| 摘要 |
PURPOSE:To eliminate the malfunction of tracking by making the layer thickness of a semiconductor laser thin so that the return light of a tracking signal is not irradiated to the cleavage face of a semiconductor laser. CONSTITUTION:When a distance between the cleavage face 20a of the semiconductor laser 20 and a grating 3a is R3 and the irradiating angle of the return light from the grating 3a is theta, then a distance R4 from a laser oscillator face 25 up to a position shown in captions B' or C' is expressed as R4=R3.tantheta. Then the thickness D1, D2 of P-type semiconductor layer 21 and N-type semiconductor layer 23 of the semiconductor laser 20 are selected smaller than the distance R4. Thus, the return light of the tracking signal from the grating 3a is hardly irradiated onto the cleavage face 20a of the semiconductor laser 20 and the error detection of photodiodes 10a, 11a due to interference fringes is prevented. |
