Based on the real-time adaptive femtosecond pulse shaping system, the phase compensating algorithms
which can effectively compensate the output shaping waveform distortions are investigated in detail.
The simulated-annealing algorithm that can modify the output pulse temporal waveforms iteratively
toward the target shapes using the second harmonic generating frequency resolved optical gating
(SHG-FROG) measurement as feedback is proposed. Compared with the cross-correlation feedback
measurement method, the output based on the SHG-FROG measurement method is better and the
temporal chirp of the output pulse is compensated more effectively. Moreover the performance of the
SHG-FROG measurement feedback algorithm is compared to other exemplary standard approaches
such as the Genetic Algorithm based on the cross-correlation feedback measurement method, the result
is much better.
The method for generating temporal flat-top waveform and spatial flat-top profile
femtosecond pulse beam by phase and polarization controlling is proposed and demonstrated. Based on
direct wave front phase modulating, flat-top spatial intensity distribution can be obtained. Combining a
folded 4f zero-dispersion system with a polarization controlling setup, the temporal flat-top waveform
is generated. Experimental results indicate that for the input both temporal and spatial Gaussian pulse
beam with 363 fs temporal width and 1.5 mm beam waist, the temporal width of the output shaped
pulse beam is 1.2 ps and 1.9mm beam waist, and the rms variation is about 9.2%, which prove that the
temporal flat-top and spatial flat-top femtosecond pulse beam can be generated effectively.
With both ultrafast optical properties of femtosecond pulse and cylindrically symmetric polarization properties of
radially polarized light, the radially polarized femtosecond pulse beam has significant applications in super-high density
optical storage and ultra-intense lasers. A scheme for generating radially polarized femtosecond pulse beam by a
polarization plates array is proposed, in which a phase-only liquid crystal spatial light modulator (LC-SLM) is used to
load different phase retardation distribution in transverse into linearly polarized femtosecond pulse beam. Associated
with a quarter wave plate, the input linearly polarized femtosecond pulse beam will be converted to radially polarized
femtosecond pulse beam at the back of the polarization plates array. The experimental results indicate that the scheme
can be well used to generate radially polarized light, and more effective results can be obtained with the increase of
sectored polarization plates.
A temporal femtosecond pulse shaping device, based on all-diffractive method, is designed for arbitrary
waveform generation. The key components of the device are micro-gratings arranged in line. By changing the period
and phase pattern of each grating, the diffraction angle, phase and amplitude of the first order diffraction light can be
modulated. Experimental results are consistent well with simulation results, which indicate that arbitrary temporal
waveforms can be gained by using micro-gratings array. Additionally, the configuration of the device allows for
multiple outputs and can operate over a large wavelength range from ultraviolet to infrared pulse.