arXiv subjects

Dip Joti Paul

Publications and source records attributed to Dip Joti Paul.

5 recordsLinked to original sources

arXiv2026

Dark Matter Haloscope with a Disordered Dielectric Absorber

Light dark matter candidates such as axions and dark photons generically couple to electromagnetism, yielding dark-matter-to-photon conversion as a key search strategy. In addition to resonant conversion in cavities and circuits, light dark matter bosons efficiently convert to photons on material interfaces, with a broadband power proportional to the total area of these interfaces. In this work, we make use of interface conversion to develop a new experimental dark matter detector design: the disordered dielectric detector. We show that a volume filled with dielectric powder is an efficient, robust, and broadband target for axion-to-photon or dark-photon-to-photon conversion. We perform semi-analytical and numerical studies in small-volume 2D and 3D disordered systems to compute the conversion power as a function of dark matter mass. We also discuss the power gathered onto a sensitive photodetector in terms of the bulk properties of the disordered material, making it possible to characterize the predicted dark-matter-to-photon conversion rate across a wide range of wavelengths. Finally, we propose DPHaSE: the Dielectric Powder Haloscope SNSPD Experiment which is composed of a disordered dielectric target, a veto system, and a photon collection chamber to maximize the coupling between the powder target and a low noise superconducting nanowire single photon detector (SNSPD). With ambitious but realistic improvements to sensor area and detection efficiency at low energy, the projected reach in the 10 meV-eV mass range is sensitive to QCD axion-photon couplings and exceeds current constraints on dark photon dark matter by up to 5 orders of magnitude.

hep-ph↗

arXiv2026

Enhanced Mid-Infrared Single-Photon Detection with Antenna-Coupled Superconducting Nanowires

Scaling the photon-detection area of superconducting nanowire single-photon detectors (SNSPDs) has traditionally been achieved by nanowire meandering. However, material inhomogeneities and fabrication-induced defects, such as line-edge roughness, increase with nanowire length, leading to reduced internal photon-detection efficiency and elevated dark-count rates. This trade-off becomes increasingly pronounced as nanowires are scaled to sub-100 nm widths and sub-5 nm thicknesses required for mid- to far-infrared sensitivity. Here, we demonstrate an antenna-coupled SNSPD architecture that enhances the effective photon-detection area without increasing nanowire length. A crossed bowtie antenna integrated with an 80 nm-wide, 3 nm-thick WSi nanowire yields 15.7$\times$ increase in effective detection area at 7.4 $μ$m compared to a bare nanowire of identical geometric footprint, while maintaining the same internal detection efficiency and dark-count rate. Antenna coupling provides a scalable approach to increasing photon-detection area while reducing the noise-equivalent power, offering performance benefits for applications in astronomy, biological imaging, and molecular spectroscopy.

physics.optics↗

arXiv2025

Fast-Recovery Epitaxial NbN Superconducting Nanowire Single-Photon Detectors with Saturated Efficiency at 1550 nm in Liquid Helium

Achieving both high internal efficiency and fast reset times at elevated temperatures remains challenging due to limited understanding of how film properties govern SNSPD performance. We demonstrate that epitaxial NbN films on sapphire enable simultaneous high efficiency and rapid response. We fabricate and characterize SNSPDs based on these films deposited via DC magnetron sputtering on c-cut sapphire. High-quality epitaxial growth preserves a low electron diffusion coefficient and promotes strong electron-phonon coupling, yielding a high critical temperature and efficient hotspot formation in the dirty limit. X-ray diffraction and transmission electron microscopy confirm epitaxial alignment and lattice order. Nanowires of 20 nm width exhibit saturated internal efficiency at 1550 nm wavelength and short reset times at 4.2 K, enabled by lattice matching and high thermal conductance of the sapphire interface. Ab initio modeling reproduces photon count rates, linking device performance quantitatively to film properties such as diffusivity and electron-phonon coupling.

physics.app-ph↗

arXiv2025

Photolithography-Compatible Three-Terminal Superconducting Switch for Driving CMOS Loads

Superconducting devices have enabled breakthrough performance in quantum sensing and ultra-low-power computing. Nevertheless, the need for a cryo-electronics platform that can interface superconductor electronics with Complementary Metal-Oxide-Semiconductor (CMOS) devices has become increasingly evident in many cutting-edge applications. In this work, we present a three-terminal micrometer-wide superconducting wire-based cryotron switch (wTron), fabricated using photolithography, that can directly interface with CMOS electronics. The wTron features an output impedance exceeding 1 k$Ω$ and exhibits reduced sensitivity to ambient magnetic noise, similar to its nanoscale predecessor, the nanocryotron. In addition, its micrometer-wide wires support switching currents in the mA range, making wTrons well-suited for driving current-hungry resistive loads and highly capacitive CMOS loads. We demonstrate this capability by using the wTron to drive room-temperature CMOS electronics, including an LED and a MOSFET with a gate capacitance of 500 pF. We then examine the optimal design parameters of wTrons to drive CMOS loads, such as MOSFETs, HEMTs, and electro-optic modulators. Furthermore, to demonstrate the foundry readiness of the wTron, we fabricated wTrons using MIT Lincoln Laboratory's SFQ5ee superconducting process and characterized their switching behavior. Our work shows that wTron will facilitate the interface between superconductor electronics and CMOS, thereby paving the way for the development of foundry-compatible cryo-electronic ecosystems to advance next-generation computing and quantum applications.

physics.app-ph↗

arXiv2025

Determination of Mid-Infrared Refractive Indices of Superconducting Thin Films Using Fourier Transform Infrared Spectroscopy

In this work, we present a technique to determine the mid-infrared refractive indices of thin superconducting films using Fourier transform infrared spectroscopy (FTIR). In particular, we performed FTIR transmission and reflection measurements on 10-nm-thick NbN and 15-nm-thick MoSi films in the wavelength range of 2.5 to 25 $μ$m, corresponding to frequencies of 12-120 THz or photon energies of 50-500 meV. To extract the mid-infrared refractive indices of these thin films, we used the Drude-Lorentz oscillator model to represent their dielectric functions and implemented an optimization algorithm to fit the oscillator parameters by minimizing the error between the measured and simulated FTIR spectra. We performed Monte Carlo simulations in the optimization routine to estimate error ranges in the extracted refractive indices resulting from multiple sources of measurement uncertainty. To evaluate the consistency of the extracted dielectric functions, we compared the refractive indices extrapolated from these dielectric functions in the UV to near-infrared wavelengths with the values separately measured using spectroscopic ellipsometry. We validated the applicability of the extracted mid-infrared refractive indices of NbN and MoSi at temperatures below their critical temperatures by comparing them with the Mattis-Bardeen model. This FTIR-based refractive index measurement approach can be extended to measure the refractive indices of thin films at wavelengths beyond 25 $μ$m, which will be useful for designing highly efficient photon detectors and photonic devices with enhanced optical absorption in the mid- and far-infrared wavelengths.

physics.optics↗