Investigation On The Physical Characteristics Of Orthogonal Polarized He-Ne Laser With Integrated Y-shaped Cavity

As the core component of precision measurement system,dual frequency laser has been a hot research topic in the world.For its large and tunable frequency difference,orthogonal polarized He-Ne laser with integrated Y-shaped cavity plays an important role in the precision measurements.In this dissertation,physical characteristics research of orthogonal polarized He-Ne laser with integrated Y-shaped cavity are researched comprehensively and systematically,which lay the foundation for laser accelerometer sensor element research and micro-nano force transfer value standard technology.Firstly,characteristics,categories and current status of dual-frequency lasers are summarized.Research status of dual-frequency He-Ne lasers,dual-frequency microchip lasers and dual-wavelength semiconductor lasers are reviewed.Orthogonal polarized He-Ne laser with integrated Y-shaped cavity structural and its applications are introduced.The necessity for an intensive research of the laser is presented.Secondly,the laser's basic structure and working principles are introduced and major output characteristics are measured.The conclusions indicate that laser can work in a certain mode which is a superposition of a fundamental transverse mode and two longitudinal modes.When the current is in the range of 0~3mA,the output power increases linearly with current,peaking at 0.64 mW.The laser output light is orthogonal polarized.The threshold of output frequency difference is 12 MHz.The long-term frequency difference stability is about 3MHz and the short-term frequency difference stability is about 0.75 MHz.Thirdly,the laser intensity tuning and frequency difference tuning characteristics are studied through the experiments.Intensity tuning curve and corresponding beat frequency for two light beams are tested.Several different factors and mechanisms influencing light intensity tuning are analyzed and summarized theoretically.Research demonstrates that single gain and single pass loss,self-saturation effect and mutual saturation effect are the main factors that affect the light intensity tuning.Laser has an output frequency difference of 12MHz~1038MHz.Finally,the laser's thermodynamic model is built by ANSYS software.The temperature field distribution of laser cavity under steady state and transient state are simulated by ANSYS.The real temperature of the cavity surface is recorded by a thermal infrared imager.The differences between the simulation and experiment are less than 1% which indicates the accuracy and reliability of the simulation model.Experiment results show that the laser would reach a steady state in 2 hours after start-up.In the whole process,the heat is gradually conducted from the gain region to the non gain region.When the laser comes to a stable state of temperature distribution,there is an obvious temperature gradient distribution in the cavity.The highesttemperature of the upper surface near the cathode and the lowest temperature at the P sub-cavity bottom which is beyond gain region.The temperature difference between the two sub-cavities is 0.433?,which results in a frequency difference drift about0.58 MHz.The time-dependent temperature differences between two sub-cavities are still the main factors restricting the laser output frequency difference stability.