Narrow-linewidth Tm-doped Fiber Laser Output At 1750nm Region

Tm-doped fiber lasers, whose emission spectra cover from 1.6 to 2.1 ?m, have been widely applied in many areas, such as laser radar, space communication, and infrared remote sensing. What’s more, laser in this wavelength region can be effective pump source for 3-5 ?m mid-infrared laser. Currently, 4.3 ?m laser attracts widespread concern due to its important strategic significance in military defense. Because methods to get 4.3 ?m laser are limited, it is an important subject to develop simple-structure and effective fiber laser at 1700 nm wavelength region, which will be critical pump source for special 4.3 ?m fiber laser.In this paper, 1750 nm narrow-linewidth fiber laser based on volume Bragg grating(VBG) is made successfully by building theory model of Tm-doped fiber laser. Moreover, fiber laser based on fiber Bragg grating(FBG) is also studied to lay groundwork for high power Tm-doped fiber and amplifier. The main contents and innovation point are summarized as follows:1. The based theory of Tm-doped fiber laser is introduced. Three kinds of pump scheme of Tm-doped fiber laser are analyzed based on the energy level structure and absorption spectrum of thulium in silica fiber. Rate equation of Tm-doped fiber laser under 3H6-3F4 pump is mentioned, while relevant theory model is set up.2. Investigation of Tm-doped fiber laser based on spatial coupling has been studied through two experiments. Laser at wavelength of 1954 nm is output without VBG. In the circumstance of using VBG, narrow-linewidth laser with maximum output of 400 m W, central wavelength of 1749.62 nm and FWHM of 54 pm is realized, which is also the greatest innovation point in this work.3. All fiber Tm-doped fiber laser using FBG as feedback element is established and continuous wavelength laser with center wavelength of 1809 nm and FWHM of 2.2 nm is obtained. Finally, this paper summarizes experimental results, raises unsolved problems and makes reasonable suggestions.