Elasticity is an important parameter that describes the physical meaning of matter, and in medicine, changes in elasticity are often associated with pathological changes. Therefore, elastic imaging is widely used to characterize changes in the mechanical properties of biological tissues. Traditional elastic imaging has problems such as low resolution, low penetration depth, or invasive measurement. Optical imaging technology is increasingly favored by researchers due to its advantages of non-destructive, non-contact, non-invasive, and high-resolution high penetration depth. Several optical imaging techniques that can be used for elastic performance measurement such as optical coherence tomography, optical coherence elastic imaging, and photoacoustic imaging are mainly introduced. TheirKimeyagiwnogrpdrsi:nciples, research progress, and application scenarios are introduced separately.

The accurate measurement of turbine blade surface temperature is crucial for ensuring the safe and stable operation of an aeroengine, as it can prevent overheating and damage to the blades, extend the engine′s lifes-pan, and ensure the aircraft′s safe flight. Non-contact radiation thermometry is widely used in temperature measurement due to its wide range, high precision, and non-destructive nature towards the object′s original temperature field. However, in high-temperature environments where turbine blades operate, various factors interfere with radiation temperature measurements and cause errors. Among these factors, reflected radiation error accounts for the largest proportion. Therefore, suppressing such errors is vital for accurately measuring blade temperatures. The methods for correcting reflection radiation errors are summarized, such as establishing a reflection radiation model, designing reflection radiation error correction algorithms, and using dual-spectrum area pyrometry (DSAP) temperature measurement and optical path optimization methods. Based on this, the development of reflection radiation correction methods is prospected.

Based on thermodynamics and internal ballistic theory, the energy characteristics and internal ballistic of dynamic infrared decoys are analyzed, and the mathematical models for the energy characteristics and internal ballistic of dynamic infrared decoys are established. Taking the formula of AP-PTFE-Mg-Al as an example, the detailed calculations and analysis are carried out for dynamic infrared decoys. The combustion heat, total enthalpy and entropy of the products, as well as the theoretical specific impulse and characteristic velocity of the engine of the dynamic infrared decoys are obtained. By using a self-programming with the Runge-Kutta method, the curves of pressure variation with time at different working stages are obtained. A method and theoretical reference are provided for the design of dynamic infrared decoys.

In distributed optical fiber sensing technology, the optical frequency-domain reflectometry (OFDR) has a great advantage in measuring physical quantities such as stress and temperature by virtue of its high spatial resolution and high sensitivity. A set of OFDR distributed sensing system is built by combining weak-reflection fiber grating array, and the visual programming platform is used to realize the collection and processing of data, and ultimately the strain or temperature measurement results at any point in the weak-reflection fiber grating array can be displayed in real time. Experimental results show that the distributed sensing system constructed has a spatial resolution of 0.08 mm, a strain measurement accuracy of 6.9 με, a measurement capability of 1 Hz strain measurement refresh rate, and the ability of distributed dynamic strain monitoring in real time. In petrochemical, aerospace and other fields that require high spatial resolution and real-time dynamic strain sensing capability, the distributed optical fiber strain sensing system developed will have a broad application prospect.

To achieve high reliability and low resistance ohmic contact is the premise of obtaining high performance silicon carbide power semiconductor devices, which directly determines the energy consumption level of power devices. Laser annealing has become a new generation of mainstream annealing technology for silicon carbide power devices due to its advantages of localization, fast temperature rise, flexible control, high precision and stable continuous energy output. The research progress of laser annealing of silicon carbide power devices are summarized at home and abroad in recent years, simulates and analyzes the light and heat transfer characteristics of laser annealing principle in detail. It also designs a 355 nm ultraviolet laser annealing experimental system and conducts laser annealing experiments on Ni/SiC. Under the condition of laser energy density of 2.55 J/cm2, and the specific contact resistance is 9.49×10-5 Ω·cm2. Research results provide theoretical and data support for laser annealing and performance improvement of SIC power devices.

