| Mid-infrared 3μm band laser,located in the "molecular fingerprint" region,which can be strongly absorbed by H2O,CO2,CH4,N2O and other compounds,has widely application value in gas detection,biomedicine,infrared countermeasures and other fields.At present,the technical means to realize the 3 μm laser include but not limited to:optical parametric oscillation technology,quantum cascade semiconductor laser technology,transition metal/rare earth-doped solid laser technology and fiber laser technology.With the development of Laser Diode(LD),Er3+-doped solid-state lasers that directly generate～3 μm laser with LD pumping have been rapidly developed due to their advantages of compact structure,low cost and high conversion efficiency.It has become one of the main technologies of obtaining 2.8 μm laser.In this paper,Er:Lu2O3 crystals with higher thermal conductivity and lower phonon energy are taken as the research object.The spectral characteristics of the crystals are studied systematically,and the performance of continuous laser in the 2.8 μm band is explored.Moreover,the unique characteristics of self-Q-switched laser are studied experimentally and theoretically.The concrete research content is as follows:1.Aiming at the application requirements of 3 μm band laser in the fields of environmental monitoring,precision medicine,military confrontation and so on,this paper analyzed the main generation technologies of 3 μm laser with them advantages and disadvantages,and introduced the common rare earth activated particles and host materials in 3μm band in detail.According to the research of Er3+-doped solid-state continuous and pulsed laser in recent years,the main content and significance of the research of laser with 3μm band based on Er:Lu2O3 crystal were pointed out.2.The spectroscopic properties of Er:Lu2O3 crystal were measured and analyzed in detail.Combining the absorption spectrum and emission spectrum,the absorption and emission cross-sections were calculated according to the Judd-Ofelt theory and Fuchtbauer-Ladenburg formula,and the excited-state-absorption cross-section was given according to the McCumber theory.The gain cross-section of the crystal was analyzed,and the excellent luminescence performance of Er:Lu2O3 crystal in the 2.8 μm band was proved.It provides theoretical and data support for the follow-up laser research.3.In the field of continuous laser,aiming at the backward development of the domestic 3 μm erbium-doped solid state laser,the first Er:Lu2O3 crystal laser with an output power of 5 W was obtained by single-end pumping method,using an Er:Lu2O3 crystal which was independently grown in China,narrowing the development gap at home and abroad.In the single-end pumping scheme,10.1 W continuous laser was achieved by using more precise thermal management.The power level of Er:Lu2O3 laser was further improved by homogenizing the heat distribution inside the crystals by dual-end pumping.At room temperature,2.85 μm laser with output power of 14 W was obtained,which is the highest laser output power produced by Er:Lu2O3 crystal in the world at present.4.The characteristics of self-Q-switched laser at 2.74 μm of Er:Lu2O3 crystal were studied experimentally and theoretically.Self-Q-switched pulse laser with pulse width of 145 ns was obtained in the experiment,and the maximum average output power was 877 mW.In order to study the self-Q-switched laser generation mechanism,a self-Q-switched rate equation model was established based on the energy level lifetime characteristics and excited-state-absorption characteristics of Er:Lu2O3 crystal.The numerical solution was performed by Runge-Kutta method,theoretically confirmed that the Er:Lu2O3 crystal has unique self-Q-switched properties.It provides a new technical route for the generation of 3μm pulsed laser. |
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