame is the inverse transform of independently modified target images, Single-Transform Time-Multiplexed (STTM) hologram generation produces multiple sub-frames from a single inverse transform. Uniformly spacing complex rotations on the diffraction field then allows the emulation of devices containing 2^N modulation levels on binary devices by using N sub-frames. In comparison to One-Step Phase Retrieval (OSPR), STTM produces lower mean squared error for up to N = 5 than the equivalent number of OSPR sub-frames with a generation time of 1/N of the equivalent OSPR frame. A mathematical justification of the STTM approach is presented and a hybrid approach is introduced allowing STTM to be used in conjunction with OSPR in order to combine performance benefits.

A major unaddressed challenge for food science remains the accurate characterisation of contents in sealed containers with a non-invasive method. This issue is particularly pressing for tackling fraud in the red wine industry, valued at billions of dollars globally, where product authenticity, brand reputation, and consumer trust are paramount. Whilst many techniques exist for authenticating wine externally, to date performing accurate classification of the contents within unopened bottles remains elusive. Using only a single near-infrared optical excitation source operating at a wavelength of 785 nm, in combination with a bespoke geometry to circumvent the confounding signal of the glass, we demonstrate that through-bottle fluorescence spectra can distinguish between twenty different red wines in their original, intact bottles. All twenty wine bottles were correctly classified with linear discriminant analysis (LDA) and principal component analysis (PCA) revealed strong varietal grouping. This non-invasive and rapid technique has the potential to enable on-site, routine wine authentication to combat the growing issue of wine fraud. The geometry itself is applicable across multiple fields for the analysis of other high-value products through their packaging, where authenticity verification is critical.

Food and beverage contamination poses a persistent global threat. A prime example is the presence of methanol in counterfeit or illicit spirits, causing severe and often fatal poisoning worldwide. Rapid, non-destructive, and on-site screening methods capable of molecular analysis directly through commercial packaging are therefore urgently needed for quality control and consumer safety. Here, we introduce a non-invasive optical approach based on Raman spectroscopy that judiciously combines wavefront shaping with wavelength modulation to enhance the signal-to-noise ratio and enable quantification of methanol in unopened bottled spirits. A limit of detection of 0.2% (v/v) methanol in 40% ethanol was achieved, well below the 2% (v/v) threshold for safe human consumption. This truly non-invasive method remains robust through coloured glass bottles, with calibration validated in a real spirit sample. By enabling through-container methanol detection, the technique offers a practical tool to protect consumers and streamline routine screening across the beverage supply chain. Moreover, this Raman geometry establishes a versatile platform for assessing authenticity, composition, and contaminants directly through packaging.

Food and beverage contamination poses a persistent global threat. A prime example is the presence of methanol in counterfeit or illicit spirits, causing severe and often fatal poisoning worldwide. Rapid, non-destructive, and on-site screening methods capable of molecular analysis directly through commercial packaging are therefore urgently needed for quality control and consumer safety. Here, we introduce a non-invasive optical approach based on Raman spectroscopy that judiciously combines wavefront shaping with wavelength modulation to enhance the signal-to-noise ratio and enable quantification of methanol in unopened bottled spirits. A limit of detection of 0.2% (v/v) methanol in 40% ethanol was achieved, well below the 2% (v/v) threshold for safe human consumption. This truly non-invasive method remains robust through coloured glass bottles, with calibration validated in a real spirit sample. By enabling through-container methanol detection, the technique offers a practical tool to protect consumers and streamline routine screening across the beverage supply chain. Moreover, this Raman geometry establishes a versatile platform for assessing authenticity, composition, and contaminants directly through packaging.

Holographic Predictive Search (HPS) is a novel approach to search-based hologram generation that uses a mathematical understanding of the optical transforms to make informed optimisation decisions. Existing search techniques such as Direct Search (DS) and Simulated Annealing (SA) rely on trialling modifications to a test hologram and observing the results. A formula is used to decide whether the change should be accepted. HPS operates presciently, using knowledge of the underlying mathematical relationship to make exact changes to the test hologram that guarantee the 'best' outcome for that change. In this work, we extend the scope of the original research to cover both phase and amplitude modulating Spatial Light Modulators (SLMs), both phase sensitive and phase insensitive systems and both Fresnel and Fraunhofer diffraction. In the cases discussed, improvements of up to 10x are observed in final error and the approach also offers significant performance benefits in generation time. This comes at the expense of increased complexity and loss of generality.

Spatial light modulators can typically only modulate the phase or the amplitude of an incident wavefront, with only a limited number of discrete values available. This is often accounted for in computer-generated holography algorithms by setting hologram pixel values to the nearest achievable value during what is known as quantisation. Sympathetic quantisation is an alternative to this nearest-neighbour approach that takes into account the underlying diffraction relationships in order to obtain a significantly improved post-quantisation performance. The concept of sympathetic quantisation is introduced in this paper and a simple implementation, soft sympathetic quantisation, is presented which is shown to improve mean squared error and structural similarity index error metrics by 50% for the considered case of single-transform algorithms.

A first investigation into the use of microwaves for the non-destructive testing for the presence of black heart cavities is presented. Additionally a potato's complex permittivity data between 0.5 GHz to 20 GHz measured using a coaxial sensor and the recipe for a potato phantom are also presented. Electromagnetic finite-difference time-domain simulations of potatoes show that changes to how microwaves propagate through a potato caused by a cavity can produce measurable changes in S21 at the potato's surface of up to 26 dB. Lab-based readings of the change in S21 caused by a phantom cavity submerged in a potato phantom liquid confirms the results of the simulation, albeit at a much reduced magnitude in the order of 0.1 dB.