A high power, high-repetition picosecond amplifier with an all-fiber picoseconds seed source, Nd:YVO<sub>4</sub> and Nd:YAG gain medium was designed and experimentally studied. For a injected seeder laser with a repetition rate of 1 MHz and an average power of 2.34 W, a 55 W laser power output was obtained by the two-stage solid-state amplification, and the measured pulse width was 9.2 ps, and the laser wavelength was 1064.5 nm. The laser output characteristics of different repetitive modes were experimentally studied, and the laser output power was 18.4 W in the (1 × 4) MHz burst mode. Since the spectrum of the fiber picosecond seed light is much larger than the gain spectrum width of the amplifying medium, the output power of the entire system does not reach the design index. Next, the fiber seed source parameters need to be optimized to achieve a larger amplification power output.
A theoretical model for the effect of optical path difference on coherent polarization beam combination of ultrashort laser pulses is established, and the effects of optical path difference and spectral width on coherent polarization beam combination efficiency of ultrashort laser pulses are studied. The corresponding control index is put forward, and this research has certain guiding significance for the design of coherent polarization beam combination system of ultrashort laser pulses.
The singular point of the dissipative soliton mode-locked fiber laser is demonstrated experimentally. Mode-locked pulses are severely disturbed under certain pump power. The peak-valley (P-V) of the output power reaches up to 26.5% under the pump power of 918mW. However, mode-locked fiber laser can operate stably under higher or lower pump power. A numerical model based on nonlinear Schrödinger equation (NLSE) is established. And the singular point of the mode-locked state is theoretically proved.
The thermal problems of CPS and YDF were studied. And the thermal management technologies are developed separately to the problems. Experimental results showed that the thermal management technologies worked well.
In order to suppress the mode noise of large mode area fiber amplifier system and enhance the signal to noise ratio
of the output pulse, spatial and temporal self shaping for large mode area fiber laser system are studied in this paper. For
removing off the mode noise, method of beam's spacial self-shaping based on mode matching is used. By the method of
mode matching, the cladding mode are removed off clearly. Then a large mode fiber amplifier with a strictly single mode
is obtained. For enhancing the signal to noise ratio of the output pulse, method of beam's temoral self-shaping based on
Optical Kerr effct in fiber is used. By using Optical Kerr effect, the pulse get nonlinear polarization ratation, which make
pulses selfly shaped in time and the ASE pedestal is removed off clearly. As a result, by spatial and temporal self shaping,
cleared pulses with a strictly single mode in spatial and cleaned pulses without ASE pedestal are obtained.
The optical pulse generation system of SG-III laser facility is presented. The optical time division
multiplexing (OTDM) technique, high speed electro-optic modulation technique, pulse
single-selected based on polarization independently acousto-optic modulation technique and pulse
polarization stabilization technique applied in low repetition rate mode are successfully employed in
the system. And also the phase modulation unit is at the last stage of the system, which could avoid
FM-AM effect induced in fiber system. The test experiment results showed that the demonstrated
specification is better than the designed to a certain degree.
A type I phase matching MgO:LiNbO<sub>3</sub> optical parametric amplification (OPA) system were demonstrated. The OPA system was synchronously seeded with a super continuum and pumped by a laser pulse of 1Hz, 55fs, 3.5mJ, centered at 812nm. The super continuum was got by a sapphire plate and the MgO:LiNbO<sub>3</sub> crystal which was 30mmx30mmx15mm in size. In order to avoid the three waves' temporal walk-off, pump wavelength and seeded signal wavelength were tuned simultaneously in simulation, and the result was that it can't be avoided in the collinear phase matching OPA. For the purpose of compensating the group velocity's mismatching, the non-collinear phase matching was adopted, then the non-collinear angles and the best amplified signal wavelengths which changing with the pump wavelengths were also optimized in numerical simulation for the non-collinear phase matching OPA. As a result, pulse energy of as much as 126uJ was achieved at wavelengths ranging from 3.2μm to 4.3μm.