arXiv subjects

Yuichiro Kunai

Publications and source records attributed to Yuichiro Kunai.

3 recordsLinked to original sources

arXiv2026

Dynamic Coherent Diffractive Imaging Using Only a Support Constraint in the Complex Plane

We show that a bounded temporal increment prior on the sample dynamics is sufficient to reconstruct a time-varying phase object from a near-field diffraction movie, under the thin-film approximation. The time evolution of the field is parameterized by a multiplicative inter-frame update factor, and a bound on its complex-plane support enforces a bounded phase increment and a passive amplitude constraint. Reconstruction of the dynamic field is thereby converted into a feasibility problem with two projection operators: a measurement-domain modulus projection and an object-domain circular-sector projection. We validate the approach experimentally using a spatial light modulator as a calibrated dynamic sample in two cases: a reaction--diffusion phase pattern with spatially expanding extent, and a growing phase pattern whose accumulated phase reaches $10π$. In both cases the reconstructed phase trajectory agrees well with the ground truth. We then apply the same framework, without modification, to in-situ monitoring of a photo-polymer 3D printing process, recovering the spatiotemporal phase induced by polymerization under a spatially patterned blue light. The reconstructed phase trajectory provides an observable for photo-chemical system identification and process control.

physics.optics↗

arXiv2026

Laterally Differentiated Polymorphs: a route to multifunctional nanostructures

Multifunctional materials can exhibit emergent behavior from the coupling of two or more different properties. For example, coupling between magnetic and ferroelectric order enables electrical control of the magnetic state, enabling for example magnetoelectric memory or logic devices that combine the nonvolatility of magnetic order with the energy efficiency of voltage control. Magnetic iron garnets have outstanding magnonic and magnetooptical properties making them valuable in a range of technologies, but they have not been successfully incorporated into thin film two-phase magnetoelectric nanocomposites. Taking advantage of heterogeneously patterned substrates, this work demonstrates the engineering of garnet-perovskite composites in which both phases are polymorphs with the same composition but dramatically different structures and properties. Applying an electric field to the perovskite phase modulates the magnon dispersion and magnetooptical response of the garnet, opening a path to voltage-controlled garnet devices.

cond-mat.mtrl-sci↗

arXiv2024

QuATON: Quantization Aware Training of Optical Neurons

Optical processors, built with "optical neurons", can efficiently perform high-dimensional linear operations at the speed of light. Thus they are a promising avenue to accelerate large-scale linear computations. With the current advances in micro-fabrication, such optical processors can now be 3D fabricated, but with a limited precision. This limitation translates to quantization of learnable parameters in optical neurons, and should be handled during the design of the optical processor in order to avoid a model mismatch. Specifically, optical neurons should be trained or designed within the physical-constraints at a predefined quantized precision level. To address this critical issues we propose a physics-informed quantization-aware training framework. Our approach accounts for physical constraints during the training process, leading to robust designs. We demonstrate that our approach can design state of the art optical processors using diffractive networks for multiple physics based tasks despite quantized learnable parameters. We thus lay the foundation upon which improved optical processors may be 3D fabricated in the future.

cs.LG↗