arXiv subjects

Martin Booth

Publications and source records attributed to Martin Booth.

8 recordsLinked to original sources

arXiv2026

Integrated photonic computing: towards high-dimensional information processing

The rapid growth of artificial intelligence, coupled with the slowing of Moore's law, is straining computing infrastructure, as CMOS electronics face inherent limits in bandwidth, energy efficiency, and parallelism. Integrated photonic computing encodes and processes information using the phase, amplitude, spatial modes, wavelength channels, and polarisation of guided optical fields, offering a scalable and energy-efficient route beyond charge-based signalling. Here, we review on-chip photonic computing, emphasising the progression from low-dimensional to high-dimensional architectures. At the foundational level, low-dimensional approaches manipulate the phase and amplitude of guided light through Mach-Zehnder interferometers, diffractive structures, microring resonators, and absorptive elements, forming a programmable basis for optical matrix-vector multiplication. Crucially, high-dimensional architectures exploit spatial modes and wavelength channels to carry multiple independent data streams through a single waveguide, achieving higher throughput with moderate hardware overhead. Practical deployment, however, demands more than device innovation. We examine how system-level techniques, from time-wavelength interleaving to hardware-aware training, address energy efficiency, precision, and algorithm-hardware co-design. Five challenges nevertheless remain: electro-optic conversion efficiency, computing parallelism, spatial integration, reconfigurability, and robustness. We highlight emerging topological structures, such as optical skyrmions, as a promising route to fault-tolerant, topologically protected encoding that exploits the largely untapped polarisation degree of freedom. We argue that, by embracing the higher dimensionality of light, photonic computing can offer not merely an incremental improvement but a new paradigm for high-performance, energy-efficient information processing.

physics.optics↗

arXiv2026

A Physics-Guided Neural Framework for Rheology Measurement from Dynamical Laser Speckles

Critical breakthroughs in the area of biomedicine and materials science increasingly depend on rapid, non-contact methods for viscoelastic characterization. Laser Speckle Rheology (LSR) is positioned to meet this demand, effectively circumventing the speed and invasiveness bottlenecks inherent to traditional mechanical rheometer. However, its application in turbid fluids is severely constrained by multiple scattering, where standard physical inversions rely heavily on precise, sample-specific optical transport parameters that are difficult to measure in situ. To overcome this barrier, we propose a physics-guided deep learning framework that infers a Maxwell relaxation spectrum from the intensity autocorrelation g2(t) and speckle-intensity histogram statistics. The resulting spectrum is then propagated through a Maxwell forward model to predict G'and G'' under physics-consistency constraints. Quantitatively, the framework achieves RMSElog as low as 0.009 against reference and generalizes to previously unseen scattering conditions, preserving physically plausible frequency dependence and G'- G'' phase behavior. It reduces reliance on optical transport parameters that are hard to determine in situ and returns an interpretable generalized Maxwell relaxation spectrum, improving the practicality of LSR in turbid media.

physics.optics↗

arXiv2024

On the localization of the high-intensity region of simultaneous space-time foci

Simultaneous space-time focusing (SSTF) is sometimes claimed to reduce the longitudinal extent of the high-intensity region near the focus, in contradiction to the original work on this topic. Here we seek to address this confusion by using numerical and analytical methods to investigate the degree of localization of the spatio-temporal intensity of an SSTF pulse. The analytical method is found to be in excellent agreement with numerical calculations and yields, for bi-Gaussian input pulses, expressions for the three-dimensional spatio-temporal intensity profile of the SSTF pulse, and for the on-axis bandwidth, pulse duration, and pulse-front tilt (PFT) of the SSTF pulse. To provide further insight, we propose a method for determining the transverse input profile of a non-SSTF pulse with equivalent spatial focusing. We find that the longitudinal variations of the peak axial intensities of the SSTF and spatially equivalent (SE) pulses are the same, apart from a constant factor, and hence that SSTF does not constrain the region of high intensity more than a non-SSTF pulse with equivalent focusing. We demonstrate that a simplistic method for calculating the pulse intensity exaggerates the degree of intensity localization, unless the spatio-temporal couplings inherent to SSTF pulses are accounted for.

