Research On Medical Green Semiconductor Laser With Large Spot And High Uniformity

In recent years,with the technology breakthrough of epitaxy growth,doping process and microstructure design,the semiconductor lasers have expanded from infrared to visible light.Therefore,they have been widely used in laser medical treatment.Especially in clinical photodynamic therapy of angiomas,it has gradually replaced traditional solid-state laser,gas lasers and other light sources in therapy,and has become one of the most popular light sources.The thesis is based on the requirements of laser wavelength,power,spot size and uniformity for photodynamic therapy of angiomas.Selecting the 520 ± 5nm semiconductor laser diode nearest the characteristic peak of the photosensitizer hematoporphyrin as the light source.By the fiber coupling module to realize the demand for power and continuous and stable output,and through large spot high uniformity shaping module to design spot size and uniformity.Finally,by two-part module is combined to obtain a green laser with large spot and high uniformity for photodynamic therapy.This paper will design and study the two parts of the fiber coupling module and the large spot high uniformity shaping module.First,the thesis is based on the comprehensive analysis semiconductor laser diode emission characteristics,using ZEMAX to design a small and simple single-chip aspheric lens fiber coupling scheme,to achieve 400?m,NA = 0.22 fiber,the average coupling efficiency of 90.63%.Then bundle the other ends of the 19 coupled optical fibers into bundles to achieve module power expansion.Finally,on the basis of the completed optical system structure,the mechanical structure and refrigeration system adapted to the selected single tube structure are designed.In the working,it can ensure a stable operating environment of 18? for single tube.The tested center wavelength is 517.2nm,the output power reaches 17.22 W under the rated voltage of 1.5A,and the instability is only ± 0.3% within 6 hours at full power.After testing the optical fiber coupling module,the spot uniformity at 30 cm directly output is only 47.2%.In order to meet the requirements of long distance,high uniformity and spot size of the output spot,selecting a liquid-core fiber with a length of 3m,a core diameter of 2mm,NA = 0.59,and a transmission rate of 90.45% to achieve efficient and long-range transmission of light energy.Then,in order to improve the spot uniformity,the input-output beam mapping relationship is calculated based on the energy conservation principle.While,using ZEMAX self-written ZPL language to add custom operands,then designing an aspheric Galileo flat top shaping system to achieve high uniformity spot output.However,because the size of the end of Galileo system lens is too thick,using angle method to design the equivalent Fresnel to reduce the lens thickness which is reduced from 35 mm to 3.6mm.The shaped spot is tested to have a uniformity of 91.5% and a diameter of 10.6cm at an output of 30 cm.The research shows that the green semiconductor optical fiber coupling module can achieve compact,high power,continuous and stable output,matching the appropriate beam shaping module,and can form a large spot high uniform green semiconductor laser design.Compared with green solid lasers,semiconductor lasers solve the problems of high conversion efficiency and continuous wave output,while reducing the volume and cost,and providing ideal light source equipment for photodynamic therapy.