Research On Mid-infrared Carbon Dioxide Gas Laser Source Based On Anti-resonance Hollow-Core Fiber

Mid-infrared laser(3?5?m band)has important applications in many fields such as space communication,remote sensing,optoelectronic countermeasures,medical treatment,and atmospheric monitoring.At present,there are many solutions for generating mid-infrared lasers.Among them,soft glass fiber lasers based on rare earth-doped ions are most promising to achieve efficient and compact mid-infrared laser output.However,due to the limitations of soft glass fiber material characteristics,the level of drawing technology and the type of rare-earth-doped materials,the mid-infrared fiber laser has technical bottlenecks in terms of output power increasing and wavelength expansion.The output power decreases exponentially as wavelength increasing.The new source based on gas-filled hollow-core fiber in recent years perfectly combines the advantages of traditional gas lasers and fiber lasers.In this paper,a self-built tunable narrow linewidth 2?m fiber amplifier was used to pump a section of anti-resonant hollow-core fiber filled with low-pressure carbon dioxide gas.For the first time in the world,a 4.3?m band continuous wave fiber laser output was achieved.The main content and results of this article are as follows:1.The characteristics,applications and main production methods of mid-infrared laser sources are introduced,and it is pointed out that there are technical bottlenecks in power enhancement and wavelength expansion of mid-infrared lasers based on rare-earth-doped fibers.By reviewing and analyzing the development history and research status of hollow-core fiber and hollow-core fiber gas lasers,it is pointed out that anti-resonant hollow-core fiber gas lasers provide an effective way to solve the technical bottleneck encountered by traditional mid-infrared fiber lasers,which is expected achieving high power tunable mid-infrared fiber laser output.2.A theoretical analysis of a 4.3?m band carbon dioxide gas laser based on an anti-resonant hollow core was carried out.Aiming at the demand of 4.3?m CO₂ laser output,a simulation model of anti-resonant hollow-core fiber was established,and the energy distribution and transmission loss characteristics of the corresponding mode field were analyzed.It is pointed out that the anti-resonant hollow-core fiber with smaller core diameter and thicker tube wall is more conducive to the transmission of fiber lasers in the 2?4.5?m band.Combined with the transmission characteristics of anti-resonant hollow-core fiber,the energy level characteristics of carbon dioxide molecules and the absorption characteristics of carbon dioxide molecules are analyzed which provide theoretical guidance to the research.3.An experimental study of a 4.3?m band carbon dioxide gas laser based on anti-resonant hollow-core fiber was carried out.A homemade tunable narrow line-width2?m fiber laser amplifier with a maximum output power of about 2.2 W is set as the pump source,a section of anti-resonant hollow-core fiber filled with low-pressure carbon dioxide was pumped.Under the pressure of 5 mbar carbon dioxide pressure,a maximum output power of 4.3?m laser output of 82 m W was obtained,which is the longest wavelength of the current continuous wave fiber laser output..4.An experimental study of a high-power 4.3?m band carbon dioxide gas laser based on anti-resonant hollow-core fiber was preliminarily carried out.After preliminary optimization design of the 2?m pump source,a 155 m W 4.3?m laser output was achieved with a 10 m long hollow-core fiber with the core diameter of 80?m and 5 mbar carbon dioxide pressure.The slope efficiency of 19.2%is achieved in terms of the absorbed pump power.By further optimizing the design of anti-resonant hollow-core fiber,increasing the power of the 2?m narrow line-width pump source,and introducing a suitable buffer gas,it is expected to obtain a tunable 4.3?m fiber gas laser output from the watt level to the ten watt level.