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Research On The Growth Of High Performance Single Crystal Fibers And Their Applications In High Temperature Sensors And Fiber Lasers

Posted on:2010-03-01Degree:DoctorType:Dissertation
Country:ChinaCandidate:J W ShenFull Text:PDF
GTID:1118360305490155Subject:Physics
Abstract/Summary:PDF Full Text Request
Single crystal fibers (SCFs) are special crystals with fiber appearances. They have many advantages of the general optical fibers, such as good light guiding, light weight, small size and strong ability of anti-electromagnetic interference. Meanwhile, they have the inherent characteristics of the single crystal. In recent years, along with the development of optical fiber sensing and laser technology, especially with the maturity of the fabrication technique of SCFs, much attention has been paid to the growth and utilization of the SCFs with different medium.The aim of the work in this thesis is to develop high temperature sensors and high power lasers by adopting the SCFs. A series of sapphire fibers and Nd:YAG fibers have been grown by the laser heated pedestal growth (LHPG) method. The mechanism of growth was deeply analyzed. The effects of growing interface on stability of growth and involvement of bubbles have been further discussed. High quality SCFs were grown by optimization of growing parameters.Different from the general FBG fabrication methods, the vacuum coating technology was used for fabricating high temperature FBG stack sensors. Through repeated experimental investigation, a composite nano-crystalline structured thin film was realized on the sapphire substrate, and the devitrification effect at high temperature has been eliminated. Based on this, fiber Bragg grating (FBG) stacks were successfully fabricated at the end surface of sapphire fibers by adopting appropriate materials and thin film structures. The device thus fabricated can be used as a high temperature sensor, with a maximum working temperature of 1050℃. To explain the phenomenon of reflection peak disappearance after annealing at high temperature of 1100℃, a control experiment was carried out. A conclusion of inter-diffusion between layers of stack, which resulted in reflection disappearance, was obtained.In the aspect of laser, the single crystal fiber laser was investigated by adopting a high quality Nd:YAG single crystal fiber as the gain medium. Because the factors that affect laser performance were very complicated. a large number of experiments were carried out to study these factors respectively. e.g. cooling for the single crystal fiber, spectral matching of the pumping laser and crystal absorption spectrum, selection of the cavity mirrors, etc. After a general consideration for those parameters, a maximum output power of 13W was obtained at a pump power of 60W. Besides, an attempt was made to study the laser amplification by using the same Nd:YAG single crystal fiber as the gain medium. In particular, the water cooling systems were separately used for seed laser. single crystal fiber and pumping source. By comparing the results of repeated experiments, the factors which affect the signal amplification were studied, and a conclusion was made to optimize the performance of the system.Results thus obtained show the great prospect of using those sapphire fibers and Nd:YAG fibers in high temperature sensing and fiber laser applications.
Keywords/Search Tags:LHPG Method, Single Crystal Fiber, Fiber-High Temperature Sensor, Fiber Laser
PDF Full Text Request
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