Random distributed feedback fiber lasers (RDFFL) are now attracting more and more attentions for their unique cavity-free, mode-free and structural simplicity features and broadband application potentials in many fields, such as long distance sensing, speck free imaging, nonlinear frequency conversion as well as new pump source. In this talk, we will review the recent research progresses on high power RDFFLs. We have achieved (1) More than 400 W RDFFL with nearly Gaussian beam profile based on crucial employment of fiber mismatching architecture. (2) High power RDFFL with specialized optical property that include: high power narrow-band RDFFL, hundred-watt level linearly-polarized RDFFL, hundred-watt level high-order RDFFL. (3) Power enhancements of RDFFL to record kilowatt level are demonstrated with the aid of fiber master oscillator power amplifier (MOPA) with different pump schemes.
Fiber lasers are now attracting more and more research interest due to their advantages in efficiency, beam quality and flexible operation. Up to now, most of the high power fiber lasers have random distributed polarization state. Linearlypolarized (LP) fiber lasers, which could find wide application potential in coherent detection, coherent/spectral beam combining, nonlinear frequency conversion, have been a research focus in recent years. In this paper, we will present a general review on the achievements of various kinds of high power linear-polarized fiber laser and its application. The recent progress in our group, including power scaling by using power amplifier with different mechanism, high power linearly polarized fiber laser with diversified properties, and various applications of high power linear-polarized fiber laser, are summarized. We have achieved 100 Watt level random distributed feedback fiber laser, kilowatt level continuous-wave (CW) all-fiber polarization-maintained fiber amplifier, 600 watt level average power picosecond polarization-maintained fiber amplifier and 300 watt level average power femtosecond polarization-maintained fiber amplifier. In addition, high power linearly polarized fiber lasers have been successfully applied in 5 kilowatt level coherent beam combining, structured light field and ultrasonic generation.
In our experiment, a kind of novel gold nanoparticles – concave gold bipyramids (CAuBPs) withlarge electromagnetic-field enhancement and broader plasmonic tuning rangehave been used as a saturable absorber (SA). Passively Q-switched thulium-doped and ytterbium-doped fiber lasers have been demonstrated based on CAuBPs SAs, the longitudinal surface plasmon resonance (LSPR) bands of which are located at 1 μm and 2 μm. In the 1 μm region, the maximum average output power of 9.61 mW is obtained with the shortest pulse width of 1.83 μs at the pulse repetition rate of 97.47 kHz.In the 2μm waveband, 9.72 mW average output power is obtained with the minimum pulse width of 4.56μs at the repetition rate of 19.9 kHz. To the best of our knowledge, it’s the first time that CAuBP has been used as SA, which verifies the saturable absorption properties of CAuBPs in the infrared range experimentally.
We demonstrate a monolayer graphene based passively Q-switched fiber laser with cascaded amplifiers that can deliver 84.1 W average power at 1064 nm, with pulse energy of 1.67 mJ. To the best of our knowledge, this is the first time for a high power passively Q-switched fiber laser in the 1 μm range reported so far. More importantly, the Q-switched fiber laser operates stably during a week few-hours-per-a-day tests, which proves the stability and practical application value of graphene in high power pulsed fiber lasers.
Ytterbium-doped fiber laser (YDFL) and Thulium doped fiber laser (TDFL) have been two kinds of the most widely
studied fiber laser in recent years. Although both silica-based Ytterbium-doped fiber and Thulium doped fiber have wide
emission spectrum band (more than 200 nm and 400 nm, respectively), the operation spectrum region of previously
demonstrated high power YDFL and TDFL fall into 1060-1100 nm and 1900-2050nm. Power scaling of YDFL and
TDFL operates at short-wavelength or long-wavelength band, especially for extreme wavelength operation, although is
highly required in a large variety of application fields, is quite challenging due to small net gain and strong amplified
spontaneous emission (ASE). In this paper, we will present study on extreme wavelength operation of high power YDFL
and TDFL in our group. Comprehensive mathematical models are built to investigate the feasibility of high power
operation and propose effective technical methods to achieve high power operation. We have achieved (1) Diodepumped
1150nm long wavelength YDFL with 120-watt level output power (2) Diode-pumped 1178nm long wavelength
YDFL operates at high temperature with 30-watt level output power (3) Random laser pumped 2153nm long wavelength
TDFL with 20-watt level output power (4) Diode-pumped 1018nm short wavelength YDFL with a record 2 kilowatt
output power is achieved by using home-made fiber combiner.
High power fiber laser is attracting more and more attention due to its advantage in excellent beam quality, high electricto- optical conversion efficiency and compact system configuration. Power scaling of fiber laser is challenged by the brightness of pump source, nonlinear effect, modal instability and so on. Pumping active fiber by using high-brightness fiber laser instead of common laser diode may be the solution for the brightness limitation. In this paper, we will present the recent development of various kinds of high power fiber laser based on tandem pumping scheme. According to the absorption property of Ytterbium-doped fiber, Thulium-doped fiber and Holmium-doped fiber, we have theoretically studied the fiber lasers that operate at 1018 nm, 1178 nm and 1150 nm, respectively in detail. Consequently, according to the numerical results we have optimized the fiber laser system design, and we have achieved (1) 500 watt level 1018nm Ytterbium-doped fiber laser (2) 100 watt level 1150 nm fiber laser and 100 watt level random fiber laser (3) 30 watt 1178 nm Ytterbium-doped fiber laser, 200 watt-level random fiber laser. All of the above-mentioned are the record power for the corresponded type of fiber laser to the best of our knowledge. By using the high-brightness fiber laser operate at 1018 nm, 1178 nm and 1150 nm that we have developed, we have achieved the following high power fiber laser (1) 3.5 kW 1090 nm Ytterbium-doped fiber amplifier (2) 100 watt level Thulium-doped fiber laser and (3) 50 watt level Holmium -doped fiber laser.
In this paper, we demonstrate a narrow linewidth random fiber laser (RDFL), which employed a narrow-band fiber Bragg grating (FBG) to construct a half-open cavity and function as filtering element. Spectral linewidth down to 40 GHz has been measured. The maximum output power reaches 2.15 W at 1081.4 nm when 8.97 W pump light centered at 1036.5 nm is launched into the half-open cavity, which is more powerful than the previous reported results with ~100 mW output power.