Infrared spectrum detection is to detect and analyze the light wavelength information of matter through detectors, like Sun Wukongs piercing eyes, which can see the essence through appearance and accurately identify the material information that cannot be judged by humans eyes. The short-wave infrared (SWIR) band is rich in material spectral information, and has the ability to penetrate clouds and fog. It has a wide range of applications in food, agriculture, remote sensing imaging and other fields.

Methane as the main component of natural gas is an important industrial raw material and fuel gas with flammability and explosion. Real-time monitoring the generation and leakage of methane has great practical significance for using natural gas resources safely and effectively. Many detection technologies can be used for methane gas detection, such as infrared spectroscopy, gas chromatography, electrochemical sensors and so on. Tunable diode laser absorption spectroscopy (TDLAS) technology as a kind of infrared spectroscopy technology, utilizes the narrow linewidth and wavelength tunability of semiconductor lasers to focus single or several absorption lines of gas molecules. When the lasing wavelength is matched with the center frequency of the methane absorption line, the gas molecules will absorb photons and move to a higher energy level, and the laser power will decay at the same time. Methane gas detection can be realized by comparing the output optical power after absorption with the initial output optical power. This technology has many unique advantages, such as intrinsic safe, good stability, good selectivity, and long working life etc..

Photon sieves composed of etched holes on an opaque film have been proposed firstly, to the best of our knowledge, to reduce the focal spot size and alleviate high diffraction orders in soft X-ray and the optical spectrum. With the rapid development of nano-fabrication technology, photon sieves have been demonstrated at nanoscale and worked as binary-amplitude metasurfaces for optical focusing. The photon nanosieves have the advantages of polarization independence and more degrees of freedom in design than the concentric rings in zone plates, which therefore enable more complex manipulation of light, such as hologram, by arranging the locations of holes in a customized way. Due to the subwavelength feature of nanosieves, their related holograms usually support broadband operation. In addition, the non-resonating mechanism of amplitude modulation makes the nanosieve hologram have a wider spectrum than other metasurface devices with resonating nano-structures. The nanosieve hologram also enables a large field of view for holographic display when combined with tunable phase realized by a spatial light modulator. Beyond the circular shape, rectangle nanosieves have also been proposed to control the geometric phase of a circularly polarized light by rotating the orientations of the rectangular nanosieves, thus enabling full-color holography and the generation of optical vortices in various electromagnetic spectra such as X-ray and vacuum ultraviolet wavelengths.

Light field imaging is a 3D imaging technology. In light field imaging, the projection of 3D object to light field information on 2D image plane (including spatial and directional information of incident light) will be conducted by micro-lens array. Then 3D reconstruction of object will be realized through the processing of light field information. Light field imaging has the feature of high-temporal-resolution with scanning-free 3D imaging process and has no requirement of special illumination. Therefore, light field imaging has shown significance in research fields and applications, such as biological imaging, industrial measurement and machine vision.