全光纤波长可调石墨烯调Q掺铒光纤激光器.docVIP

  All-fiber passively wavelength precise tunable graphene Q-switched erbium-doped ring laser# 5 10 Zhang Shumin, Han Mengmeng* (College of Physics Science and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China) Abstract: An all fiber, wavelength tunable, Q-switched erbium-doped fiber laser (EDFL) based on a graphene saturable absorber (SA) has been demonstrated. The wavelengths of the Q-switched laser can be accurately tuned over a range of ~35 nm by inserting into the cavity an unbalanced Mach-Zehnder interferometer (UMZI) with a variable optical delay line (OVDL) in one arm, which acts as an optical beam filter into the cavity. The Q-switched pulse duration and the pulse energy have all been characterized. A maximum pulse energy of 36.9 nJ was obtained. Key words: fiber laser；graphene；Q-switched；tunable. 15 0 Introduction Tunable Q-switched fiber lasers have attracted significant attention because of their wide fields applications, such as in materials processing, fiber optical sensing and wavelength division multiplexing (WDM) for communications. In addition, in many cases one tunable light source can 20 25 30 35 40 be used to replace several sources with different wavelengths. In the early days, researchers typically used a volume diffraction grating [1], an F-P filter [2] or a bulk tunable filter [3-5] as a wavelength selection device. Large coupling losses and stringent alignment requirements or the high cost of these lasers encouraged researchers to develop all fiber, cost effective, wavelength tunable, Q-switched lasers. Recently, tunable Q-switched fiber lasers that use a fiber Bragg grating (FBG) have been demonstrated [6-7]. However, the tunable range was limited to less than 5 nm, and the central wavelength could not easily be placed at a specific position by applying only axial strain or lateral stress to the FBG. In many practical applications, the requirements for wavelength tuning in lasers are very rigorous, so it i