Proc. SPIE. 11048, 17th International Conference on Optical Communications and Networks (ICOCN2018)
KEYWORDS: Signal to noise ratio, Wavelength division multiplexing, Single mode fibers, Fiber lasers, Atomic force microscopy, Scanning electron microscopy, Raman spectroscopy, Phosphorus, Pulsed laser operation
We demonstrated the dark pulse in a Yb-doped fiber laser based on black phosphorus (BP). The dark pulse could be obtained by adjusting intra-cavity polarization state and pump power. The dark pulse operating at fundamental frequency has the high stability with a signal to noise ratio (SNR) of ~53dB. By only adjusting the polarization state in the cavity, the high-order dark pulses were also observed.
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.
As for multi-channel SAR, the spectrum of the clutter is spatially-temporally coupled, and the echo of the moving target
is chirp signal. A novel method based on STAP and FrFT is proposed in this paper, which is used for moving target
detection and parameter estimation. Two steps are used for fast target detection : the coarse detection in low range
resolution and parameter estimation for the specific data where the moving target appears. This paper discusses the
principle of frequency STAP for clutter suppression firstly, and subsequently infers that the signal after clutter
suppression is chirp signal. Then FrFT is introduced to estimate the parameters of the output signal, which can be used to
estimate the parameters of the moving target. Finally, the process of the proposed method is introduced. Matching
function is constructed to compensate the phase deviation caused by movement and focus the moving target. The
effectiveness of the proposed method is validated by the simulation.