Archives 2025

congratulation to Our new paper in Journal of Optic

Temperature Dependent Random Laser Performance of Au@Cu and Cu@Au Core-Shell Nanoparticles in a Rhodamine 6G–PNIPAM Smart Polymer Matrix Medium

Mariam Kadhim Jawad, J. M. Jassim, S. F. Haddawi, S. M. Hamidi

Abstract:
This study aimed to investigate the temperature-dependent performance of random lasers using Rhodamine 6G (R6G) dye embedded in a thermoresponsive PNIPAM polymer matrix with Au, Cu, Au@Cu, and Cu@Au nanoparticles serving as scattering centers. At 25 °C, only fluorescence was observed due to the hydrophilic state of PNIPAM, resulting in high optical absorption and insufficient refractive index contrast for lasing. As temperature increased to 30–45 °C, PNIPAM became hydrophobic, enhancing index contrast and reducing absorption, which facilitated random lasing. Among the nanoparticles, Au showed the highest emission intensity (62618 a.u.) and narrowest FWHM (4.6 nm), followed by Cu@Au (59908 a.u., 5.3 nm), attributed to the strong plasmonic response of the Au shell. Conversely, Au@Cu and Cu exhibited weaker outputs due to higher damping and less effective plasmonic resonance. Temperature-dependent spectral analysis showed that Cu had the most pronounced bandwidth narrowing (7.5 nm to 3.4 nm), while Au@Cu demonstrated the highest intensity modulation (30913 a.u. to 65195 a.u.). A temperature-induced blue shift in peak emission was observed, most prominently in PNIPAM alone (6.2 nm), with smaller shifts in nanocomposite systems due to varied thermal coupling. These results highlight the pivotal role of PNIPAM’s thermal transition in controlling random laser behavior, offering new strategies for designing tunable or thermally stable laser systems.

Long-range hyperbolic polaritons on a non-hyperbolic crystal surface

Lu Liu, Langlang Xiong, Chongwu Wang, Yihua Bai, Weiliang Ma3, Yupeng Wang1, Peining Li, Guogang Li, Qi Jie Wang, Francisco J. Garcia-Vidal, Zhigao Dai & Guangwei Hu

Nature,Springer Nature

https://doi.org/10.1038/s41586-025-09288-1

Abstract:

Hybridized matter–photon excitations in hyperbolic crystals—anisotropic materials characterized by permittivity tensor components with opposite sign—have attracted substantial attention owing to their strong light–matter interactions in the form of hyperbolic polaritons. However, these phenomena have been restricted to hyperbolic crystals, whose optical responses are confined to fixed spectral regions and lack tunability, thereby limiting their broader applicability. Here we demonstrate the emergence of hyperbolic surface phonon polaritons in a non-hyperbolic yttrium vanadate (YVO₄) crystal. Using real-space nanoimaging combined with theoretical analyses, we visualize hyperbolic wavefronts of surface phonon polaritons on YVO₄ crystal surfaces within its non-hyperbolic frequency range, where the permittivity tensor components of the material have the same negative sign. Furthermore, by varying the temperature from room temperature to cryogenic levels, we realize in situ manipulation of polariton dispersions, enabling a topological transition from hyperbolic to canalization and eventually to the elliptic regime. This temperature-controlled dispersion engineering not only provides precise control over polariton topology but also modulates their wavelength and group velocity, showing remarkable sensitivity alongside low-loss, long-range propagation. These findings extend the realm of hyperbolic nano-optics by removing the reliance on hyperbolic crystals, unlocking opportunities for applications in negative refraction, superlensing, polaritonic chemistry ntegrated photonics and beyond.

congratulation to Our new paper in Journal of Pioneering Advances in Materials

High Signal to Noise Ratio in Miniaturized Atomic Cells by Frequency Modulation Spectroscopy Method

A. Mirazei, M. Sotoudeh, M. Asadolahsalmanpour, M. Mosleh, S. M. Hamidi

Magneto-plasmonic Lab, Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran.

