arXiv subjects

Kalpak Gupta

Publications and source records attributed to Kalpak Gupta.

2 recordsLinked to original sources

arXiv2025

Decoding angular light paths for solving the inverse scattering problem

Multiple scattering in complex media scrambles the deterministic mapping between input and output fields, limiting wave control and imaging. Conventional inverse scattering strategies rely on discrete spatial layers, but this assumption breaks down in volumetric media where scattering is continuously distributed, particularly near the object plane. Here we introduce a framework that reformulates light transport in terms of scattering angles rather than spatial layers. We show that decomposing scattered waves into angular deflection components--each associated with a spatially invariant point spread function--provides a compact and depth-independent description of volumetric scattering. This representation is particularly effective in forward-scattering biological tissues, where most scattered energy is confined to a narrow angular range. Leveraging this angular sparsity, we develop a progressive inverse algorithm that retrieves dominant angular components from reflection measurements, converting multiply scattered light into usable signal by more than an order of magnitude of the ballistic signal. We demonstrate in vivo recovery of subcellular osteocyte networks through intact mouse skulls, a regime inaccessible to existing methods. These results establish the scattering-angle basis as a general physical framework for decoding information scrambled by disorder, extending the reach of deep optical imaging.

physics.optics↗

arXiv2024

Multiphoton super-resolution imaging via virtual structured illumination

Imaging in thick biological tissues is often degraded by sample-induced aberrations, which reduce image quality and resolution, particularly in super-resolution techniques. While hardware-based adaptive optics, which correct aberrations using wavefront shaping devices, provide an effective solution, their complexity and cost limit accessibility. Computational methods offer simpler alternatives but struggle with complex aberrations due to the incoherent nature of fluorescence. Here, we present a deep-tissue super-resolution imaging framework that addresses these challenges with minimal hardware modification. By replacing the photodetector in a standard laser-scanning microscope with a camera, we measure an incoherent response matrix (IRM). A dual deconvolution algorithm is developed to decompose the IRM into excitation and emission optical transfer functions and the object spectrum. The proposed method simultaneously corrects excitation and emission point-spread functions (PSFs), achieving a resolution of {\lambda}/4, comparable to structured illumination microscopy. Unlike existing computational methods that rely on vector decomposition of a single convoluted PSF, our matrix-based approach enhances image reconstruction, particularly for high spatial frequency components, enabling super-resolution even in the presence of complex aberrations. We validated this framework with two-photon super-resolution imaging, achieving a lateral resolution of 130 nanometers at a depth of 180 micrometers in thick mouse brain tissue.

physics.optics↗