| Medium(deep)UV laser at 200 nm to 250 nm wavelength plays a very important role in biological detection.It can help identify and analyze targets when detecting chemical and biological warfare agents that may appear in battlefield or large-scale terrorist attacks.In order to replace the huge and expensive ultraviolet detection system used in the military,the portable ultraviolet detection equipment with compact structure,reliable performance,high efficiency and low cost is being developing which has great application potential.Solid-state UV laser,as one of the best schemes for UV laser generation,has excellent properties such as high beam quality,stable output power and low noise.Because the wavelength of semiconductor laser depends on the quantum well characteristics of gain medium,it overcomes the difficulty of limited selection of the fundamental frequency wavelength of solid state laser,and can realize 200nm-250nm narrow linewidth continuously tunable medium(deep)ultraviolet laser.However,due to the limited output power of single-frequency single-mode semiconductor lasers,there are many kinds of laser amplification structures using cone-shaped semiconductor lasers in foreign countries.Our paper is based on the project of the president of the Chinese Institute of engineering physics,"the medium-ultraviolet fund project",and takes the conical semiconductor laser as the main experimental device,aiming at three cavity structures:seed injection type,Littrow external cavity feedback structure,and ring cavity structure.The tunable narrow linewidth(<250nm)tunable narrow linewidth(<0.01nm)laser with high beam quality and high power output is realized to provide the fundamental frequency source for the generation of medium(deep).The main research contents include:1.The present situation and trend of the development of conical semiconductor lasers and three kinds of cavity structure lasers at home and abroad are introduced.The structure characteristics of cone semiconductor lasers and three kinds of cavity types are analyzed and summarized.2.The working principles of three kinds of conical semiconductor lasers are analyzed,the key and difficult points of the experimental realization are discussed,and the experimental system is designed and analyzed.3.The laser output of three kinds of conic semiconductor lasers has been successfully realized.The output characteristics(spectral,power,line,beam quality,wavelength tunable,etc.)of three kinds of conical semiconductor lasers have beenThe following is the experimental results and comparative analysis of three kinds of conic semiconductor lasers.The cone semiconductor laser amplifier mainly uses seed light with good laser characteristics and is injected into the cone waveguide amplifier to realize the amplification of laser power.In this paper,the maximum output power is 1.3w,the wavelength is 910nm/930nm,the linewidth is kept in the single frequency of 640fm-800fm,and the tunable laser output is achieved.The relationship between the output power,the injection current and the seed optical power of the conical semiconductor amplifier system is studied.The external cavity of the conical semiconductor laser is the introduction of grating external cavity in the external part of the cone semiconductor laser.The film with different reflectivity is plated on the front and back surfaces of the laser,which makes the external feedback element and the end face of the semiconductor chip make up the external cavity.In this paper,a series of single-frequency laser outputs with a center wavelength of 927 nm,a tunable range greater than 20 nm and a linewidth<980fm under continuous pumping at room temperature are realized by using the grating external cavity locking wavelength and narrow linewidth.When the injection current is 4a,the maximum output power is 1.906w.the electro-optic efficiency is 21.7%,the linewidth is 700fm,the beam quality is 1.948 and 3.788 in the directions of fast and slow axis.Ring-shaped cone semiconductor laser is based on the grating external cavity cone-shaped semiconductor laser,the cavity shape is closed,and the ring oscillation of the laser is realized.In this paper,a ring cavity grating cone semiconductor laser is studied and designed,and the output of the ring cavity cone semiconductor laser with full reflector is successfully realized.When the ring cavity is formed,the threshold current of the laser is about 1.2 a.The slope efficiency is 0.286 w/a;When the injection current is increased to 4a.the output laser power is 805MW and the electro-optic efficiency is 10.1%.In general,the cone-shaped semiconductor laser amplifier is simple and easy to realize,but the single-pass structure is limited in power amplification.Moreover,the selection of seed source is very important for obtaining narrow linewidth,tunable wavelength and high beam quality laser output.The key of this experiment is to use seed light with good laser characteristics.The external cavity cone-shaped semiconductor laser introduces the grating external cavity and selects the appropriate blazed grating,which can not only avoid the extra internal cavity oscillation,but also solve the problems such as the instability of the mode in the cone region and the damage to the laser beam quality by the optical catastrophe effect.It can further narrow the linewidth and achieve tunable wavelength.Moreover,by introducing an external cavity,the continuous laser oscillation can obtain a larger output power.Compared with the grating external cavity,the ring external cavity cone-shaped semiconductor laser avoids the problems of multi-mode oscillation and post-cavity surface burning,and further ensures the stable frequency and high beam quality laser output.Compared with the cone-shaped semiconductor amplifier,the output power of the laser ring oscillation is higher than that of the conical semiconductor amplifier.However,it is difficult to set up the whole system,and the coupling injection design of the surface reflector is complicated and difficult to adjust.The innovations of this paper are as follows:the high efficiency coupling of seed light and conical waveguide amplifier is realized by coupling simulation design and submicron scale high precision alignment of six-dimensional space in this paper.Compared with the related domestic research results,the laser amplification ratio is 20.21 dB.In addition,this paper is the first time in China to apply the grating external cavity structure to a conical semiconductor laser.The diffraction grating is used to lock the wavelength,narrow the linewidth,and make use of the continuous oscillation of the external cavity to realize the tunable,narrow linewidth and high beam quality.The output of high power laser is about 2W,the wavelength is 915nm 935nm,the linewidth is 700-980fm,the M2 of fast and slow axis is 1.948 and 3.788,respectively. |
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