High-power All-fiber Super Continuum Generation From Photonic Crystal Fiber

Compared to the traditional broadband light source, there are some advantages for supercontinuum source, such as ultra-broad spectal coverage, high spacial coherence, and high brightness. Consequently, supercontinuum source would be applied in a wide market, for example, biophotonics, spectroscopy microscopy, and so on. To obtain a supercontinuum source with a high average output power and subsequently a high spectral power density is one research topic in this field. In this thesis, the theme is focused on how to generate high-power all-fiber-integrated supercontinuum from photonic crystal fibers. The main contents of this dissertation are presented as follows:1. The physical mechanisms of supercontinuum generation in optical fibers are reviewed, the fiber parameters of the single-core and seven-core photonic crystal fibers involved in this thesis are presented and the mode properties of the seven-core photonic crystal fibers are numerical calculated, which is helpful for the investigation and analysis of the following supercontinuum generation experiments. The super-low splice technology between the 15/130 double cladding large mode area fiber and the photonic crystal fibers has been realized, which paves the way for structuring the high-power all-fiber-integrated supercontinuum system.2. High-power supercontinuum generation in single-core photonic crystal fibers have been investiged: by using the high-doped gain fiber in the pre-amplifiers and the low-doped gain fiber in the power amplifier, a pulse-repetition-rate-tunable picosecond fiber laser with 125 W output from 15 μm fiber core is demonstrated. A compact high-power supercontinuum source is formed by directly splicing the output fiber of the picosecond MOPA laser with a photonic crystal fiber. A supercontinuum with an average output power of up to 101 w, spanning from about 700 nm to beyond 1700 nm, is obtained. The pump-to-supercontinuum conversion efficiency is 78.9%. This is the first reported supercontinuum source with an average output power beyond 100 W from the photonic crystal fiber.3. High-power supercontinuum generation in multi-core photonic crystal fibers also have been investiged: the first all-fiber supercontinuum generated from the multi-core photonic crystal fiber is reported. Using the self-made high-power picosencond MOPA laser as the pump source, over one-hundred-watt supercontinuums are generated in two kinds of home-made seven-core photonic crystal fibers. The influences of photonic crystal fiber structure and pulse repetition rate on the supercontinuum generation are investigated in detail. The potential of extending the spectral range and scaling the output power for the supercontinuum source based on multi-core picosecond fiber lasers is analyzed and discussed. With the development of fiber laser technology and the advancement of photonic crystal fiber fabrication capability, broad-band supercontinuum with higher average output could be expected through the combination of 1 μm Yb-doped fiber laser and suitable silica multi-core photonic crystal fibers. The research results will make a contribution to the further development of high-power supercontinuum source.