Halide perovskite (ABX3) have demonstrated great advantages over conventional semiconductors for the next-generation photoelectronic devices due to their outstanding photophysical properties, such as tunable band gaps, long carrier diffusion length, long carrier lifetime, and high quantum efficiency. In addition, it is also very suitable for humidity sensing because of its environmental sensitivity. However, halogen elements have a great impact on the photophysical properties of perovskite because of their different exchange properties with the environment and mobility. In this work, the samples with three different anions of CsPbCl3, CsPbBr3, and CsPb(Br0.5Cl0.5)3 were used, and humidity sensing and stability experiments were carried out in a humidity environment at a relative humidity (RH) of 30%-90%. It is found that the single-anion halide perovskite materials possess low sensitive at low humidity and possess poor stability at high humidity. While the mixed-halide perovskite CsPb(Br0.5Cl0.5)3 demonstrated better sensitivity and reversible in the range of 30%-90% RH. It shows that this is related to the shallow-level defect types of different halide anions, which lead to different phenomena. The ability of different materials to bind water molecules is also an important reason. Therefore, it indicates that the anion-mixed halide perovskite humidity sensor can be used in future environmental detection applications has great potential.
With the development and progress of science and technology, multi-spectral and multi-optical axis system has become an important trend of the photoelectric equipment on visible, laser and infrared wavebands. Multi-spectral and multi-axis photoelectric system usually has 3~4 optical axes, and the consistency of optical axes among different wavebands plays a major role in accurately searching, tracking and aiming at targets. The accuracy of the consistency of multi-optical axes can't be separated from the beam parallelism of its testing device. To improve the optical axis consistency of photoelectric system and ensure accurate and reliable value, the first task is to reduce the systematic error of the optical axis consistency testing device, which reduces the beam parallelism error. In this paper, the beam parallelism error is analyzed from six aspects: spatial position accuracy of target, parameter of calibrating pentaprism, accuracy of calibrating guide rail, wavefront aberration of parabolic mirror, collimating error of calibrating autocollimator and wavefront aberration of calibrating interferometer. According to the requirements of the optical axis consistency, a reasonable multi-spectral and multi-optical axis calibrating scheme is proposed. The calibrating error is rationally distributed, and the testing device is effectively installed, therefore, the beam parallelism of the testing device for multi-spectral and multi-optical axis system is superior to 5″ for 300 mm in diameter and 3″ for 100 mm in diameter, which can meet the testing requirements the consistency of multi-optical axis. The final result shows that this scheme is effective and feasible.
The abbe number of diffractive optical element is negative, which is opposite to that of traditional refraction optical element. So diffractive optical element has unique advantages on achromatic and thermal compensation. Therefore, it can be applied to diffractive and refraction hybrid optical systems to simplify the optical structure and improve the imaging quality. However, the diffraction efficiency of the single-layer diffractive optical element depends on the wavelength mightily , However, the diffraction efficiency of the design order of the double-layer diffractive optical element in the whole working band is coincident basically and more than 90%, which can significantly suppress the stray light of the non-design order and advance the image contrast. Therefore, the double-layer diffractive optical elements are adopted in this long-wave infrared wide waveband optical system, and the design idea of superposing the diffractive surface on the aspheric surface is proposed. Only two lenses and two materials were used to realize the optimal design. By matching the microstructure parameters of the double-layer diffractive elements ,the diffraction efficiency of the whole working band reached more than 97%. Imaging quality analysis shows that the chromatic aberration of 8μm-14μm is well corrected. the secondary spectrum is well controlled also, and the MTF is close to the diffraction limit, which meets the design requirements.
The infrared continuous zoom optical system can realize the continuous change of focal distance in a certain range and keep the image surface stable and clear in the whole process of field of view change. Further integration and coordination of optical and mechanical design are required as infrared thermal imaging systems are increasingly used in high-precision applications of military and civil fields. However, the mid-wave infrared zoom system contain a large number of mirrors, a complex mechanism and higher design difficulty compared with other types of infrared zoom system. This paper introduced a mid-wave infrared zoom system, considering the design of optics and structures as well as the simplicity of assembly and adjustment. A stable and reliable small-F-number zoom infrared camera system which can meet the constraint condition was designed aiming at the key indicators such as imaging quality, optical axis shaking and adjusting operation. The operating wavelength band of the system was from 3.7 μm to 4.8 μm, the focal length was 30mm to 300mm, and the medium-wave refrigeration focal plane detector of pixels of 1024×768 was adopted. The optical imaging performance was close to diffraction limit, besides, image plane had a high consistency during the whole zooming process.
Halide perovskites (ABX3) have advantages of high photoluminescence quantum yield (PLQY), high gain coefficient, high carrier mobility and tunable bandgaps, which has great development potential and application prospects in tunable photoelectronic devices. However, blue emission perovskite LEDs lag behind their red and green counterparts in efficiency due to their high defect density and difficulties of maintaining quantum efficiency, which greatly restricts the development of the white light LEDs and display devices. Localized surface plasmon resonance (LSPR) can cause the resonant interactions of electromagnetic waves and free electrons in solid-state materials that have demonstrated great advantages in the field of Raman mapping, photodetector and laser. In addition, photoelectric properties of materials can also be manipulated by it that have great advantages for tunable photoelectric devices. In this work, the finite difference time domain (FDTD) method was used to simulate the extinction spectra of Au or Ag nanoparticles on SiO2, as well as study the influences of the shape of the nanoparticles on the position of extinction spectral peak. Then the influence of luminescence efficiency of the blue emission perovskite was analyzed by this model. Finally, the optimal optical enhancement structure of BE perovskite was obtained. According to the simulation results, compared with Au and Ag solid spheres, the Ag hollow sphere not only has the best optical enhancement effect on blue emission perovskite, but also has wide tunable ranges that can cover the entire optical band. Therefore, based on the regulation sensitivity of the Ag hollow spheres in the optical band, it provides an effective solution and simulation results for the performance optimization of perovskite-based tunable photoelectronic devices.
