Semiconductor laser apparatus, optical pick-up and optical information apparatus

• Main Authors: WADA HIDENORI, SHIROIWA HIROSHI, MIZUNO SADAO, KOMMA YOSHIAKI, SHIONO TERUHIRO, NISHINO SEIJI
• Format: Patent
• Language: English
• Published: 22.03.2007
• Subjects: INFORMATION STORAGE; INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORDCARRIER AND TRANSDUCER; PHYSICS

A transmission diffraction grating body including a base material being substantially transparent with respect to wavelength lambda 1 and having a refractive index n 0 ; another base material being substantially transparent with respect to wavelength lambda 1 and having a refractive index n 1 , which is formed on the base material having a refractive index n 0 ; and a relief diffraction grating formed on the base material having a refractive index n 1 ; wherein the refractive indexes n 1 and n 0 satisfy the relationship: n 1 >n 0 . Thus, the base material having a refractive index n 1 can be formed of a high refractive index material, and when the depth of grating of the diffraction grating is set so that the diffraction grating diffracts the light with wavelength lambda 1 and does not diffract the light with wavelength lambda 2 , the depth of grating of the diffraction grating can be made to be shallow, thus preventing the loss of the amount of the light with wavelength lambda 1 . Furthermore, since base materials each having a different refractive index are bonded to each other to form a diffraction grating body, it is possible to minimize the use amount of the relatively expensive material having a high refractive index. Furthermore, since the most of the diffraction grating body can be formed of a material having a low refractive index, it is possible to lower the height of the diffraction index body.