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Narrowband, infrared absorbing metasurface using polystyrene thin films
摘要： We present the results of an experimental investigation of polystyrene’s suitability as a dielectric material for designing narrowband, infrared metasurface-based absorbers. Our study included characterization of processing parameters of polystyrene films, such as surface roughness and film thickness, which are critical for device fabrication, and the dielectric properties, which we measured, using spectroscopic ellipsometry. Our results confirm that thin film polystyrene is a relatively low-loss dielectric material at long-wave infrared (LWIR) frequencies. Subsequently, this material was used as the dielectric substrate of a thin, narrowband, metasurface-based absorber at LWIR frequencies. The fabricated narrowband absorber demonstrates excellent performance in the LWIR band with absorptivity as high as 96% and a full-width-at-half-maximum bandwidth of 0:502 μm or 4.87%.
关键词： metasurface,infrared,absorber,polystyrene,narrowband,LWIR
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Spectrally-selective Photovoltaics via Photonic Band Engineering in Absorbing Media
摘要： Partial discharge (PD) detection has been proved as an effective tool for insulation condition monitoring of power equipment. The energy of PD pulses is valuable for studying the characteristics of PD activities. This paper proposes a method for estimating the energy of PD pulses in the presence of white noise and narrowband noise. First, a maximum likelihood (ML) estimator of the pulse energy is derived from the probability distribution of the energy spectral coefficients. To implement the ML method, the sampled data are divided into signal frames and noise frames. The noise frames are then utilized for extracting noise parameters using the 3F-C method. Eventually, these noise parameters are applied to the signal frames to find the ML estimate of the pulse energy. To verify the effectiveness of the proposed method, both simulated data and measured data have been processed using the proposed method and the conventional wavelet packet (WP) denoising method. Compared with the WP denoising method, the proposed method has a higher accuracy and is less susceptible to the lengths of the sampling time windows. The advantage of the method is more significant in unfavorable conditions where the signal-to-noise ratio is low and the accurate lengths of the PD pulses are difficult to determine.
关键词： white noise,maximum likelihood (ML) estimation,3F-C method,Partial discharge (PD),narrowband noise,energy estimation
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 8th Global Conference on Consumer Electronics (GCCE) - Osaka, Japan (2019.10.15-2019.10.18)] 2019 IEEE 8th Global Conference on Consumer Electronics (GCCE) - Generating Hand Contour Images with Information of the Fingers Curled using a Colored Glove
摘要： In this paper we investigate the possibilities of narrowband FSK detection using a superregenerative (SR) receiver. Previous SR FM demodulation techniques rely on detecting the amplitude variations caused by the different frequencies involved in FSK modulation. However, this requires relatively high frequency deviations because the frequency response of SR receivers is not very selective. In this paper we take a different approach, exploiting the distinct phase trajectories of FSK modulations resulting from the transmitted data. The well-known fact that the SR oscillator response preserves the phase information of the received signal is successfully exploited to allow the detection of several FSK modulations. These include the special case of MSK, opening the way to applying the SR principle to several communication standards, such as IEEE 802.15.4. The key ideas for symbol synchronization are also presented. Experimental results on a 10 kbit/s proof-of-concept MSK receiver, achieving a sensitivity better than 114 dBm in the HF band, validate the proposed approach.
关键词： narrowband FSK demodulation,Low-power communication receivers,RF receivers,MSK demodulation,superregenerative receiver
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 5th International Conference for Convergence in Technology (I2CT) - Bombay, India (2019.3.29-2019.3.31)] 2019 IEEE 5th International Conference for Convergence in Technology (I2CT) - Detection and Quantification of Milk Adulteration by Laser Induced Instumentation
摘要： In this paper we investigate the possibilities of narrowband FSK detection using a superregenerative (SR) receiver. Previous SR FM demodulation techniques rely on detecting the amplitude variations caused by the different frequencies involved in FSK modulation. However, this requires relatively high frequency deviations because the frequency response of SR receivers is not very selective. In this paper we take a different approach, exploiting the distinct phase trajectories of FSK modulations resulting from the transmitted data. The well-known fact that the SR oscillator response preserves the phase information of the received signal is successfully exploited to allow the detection of several FSK modulations. These include the special case of MSK, opening the way to applying the SR principle to several communication standards, such as IEEE 802.15.4. The key ideas for symbol synchronization are also presented. Experimental results on a 10 kbit/s proof-of-concept MSK receiver, achieving a sensitivity better than 114 dBm in the HF band, validate the proposed approach.
