Study Of Metasurface-integrated Vertical Cavity Surface Emitting Lasers

The focusing,collimation and deflection of laser beams have important application value in precision laser drilling,free space optical interconnection,lidar,etc;Non-diffraction Bessel beams,vortex beams and holographic displays are used in optical communications,particle manipulation,self-imaging,quantum communication and 3D sensing have important application prospects.Generally,in order to obtain these special laser beams,the light sources need to be obtained by wavefront shaping through a complex optical system.These optical systems composed of multiple optical lenses or mirrors are often bulky,which is not conducive to device development of integration and miniaturization.Metasurface has the advantages of flexible design,semiconductor process compatibility,light volume,easy integration,and high control efficiency.It has important application value in the design of multi-functional devices such as optical communications,conformal antennas,and lidar stealth.The vertical cavity surface emitting laser(VCSEL)has the characteristics of low power consumption,circular spot output,planar technology compatibility,and easy integration.It is widely used in optical communication,optical interconnection,distance sensing,lidar,and face recognition,etc.This thesis proposes a metasurface-integrated vertical cavity surface emitting laser(MS-VCSEL)design.This device combines the advantages of Metasurface and VCSEL,and realizes the function of directly emitting a variety of special beams by directly etching and integrating the Metasurface on the VCSEL light-emitting surface.In this thesis,a detailed study of MS-VCSEL that realizes a variety of laser beam output is carried out,and the mechanism of Metasurface's regulation of electromagnetic wavefront is systematically analyzed,as well as the structural design,device preparation and performance characterization of MS-VCSEL.This integrated structural design avoids the addition of optical system components that are not conducive to miniaturization,effectively reduces the volume of the special beam light source,expands its application range,and provides new technologies and new methods for simplifying the design of the light source.The main contents of this thesis are as follows:1.Research on the working mechanism,structured design and preparation process of MS-VCSELMS-VCSEL is based on the back-emitting VCSEL as the basic light source,through the micro-nano structure Metasurface for wavefront control to achieve a variety of laser beam output.We are mainly divided into two parts for research.First,we research and fabricate a back-emitting VCSEL that meets the requirements.Usually based on metasurface design,we need to control the basic light source mode by controlling the size of the oxidation aperture.When the oxidation aperture is about 3?m,the laser emits a single-mode Gaussian beam;When the oxide aperture is larger than 3 ?m,with the injection of currents of different sizes,the laser will appear multimode lasing.At this time,the design for Metasurface will become more complicated.In addition,the basic unit structure parameters of Metasurface need to be designed and optimized.To meet the specificity of the output beam of the MS-VCSEL laser chip and realize the output with high control efficiency,it is necessary to design and optimize different nanostructure parameters,such as etching depth,period,diameter,etc.,and select a large phase span,high transmittance,nano structure unit allowed by the preparation process.We finally determined the 4 phase levels nanopillars with basic unit size radii of 56 nm,82 nm,98 nm,and 116 nm,with the nanopillar period P=260nm and the etching depth H=500 nm.Finally,we discretized the design of the phase control functions for different functions,matched and replaced the nano-pillar structures of the four basic unit sizes as required,and finally obtained a Metasurface that can achieve specific beam manipulation.2?Study of MS-VCSELs array chip capable of addressing and directional emissionAccording to the small oxide aperture single-mode output,the wavefront of the back-emitting VCSEL from the active region to the light-emitting end conforms to the hyperbolic phase profile distribution.We propose to control and compensate the laser light field with a hyperbolic phase function through metasurface design,and prepare MS-VCSELs that realize collimation and focusing functions.The collimating Metasurface lens with a focal length of 630 ?m is designed to achieve the collimated output of the beam;the focal length of the metasurface lens from 580 to 616 ?m is used to achieve the convergence of the beam.The device is packaged on the PCB in a 10×10array layout,and the development of an addressable collimated and focused output laser array chip is realized.The design of the deflection phase function superimposed on the collimation phase function with a focal length of 630 ?m,integrated on an 8×8 VCSELs array,can realize the development of a multi-angle deflection laser beam array chip,and the deflection angle covers 0° to 60°.This integrated non-mechanically controlled beam deflection device provides a new method for realizing the small size and light weight of the beam scanning device.In addition,we have superimposed the multichannel beam splitting phase function and the collimated phase function and integrated them into VCSELs to realize the generation of multi-channel beam arrays.We fabricate laser chips with 1×3,3×1 and 3×3 beam splitting functions.The addressable directional emission laser array chip design of MS-VCSELs will expand its application in laser radar,optical communication,multi-channel laser transmission and other fields3?Study of structured light output MS-VCSEL chip with special light field distributionIn this thesis,the structured light with special light field distribution mainly includes vortex beam,non-diffraction Bessel beam and holographic imaging beam.By designing a metasurface with a collimation function superimposed on an axicon delay function and integrating it into a single-mode output VCSEL,the laser chip can directly output zero-order non-diffraction Bessel beams(full width at half maximum(FWHM)=1.4 ?m).By integrating the collimation function and the axicon function of the Metasurface into the large oxide aperture multi-mode VCSEL,the electronically controlled and adjustable order of Bessel beam output is obtained.The delay function of Orbital Angular Momentum(OAM)of different topological charges is superimposed with the collimation phase function,and a variety of different topological charges(l=-2,-1,0,1,2,5)have been developed.MS-VCSELs laser chip output by the orbital angular momentum vortex beam(Vortex Beam).The phase of the hologram is constructed by the phase recovery method in computational GS(Gerchberg-Saxton)algorithm,and the collimated phase function is superimposed to prepare the holographic imaging MS-VCSEL,which can directly output the hologram with a large field of view(124°)display beam.Related research results have broad application potential in three-dimensional imaging,display,robot vision,human-computer interaction and AR/VR,identity verification and encrypted transmission,and will promote the development of structured beam compact systems.