A temperature sensor based on the principle of optical interference is proposed. A Gaussian beam is generated by introducing a single-mode fiber in the reference optical path, and the fiber Bragg grating structure is introduced into the measurement optical path. Parallel Gaussian beams are generated by incident light passing through the fiber Bragg grating and collimator. The Laguerre-Gaussian beams with orbital angular momentum are generated through a spiral phase plate. The two beams of light are interfered on the beam combiner, and the spiral interference image is generated. The fiber Bragg grating structure is introduced into the measurement optical path, which mainly uses the optical delay characteristic of fiber Bragg grating. The phase delay of light propagation is generated in the fiber Bragg grating when the ambient temperature changes. The phase difference between the measurement optical path and the reference optical path is changed, resulting in rotation of the spiral interference image. The interference image is detected in real time by a high-resolution camera. Image processing of interference image is executed to extract the change information of interference image accurately. The temperature sensitivity of the sensor reaches 4.08 °/℃ by the above method, which will have important application value in the field of temperature sensing.

The bandwidth testing of a beam stabilization system based on a four-quadrant detector is discussed in detail. At first, the working principle, importance, and main application scenarios of the beam stabilization system are introduced. And then, a detailed explanation is given on the working principle, advantages, and application of beam inclination sensors, especially four quadrant detectors, in beam stabilization systems. Next, a detailed introduction to the composition, working principle, and importance of beam stabilization systems in practical applications are provided. In the system testing section, a detailed description of the testing environment, methods, and analysis of the testing results are provided. The testing results indicate that the beam stabilization system based on the quadrant detector has an effective suppression bandwidth of 138.35 Hz for the X-axis and 131.96 Hz for the Y-axis. At last, the testing results are summarized and future work prospects are proposed.

Frequency domain parameters such as bandwidth and response flatness of electro-optical modulator chip are important evaluation indexes to measure the performance of electro-optical modulator chip. The frequency domain parameter testing method of electro-optical modulator chip is studied, and a frequency response parameter testing system of electro-optical modulator chip based on ultra-wide bandwidth lightwave component analyzer is established. The core frequency response parameters of the electro-optical modulator chip are tested in the range of 10 MHz~110 GHz. Experimental results show that the measurement results of the proposed method are in good agreement with the simulation results, and it is an efficient and high-precision method for testing the frequency response parameters of the electro-optical modulator chip.

In view of the current research status of terahertz detectors, the advantages and disadvantages of existing terahertz detectors are analyzed, and the pyroelectric materials and absorbent materials of pyroelectric terahertz detectors are studied. A new design and fabrication method of terahertz detectors based on PMNT chips is proposed. Using PMNT wafer as pyroelectric material, carbon nanotubes as absorption material, using precision thinning polishing technology and sputtering electrode technology, the design and manufacture of a new pyroelectric terahertz detector are completed. And using the detector designed a terahertz power meter, after testing, the power meter in 0.1~30 THz wide band, 0.5~100 mW high power dynamic range, the power measurement accuracy reached±10%, the comprehensive index reached the international advanced level of similar products, the application effect is good.

Refractive index is an important parameter of materials. In many fields such as chemical analysis, environmental protection and medical health, the detection and measurement of refractive index have been widely used. Among them, bending or called U-shaped optical fiber is the simplest structure to achieve refractive index sensing, using the basic principle that the U-shaped bending loss of optical fiber can be affected by the external environment of bending optical fiber, combined with the advantages of ordinary single-mode fiber, which has high flexibility and hard to break, etc. A high sensing sensitivity, simple structure and low cost distributed refractive index sensing scheme based on Rayleigh scattering spectrum detection in U-shaped fiber is proposed. When the bending diameter is 0.7 cm, the sensing sensitivity reaches the maximum value of 42.57 nm/RIU in the refractive index measurement range of 1.333 0~1.377 3, and presents a good linear sensing response, which makes the application and popularization of disposable cheap refractive index sensing probes such as medical devices possible.

The propagation characteristics of oblique incidence terahertz (THz) waves through non-uniform plasma are investigated by the shift-operator finite-difference time-domain (SO-FDTD) method combined with the phase matching condition. The electron density distribution of the non-uniform plasma is assumed to be in a Gaussian profile. Validation of the presented method is performed by comparing the results with those obtained by an analytical method for a homogeneous plasma slab. Then the effects of parameters of THz wave and plasma layer on the propagation properties are analyzed. It is found that the transmission coefficients greatly depend on the incident angle, while the polarization of the incident wave has little influence on the propagation process in the range of frequency consideredr. The results confirm that the THz wave can pass through the plasma sheath effectively under certain conditions, which makes it a potential candidate to overcome the ionization blackout problem.