Femtosecond Laser-written Fluorine Indium-based Optical Waveguide And The Study On Its Optical Amplification Characteristics

Integrated photonic devices have very important applications in optical communication,photon computing,integrated optical chips and optoelectronic technology.As the most basic optical component in integrated optics,optical waveguide can effectively realize the highly integrated optical path,so the research of high performance optical waveguide has very important significance.At present,ion implantation,chemical deposition and femtosecond laser direct writing techniques have been widely used in the fabrication of high performance optical waveguides.Among the above-mentioned optical waveguide preparation methods,femtosecond laser writing optical waveguide technology is widely used in optical waveguide preparation because of its advantages of simple operation,flexible writing and wide range of materials.Multicomponent glass is the first substrate material used in femtosecond laser fabrication of optical waveguides.Multicomponent glass based optical waveguides have been used in various integrated photonic devices.In this paper,indium fluoride based glass is selected as the base material,and the femtosecond laser direct writing technology is used to successfully write optical waveguide into indium fluoride based glass.The mechanism of the interaction between femtosecond laser and indium fluoride based glass material is studied,and the effects of different laser monopulse energy,different writing speed and different writing depth on the optical waveguide cross section,loss and near-field mode distribution are studied.On this basis,an erbium-doped indium fluoride optical waveguide was fabricated by femtosecond laser direct writing technology,and the optical magnification characteristics of an erbium-doped indium fluoride optical waveguide amplifier at 1550 nm band were studied.The research results obtained in this paper are as follows:1.Femtosecond laser with a central wavelength of 800 nm,a repetition frequency of 1 k Hz and a pulse width of 100 fs is used to write a Type I optical waveguide into indium fluoride based glass by single scanning and multiple writing.The effects of laser monopulse energy,writing depth and writing speed on the cross section,loss and near-field mode distribution of optical waveguide are studied.When the femtosecond laser monopulse energy is 1.5-3.5μJ and the writing speed is 100-250μm/s,the indium fluoride based glass optical waveguides can be prepared.Indium fluoride optical waveguide structures with clear near-field pattern distribution and Gaussian pattern distribution were fabricated with laser monopulse energy of 3μJ and writing speed of 200μm/s.The minimum loss（1150 nm）of is 0.85 d B/cm measured by the end face coupling method.The refractive index of the optical waveguide is 1.5166 measured by the prism coupling method,and the refractive index change is 4.7×10^-3.2.The effects of different femtosecond laser monopulse energies,different writing speeds and different writing depths on cross section,loss and near-field mode distribution of erbium-doped indium fluoride optical waveguide were studied,and erbium-doped indium fluoride optical waveguide amplifiers were prepared.The formation range of the erbium-doped indium fluoride optical waveguide was studied,and it was determined the femtosecond laser monopulse energy was 3.5μJ,the writing speed was 200μm/s,the writing depth was 200μm.The optical waveguide structure with the best light guiding effect,clear near-field mode distribution and Gaussian pattern distribution were obtained.The minimum loss（1150 nm）of erbium-doped indium fluoride based optical waveguide was measured as 1.00 d B/cm by the end face coupling method,and the refractive index of Erbium-doped optical waveguide was measured as 1.5173 and the refractive index change was 5.4×10^-3 by prism coupling method.3.The optical amplification characteristics of an erbium-doped indium fluoride based waveguide amplifier near 1.5μm are studied.In the experiment,a 980 nm laser was used as the pump source,an erbium-doped indium fluoride optical waveguide with a diameter of 8μm and a length of 1.5 cm was used as the optical amplification gain medium,and a near-infrared wideband light source was used as the signal light source.The relative gain of the Erbium-doped waveguide amplifier in the range of 1480 nm to 1560 nm was tested.The peak of the gain spectrum is 1535 nm and the maximum relative gain is 7.6 dB/cm.