We present a chirped pulse amplification (CPA) Yb:YAG laser based on Innoslab amplifier and post pulse-compression technique to achieve an average power of 83 W at a repetition rate of 175 kH with pulse width of 38 fs. The diode laser pumped Innoslab amplifier with a plane-convex hybrid cavity efficiently suppressed the self-lasing to reach high power amplification, while achieve a nearly diffraction-limited beam quality. After the grating compressor, two stages of post-compression were used for shorter pulse width. The final compressed beam quality was characterized as M2=1.2, with a measured long time power stability of 0.28%.
We present and experimentally verify a deep learning approach to synchronously measure the multi-beam pointing error for coherent beam combining systems. This approach uses only one detector by acquiring the far-field interference focal spot, which can greatly reduce the complexity in coherent beam combining systems with high accuracy. The amplitude modulation is utilized to eliminate the confusion of the label values in symmetric system. The position assist camera is used to acquire accurate label value, which solves the mismatch between sample and label value caused by ambient vibration in long-term data acquisition. In simulation and experiment, the RMS accuracy is about 0.3 and 0.5 μrad, respectively, which can greatly meet the pointing measurement requirement in coherent beam combining systems. The result shows that this approach can be well applied to multi-beam coherent combination for high-power laser systems.
High-efficiency and broadband OPCPA is one of the methods to achieve multi-petawatt or even hundreds petawatt laser system.We demonstrate broadband OPCPA centered near 800 nm in 3D space of YCOB. A maximum conversion efficiency of ~15% and compressed duration of 30.6 fs are achieved for two types of YCOB crystals with PM on the principal and non-principal planes (NPP). The amplified energies and conversion efficiencies of different PM angles confirm that the effective nonlinear coefficient (deff) on the NPP is much higher than that on the principal plane (PP). It is worth studying on PM in 3D space to support higher deff, wider amplification bandwidths, and gain wavelength ranges that cannot be amplified on the PP of nonlinear crystals. OPCPA in the 3D space of nonlinear crystal can be used as amplifiers in petawatt scale or few-cycle high-power laser systems.
Large size of YCa4O(BO3)3(YCOB) crystals were grown both by Czochralski and Bridgman methods. Large size elements as large as 60 mm clear aperture were cut and polished with surface flatness of 1/5 wavelength. Optical
homogeneity of YCOB crystal was found in the order of 10-6. Laser damage thresholds of several YCOB crystal
elements were tested using different laser facilities with different pulse widths or wavelengths, with thresholds varied
from 0.8 GW/cm2 to more than 1 TW/cm2. One SHG and two optical parametric chirped-pulse amplification (OPCPA)
experiments were executed to characterize the nonlinear optical properties of YCOB crystals and the quality of the
crystals. The results shown that YCOB had good performance in OPCPA application, especially with low content of
parameter florescence. Combined with good NLO performance and possibility to grow large size crystals, YCOB crystal
was a good choice for high power OPCPA applications.
The internal components of optical Airy beams are numerically analyzed and experimentally verified. The Airy beams
can be divided into several different areas, and the isolated and the interactional components are investigated in detail. The Poynting vector and the angular momentum are employed to describe the evolution of the internal components of optical Airy beams during propagation. The results show that each component bears different functions and the optical
properties are attributed to the interaction of the internal components. The angular momentum can not be self-recovered to keep conservation during propagation when it is broken artificially. The unbalanced angular momentum does not influence the optical propagation properties of Airy beams.
Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1-xYx) 2SiO5 (x=0.5) lasers have been demonstrated together
for the first time to the author's knowledge. For the non-soliton mode locking, output power could achieve ~1.2 W, and
pulse width was about 20ps. For the soliton mode-locked operation, the pulse width was 1.4ps at the wavelength of
1056nm and 375fs at the wavelength of 1042nm, with a pair of SF10 prisms as the negative dispersion elements. The
repetition rate was 48 MHz. The critical pulse energy in the soliton-mode locked operation against the Q-switched mode
locking was much lower than the value in non-soliton mode-locked operation.
We reports on a diode-pumped passively mode-locked Yb:SSO laser with a SESAM. Pulses
duration as short as ~2 ps with a repetition rate of 53 MHz were generated. The output power
achieved ~1.9 W at a pump power of 11.5 W.
By directly measuring the spherical wavefront near the focus, we demonstrated a approach to efficiently correct
convergent spherical wavefront by installing a common small aperture deformable mirror (DM) in the middle of
0.89PW/29.0fs Ti:sapphire CPA laser chain. It is, to our knowledge, the first time attain the near perfect correction result
in ultra-intensity laser system by correcting convergent spherical wavefront using a small aperture DM in adaptive
optical loop. Finally the maximum peak intensity of 2.59×10^21 W/cm2 was obtained with an f/4 off-axis parabola at the
output power of 0.89 PW.
A new alloyed crystal, Yb:LYSO, has been grown by the Czochralski method in our institute for the first time, and its
effective diode-pumped cw tunable laser action was demonstrated. The alloyed crystal retains excellent laser properties
of LSO with reduced growth cost, as well as the favorable growth properties of YSO. With a 5-at.% Yb:LYSO sample,
we achieved 2.84 W output power at 1085 nm and a slope efficiency of 63.5%. And its laser wavelength could be tuned
over a range broader than 80nm, from 1030nm to 1111 nm. This is the broadest tunable range achieved for Yb:LYSO
laser, as far as we know.
Near-degenerative near-collinear phase-match geometry for broadband optical parametric chirped-pulse amplification (OPCPA) at 780 nm is calculated in comparison with nondegenerate noncollinear phase-match geometry. In an experiment on LBO-I near-degenerate near-collinear OPCPA, high gain with broad gain bandwidth (71 nm, FWHM) at 780 nm is achieved by using an 390-nm pumping pulse. The stretched broadband chirped signal pulse near 780 nm is amplified to 412 µJ with a pumping energy of 15 mJ, and the total gain is >3.7×106, which agrees well with the calculation. For a broadband (covering 100 nm) chirped signal pulse, the theoretical gain bandwidth has been attained experimentally for the first time.
A new cw self-frequency-doubling laser operating on high-gain polarization of Nd:MgO:LiNbO3 has been demonstrated in a nearly concentric resonator. A maximum second-harmonic output of 4.6 mW and a conversion efficiency up to 11.7% per watt were achieved.
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