H - Electricity – 01 – L
Patent
H - Electricity
01
L
356/192, 345/62
H01L 31/18 (2006.01) G02B 5/32 (2006.01) G02B 6/124 (2006.01) G03F 7/00 (2006.01) G03F 7/20 (2006.01) G03H 1/04 (2006.01) H01L 33/00 (2006.01)
Patent
CA 1211868
SO-2-31271M/MS/83 ABSTRACT OF THE DISCLOSURE A method for making a diffraction grating utiliz- ing a laser source, a beam splitter to split the light from the laser source into two light fluxes, a collimator to convert each light flux into a light flux which is parallel and enlarged in diameter, a mirror to irradiate each light flux on a substrate coated with a photoresist, and a photomask on the photoresist. The use of an inter- mediate mask and focusing lens enables the formation of a diffraction grating within a limited area. A blazed diffraction grating may be formed by splitting a laser beam into two beams having an increased beam radius, and irradiating a light-sensitive material with the resulting two beams to form an interference fringe. This method is characterized in that in a first exposure the two beams are incident on the light sensitive material through air to form an interference fringe having a clearance width of d, and in a second exposure, the two beams are irrad- iated on the light sensitive material through a symmetri- cal transparent member having an isosceles triangular cross section in such a manner that the origin coincides to form an interference fringe having a clearance width of d/2, and furthermore, in that the ratio of the first exposure energy to the second exposure energy is made equal to the ratio of the first term to the second term of a Fourier series obtained by expanding the periodical function of the waveform of the blazed diffraction grating. - 2 - An optical branching filter element comprised of a sub- strate having a wave guide thereon of a material capable of reversibly changing its refractive index may have a diffraction grating formed in the waveguide by either of the disclosed methods. The grating may be erased by the selective application of infrared light, electric current or heat.
425909
Matsuoka Shunji
Nishiwaki Yoshikazu
Okamoto Kenji
Riches Mckenzie & Herbert Llp
Sumitomo Electric Industries Ltd.
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