This paper proposes a polarization-sensitive, metal-dielectric-metal (MDM) subwavelength grating structure based on surface plasmon resonance that achieves wide-angle, narrow-band, and high absorption in the long-infrared region. The resonance characteristics of the MDM structure, excited by magnetic resonance (MR), cause the transverse magnetic (TM) and transverse electric (TE) modes to polarize. A model of the inductor capacitor (LC) circuit is also presented. Structural simulations demonstrate a near-perfect absorption characteristic (99.99%) at 9 µm center wavelength. For TM polarization with incident angles ranging from 0° to 89°, the MDM grating structure produced absorption rates over 90%, 81%, and 71% for incident angles of 66°, 73°, and 77°, respectively. The absorption peaks in the long-wave infrared band can be adjusted by varying the duty cycle or period, without adjusting structural parameters. The spectral absorption curve shows a red shift and maintains high absorption, with wide-angle and narrow-band, across various azimuth angles (0–90°), during an increase in duty cycle or period. This method reduces the difficulty and complexity of micro-nano processing, and enables multiple absorbers in the long-infrared band (7.5–13 µm) to be processed and prepared on the same substrate surface.

Infrared invisibility has continued to develop in recent decades, triggered by novel physics, advanced fabrication technology and raw materials. However, the quick response of infrared stealth during transmedia (water–air/water–land) movement, which is important in practical scenarios, has not been investigated. Here, we employ the random thermal effect of the interaction between laser and matter to construct a bionic flexible thin-film superhydrophobic infrared invisibility cloak. The average emissivity of invisibility cloak is 0.224 over 8–14 ${{\mu }}\text{m}$ , and specular reflectivity at the incident angle of 10 degree is 1.1% over 2.5–16 ${{\mu }}\text{m}$ . These characteristics indicate the integrated stealth functionality against active (laser) and passive (thermal) detection, respectively. The contact angle between the cloak and water is 154°, which also indicates its unique cross-media response capability. We also show that the developed infrared stealth cloak is robust to practical (nonideal) manufacturing conditions. Our design strategy expands the concept of infrared stealth to cross-media applications.

This paper presents the design of an ultra-wide-angle multispectral narrow-band absorber for reconstructing infrared spectra. The absorber offers several advantages, including polarization sensitivity, robustness against structural wear, wide azimuthal angle coverage, high narrow-band absorption, and adjustable working wavelength. To accomplish infrared spectrum reconstruction, an absorber is employed as a spectral sampling channel, eliminating the influence of slits or complex optical splitting elements in spectral imaging technology. Additionally, we propose using a truncation regularization algorithm based on the design matrix singular value ratio, namely IReg, which can enable high-precision spectral reconstruction under largely disturbed environments. The results demonstrate that, even when the number of absorption spectrum curve is reduced to a range of 1/2 to 1/3, high-precision spectral reconstruction is achievable for both flat and high-energy steep mid- and long-infrared spectral targets, while effectively accomplishing data dimension reduction.

Currently, the engineering of miniature spectrometers mainly faces three problems: the mismatch between the number of filters at the front end of the detector and the spectral reconstruction accuracy; the lack of a stable spectral reconstruction algorithm; and the lack of a spectral reconstruction evaluation method suitable for engineering. Therefore, based on 20 sets of filters, this paper classifies and optimizes the filter array by the K-means algorithm and particle swarm algorithm, and obtains the optimal filter combination under different matrix dimensions. Then, the truncated singular value decomposition-convex optimization algorithm is used for high-precision spectral reconstruction, and the detailed spectral reconstruction process of two typical target spectra is described. In terms of spectral evaluation, due to the strong randomness of the target detected during the working process of the spectrometer, the standard value of the target spectrum cannot be obtained. Therefore, we adopt the method of joint cross-validation of multiple sets of data for spectral evaluation. The results show that when the random error of +/− 2 code values is applied multiple times for reconstruction, the spectral angle cosine value between the reconstructed curves becomes more than 0.995, which proves that the spectral reconstruction under this algorithm has high stability. At the same time, the spectral angle cosine value of the spectral reconstruction curve and the standard curve can reach above 0.99, meaning that it realizes a high-precision spectral reconstruction effect. A high-precision spectral reconstruction algorithm based on truncated singular value-convex optimization, which is suitable for engineering applications, is established in this paper, providing important scientific research value for the engineering application of micro-spectrometers.