Zhan Sui

Pulsed-pumped optical fiber amplifier

With the use of pulsed pumping, an optical fiber amplifier with all-fiber structure is developed based on the fused tapered fiber combiner and Yb+{3+}-doped double cladding fiber (YDCF). From the experimental results, 47-dBm peak power and 100-ns pulse duration are obtained when the repetition rate of pumping pulses is 100 Hz. The gain of the amplifier is up to 30 dB. It is shown that due to the use of pulsed pumping, pump light emits only when the signal light reaches the amplifier and thus the amplified spontaneous emission (ASE) is significantly suppressed.

Temporal pulse shaping by chirped pulse stacking in fiber time delay lines

The laser pulse shape should be varied to meet different requirements of the inertial confinement experiments. Chirped pulse-stacking is an effective method to obtain a long pulse with desired pulse shape using short pulses. We introduce a method to obtain a long pulse shaped by chirped pulse stacking in fiber time-delay lines. We demonstrate an all fiber pulse shape generator that can generate arbitrary pulse shapes by stacking a set of 20-ps pulses output from fiber mode-locking laser. The device offers a 2.2ns arbitrary waveform optical pulse with power up to 30dBm, bandwidth of 0.2nm and a rise time less than 50ps. The output optical pulse has a temporal adjustment precision of 32bit and an amplitude adjustment precision of 10bit. Experimental and theoretical results show that the generator provided the required stability, flexibility, fast rise time and high contrast pulse for laser fusion research.

High contrast research in the Nd:glass laser system based on optical parametric amplification temporal cleaning device

We demonstrate high amplified spontaneous emission (ASE) contrast pulses in a Nd:glass laser system based on the hybrid double chirped pulse amplification (double CPA) scheme. By an OPA temporal cleaning device, ~100 uJ/46 fs/ 1011 clean pulses are generated and amplified in the next Nd:glass laser. After compressor, >150 mJ/~0.5 ps/1 Hz pulses can be obtained. The ASE temporal contrast of amplified pulses is ~1011 with energy gain ~2.5×104 in the Nd:glass amplifiers.

High amplified spontaneous emission contrast of 1011 in a Nd:glass laser based on a hybrid double chirped pulse amplification scheme

By using a Ti:sapphire-Nd:glass hybrid double chirped pulse amplification scheme and a pulse cleaner based on optical parametric amplification and second harmonic generation, we demonstrate high amplified spontaneous emission (ASE) contrast at 1053 nm. The optimized ASE temporal contrast of the output pulse is about 1011 at about 160 ps before the main peak with an output of 140 mJ/500 fs. And the potential of 10 J level output with high ASE contrast is demonstrated in a laser system with attenuated injection.

Comparison of fused silica and oxyfluoride glass on laser induced initial damage morphology

A novel oxyfluoride glass (OFG) was prepared. The laser induced damage threshold (LIDT) of the novel OFG is 24.9% higher than fused silica under 355nm nanosecond laser irradiation by R-on-1 procedure. Characterization by optical microscope and scanning electron microscope shows that the initial damage morphologies of two kind of materials are significantly different. Experiment results indicate that the novel OFG can be a good candidate component material for high energy laser applications.

Optimized Design of Parameters for Wedge-Crystal Depolarizer

The principle of wedge-crystal depolarizer was introduced and an optimal parameters combination of polarization direction, wedge angle, pupil size was obtained by using Mueller matrix. The design of depolarizer should be determined by crystal refraction index, wavelength, and incident pupil size. Calculation and simulation based on software show that degree of polarization (DOP) can be improved by increasing pupil size and wedge angle. Some significant conclusions for the optimized design of parameters were gained for fabricating crystal depolarizers.

Switching Characteristics of Large-Aperture Electro-Optical Switches With Plasma Electrodes Part II—Comparison With Experiment

The large-aperture optical switches with plasma-electrode Pockels cell (PEPC) are important elements for the multipass laser amplifiers in the inertial-confinement fusion. In this paper, an optical switch of the PEPC driven by one-pulse process (OPP) is simulated by using a fluid model developed in a previous paper. We computationally study the physical processes of the discharge evolvements and discharge fading away in the large-aperture PEPC switches driven by the OPP. Charging on the surfaces of potassium dihydrogen phosphate crystal in the discharge determines the switching characteristics of the PEPC. The simulation results nearly coincide with the experimental measurement.

Research on Yb3+-doped mode-locked fiber ring laser

Theory and experimental results on the self-starting passive mode-locked Yb fiber ring laser generating short pulse are reported. The relations between the laser cavity parameters and mode-locked pulse characters are discussed. 980nm LD pumped laser is used as the pump source and high concentration Yb3+-doped fiber is adopted as gain medium. Using the nonlinear polarization rotation (NPR) effect of the fiber, self-starting stable mode-locked pulse is obtained, with center wavelength of 1046nm, 3dB bandwidth of 6.01nm and 20dB bandwidth of 16nm. The mode-locked threshold power is 150mW and output power is 26mW with 50MHz repetition rate.

Design of highly doped Yb3+ fiber ring laser

Ytterbium-doped silica fibers exhibit very broad absorption and emission bands, from 800nm to 1064nm for absorption and 970nm to 1200nm for emission. Therefore wide band lasers can be obtained using a wide variety of pump lasers. In this paper, the characteristics of high-doped Yb3+ fiber are analyzed and verified by experiment and a highly-doped Yb3+ fiber ring laser with short cavity has been presented. Comparing with normal Yb3+doped fiber, the relationship between the important characteristics of the Yb3+doped fiber laser such as threshold power, output power and laser parameters such as pump power, fiber length, output couple ratio is analyzed. Numerical results are coincident with the experiment phenomenon very well. A 1053 nm pulse has been achieved in our fiber laser. The output power is 6mW as pump power is 110mW and the slope efficiency is 17%. The Yb3+ fiber laser we produced can be used as a stable source in obtaining ultrafast pulse, fiber sense and optical communications.

A stable Q-switched laser source for free-space optical communication

A stable acousto-optic Q-switched Nd:YVO4 laser is presented. It is pumped by a high power continuous wave (CW) laser diode (LD). At the repetition rate of 10 kHz and the pulse width of 16.3 ns, a maximum single pulse energy of 286 μJ and a peak power of 13 kW are acquired. Used as a signal source for free-space optical communication, the output signals of the laser agree with the modulating signals perfectly well and it works stably.