We propose an approach to reconstruct spectrum using artificial neural networks (ANNs) instead of directly solving a matrix equation using calibration coefficients. ANNs are particularly effective in reconstructing spectra in noise environment by learning the relationship between inputs and outputs with large amount of data training. There are several different training methods for ANNs. Compared with scaled conjugate gradient algorithm and Levenberg–Marquardt algorithm, Bayesian regularization (BR) algorithm is demonstrated to be a better training algorithm for spectral reconstruction. We also compare the spectral reconstruction of BR algorithm and that of the traditional algorithms. Experimental results indicate that the spectral reconstruction of BR algorithm is nearly in line with that measured by a commercial spectrometer. Obvious deviations are occurred in the spectral reconstruction of the traditional algorithms due to inevitable background noise, rounding errors, and temperature variations. Therefore, spectral reconstruction using ANNs with a train method of BR algorithm is a more suitable choice for the disorder dispersion spectrometer.
By using a frosted glass plate and an infrared sensor card, we demonstrate a miniature imaging spectrometer design that covers a broad wavelength range from visible to infrared with high spectral resolution. The spectral contents of the incident probe beams are reconstructed by solving a series of matrix equations with a nonlinear optimization algorithm. The proposed imaging spectrometer offers significant advantages over current instruments that are based on Fourier transform and grating dispersion, in terms of size, resolution, spectral range, cost and reliability. The imaging spectrometer consists of five primary components for performing the functions of collimation, dispersion, modulation, detection, and calculation, respectively. Disordered small particles of the frosted glass in dispersion component reduce the fabrication complexity. An infrared sensor card in the conversion component broaden the operational spectral range of the system into visible and infrared bands. Since the CCD used in the detection component provides very large number of intensity measurements, one can reconstruct all spectra with high resolution.
In this paper, a compact spectrometer based on disordered rough surfaces for operation in the terahertz band is presented. The proposed spectrometer consists of three components, which are used for dispersion, modulation and detection respectively. The disordered rough surfaces, which are acted as the dispersion component, are modulated by the modulation component. Different scattering intensities are captured by the detection component with different extent of modulation. With a calibration measurement process, one can reconstruct the spectra of the probe terahertz beam by solving a system of simultaneous linear equations. A Tikhonov regularization approach has been implemented to improve the accuracy of the spectral reconstruction. The reported broadband, compact, high-resolution terahertz spectrometer is well suited for portable terahertz spectroscopy applications.
By using a preaggregated silver nanoparticle monolayer film and an infrared sensor card, we demonstrate a miniature spectrometer design that covers a broad wavelength range from visible to infrared with high spectral resolution. The spectral contents of an incident probe beam are reconstructed by solving a matrix equation with a smoothing simulated annealing algorithm. The proposed spectrometer offers significant advantages over current instruments that are based on Fourier transform and grating dispersion, in terms of size, resolution, spectral range, cost and reliability. The spectrometer contains three components, which are used for dispersion, frequency conversion and detection. Disordered silver nanoparticles in dispersion component reduce the fabrication complexity. An infrared sensor card in the conversion component broaden the operational spectral range of the system into visible and infrared bands. Since the CCD used in the detection component provides very large number of intensity measurements, one can reconstruct the final spectrum with high resolution. An additional feature of our algorithm for solving the matrix equation, which is suitable for reconstructing both broadband and narrowband signals, we have adopted a smoothing step based on a simulated annealing algorithm. This algorithm improve the accuracy of the spectral reconstruction.
A multiple-input multiple-output visible light communication (VLC) system based on disorder dispersion components is presented. Instead of monochromatic sources and large size photodetectors used in the traditional VLC systems, broadband sources with different spectra act as the transmitters and a compact imaging chip sensor accompanied by a disorder dispersion component and a calculating component serve as the receivers in the proposed system. This system has the merits of small size, more channels, simple structure, easy integration, and low cost. Simultaneously, the broadband sources are suitable to act as illumination sources for their white color. A regularized procedure is designed to solve a matrix equation for decoding the signals at the receivers. A proof-of-concept experiment using on–off keying modulation has been done to prove the feasibility of the design. The experimental results show that the signals decoded by the receivers fit well with those generated from the transmitters, but the bit error ratio is increased with the number of the signal channels. The experimental results can be further improved using a high-speed charge-coupled device, decreasing noises, and increasing the distance between the transmitters and the receivers.
Optical modulation of terahertz surface plasmon polaritons (THz SPPs) propagating in an intrinsic indium antimonide surface is demonstrated in this paper. The modulation is mediated by the modification of free carrier density with optical illumination. Simulation and experimental results show that a THz modulator can be realized by tuning the propagation lengths of THz SPPs, which could be controlled to be larger or shorter than the distance of two razor blades used for the coupling of the THz wave and the THz SPPs. In comparison with conventional THz modulation approaches, this method of manufacturing is simpler and the switching bandwidth is wider. The maximum modulation frequency of the modulators is anticipated to be above gigahertz, thus leading to the possibility of communication applications using the THz baseband.
The signal of a novel waveguide multilayer memory (WMM) is the side-scattered beam emitted from information pits. Side scattering plays a key role in the data readout of the WMM. In this paper, a model is proposed to investigate the side-scattering properties of the WMM. We not only theoretically and experimentally confirm the exponential attenuation distribution of the side-emission scattered light intensity of a waveguide with constant attenuation coefficient, but also deduce an expression for the relation between the attenuation coefficient and the light propagation distance of a waveguide with distributed attenuation coefficient when the side-scattered light intensity is uniform. Furthermore, a possible method to realize the uniformity of the side-emitted light intensity is demonstrated. These results will contribute to the improvement of the performance of the WMM.
KEYWORDS: Waveguides, Multilayers, 3D optical data storage, Optical storage, Refractive index, Digital recording, Luminescence, Optical components, Optical discs, Chemical elements
In this paper, we propose a novel method of three dimensional optical storage by the use of multilayered waveguide memory (MWM). The MWM structure is described and its work principle is introduced. Some properties and merits of MWM are also discussed in comparison with other 3D optical data storage methods.
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