We report for the first time (to our knowledge) a diode-pumped Nd:YAG laser emitting at 869 nm based on the (4)F(3/2)-(4)I(9/2) transition, generally used for a 946 nm emission. Power of 453 mW at 869 nm has been achieved in cw operation with a fiber-coupled laser diode emitting 35.4 W at 809 nm. Intracavity second-harmonic generation in the cw mode has also been demonstrated with power of 118 mW at 435 nm by using a BiB(3)O(6) nonlinear crystal. In our experiment, we used a LiNbO(3) crystal lens to complement the thermal lens of the laser rod, and we obtained good beam quality and high output power stability.

Efficient and compact blue laser output at 468 nm is generated by intracavity frequency doubling of a continuouswave (CW) diode‐pumped Nd:CNGG laser at 935 nm. With 17.8 W of diode pump power and the frequency‐doubling crystal BiB3O6 (BiBO), a maximum output power of 490 mW in the blue spectral range at 468 nm has been achieved, corresponding to an optical‐to‐optical conversion efficiency of 2.8%; the output power stability over 4 h is better than 2.6%. To the best of our knowledge, this is first work on intracavity frequency doubling of a diode pumped Nd:CNGG laser at 935 nm. (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA) (© 2011 by Astro Ltd., Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)

A new kind of hollow beams, double half-Gaussian hollow beams，was put forward. With the help of the Collins formula, the analytical equation of propagation and transformation of the hollow laser beams in free space was deduced. The simulation shows that the intensity exhibits the three-dimensional trap distribution in the near-field, while the double half-Gaussian hollow beams turn into solid laser beams when propagating a certain distance, which shows the characteristics of self-focus. The double half-Gaussian hollow beams were obtained by means of the dual-reflecting splitting optical system. The intensity of the vertical loop in different distances was tested, which shows that the analytical equation of propagation and transformation is in agreement with the result.double half-Gaussian hollow beams, three dimensioned trap, self-focus, dual-reflecting splittingWith the broad application of hollow laser technology in the biology, laser processing and atomic cooling, etc. [1][2][3][4] , the hollow laser beams with different intensity distributions were generated by different methods [5][6][7][8][9][10] , such as the double Gaussian hollow beams (DGHB) and the contrary Gaussian hollow beams. The common characteristics of them are that the light intensity of the beams from the edge of annular to the center is decrescent-distribution, and only the light intensity on the center point of hollow laser beams is zero in theory, which would limit the application of this kind of beams in the invisible detection, invisible control and so on. To resolve the question that the light intensity at the certain hollow area is not zero, a new kind of hollow beams, double half-Gaussian hollow beams was put forward in this paper. The intensity distribution of the vertical axis section annular in the near field is that the intensity of all the hollow parts is zero and boosts up at the inner edge of the annular beams, which turns out to be the step-distribution; The intensity wears off with the rule of Gaussian function from the inner margin to the outer margin and forms the double-half Gaussian distribution. In theory, we constructed the propagation model of double half-Gaussian hollow beams, and got the 2-D and 3-D light intensity distribution of the near field and far field after simulation. By use of the method of ray tracing, we designed the dual-reflecting splitting optical system, and obtained the double half-Gaussian hollow beams in the experiment. We also tested the light intensity vertical axis section annular beams at different distances. The results show that the experimental value and the propagation model are in an excellent agreement.

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