Optical element, light source apparatus, optical head apparatus, and optical information processing apparatus

摘要

A first semiconductor laser emits a light beam L1 with a first wavelength polarized in an x-axis direction. A second semiconductor laser emits a light beam L2 with a second wavelength polarized in the x-axis direction. A wavelength plate functions as a (2m+1)lambd/2 plate (m is an integer) with respect to the light beam L1, and functions as a nlambd plate (n is an integer) with respect to the light beam L2. A polarization anisotropic hologram element diffracts the light polarized in the x-axis direction, and transmits the light polarized in the y-axis direction. Consequently, an apparent emission point of diffracted light L2' may be allowed to coincide with an emission point of the light beam L1. A light source apparatus thus constructed can emit two light beams with different wavelengths at a low cost and a high efficiency with optical axes aligned in a simple configuration.