DOI:10.48308/piadm.2025.105969

Abstract:

Miniaturized atomic vapor cells are emerging as essential components in various applications such as brain signal tracking, nitrogen-vacancy center magnetometry, and electric and magnetic field sensing. However, achieving a high signal-to-noise ratio (SNR) in these compact systems remains a key challenge, which can be addressed using selective spectroscopic techniques. In this study, we present a novel type of atomic vapor cell based on hot rubidium vapor, designed to enhance the spatial resolution of magnetometers. We also demonstrate the advantages of frequency modulation spectroscopy in improving spectral resolution. The cells are fabricated under a base pressure of 10⁻³ mbar and filled with nitrogen gas in a clean vacuum environment. The integration of these miniaturized cells with spectroscopic techniques enables their use in laser feedback loops to lock onto specific atomic transitions. This approach provides new possibilities for next-generation quantum technologies, including quantum sensors, atomic clocks, and quantum computing systems.

Schematic diagram of the experimental setup, with the circular cell shown in the inset

congratulation to Dear Dr Salmanpour for her PhD defense

congratulation to Our new paper in Journal of nanophotonics and nanostructure

Exploring the Interaction between Bloch Surface Waves and Atomic Hot Vapor: A Theoretical Perspective

A.Sohrabi, M. Asadolah Salmanpour, M. Mosleh, S. M. Hamidi,*

Abstract:

The miniaturization of atom-light interaction platforms is pivotal for the advancement of modern optical technologies, enabling significant improvements in sensing, communication, and quantum information processing. In this paper, we present a theoretical investigation onto the coupling of Bloch surface waves (BSWs) of one-dimensional photonic crystal with atomic hot vapor, emphasizing the miniaturization of atomic structures. These surface waves are known for their strong field confinement and high sensitivity to environmental changes which offer a promising avenue for enhancing light-matter interactions at reduced scales. Our findings highlight the potential of Bloch surface waves to enhance and control the localized density of states thus improving the resolution of atomic transition lines. This study underscores the importance of integrating Bloch surface waves with atomic hot vapor for developing next-generation miniaturized optical devices, which can lead to breakthroughs in precision metrology, high-resolution spectroscopy, and quantum technologies.

Alchemically-glazed plasmonic nanocavities using atomic layer metals: controllably synergizing catalysis and plasmonics

Shu Hu ,EricS.A.Goerlitzer ,QianqiLin Vyacheslav M. Silkin,& Jeremy J. Baumberg, Bart de Nijs

https://doi.org/10.1038/s41467-025-58578-9

Plasmonic nanocavities offer exceptional confinement of light, making them effective for energy conversion applications. However, limitations with stability, materials, and chemical activity have impeded their practical implementation. Here we integrate ultrathin palladium (Pd) metal films from sub- to few- atomic monolayers inside plasmonic nanocavities using underpotential deposition. Despite the poor plasmonic properties of bulk Pd in the visible region, minimal loss in optical field enhancement is delivered along with Pd chemical enhancement, as confirmed by ab initio calculations. Such synergistic effects significantly enhance photocatalytic activity of the plasmonic nanocavitiesaswelasphotostabilityby suppressing surface atom migration. We show the atomic alchemical-glazing approach is general for a range of catalytic metals that bridge plasmonic and chemical catalysis, yielding broad applications in photocatalysis for optimal chemical transformation.

Fig. Alchemical space for atomic-glazing on Au substrates.

congratulation to Our new paper 🎉

M.Asadolah Salmanpour, M. Mosleh & S. M. Hamidi^*
Laser and Plasma Research Institute, Shahid Beheshti University, Tehran, Iran.

This study presents a dual-frequency modulation scheme in which both optical and microwave fields are simultaneously modulated in a microwave–optical double resonance system within a hot rubidium vapor cell. The combined modulation produces harmonic spectral features at the sum and difference of the individual modulation frequencies, indicating nonlinear coupling between the fields. Experimental results reveal that this approach enables modulation of atomic population dynamics and facilitates efficient population transfer between hyperfine levels. The observed frequency mixing highlights the system’s sensitivity to dual modulation and suggests its potential for enhancing the spectral control of atomic transitions. These findings may support future developments in atomic clocks, high-precision magnetometers, and quantum information processing systems.

