| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a diffraction grating capable of realizing high diffraction efficiency by reducing the grating pitches, and to provide an optical pickup having high detection efficiency and capable of recording/reproducing at high speed by using the diffraction grating. <P>SOLUTION: On the surface of a transparent material such as SiO<SB>2</SB>of the diffraction grating, rectangular grooves (recesses) are formed by etching or the like. Of the diffraction grating, the pitch Λ between protrusions (gratings) is 8 μm, the depth T of the groove is 1 μm, the incident light side is the air whose refractive index n<SB>1</SB>is 1, and the transmission light side is SiO<SB>2</SB>whose refractive index n<SB>2</SB>is 1.45. Monochromatic light whose wavelength λ is 0.66 μm is made incident from the incident light side to measure the 0th-order diffracted light and the ±1st order diffracted light of the transmission light side. When the width of the grating on the SiO<SB>2</SB>side is represented by D and the pitch Λ is made constant, the measured diffraction efficiency of the ±1st order diffracted light with respect to the variations of D/Λ reaches 26.4 % when the pitch Λ is 8μm (the broken line in the figure) and the D/Λ is close to 0.5. Further, when the pitch Λ is 1.5 μm (solid line) and D/Λ is 0.5, the diffraction efficiency is 20.9%. That means that, when D/Λ is made smaller, that is, when the width of the SiO<SB>2</SB>side D is made smaller, the diffraction efficiency is improved. <P>COPYRIGHT: (C)2004,JPO |
