Huide Gao

Investigation of diffractive optical element for shaping a Gaussian beam into a ring-shaped pattern

Abstract To convert a given single-mode He–Ne laser beam into a ring-shaped intensity distribution, a diffractive optical element with 16 levels was designed by YG amplitude-phase retrieval and iteration algorithm. This beam shaper is investigated experimentally and compared with the results of the computer design. The results show good conformity, and the measured diffraction efficiency is 87.2%. In addition, the diffractive effect is observed when the distance between diffractive optical element and CCD is changed.

Theoretical and experimental research on excimer like (N2)2 dimer: potential energy curves and spectra

Abstract Theoretical ab initio calculations for a number of symmetry groups of (N2)2 dimer are performed with an emphasis on the intermolecular distance 1.2⩽R⩽2.5 A. Except for the D2h group, the ground and excited state potential energy curves of most of the symmetry groups are repulsive in this region. The theoretical results indicated that there exists an excimer like electric dipole transition between the excited singlet states a 1 B 2g and a 1 B 3u of the D2h symmetry group. The oscillator strength and theoretical spectra are calculated. Experimentally observed emission spectra for the excimer-like (N2)2 dimer is found to be in good agreement with our theoretical calculations.

A new method of coherent summation of laser beams by diffraction optical element

A new method of coherent summation of laser beams is proposed. Two-dimension numerical simulation based on the conjugate gradient algorithm shows that the combination efficiency is about 94.8%, and an error less than 2.4% with a 16-level phase quantized diffraction optical element. Error analysis has also been performed.

New blue laser of the O2(1Δg)dimer: [O2(1Δg)]2*

A new band, with two peaks at 486 nm and 656 nm, respectively, has been observed in microwave-excited high pure oxygen. The reason that the new band is assigned to O2(1Δ g) dimer transitions is presented. A net gain of 2.2% cm-1 for 486 mm emission has been obtained by the method of amplified spontaneous emission. The laser oscillation has been realized at 486 nm with a flat-concave stable resonator, its maximum output power is about 130 (mu) w.

Research of the laser oscillation of the dimer of O2(1deltag)

The laser output power of the dimer of O2(1(Delta) g) has been estimated theoretically. The dimer of O2(1(Delta) g) was generated by microwave (2.450 GHz) exciting high pure oxygen. The laser oscillation of the dimer of O2(1(Delta) g) was realized at 656.3 nm for the first time, and the laser power was as high as 100 (mu) w, which corresponded to theoretical estimation in order of magnitude. In addition, the divergent angle measured was about 37.3 mrad.