When the optical properties of a portion of a planar waveguide are caused to vary in a periodic fashion the resulting structure may be used to couple energy from a collimated beam, e. g. a laser beam, into the waveguide. In principle, the device may be used to couple the light in a beam of any size into a film that need only be thick enough to support one guided mode. Because the coupling length, i. e., the beam size, may be arbitrarily large, the device belongs to the class of wide aperture couplers. The prism coupler also belongs to this class. As might be expected, the coupling length of practical structures is not arbitrary but is limited by tolerance requirements on the uniformity of the waveguide and the periodicities. These requirements not withstanding, couplers exhibiting high efficiency have been demonstrated with coupling lengths approaching one thousand times the thickness of the film into which the light is introduced.
KeywordsPropagation Constant Coupling Efficiency Diffraction Order Collimate Beam Reciprocity Theorem
Unable to display preview. Download preview PDF.
- 4.H. Kogelnik and T. P. Sosnowski, Bell Syst. Tech. J. 49, 1602 (1970).Google Scholar
- 6.F. R. Gfeller and C. W. Pitt, Co-linear Acousto-Optic Deflection in Thin Films, Dept. Electronics and Elect. Engrg. Rept., U. College, London (Sept. 1972).Google Scholar
- 8a.K. Ogawa, W. S. Chang, B. L. Sopori, and F. J. Rosenbaum, IEEE Trans. QE-9, 29 (1973).Google Scholar
- 9.L. V. Iogansen, Soviet Phys. -Tech. Phys. 11, 1529 (1967).Google Scholar
- 9b.J. E. Midwinter, IEEE Trans. QE-6, 583 (1970).Google Scholar
- 9e.J. H. Harris and R. Shubert, IEEE Trans. MTT-19, 269 (1971).Google Scholar