Investigation Of Bismuth-Doped Germanate Glass Microspheres Laser Device

In recent years,the miniaturization of photonic devices has become one of the important trends in scientific research and technology applications.The research of photonic devices originated in the optical fiber communication industry with ultra-large-scale data transmission.At present,the size of photonic devices is relatively large,and the design and integration of micro-photonic devices has become an important topic in the field of photonics research.Micro-cavity resonators and micro-nano optical waveguides as coupling waveguides are basic units in micro-nano integrated optics.They are the cornerstones for studying micro-nano optical phenomena and constructing photonic devices.The microsphere laser is an important miniature optical device,which represents a number of exceptional properties,such as extremely small mode volume,very high Q value,very low threshold and very narrow spectral linewidth.It has great application value in the field of integrated optical system and low threshold laser.Bismuth-doped gain medium has exhibited ultra-broadband lasing emissions in the near-infrared region.Furthermore,the near-infrared emission spectra of Bi-doped glasses effectively fill up the vacant spectral region of traditional rare-earth doped active glasses.These unique photoluminescent properties indicate that Bismuth-doped glass is a good candidate for an ultra-broadband lasing application at unconventional wavelengths and for tunable lasers working in near-infrared wavelength range.The purpose of this dissertation is to investigate a novel fiber coupled integrated device based on bismuth-doped germanate glass gain microsphere resonator coupled with microfiber coupling waveguide.It provides a new idea for the development of the new band miniature laser devices and a new light source for the integrated optical systems.The content of this dissertation is shown as follows:1.The fabrication of bismuth-doped germanate glass and their optical properties are studied.A glass composition of Ge O2-Ga2O3-Ba O-Bi2O3 system is designed and obtain the glass by melting,homogenization and molding by the traditional high temperature melt quenching method.We test the absorption spectrum,photoluminescence spectrum,life of the glass.Through the analysis of the test results,we can get the glass composition and bismuth-doped concentration with the best ultra-wideband luminescence efficiency.2.The glass fiber is fabricated using the glass as the substrate by the pulling method and the glass microsphere is fabricated by local heating the glass fiber using CO2 laser.We test the optical properties of microspheres and adjust the preparation process.The XRD patterns are used to identify the amorphous and crystalline phases in glass,fiber and microsphere.These ensure that microspheres have a good optical quality.We fabricate bismuth-doped glass microspheres with good optical properties.3.Characterization of bismuth-doped germanate glass microspheres laser device.A fabrication platform for drawing quartz tapered optical fiber was established,and a tapered optical fiber was fabricated by flame scanning.Use optical spectral analyzer to measure the loss characteristics of a tapered fiber and ensure that it has sufficient light intensity to couple into the microsphere.The bismuth-doped glass microspheres serve as both gain medium and resonator.The pump light and output laser are both coupled to the microsphere through a quartz taper fiber to achieve bismuth-doped glass microspheres laser.The coupling conditions and microsphere parameters were adjusted.The laser beam with a wavelength of 1305.8nm was detected by the optical spectrum analyzer under the excitation of 808 nm pump laser and the threshold pump power was 30 m W.The laser transmission spectrum linewidth is measured at 0.61 GHz by frequency sweep.The curve of absorption pump power and output power shows that the threshold absorption pump power is 215?W,and the maximum output laser power is 3.56?W.It lays the foundation for the development of bismuth-doped laser devices.