With the continuous improvement of detection technology, higher requirements are put forward for infrared camouflage. Conventional low-emissivity materials have serious thermal instability, which increases the risk of detection. There is an urgent need to investigate more efficient infrared stealth materials. We design a metamaterial selective broadband emitter that utilizes multi-resonance coupling of metal patterns for infrared stealth. The proposed design exhibits low emissivity in the infrared atmosphere windows (3 to 5 μm and 8 to 14 μm) for infrared suppression and high emissivity in the non-infrared atmosphere window (5 to 8 μm) for radiative cooling. We introduce a supplementary design for high-temperature environments to meet a broader application need. Moreover, the low angle-dependence of the metamaterial emitter enables it to maintain broadband absorption characteristics even under large-angle incidence. This proposed approach serves as an effective supplement to the design of metamaterial broadband emitters and holds great potential for applications in infrared stealth, radiative cooling, thermal detection, sensors, thermophotovoltaics, and various other fields.
Radome is the typical microwave (MW) and infrared (IR) source, but the stealth principles of these two bands are the contradictory, making it difficult to achieve MW-IR compatible camouflage with a single material. Metamaterials, due to their unique structure, can manipulate electromagnetic waves to achieve specific functions. In this paper, a compatible stealth flexible metamaterial is proposed, which can realize passband filtering in MW band and selective radiation in IR band. For achieving optimal IR selection radiation and maximum MW selective transmission, the inverse design is used for optimization. Accordingly, the flexible metamaterial integrates IR-MW compatible stealth, MW communication and radiation cooling. It shows low emissivity in the two main bands of IR detection (ε3~5 μm=0.098, ε8~14 μm=0.100), and relatively high emissivity outside these two bands (ε5~8 μm=0.513), while achieving a high transmittance of 98.8% in the WM band. This provides a reasonable guidance for the design of MW-IR stealth materials with specific frequency selection.
Based on the luminescence of the X-ray in the scintillator, this article builds a new hexagonal microcolumn model of CsI(Tl) thin film coupled with the charge-coupled device (CCD). The study proposes a fluorescence transport structure for X-ray luminescence and investigates the fluorescence transformation efficiency of the CsI(Tl) crystal to X-ray. Simulation results reveal that the different thickness and crystal column diameter has a significant impact on the fluorescence transmittance efficiency. The comprehensive discussion indicates that the maximum efficiency can be acquired under an appropriate grain diameter and film thickness.
It’s necessary that higher education experimental teaching reforms on the basis of general education. This paper put forward the experimental teaching reform mode of optical fiber communication in the context of general education. With some reform measures such as improving the experimental content, enriching the experimental style, modifying the experimental teaching method, and adjusting the evaluation method of experimental teaching, the concept of general education is put throughout the experimental teaching of optical fiber communication. In this way, it facilitates the development of students and improvement of experimental teaching quality.
We investigate the phase modulation to intensity modulation conversion in dispersive fibers for measuring frequency
responses of electro-optic phase modulators, and demonstrate two typical measurements with cascade path and fold-back
path. The measured results achieve an uncertainty of less than 2.8% within 20 GHz. Our measurements show stable and
repeatable results because the optical carrier and its phase-modulated sidebands are affected by the same fiber
impairments. The proposed method requires only dispersive fibers and works without any small-signal assumption,
which is applicable for swept frequency measurement at different driving levels and operating wavelengths.
Along with the wide usage of realizing Bayer color interpolation algorithm through FPGA, better performance, real-time processing, and less resource consumption have become the pursuits for the users. In order to realize the function of high speed and high quality processing of the Bayer image restoration with less resource consumption, the color reconstruction is designed and optimized from the interpolation algorithm and the FPGA realization in this article. Then the hardware realization is finished with FPGA development platform, and the function of real-time and high-fidelity image processing with less resource consumption is realized in the embedded image acquisition systems.
All-optical sampling attracts considerable attention due to its crucial applications in high-speed optical analog-to-digital conversion. We present an all-optical sampling scheme using a single semiconductor optical amplifier. In the experiment, 40 GSa/s all-optical sampling for 2.5 GHz analog optical signal is successfully demonstrated with commercially available fiber-pigtailed components. The all-optical sampling shows a fundamental conversion efficiency of 1.35 and a total harmonic distortion of 2.01% at the operating power of 5 mW. Our scheme requires only one semiconductor optical amplifier and has low power consumption, which shows much potential for the high-speed optical analog-to-digital conversion.
KEYWORDS: Polarization, Picosecond phenomena, Semiconductor optical amplifiers, Distortion, Beam splitters, Ultrafast phenomena, All optical signal processing, Signal attenuation, Signal processing, Refractive index
A scheme for improving the self-induced polarization rotation (SPR) in a semiconductor optical amplifier (SOA) based on holding beam injection is proposed. Gain recovery of TE and TM modes can be largely accelerated through an appropriate holding beam injection, with which the response of SPR in the SOA for ultrafast signal can be speeded up. Holding beam injection is employed in SPR-based optical power equalization as an example of validation, in which the distortion of RZ (return-to-zero)and the overshoot of NRZ (non-return-to-zero) signal are largely suppressed, and the extension ratio are improved by 10 dB and 7 dB, respectively.
An all-optical power equalization based on nonlinear polarization rotation in a single semiconductor optical amplifier
(SOA) is proposed for waveform distortion reduction. Simulations have been done for the degraded data signals to
demonstrate the feasibility of the proposed scheme. The primarily simulated results indicated that the switching power is
less than 10 mW. The all-optical power equalization mentioned in this paper has promoting potential to improve the
signal quality and needs low optical power. Our approach has a simple configuration and allows for photonic integration,
which can be constructed by commercially available components.
In this paper, we design a structure of CsI(Tl) thin film crystal cell, and cover the CsI(Tl) thin film on the surface of the
CCD directly. In order to prevent the photons emit from the surface of film, which result in depressing the fluorescence
efficient, we cover the film with alumina to form reflective layer. Al layer is used to separate the CsI(Tl) crystal
according to the size of CCD photosensitive cell, which solve problem that fluorescence cross talk between the different
photosensitive cell. The fluorescence transmission efficiency of CsI(Tl) film crystal cell model is also researched , the
results show the fluorescence transmission efficiency is maximum when the thickness of film is 40 μm.
The thermo-resistance effect in silicon has been exploited for the fabrication of uncooled infrared detectors. In this paper,
based on the Schrodinger equation of material radiation system and the micro-structure of silicon, the infrared absorption
theory of silicon is analyzed. The results show that the infrared activity of amorphous silicon is more activate than
crystalline silicon because of the fault and long range disorder, and using the impurity B, Li, and H, the infrared activity
of silicon also will be activated.
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