physics.optics↗

arXiv2020

Antimony thin films demonstrate programmable optical non-linearity

The use of metals of nanometer dimensions to enhance and manipulate light-matter interactions for a range of emerging plasmonics-enabled nanophotonic and optoelectronic applications is an interesting, yet not highly explored area of research outside of plasmonics1,2. Even more importantly, the concept of an active metal, i.e. a metal that can undergo an optical non-volatile transition has not been explored. Nanostructure-based applications would have unprecedented impact on both the existing and future of optics with the development of active and nonlinear optical tunabilities in single elemental metals3-5. Compared to alloys, pure metals have the material simplicity and uniformity; however single elemental metals have not been viewed as tunable optical materials, although they have been explored as viable electrically switchable materials. In this paper we demonstrate for the first time that antimony (Sb), a pure metal, is optically distinguishable between two programmable states as nanoscale thin films. We then show that these states are stable at room temperature, and the states correspond to the crystalline and amorphous phases of the metal. Crucially from an application standpoint, we demonstrate both its optoelectronic modulation capabilities as well as speed of switching using single sub-picosecond (ps) pulses. The simplicity of depositing a single metal portends its potential for use in applications ranging from high speed active metamaterials to photonic neuromorphic computing, and opens up the possibility for its use in any optoelectronic application where metallic conductors with an actively tunable state is important.

cond-mat.mtrl-sci↗

arXiv2018

Laser writing of scalable single colour centre in silicon carbide

Single photon emitters in silicon carbide (SiC) are attracting attention as quantum photonic systems. However, to achieve scalable devices it is essential to generate single photon emitters at desired locations on demand. Here we report the controlled creation of single silicon vacancy ($V_{Si}$) centres in 4H-SiC using laser writing without any post-annealing process. Due to the aberration correction in the writing apparatus and the non-annealing process, we generate single $V_{Si}$ centres with yields up to 30%, located within about 80 nm of the desired position in the transverse plane. We also investigated the photophysics of the laser writing $V_{Si}$ centres and conclude that there are about 16 photons involved in the laser writing $V_{Si}$ centres process. Our results represent a powerful tool in fabrication of single $V_{Si}$ centres in SiC for quantum technologies and provide further insights into laser writing defects in dielectric materials.

cond-mat.mes-hall↗

arXiv2018

Anisoplanatic adaptive optics in parallelized laser scanningmicroscopy

Inhomogeneities in the refractive index of a biological sample can introduce phase aberrationsin microscopy systems, severely impairing the quality of images. Adaptive optics can be employed to correct for phase aberrations and improve image quality. However, conventional adaptive optics can only correct a single phase aberration for the whole field of view (isoplanatic correction) while, due to the three dimensional nature of biological tissues, sample induced aberrations in microscopy often vary throughout the field of view (anisoplanatic aberration), limiting significantly the effectiveness of adaptive optics. This paper reports on a new approach for aberration correction in laser scanning confocal microscopy, in which a spatial light modulator is used to generate multiple excitation points in the sample to simultaneously scan different portions of the field of view with completely independent correction, achieving anisoplanatic compensation of sample induced aberrations. The method was tested in 150 {\mu}m thick whole Drosophila brains, showing a dramatic improvement in resolution and sharpness when compared to conventional isoplanatic adaptive optics.

physics.optics↗

arXiv2018

Microscope calibration using laser written fluorescence

There is currently no widely adopted standard for the optical characterisation of fluorescence microscopes. We used laser written fluorescence to generate two- and three-dimensional patterns to deliver a quick and quantitative measure of imaging performance. We report on the use of two laser written patterns to measure the lateral resolution, illumination uniformity, lens distortion and colour plane alignment using confocal and structured illumination fluorescence microscopes.

physics.optics↗

arXiv2010

Three-dimensional imaging of direct-written photonic structures

Third harmonic generation microscopy has been used to analyze the morphology of photonic structures created using the femtosecond laser direct-write technique. Three dimensional waveguide arrays and waveguide-Bragg gratings written in fused-silica and doped phosphate glass were investigated. A sensorless adaptive optical system was used to correct the optical aberrations occurring in the sample and microscope system, which had a lateral resolution of less than 500 nm. This non-destructive testing method creates volume reconstructions of photonic devices and reveals details invisible to other linear microscopy and index profilometry techniques.

physics.optics↗