arXiv subjects

Nicholas E. Grant

Publications and source records attributed to Nicholas E. Grant.

3 recordsLinked to original sources

arXiv2026

Real-time THz ptychography using an optically modulated aperture

Ptychography allows ordinary cameras to perform both quantitative phase and intensity imaging. However, the requirement for relative object to probe motion and high measurement count significantly limits imaging speed and application scope. In this work, we introduce optically modulated aperture ptychography, using a silicon photomodulator as a rapidly reconfigurable aperture, deployable across the microwave, millimeter wave and terahertz bands. We demonstrate experimentally at ~ 0.1 THz real-time ptychographic image capture, without moving parts. Furthermore, a reconfigurable aperture facilitates diverse and spatially multiplexed probes. We use a multiplexed known-probe reconstruction strategy that improves signal-to-noise ratio and increases the information content per measurement, enabling the capture of fluid dynamics at 16 fps. Our optical modulation approach enables high-throughput ptychographic imaging of dynamic samples, for applications such as non-destructive evaluation and in-vivo biomedical imaging.

physics.optics↗

arXiv2026

A microwave super-resolution imaging approach towards breast cancer margin mapping

Accurate characterisation of margins in excised breast cancer tumours is critical to the success of surgical interventions. Yet margin status is typically confirmed post-operatively using histopathology. Here we present a microwave single pixel imaging technique designed for use in intraoperative margin assessment. By leveraging the photo-induced change in microwave transparency of a silicon modulator placed under the sample, we map the microwave reflectivity of tissue-mimicking phantoms with deeply sub-wavelength resolution, allowing hydration mapping across large areas (10 x 10 cm) at ~1 mm resolution. We evaluate the discriminatory capability of our method using gelatine-based tumour phantoms with water-content variations designed to mimic the contrast between malignant tissue and tumour margins in resected breast specimens. We demonstrate the capability to identify, locate and quantify inadequate margins up to the typically targeted minimum thickness of 2 mm. Furthermore, using numerical modelling, we show that our approach is expected to be resilient to patient-specific tissue differences. These results establish microwave single-pixel imaging as a promising route towards real-time intraoperative assessment of margins in excised breast tumours.

physics.optics↗

arXiv2023

Terahertz imaging through emissivity control

Adoption of terahertz technologies is hindered by the lack of cost-effective THz sources. Here we demonstrate a fundamentally new way to generate and control THz radiation, via spatio-temporal emissivity modulation. By patterning the optical photoexcitation of a surface-passivated silicon wafer, we locally control the free-electron density, and thereby pattern the wafer's emissivity in the THz part of the electromagnetic spectrum. We show how this unconventional source of controllable THz radiation enables a new form of incoherent computational THz imaging. We use it to image various concealed objects, demonstrating this scheme has the penetrating capability of state-of-the-art THz imaging approaches, without the requirement of femto-second pulsed laser sources. Furthermore, the incoherent nature of thermal radiation also ensures the obtained images are free of interference artifacts. Our spatio-temporal emissivity control paves the way towards a new family of long-wavelength structured illumination, imaging and spectroscopy systems.

physics.optics↗