Thulium doped fiber based lasers and amplifiers

• Main Author: Chen, Shaoxiang
• Other Authors: Yoo Seongwoo
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Optics, optoelectronics, photonics
• Online Access: https://hdl.handle.net/10356/90133; http://hdl.handle.net/10220/48428
• Institution: Nanyang Technological University

In general, the work in this thesis could be divided into two parts, but more work is focused on the first part. Compared with aluminosilicate based Thulium-doped fibers (TDF), germanosilicate based TDFs have a blue-shifted absorption and emission cross-section in the transition from level 3F4 to level 3H6. Due to the quasi-three-level nature and broad fluorescence emission from level 3F4 to level 3H6, the germanosilicate based TDFs is envisaged to provide much higher gain at short wavelength below 1700nm. Combination of aluminosilicate based TDF and germanosilicate based TDF will provide a broadened emission window in the transition from level 3F4 to level 3H6. Literately, aluminosilicate based Thulium-doped fiber amplifiers (TDFAs) have been demonstrated from 1660nm to 2050nm. This broadband TDFAs combined with hollow-core photonic bandgap fiber provide a solution to the next generation fiber communication. Considering the long wavelength edge of extended L-band EDFA at 1620nm, there is an obvious gap between L-band EDFA and state-of-the-art TDFAs. In order to seamlessly fill the gap, the short wavelength gain of a new germanosilicate based TDF (Tm/Ge co-doped fiber) is exploited by low-loss cavity management, long wavelength amplified spontaneous emission (ASE) suppression, thus realizing continuous wavelength lasing at short wavelength. Particularly wavelength tuning in the 1620-1660nm is realized by a compressively tunable fiber Bragg grating. When a band-pass filter is employed, ultrafast fiber lasers at 1650nm waveband is realized, which potentially unleash the application of thulium-doped fiber laser in the wavelength region below 1700nm. Intriguingly, for the germanate glass (multi-component glass mainly GeO2, but without SiO2), it provides a distinct environment for Tm3+ ions, in particular, the germanate glass host provide a much higher Tm-doping concentration capacity and longer fluorescence lifetime compared with silica glass. In the second part of the thesis, all the work are based on Tm-doped germanate glass fiber, which includes three main topics. The first topic focuses on the characterization of an in-house fabricated large mode area (LMA) Tm3+-doped germanate glass fiber (TGF). Secondly, based on the in-band core-pumping scheme, a single-mode fiber laser at 1950nm incorporating short length TGF is demonstrated with very high slope efficiency. Finally, with the short length of double-clad TGF, a compact TDFA with attractive gain is built operating in the 1880-2000nm waveband. Moreover, the double-clad TGF is incorporated as power amplifier in a master oscillator power amplifier (MOPA) system seeded by dissipative solitons, showing promise as a candidate for high-power pulse fiber laser with mitigated nonlinearity.