Multi-Band Absorption Properties and Near-Field Enhancement in Mid-Infrared Based on the Interference Theory

AbstractMid-infrared (mid-IR) optical spectroscopy of molecules is of large interest in physics, chemistry, and biology. However, probing nanometric volumes of molecules is challenging because of the strong mismatch of their mid-infrared absorption and scattering cross-sections with the free-space wavelength. We suggest overcoming this difficulty by nanofocusing acoustic graphene plasmon polaritons (AGPs) – oscillations of Dirac charge carriers coupled to electromagnetic fields with extremely small wavelengths – using a taper formed by a graphene sheet above a metallic surface. We demonstrate that due to the appreciable field enhancement and mode volume reduction, the nanofocused AGPs can efficiently sense molecular fingerprints in nanometric volumes. We illustrate a possible realistic sensing sсenario based on AGP interferometry performed with a near-field microscope. Our results can open new avenues for designing tiny sensors based on graphene and other 2D polaritonic materials.

Download Full-text

Numerical Study on the Absorption Characteristics of Subwavelength Metallic Gratings Covered with a Lossy Dielectric Layer

Applied Sciences ◽

10.3390/app8091445 ◽

2018 ◽

Vol 8 (9) ◽

pp. 1445

Author(s):

Chi-Young Hwang ◽

Yong-Hae Kim ◽

Ji Choi ◽

Gi Kim ◽

Jong-Heon Yang ◽

...

Keyword(s):

Dielectric Layer ◽

Numerical Study ◽

Structural Parameters ◽

Resonant Cavity ◽

Visible Range ◽

Absorption Properties ◽

Perfect Absorption ◽

Metallic Gratings ◽

Band Absorption ◽

Multi Band

Optical absorbers have been a topic of intense research due to their importance in many applications. In particular, multi-band and perfect absorption features in a desired frequency range are essential in broadband applications. In this work, we numerically studied the absorption properties of subwavelength metallic gratings coated with a dielectric layer. Here, the structure is considered to be an integration between a resonant cavity and a subwavelength metallic grating. Two appropriately designed structures can exhibit multi-band absorption properties. In addition to the numerical simulation results, we elaborate on determining the appropriate structural parameters that yield the desired spectral absorption profile in the visible range. We also numerically identify critical coupling conditions for perfect absorption.

Download Full-text

Synthesis and Infrared Multi‐band Absorption Properties of Core‐shell NaYF 4 :Yb 3+ , Er 3+ @SiO 2 Nanoparticles

Zeitschrift für anorganische und allgemeine Chemie ◽

10.1002/zaac.201900181 ◽

2019 ◽

Vol 645 (21) ◽

pp. 1240-1246

Author(s):

Lu Yuan ◽

Ming Kang ◽

Guanjun Chang ◽

Xiangmeng Lv ◽

Simin Shen ◽

...

Keyword(s):

Core Shell ◽

Absorption Properties ◽

Band Absorption ◽

Multi Band

Download Full-text

Visualization of microwave near-field distribution in sodium chloride and glucose aqueous solutions by a thermo-elastic optical indicator microscope

Scientific Reports ◽

10.1038/s41598-020-80328-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Zhirayr Baghdasaryan ◽

Arsen Babajanyan ◽

Levon Odabashyan ◽

Jung-Ha Lee ◽

Barry Friedman ◽

...

Keyword(s):

Aqueous Solution ◽

Aqueous Solutions ◽

Field Distribution ◽

Near Field ◽

Absorption Properties ◽

Novel Approach ◽

Concentration Changes ◽

Biological Liquids ◽

Optical Indicator ◽

Distribution Intensity

AbstractIn this study, a new optical method is presented to determine the concentrations of NaCl and glucose aqueous solutions by using a thermo-elastic optical indicator microscope. By measuring the microwave near-field distribution intensity, concentration changes of NaCl and glucose aqueous solutions were detected in the 0–100 mg/ml range, when exposed to microwave irradiation at 12 GHz frequency. Microwave near-field distribution intensity decreased as the NaCl or glucose concentration increased due to the changes of the absorption properties of aqueous solution. This method provides a novel approach for monitoring NaCl and glucose in biological liquids by using a CCD sensor capable of visualizing NaCl and glucose concentrations without scanning.

