Research On Sensing And Shaping Of Wavefront Based On Liquid Crystal Spatial Light Modulator And Their Applications

The curved surface composed of photons in the same vibration state is called a wave surface.At a certain moment,the wave surface emitted by the light source is called a wavefront.The light wave wavefront carries important information related to the internal refractive index,density or surface profile of the object,and wavefront sensing is a method that can achieve the measurement and reconstruction of wavefront complex amplitude information(including amplitude and phase).Wavefront control is a technique to adjust the parameters such as the amplitude,phase,and polarization state of the wavefront of the optical wave.This technique is also called wavefront shaping.Wavefront sensing and wavefront shaping have attracted great research interest because of their wide applications in the fields of adaptive optics,optical detection,and laser beam shaping.The invention and application of spatial light modulator provide a new research idea for wavefront sensing and shaping.This paper mainly carried out research work on wavefront sensing based on liquid crystal spatial light modulator and incremental binary random sampling,vector transmission matrix measurement and vector wavefront shaping based on vector liquid crystal spatial light modulator.First,this paper studies a wavefront sensing method based on a liquid crystal spatial light modulator.This method requires a liquid crystal spatial light modulator placed in front of the image sensor to load a set of incremental binary random sampling masks.The wavefront of the light wave is modulated by the sampling masks,which increases the constraints required in the iterative algorithm and improves the accuracy and efficiency of wavefront recovery.Secondly,this paper applies this method to high-resolution quantitative phase imaging.In this imaging method,an optical microscope system composed of an objective lens and a collimating lens images the sample to be measured on an image sensor,and a liquid crystal spatial light modulator is inserted between the image sensor and the collimating lens to modulate the light wave,the image sensor records the diffraction pattern of the modulated light wave,and then quantitatively recovers the complex amplitude information(especially phase information)of the sample from the recorded diffraction pattern.We compared our method with digital holography,found that the phase contours recovered by the two phase recovery methods were basically the same,thus proving the accuracy of the phase recovery method.Compared with holographic technology,the high-resolution quantitative phase imaging method based on incremental binary random sampling algorithm can achieve single-beam quantitative phase imaging without introducing reference light,so it has the advantages of simple structure and strong anti-interference ability.At the same time,since this method does not require the introduction of reference light,this method can be applied to the field of optical imaging and wavefront detection with short coherent length light waves.Finally,this paper studies the measurement of the vector transmission matrix of the scattering medium based on the vector liquid crystal spatial light modulator and the controllable focusing of the light field of any spatial structure through the scattering medium.In this method,a set of polarization holographic measurement experimental device based on Mach-Zehnder interferometric system is built.With the help of digital reconstruction algorithm,the complex vector transmission matrix of the scattering medium can be extracted from the polarization digital hologram recorded by the image sensor.Calculate the required input light field by pre-designing the focused light field and combining with the digital phase conjugation technology,and then encode the designed input light field into a two-channel calculation hologram.Next,the dual-channel computational hologram is loaded on the vector liquid crystal spatial light modulator to modulate the incident wavefront,and the arbitrary spatial structure light field can be focused through the scattering medium.In addition,from the experimental results,we found that after introducing an analyzer with the transmission direction consistent with the polarization direction of the focused linear polarization beam,a higher intensity enhanced light field can be obtained,and the intensity enhancement factor can reach 2 Times.