| Summary: | 碩士 === 國立臺北科技大學 === 光電工程系 === 107 === Title: Continuously wavelength tunable passive-mode locked Er-doped fiber laser based on graphene oxide
School: National Taipei University of Technology Page: 55
Department: Institute of Electro-Optical Engineering
Time: June, 2019 Degree: Master
Researcher: Li-Yen Tsai Advisor: Ja-Hon Lin
Key word: Er-doped fiber laser; graphene oxide; saturable absorber; mode-locking; Tunable wavelength fiber laser; hybrid mode locking
In this work, I investigated the wavelength tunable passive mode-locked Er-doped fiber laser in combination with the graphene oxide (GO) and nonlinear polarization rotation (NPR) mechanism. In order to produce the GO/PVA film, the GO suspension in DI water will be produced by the liquid phase exfoliation technique and then centrifuge. The upper-layer GO suspension was mixed with the polyvinyl alcohol (PVA) solution and dried in plastic model to form the GO/PVA composite film. The GO/PVA film shows the high transmittance around 75.16% at 1562 nm. From micro-Raman spectrum, the characteristic peak of GO at D (1347 cm-1) and G (1589 cm-1) band was revealed with intensity ration (ID/IG) around 1.05. From nonlinear transmittance measurement, the GO/PVA film revels modulation depth around 18.4 % at 1564 nm. Unlike mode-locked mechanism based only on the GO/PVA or NPR, the widely and fine tuning wavelength from 1544 nm to 1574 nm has been demonstrated using the hybrid mode-locked mechanism. The EDFL reveals fundamental mode locked state (FML) state in operation at longer wavelength within 1566nm to 1574 nm and fourth-harmonic mode locked (FHML) state in operation at short wavelength between 1544 nm to 1565 nm. Through the theoretical estimation, the tuning mechanism was attributed to the invisible filter using the NPR mechanism. Finally, the long-term stability of PML-EDFL was confirmed by monitoring the output spectrum for three hours. The generated broader wavelength tunable PML-EDFL can meet many potential applications and high commercial value in the future.
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