Two-photon polymerization for biological applications

Alexander K. Nguyen and Roger J. Narayan

Materials Today Volume 20,Number 6 July/August 2017

UNC/NCSU Joint Department of Biomedical Engineering, North Carolina State University, Raleigh, NC 27695-7115, USA

https://doi.org/10.1016/j.mattod.2017.06.004

Two-photon polymerization (2PP) leverages the two-photon absorption (TPA) of near-infrared (NIR) radiation for additive manufacturing with sub-diffraction limit resolution within the bulk of a photosensitive material. This technology draws heavily on photosensitive polymers from the microelectronics industry, which were not optimized for TPA or for biocompatibility. 2PP with sub 100 nm resolution has been repeatedly demonstrated; however, this level of fabrication resolution comes at the expense of long fabrication times. Manufacturing of medical devices beyond surface texturing would be prohibitively slow using the current state of the art 2PP technology. Current research intoTPA-sensitivephotopolymerswithgoodbiocompatibilityandholographicprojectionsusingspatial light modulators address current technological limitations by providing materials specifically formulated for biological applications and by making better use of available laser power for applications in which nanoscale resolution is not required.

Optical setup of a femtosecond laser imaging and microfabrication system, which is capable of fluorescence lifetime imaging microscopy. Reprinted from Ref.

congratulation to Our new paper in Journal of Applied Physics A

Laser induced fluorescence enhancement by surface lattice resonance in two dimensional plasmonic nanostructure

Noor D. Abdulameer, N. S. Shnan, Lazem Hassan Aboud, S. M. hamidi

We have experimentally examined the effect of surface lattice resonance in two dimensional plasmonic structure onto the laser induced fluorescence. For this purpose, we fabricated main sample by soft nanolithography onto the polydimethylsiloxane and cover it by gold thin layer by the aid of sputtering machine. The host medium of the dye achieved by spin coating of the Rh6G over the two dimensional plasmonic sample. We recorded the spectral response of the multilayer sample as the fluorescence signal by spectrometer in all of the visible region under four different pump intensities. Our results indicate that the localized electric field due to surface lattice resonance as well as exciton of the dye medium can couple together to reach the plexciton and thus plasmon enhance laser induced fluorescence takes place which can be useful as new substrate in this area for visible region.

Effect of Neighboring Transitions on Critical Angle in Conversion between EIA and EIT in 87Rb Atoms

Preprints.org

Aisar-ul Hassan , Heung-Ryoul Noh ,and Jin-Tae Kim

Posted Date: 22 October 2024

doi:10.20944/preprints202410.1613.v1

The effects of neighboring transitions (ENT) on electromagnetically induced transparency (EIT), electromagnetically induced absorption (EIA), and the conversion between EIA and EIT in a degenerate multi-level system of 87Rb atoms were studied in mmmterms of the angle (θ) between the polarization axes of the coupling and probe beams. The predicted critical values of θ, in which EIT transitioned to EIA, were consistent with the experimental values. In this work these results were systematically conrmed using the calculated spectra by varying the frequency spacings in the excited state of 87Rb via a factor called the ratio. We observed that when the ratio was less than 0.1, the critical angle θc was inverted. This may be attributed to the interplay between the strengths of the EIA and EIT as the ENT varied. We also discovered that by modifying the frequency spacings in the excited state of 87Rb, it becomes feasible to predict ENT and the interplay between EIT and EIA in alkali-metal atoms.

Schematic of the experimental setup. SAS: saturated absorption spectroscopy; W: window; HWP: half-wave plate; PBS: polarizing beam splitter; BE: beam expander; AOM: acousto-optic modulator; M: mirror; BS: beam splitter; Bd: beam dump; PD: photodetector.