Faculty of Engineering, Okayama University
Acta Medica Okayama
0475-0071
28
2
1994
Collimation of Cerenkov-SHG Blue Light with a Parabolic Mirror
33
44
EN
Ming
Wang
Anis
Ahmed
Osami
Wada
Ryuji
Koga
Proposed here is a convenient optical system to collimate the crescent shaped blue laser beam radiated from a Cerenkov SHG in channel waveguide configuration. This collimation system is consisted of a parabolic mirror and has a very large tolerance to the mirror displacement. The anisotropy of the nonlinear crystal on which the waveguide is fabricated has been taken into account. The optimum mirror location is given to obtain a collimated blue laser beam with an aberration less than 0.07λ. By using an objective lens, the collimated beam can be focused down to a thin beam with the spot size less than 1μm.
No potential conflict of interest relevant to this article was reported.
Faculty of Engineering, Okayama University
Acta Medica Okayama
0475-0071
29
2
1995
Evaluation of Eigenmodes of Dielectric Waveguides by a Numerical Method Based on the BPM
49
55
EN
Anis
Ahmed
Shinji
Taniguchi
Osami
Wada
Ming
Wang
Ryuji
Koga
For weakly guiding dielectric waveguides, the eigenmode field distributions are calculated numerically with a simple algorithm. In this numerical method, the transverse sampling space can be chosen arbitrarily, and hence a
narrow waveguide can be analyzed. The field satisfying scalar wave equation is expressed by the discrete Fourier transform and the mode eigenvalues and eigenfunctions are calculated by solving an eigenvalue equation numerically.
The validity of this method is checked for 2-D waveguides having step and parabolic or square index distributions. It is found that for the well guided TE modes of the slab waveguide, the accuracy of this method is remarkably good, but some discrepancies are found if the mode is near cut off. In the problems where the normalized guide index b is small, caution should be taken in applying the results of this numerical method.
No potential conflict of interest relevant to this article was reported.
Faculty of Engineering, Okayama University
Acta Medica Okayama
0475-0071
30
1
1995
Experimental Collimation of Cerenkov SHG Blue Laser Beam with a Cylindric Mirror
99
110
EN
Ming
Wang
Osami
Wada
Ryuji
Koga
A cylindric mirror was used, in place of a parabolic mirror, to collimate the crescent blue laser beam radiated from the Cerenkov SHG in channel waveguide configuration. The cylindric mirror radius is requested to be twice the focal length of the parabolic mirror. The focusing effect of the cylindric mirror in collimation can be compensated by slightly lifting the mirror in its normal direction. Under the condition that the mirror was declined by 5.56° and lifted by 25 μm, we got the collimated beam with divergence angle less than 1.3 mrad. In the focusing experiment, the collimated beam was focused with spotsize of 1.8 μm. The details on the analysis and experiment are reported.
No potential conflict of interest relevant to this article was reported.