Conventional benchtop spectrometers with bulky dispersive
optics
and long optical path lengths display limitations where the significance
of miniaturization, real-time detection, and low cost transcend the
ultrafine resolution and wide spectral range. Here, we demonstrate
a miniaturized all-dielectric ultracompact film spectrometer based
on deep learning working in the single-shot mode. The scheme employs
16 spectral encoders with simple five-layer film stacks where merely
the thickness of the intermediate high-index modulation layer is varied
to realize unique encoded transmission spectra. Structural parameters
as well as transmission spectra of the filters are predesigned to
guarantee weak correlation and highly efficient encoding. Leveraging
a trained reconstruction network, the absolute spectra of various
nonluminous samples are successfully reconstructed excluding the emitting
spectrum of the light source and the spectral response of the detector.
The remarkable reconstructed spectral imaging result for the color
board is presented and the reconstructed spectra match well with the
measured ones for different patches using the identical network. We
utilized the least number of spectral encoders ever since to guarantee
efficient encoding, along with the single thickness-variant modulation
layer, which shows potential for mass, rapid, large-area production
by combining deposition with nanoimprint. Instead of the synthetic
Gaussian line shape spectra, a training dataset composed of diverse
spectrum types is adopted to achieve fine generalization of the trained
reconstruction network. In addition, by retraining the neural network,
the reconstruction network is modified to fit for the actual filter
functions of the spectral encoders, thus better reconstruction performance.
The proposed miniaturized spectrometer has great prospects in the
fields of consumer electronics, environmental monitoring, and disaster
prevention.
Colorful radiative coolers (CRCs) can be widely applied for energy sustainability especially and meet aesthetic purposes simultaneously. Here, we propose a high-efficiency CRC based on thin film stacks and engineered diffuse reflection unit, which brings out 7.1 °C temperature difference compared with ambient under ~ 700 W·m−2 solar irradiation. Different from analogous schemes, the proposed CRCs produce vivid colors by diffuse reflection and rest of the incident light is specular-reflected without being absorbed. Adopting the structure of TiO2/SiO2 multilayer stack, the nanophotonic radiative cooler shows extra low absorption across the solar radiation waveband. Significant radiative cooling performance can be achieved with the emissivity reaching 95.6% in the atmosphere transparent window (8–13 μm). Moreover, such CRC can be fabricated on flexible substrates, facilitating various applications such as the thermal management of cars or wearables. In conclusion, this work demonstrates a new approach for color display with negligible solar radiation absorption and paves the way for prominent radiative cooling.
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