Research On The Production Of Hollow Laser Beams Based On Microchip Lasers

The vortex hollow beam is a hollow beam with the characteristics of spin and orbital angular momentum.It has high practical value and broad application prospects in high-speed optical communications,optical tweezers,super-resolution microscopy and other fields.,So its generation method is widely concerned.Among them,the ring beam pumping method(a method in which pump light modulated into a ring is input into a cavity to directly generate a hollow laser)has the advantages of good beam quality,high conversion efficiency,and easy implementation.It is used in the research of generating vortex hollow beams.Highly anticipated.At the same time,the semiconductor saturable absorber mirror(SESAM)passively Q-switched microchip laser,as a laser with a very short cavity length,can output picosecond pulse lasers with good beam quality and low pulse repetition rate,which is suitable as Seed light of the amplifier.However,the laser cavity is too short,has less absorption of pump light and low gain,and the ring-shaped hollow beam has a large loss.Therefore,the use of ring-shaped beam pumping the laser to generate a hollow laser beam with a pulse width of the order of picoseconds has a certain difficult.Based on this,this thesis explored the method of generating continuous vortex hollow beams by the Nd:YVO4microchip laser with a cavity length of 300?m,constructed a low-cost ring beam pumping method,and carried out theoretical derivation and simulation Analysis and experimental verification have explored the possibility of using this method to generate pulsed vortex hollow lasers.The main research results obtained in this paper are as follows:This paper proposes a method of using an axicon-lens group to modulate a ring pump light with a controllable radius,so that the microchip laser can generate a vortex hollow laser beam.The principle of the method is: by adjusting the distance between the axicon and the convex lens,the focused ring pump light with different radius can be modulated,and the mode matching with the target transverse mode of the corresponding resonator can be performed to obtain the target mode laser output.This article has carried on the theoretical analysis to this method,has carried on the scheme demonstration according to the pattern matching principle,and uses the ZEMAX software to carry on the simulation simulation,obtains the feasible analysis result.In the experiment,an axicon with a cone angle of 5° and a convex lens with a focal length of 35 mm were used to modulate a ring pump light with a radius in the order of micrometers,so that the microchip laser output a stable ring hollow laser,and the output hollow beam The power test was carried out,and the maximum power measured was 32 m W.Finally,Mach-Zehnder(MZ)interferometry was used to detect the pattern of the obtained output light,and it was verified that it is a 01-order vortex Laguerre Gaussian beam.The research in this thesis is based on the end-pumped Nd:YVO4 microchip laser with a cavity length of 300?m.The method of generating continuous vortex hollow beams by this laser has been explored,and breakthrough results have been obtained.This is the SESAM passively Q-switched microchip laser It is possible to generate picosecond pulse vortex hollow beam.This research has important guiding significance for the establishment of the actual method of microchip laser output vortex hollow beam.