Download Full-text

Effects of gap thickness and emitter location on the photoluminescence enhancement of monolayer MoS2 in a plasmonic nanoparticle-film coupled system

Nanophotonics ◽

10.1515/nanoph-2020-0178 ◽

2020 ◽

Vol 9 (7) ◽

pp. 2097-2105

Author(s):

Xiaozhuo Qi ◽

Tsz Wing Lo ◽

Di Liu ◽

Lantian Feng ◽

Yang Chen ◽

...

Keyword(s):

Near Field ◽

Central Area ◽

Field Enhancement ◽

Coupled System ◽

Film Structure ◽

Plasmonic Nanoparticle ◽

Emitter Location ◽

Radiation Properties ◽

Radiation Enhancement ◽

Quantum Emitters

AbstractPlasmonic nanocavities comprised of metal film-coupled nanoparticles have emerged as a versatile nanophotonic platform benefiting from their ultrasmall mode volume and large Purcell factors. In the weak-coupling regime, the particle-film gap thickness affects the photoluminescence (PL) of quantum emitters sandwiched therein. Here, we investigated the Purcell effect-enhanced PL of monolayer MoS2 inserted in the gap of a gold nanoparticle (AuNP)–alumina (Al2O3)–gold film (Au Film) structure. Under confocal illumination by a 532 nm CW laser, we observed a 7-fold PL peak intensity enhancement for the cavity-sandwiched MoS2 at an optimal Al2O3 thickness of 5 nm, corresponding to a local PL enhancement of ∼350 by normalizing the actual illumination area to the cavity’s effective near-field enhancement area. Full-wave simulations reveal a counterintuitive fact that radiation enhancement comes from the non-central area of the cavity rather than the cavity center. By scanning an electric dipole across the nanocavity, we obtained an average radiation enhancement factor of about 65 for an Al2O3 spacer thickness of 4 nm, agreeing well with the experimental thickness and indicating further PL enhancement optimization. Our results indicate the importance of configuration optimization, emitter location and excitation condition when using such plasmonic nanocavities to modulate the radiation properties of quantum emitters.

Download Full-text

Photonic resonator interferometric scattering microscopy

Nature Communications ◽

10.1038/s41467-021-21999-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Nantao Li ◽

Taylor D. Canady ◽

Qinglan Huang ◽

Xing Wang ◽

Glenn A. Fried ◽

...

Keyword(s):

Signal To Noise Ratio ◽

Scattered Light ◽

Near Field ◽

Field Enhancement ◽

Protein Detection ◽

Significant Loss ◽

Photonic Band Structure ◽

Large Intensity ◽

Photonic Band ◽

Intensity Contrast

AbstractInterferometric scattering microscopy is increasingly employed in biomedical research owing to its extraordinary capability of detecting nano-objects individually through their intrinsic elastic scattering. To significantly improve the signal-to-noise ratio without increasing illumination intensity, we developed photonic resonator interferometric scattering microscopy (PRISM) in which a dielectric photonic crystal (PC) resonator is utilized as the sample substrate. The scattered light is amplified by the PC through resonant near-field enhancement, which then interferes with the <1% transmitted light to create a large intensity contrast. Importantly, the scattered photons assume the wavevectors delineated by PC’s photonic band structure, resulting in the ability to utilize a non-immersion objective without significant loss at illumination density as low as 25 W cm−2. An analytical model of the scattering process is discussed, followed by demonstration of virus and protein detection. The results showcase the promise of nanophotonic surfaces in the development of resonance-enhanced interferometric microscopies.

Download Full-text