LOW-NOISE AND HIGH-POWER OPERATION IN HIGH REFLECTIVITY COATED NONABSORBING MIRROR GAALAS LASERS

We have successfully attained low-noise and high-power operation in GaAlAs lasers by applying high reflectivity facet coating approach to nonabsorbing mirror lasers. High reflectivity coating is used to reduce feedback induced noise coming from hopping between the diode cavity modes and between the external cavity modes. A nonabsorbing mirror structure is used to obtain high-power operation by suppressing mirror degradation and catastrophic optical damage effectively even with the use of high reflectivity coating. Nonabsorbing mirror lasers with the front facet reflectivity 50% showed the relative intensity noise level less than -130 dB/Hz at 3 mW under 0%-10% optical feedback and showed the cw output power as high as 50 mW in fundamental spatial mode operation. Under 30-mW cw operation at 50°C, on the other hand, obvious degradation has not been observed over 4000 h in the nonabsorbing mirror lasers with 50% front facet reflectivity. Thus the present laser is useful as a low-noise source at a low-power level and also as a high-power source with high reliability.