Semiconductor laser device

Abstract

A semiconductor laser device has structure including: a semiconductor laser chip having an emission surface and a reflection surface which are opposing end surfaces of a resonator; and a photodiode for detecting light that exits from the reflection surface side, the photodiode being used in a wavelength band where a sensitivity of the photodiode rises as a wavelength lengthens, in which the emission surface has a first dielectric multilayer film formed thereon and the reflection surface has a second dielectric multilayer film formed thereon, and in which, when a wavelength at which a reflectance of the first dielectric multilayer film peaks is given as [lambda]f and a wavelength at which a reflectance of the second dielectric multilayer film peaks is given as [lambda]r, a relation [lambda]f<[lambda]r is satisfied.

Description

technical field [0001] The present invention relates to a semiconductor laser device including a semiconductor laser chip in which a coating film is formed on an emission surface and a reflection surface which are opposite end surfaces of a resonator. Background technique [0002] A semiconductor laser element used in an optical disc drive generally includes a built-in photodiode for detecting laser power in addition to a semiconductor laser chip, and controls the laser power based on a current value (monitor current) converted by the photodiode through the photoelectric effect. Generally, an inexpensive photodiode using silicon (Si) is used for a 780 nm range semiconductor laser element for CD and a 650 nm range semiconductor laser element for DVD. [0003] Semiconductor laser devices in the 400nm range are used for next-generation Blu-ray disks. However, although the laser power remains constant, the temperature dependence of the semiconductor laser device also causes the...

AI Technical Summary

Problems solved by technology

[0006] However, the fluctuation of the bandgap of the semiconductor laser chip itself due to the change of the ambient temperature causes the wavelength of the laser emitted by it to change.

Therefore, the sensitivity of the photodiode alone is not enough to meet the specifications of the automatic power control (APC, auto power control) drive (the power change caused by the ambient temperature change is within ±5%)