arXiv subjects

Alexander C. Trowbridge

Publications and source records attributed to Alexander C. Trowbridge.

3 recordsLinked to original sources

arXiv2026

Enhancing Speckle Metrology with Diffusion Denoising in Photon-Starved Regimes

Laser speckle is a powerful tool for precision metrology that enables highly sensitive measurements of light sources and subtle environmental perturbations. Many applications require operation in photon-limited regimes, for example when using low-power illumination or in spectral regions where sensitive detectors are unavailable. In these conditions, the structured speckle pattern that encodes the signal becomes challenging to disentangle from measurement noise, severely degrading performance. Here, we introduce a denoising framework to separate measurement noise from the underlying speckle structure in low-signal data. Using a hybrid pre-training and experimental fine-tuning strategy, the model is adapted using a small experimental dataset and integrates directly with existing speckle metrology pipelines. Applied to femtometre-scale wavelength sensing using an integrating sphere, the approach reduces root-mean-square error in low-signal conditions by up to 72% and enables accurate reconstruction where conventional speckle metrology fails.

physics.optics↗

arXiv2025

The Radiation Pressure of Light: historical perspectives and the role of structured light

Light, or electromagnetic radiation, is well known to possess momentum, and the exchange of this momentum with a reflecting surface leads to radiation pressure. More often than not, it is the radiation pressure generated by a plane wave incident on a flat mirror that is considered. The last few decades have seen the emergence of structured light beams that may possess a complex phase and amplitude structure in both their transverse and longitudinal directions. This paper provides a historical overview of radiation pressure, tracing its discovery and experimental validation, and examines how transitioning to structured light from a plane wave can influence it. In particular, we elucidate the difference in radiation pressure force for structured light fields and how this differs from that of a plane wave at an identical frequency. In particular, the well-known Gouy phase is shown to contribute to a reduction in the radiation pressure force exerted on a flat mirror in comparison to a plane wave for both HG and LG modes. As an illustrative example, we compute that the radiation pressure force for LG modes differs from that of a plane wave by approximately $20$ fN/W for each unit of orbital angular momentum. A detailed experimental proposal to quantify this variance in radiation pressure is described, and we demonstrate that this measurement is within the realm of current metrological techniques.

physics.optics↗

arXiv2023

Learning algorithms for identification of whisky using portable Raman spectroscopy

Reliable identification of high-value products such as whisky is an increasingly important area, as issues such as brand substitution (i.e. fraudulent products) and quality control are critical to the industry. We have examined a range of machine learning algorithms and interfaced them directly with a portable Raman spectroscopy device to both identify and characterize the ethanol/methanol concentrations of commercial whisky samples. We demonstrate that machine learning models can achieve over 99% accuracy in brand identification across twenty-eight commercial samples. To demonstrate the flexibility of this approach we utilised the same samples and algorithms to quantify ethanol concentrations, as well as measuring methanol levels in spiked whisky samples. Our machine learning techniques are then combined with a through-the-bottle method to perform spectral analysis and identification without requiring the sample to be decanted from the original container, showing the practical potential of this approach to the detection of counterfeit or adulterated spirits and other high value liquid samples.

cs.LG↗