Department of Electrical and Electronics Engineering
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Item Cooperative coupling of hot alkali vapors to surface plasmon: Towards room temperature quantum plasmonics with atomic media(IEEE, 2018) Arora, PankajWe demonstrate cooperative coupling between hot vapors and surface plasmons with three-fold Purcell factor enhancement. Our result can be regarded as a major step in the quest for room temperature quantum plasmonics with atomic media.Item Imaging the Engineered Polarization States of Surface Plasmon Polaritons at Visible Wavelengths(IEEE, 2014-12) Arora, PankajWe experimentally demonstrate and image the hybrid nature of surface plasmon polaritons (SPPs) at visible wavelengths excited in low aspect ratio 1D and 2D periodic plasmonic structures with periods nearly equal to the resonance wavelengths, fabricated on thin homogeneous metal-coated glass substrates. A thin homogeneous metal layer was sandwiched between the substrate and the periodic metal patterns to out-couple the SPPs as leakage radiation through the substrate. This resulted in the detection of SPP excitation as transmission peaks in a dark background, as opposed to transmission dips in a bright background in the structures without the metal layer reported earlier. Due to the periods being almost equal to the resonance wavelengths, the transmission peaks were not due to extraordinary transmission phenomenon, but because of the radiative leakage of wavelength selective SPPs excited on the surface. A cross-axis polarizer-analyzer was used in broadband leakage radiation microscopy to diminish the direct zeroth -order transmission and image the real and Fourier plane characteristics of the SPP transmission. The bright emission of different colors against a dark background corresponding to the transmission plasmonic resonances for different periods, in both real and Fourier plane revealed the hybrid nature of excited SPPs, when the polarizer was positioned at 45∘ with respect to the grating vector. The fabricated plasmonic substrates present interesting opportunities for imaging and sensing applications.Item Plasmonic Enhanced EIT and Velocity Selective Optical Pumping Measurements with Atomic Vapor(ACS, 2018) Arora, PankajIn this work, we experimentally observe for the first time nanoscale plasmonic enhanced Electromagnetically Induced Transparency (EIT) and Velocity Selective Optical Pumping (VSOP) effects in miniaturized Integrated Quantum Plasmonic Device (IQPD) for D2 transitions in rubidium (Rb). Our device consists of a vapor cell integrated on top of a prism coated with a thin layer of metal. This configuration is known to allow efficient excitation of Surface Plasmon Resonance (SPR). The evanescent field of the surface plasmon mode interacts with the atomic media in close vicinity to the metal. In spite of the limited interaction length between SPR and Rb atoms, the signature of EIT along with VSOP signals could be clearly observed in our miniaturized IQPD under proper conditions of pump and probe intensities. A gradual decrease in the contrast of the plasmonic enhanced EIT and VSOP signals was observed as the excitation was detuned from the SPR critical angle, due to reduction in electromagnetic field enhancement, leading to a reduced interaction of the evanescent field with the atomic vapor media. Following the demonstration of these effects, we also present a detailed model revealing the mechanisms and the origin of plasmonic enhanced EIT and VSOP effects in our system. The model, which is based on the Bloch equations, is in good agreement with the observed experimental results. The obtained results are regarded as an important step in the quest for the realization of nanoscale quantum plasmonic effects and devices.Item Multiwavelength plasmonic activity in aluminum-based 2D nanostructures for biosensing applications(ACM Digital Library, 2022-06) Arora, PankajSurface plasmons (SP) can be effectively tuned in the entire UV–visible–near-infrared (NIR) spectrum, bringing together a variety of optical sensors to monitor the surrounding conditions at the metal–analyte interface. To initiate such a plasmonic phenomenon, aluminum (Al) as a plasmonic metal has gained much industry-related relevance, being relatively low-cost and widely available, and furthermore is compatible with CMOS technology. In the present work, we have employed Al-based 2D plasmonic nanostructures with different periodicity in the x and y directions, placed over a thin Al film, to observe transmission peaks at SP resonances. Modulating different geometric parameters including the height, width, and thickness of the Al film deposited below the nanostructures yielded an optimized design. As a result, when light is incident normally, the 2D periodic nanostructures produce a transmission peak corresponding to SP resonance for a period (PX) = 1000 nm (along the x-direction) in the NIR region, while for PY = 500 nm (along the y-direction), a transmission peak is produced in the visible region. Structures with different periods in different directions, exhibiting multiple SP resonances, could find potential applications in optical sensors, wherein characteristics of analytes coated on the nanostructures at different wavelengths could be extracted in a single experiment. In short, the proposed engineered plasmonic nanostructures open a new door for biosensing applications in both the visible and NIR regions with the same plasmonic substrate.