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%.
We demonstrate an all-normal dispersion passively mode-locked Yb-doped fiber laser for the supercontinuum (SC) generation based on the nonlinear polarization rotation technique. A piece of polarization-maintaining fiber is utilized in the cavity as a spectral filter. By changing the pump power as well as the polarization states, pulses at repetition rates of 22.85, 45.7, 91.40 MHz can be achieved, corresponding to the fundamental and the second- and the fourth-ordered repetition rates, respectively. The output spectrum has a central wavelength of 1040 nm with steep edges, which indicates that it is a dissipative soliton (DS) mode-locking state. By launching the amplified DS pulses into a piece of photonic crystal fiber at a fundamental repetition rate, SC exhibiting a spectral range from 700 to 1700 nm is realized.
A new Pre-Temperature compensation design of Faraday isolators is proposed, for the first time to our knowledge. And
depolarization induced by linear birefringence and circular birefringence in this kind of Faraday Isolator is investigated.
For compare, depolarization in conventional Faraday isolators is also given. The results show that depolarization induced
by linear birefringence has no difference between conventional design and compensation design of isolators, and
depolarization induced by circular birefringence in Pre-Temperature compensation design is greatly reduced, which
becomes beam-radius-independent, and can be neglected when compared to depolarization induced by linear birefringence.