LIGHT PICK-UP

PURPOSE:To prevent the performance deterioration due to the wavelength fluctuation by controlling constantly a waveguide light wavelength in an integrated pick-up. CONSTITUTION:The fluctuation of the wavelength of a waveguide light projected from a semiconductor laser part 3 to a waveguide layer 5 is detected through a grating 20 for detecting a wavelength by light receiving elements 22a and 22b. The signal obtained here and the signal obtained by a light receiving element 24 are inputted to a division circuit 32 and the signal corresponding to the regularized wavelength shifting quantity is outputted. The regularized output is compared with the reference voltage, the compared output is fed back to an electrode for controlling the wavelength of the semiconductor laser and the waveguide light wavelength is constantly controlled.