Study On Amplification Characteristic And Thermal Effect Of Dual-frequency Laser

Recently,with the rising popularity of mobile phones and mobile Internet,wireless communication technology has become a hotspot in research of communication.In the use of microwave spectrum resources,currently the most widely used decimeter wave,centimeter wave spectrum resources will run out of occupied,and people have to shift the focus of research to millimeter wave with higher frequency and larger frequency range.Dual-frequency microchip laser which could output dual-frequency laser with correlated phase was used to beat frequency for generating millimeter wave.It is a relatively simple and effective way.Therefore,global researchers are attracted by dual-frequency microchip laser with high power,large frequency separation.In order to obtain ideal high power dual-frequency laser source,this paper will study dual-frequency laser from two aspects: theory and experiment.The influence of thermal effect to the laser was also studied.The main contexts could be summarized as:(1)An overview of development of millimeter wave and several technologies of optical generation millimeter wave.The superiority of dual-frequency microchip to obtain millimeter waves was illustrated.The research status of dual-frequency microchip laser at home and abroad in recent years has been introduced briefly at last.(2)Principle of common laser generation and the structure of a laser were described firstly.Then the laser gain medium and optical resonator was introduced in detail.The composition of dual-frequency laser was expounded.By analyzing the rate equation,the analysis formula of the laser output characteristics could be deduced.(3)Two laser modes were introduced: longitudinal mode and transverse mode.Principle and method to achieve high power dual-frequency laser were illustrated.MOPA system was composed of a Nd:YVO4 microchip laser and a Nd:YVO4 amplifier.Deep analysis of seed laser and amplified laser were studied.When LD pump power was 2.23 W,output power of seed laser was measured as 247.8 mW maximum;the slope efficiency was 24.34%.The corresponding output power of amplified laser was 2.38 W,amplification of 9.65.By analyzing output power and frequency spectrum of lasers,spectrum mismatch and gain saturation effects were the two main causes leading to relatively low output power.(4)Thermally induced wavelength and refractive index changes in thermal effect theory were deeply studied.Depending on the correlation of thermal effect and spectral matching,the laser crystal was put under temperature control.The output power and frequency spectrum of amplified laser were investigated.When temperature of the crystal was 53.3°C,maintain LD pump power at 2.23 W.The output power of amplified laser was measured as 2.40 W,with 45.03 GHz in frequency separation.The beam quality of amplified laser has been improved obviously compared to the seed laser.By using ANSYS simulation,the conclusion was drew under same conditions that if crystal was shorter in side length of cross section and thicker in thickness,temperature difference between inside and outside was much lower.