A high power white super-continuum (SC) fiber laser and a white SC beam combiner are demonstrated. The white SC laser structure includes a passive mode-locked seed fiber laser, master power amplifiers and the SC generation system which uses photonic crystal fiber (PCF) with small mode area as the high nonlinear medium. In this experiment, we adopt the thermally expanded core fibers technique to fabricate a high power all fiber mode field adapter (MFA) which is used to couple high power pump pulses into the PCF, and it can work successfully under the incident pulse power of 98 W with the transmission efficiency of 82%. Meanwhile, a self-made repetition frequency multiplier (RFM) is utilized to adjust the repetition frequency (RF) of pulse and control the nonlinear (NL) effects in the amplification process. Finally, a 43 W high power white SC fiber laser source is achieved, with spectrum ranging from 450 nm to 1700 nm, spectral width below 10dB flatness exceeding 1000 nm. In addition, through theoretical simulation and designed specially, a high power (7×1) white SC combiner is obtained, and its average combining efficiency is up to 87.8% with the testing source of the obtained 43 W SC.
KEYWORDS: Picosecond phenomena, Pulsed laser operation, Fiber lasers, Optical amplifiers, High power lasers, Fiber amplifiers, Laser systems engineering, High power fiber amplifiers, Oscillators, Active optics
We experimentally demonstrate a high-power, high-efficiency, near-diffraction-limited beam quality all-fiber picosecond pulse laser, which consists of a passively mode-locked seed laser and three-stage master power amplifiers. A repetition frequency multiplier and a high Yb-doped gain fiber with shorter length are utilized in the laser system to suppress the nonlinear effects and reduce the pulse broadening caused by dispersion. Moreover, the homemade light mode controllers based on a coiling and tapering fiber technique and the active fiber of the amplifier with a relatively small mode area are adopted to improve the beam quality. In addition, by experimentally adjusting the active fiber length, the optical conversion efficiency of the overall laser system can be optimized. Eventually, a 160 W high-power, high-efficiency, near-diffraction-limited picosecond pulse fiber laser is obtained, with the beam quality factor M2 at 1.12 and an optical conversion efficiency of the system of 75%.