High-efficiency And Dynamic Generation Of Fully Vectorial Optical Fields Based On A Spatial Light Modulator

As the laser technology rapidly develops,the information of light plays a more and more significant role in modern scientific and technological research.The information of light relies on the distribution of the elements including amplitude,phase and polarization,which are often required to be steerable in a variety of applications.Amplitude,phase and polarization of the light can be controlled in a linear process of light,while the frequency needs a nonlinear process.As nonlinear effects are not involved in our work,we will only discuss the amplitude,phase and polarization control of the optical fields in this dissertation.With the development of optical technology,methods to modulate amplitude and phase have been established well.Recently the studies of polarization have attracted much more interest.Vectororial optical fields are optical fields whose polarization states change with the space location.Compared with traditional optical fields whose polarization states keep identical,vectororial optical fields have a lot of unique diffraction and focusing properties.These properties make vectororial optical fields useful in focal field regulation,surface plasmon excitation and optical trapping etc.In practical application,we hope to control the vectorial optical fields' parameter dynamically,which could be achieved by a commercial spatial light modulator(SLM).However,the generation method based on SLM always has a low efficiency because dynamic modulation and modulation efficiency are often in contradiction.Therefore,it becomes an urgent problem to achieve the dynamic control and high efficiency at the same time in vectororial optical fields generation,and this is the topic of this article.Based on this thesis,we analyze the diffraction characteristics of holographic gratings on SLM and design optimal grating structures in this dissertation.There are a lot of ways to generate vectorial optical fields.Our group has proposed a method based on the 4-f system and spatial light modulator.By developing the modulator manner of the transmission function from one dimension to two dimensions,we are able to achieve a complete control of amplitude,phase and polarization.In this method,different transmission function leads to different grating structures.After filtered by a filter,certain levels beams are combined by a Ronchi grating.As we can see,SLM helps to achieve different grating structures with different efficiency.Therefore,to design and compare different grating structures can help us find the most efficient grating structure,so as to improve the efficiency of dynamic vectororial optical fields generation.This paper mainly focuses on blazed grating.We have designed a variety of possible two-dimensional blazed grating structures and analyze their efficiency.We finally generate the fully vectorial optical fields experimentally and increase the efficiency of vectorial optical fields generation based on SLM from 2%to 10%.