关键词： narrowband FSK demodulation,Low-power communication receivers,RF receivers,MSK demodulation,superregenerative receiver
更新于2025-09-23 15:21:01
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Grating on Plasmonic Nanosheet Structure for Multi-Stopband Filtering and Narrowband Emission
摘要： The narrowband emission at microscale regime is a crucial technology need in view of nanophotonic networks and lab-on-a-chip applications. Considering the significance of plasmonic nanosheet, this work proposes one such narrowband emitter in microscale regime. The proposed system is a dielectric grating on plasmonic nanosheet hybrid system. The numerical simulation results show that the proposed structure works as multi-stopband filter with band tenability as a function of refractive index of grating material. Furthermore, spectral smoothening is demonstrated due to the integration of dielectric grating to plasmonic nanosheet. Infiltration of the emitter in the grooves of the dielectric grating results in the narrowband-enhanced emission in UV region. The emission band proved to be tuned by carefully engineering the surface roughness, and can be engineered the same into broadband emitter. This new structure shows the way for realizing the on-chip spectrofluoremeter concept.
关键词： Emission engineering,Narrowband emitter,Stopband filter,Plasmonic nanosheet
更新于2025-09-23 15:21:01
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Treatment of Non-Segmental Vitiligo with Narrowband UVB Phototherapy (311 Nm): Clinical Efficacy and Mechanisms of Action
摘要： Objective: To estimate efficacy of narrowband UVB phototherapy (311 nm) in non-segmental vitiligo and its effect on subpopulations of T-cells and dendritic cells in vitiligo lesions. Methods: 56 patients with progressive non-segmental vitiligo underwent narrowband UVB phototherapy (311 nm). 11 patients had biopsies before and after therapy from lesional (depigmentation area), marginal, and perilesional skin for immunohistochemical studies of CD4+, CD8+, CD1a+ and CD83+ cells in epidermis and derma. Results: Median number of UVB procedures per course was 71, median total radiation dose-91.8 J/cm2, median percent of repigmentation-49%. Repigmentation of >25% of the affected area was reached in 67.9% of patients and repigmentation of 76-100% in 19.6% . VIDA index decreased from 2 to 1 post-treatment (P<0.035). In a subgroup who underwent immunohistochemical studies median number of UVB procedures per course was 88, median total dose of radiation-140.2 J/cm2, and median percent of repigmentation-50%. Significant activation of T-cellular immune reactions was found in lesions before treatment. There was a statistically significant increase in CD8+ lymphocytes and CD1a+ dendritic cells in marginal and perilesional normally pigmented skin in epidermis. There was an increase in CD4+ and CD8+ lymphocytes and CD83+ dendritic cells in all three zones in derma. Normalization of CD8+ and CD1+ cells in epidermis of the affected skin was observed post-treatment. There was only partial reduction of CD4+, CD8+ and CD1+ cells in dermis. Conclusions: Narrowband UVB phototherapy (311 nm) is an effective method of treatment of nonsegmental vitiligo. T-lymphocytes and Langerhans cells play a critical immunoregulatory role in narrowband UVB phototherapy (311 nm)-induced immune suppression. Lack of full normalization of immunological parameters in the skin after treatment indicates a need for optimization of narrowband UVB phototherapy (311 nm): conduction of longer courses including 150-200 procedures, or combinations of this treatment with immunosuppressive drugs.
关键词： Dendritic cells,Narrowband UVB phototherapy (311 nm),T-lymphocytes,Vitiligo,Immunohistochemical analysis
更新于2025-09-23 15:21:01
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Efficiency and spectral performance of narrowband organic and perovskite photodetectors: a cross-sectional review
摘要： The capability of detecting visible and near infrared light within a narrow wavelength range is in high demand for numerous emerging application areas, including wearable electronics, the Internet of Things, computer vision, artificial vision and biosensing. Organic and perovskite semiconductors possess a set of properties that make them particularly suitable for narrowband photodetection. This has led to rising interest in their use towards such functionality, and has driven remarkable progress in recent years. Through a comparative analysis across an extensive body of literature, this review provides an up-to-date assessment of this rapidly growing research area. The transversal approach adopted here focuses on the identification of: (a) the unifying aspects underlying organic and perovskite narrowband photodetection in the visible and in the near infrared range; and (b) the trends relevant to photoconversion efficiency and spectral width in relation to material, device and processing strategies. A cross-sectional view of organic and perovskite narrowband photodetection is thus delineated, giving fresh insight into the status and prospects of this research area.
关键词： narrowband organic photodetectors,narrowband perovskite photodetectors,NIR photodetectors,colour sensors,spectral selectivity
更新于2025-09-23 15:19:57
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Narrowbanda??Absorptiona??Type Organic Photodetectors for the Fara??Red Range Based on Fullerenea??Free Bulk Heterojunctions
摘要： Spectrally-selective photodetection via organic semiconductors manifesting narrowband absorption (NBA photodetection) is highly attractive for emerging applications that require ultrathin, lightweight, and low-cost solutions. While successful over mainstream color bands, NBA photodetectors have struggled so far to meet the functional and/or performance demands at longer wavelengths, importantly in the far-red (700–750 nm), a range relevant to diverse applications in analytical biology, medical diagnostics, remote sensing, etc. In consideration of the potential of a nonfullerene-acceptor route to address this challenge, the narrowband photodetection capabilities of SBDTIC, a recently-developed benzodithiophene-based acceptor with narrowband absorption in the far-red, are explored. Two bulk-heterojunction NBA configurations are considered, in which SBDTIC is combined with a donor either absorbing also in the far-red, or transparent through the visible. It is found that the latter configuration provides superior narrowband functionality, with peak detectivity of 1.42 × 1013 Jones and spectral width of 141 nm—the highest detectivity to date for NBA far-red-selective photodetectors, and the smallest spectral width of all solution-processed implementations. In self-powered operation, such photodetectors additionally present a quasilinear response over a photocurrent range of least four orders of magnitude, and respond in the microsecond range, further evidencing the suitability of this approach to address the wealth of target applications.
关键词： far-red,nonfullerene acceptors,narrowband-absorption photodetectors,organic photodetectors,narrowband photodetectors
更新于2025-09-23 15:19:57
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Narrowband colloidal quantum dot photodetectors for wavelength measurement applications
摘要： High performance photodetectors based on colloidal quantum dots have been demonstrated in a wide spectral range spanning from the visible to the mid infrared. Quantum dot photodetectors typically show a low-pass type spectral response with a tunable cutoff wavelength. In this paper, we propose a method for the realization of narrowband photodetectors based on the combination of photoconductors and optical filters, both realized with colloidal PbS quantum dots. We demonstrate that an array of such narrowband photodetectors can be effectively employed for the realization of a compact wavemeter operating in the visible and near-infrared spectral range.
关键词： Narrowband photodetectors,Wavelength meter,Colloidal Quantum Dots photodetectors
更新于2025-09-23 15:19:57
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Active control of narrowband total absorption based on terahertz hybrid Dirac semimetal-graphene metamaterials
摘要： A narrowband total absorber consists of a single layer of graphene, Photoactive Silicon and bulk Dirac semimetal (BDS) and has been studied in three different ways for light absorption control without changing the geometry of the structure. Numerical simulation results show that the total absorption is achieved in the narrow spectral range by the critical coupling achieved by the guided resonance, and the results are in good agreement with the coupled mode theory (CMT). Interestingly, this device exhibits exceptional polarization insensitivity and excellent absorption stability over a range of incident angles. In addition, the extremely remarkable sensing performance is more conducive to the application of bio-chemical sensors. In this article, we propose that this work achieves a significant enhancement of the interaction of light and matter in single-layer graphene without graphene plasmon response. This simple and easily fabricated narrowband total absorption structure has outstanding potential applications in the design of modulators, filters and photodetectors.
关键词： metamaterials,narrowband,absorption,critical coupling
更新于2025-09-23 15:19:57