Evaluation of InGaAsP laser material by optical pumping

A novel technique based on optical pumping has been developed to evaluate InGaAsP laser material before it is processed into electrical devices. By pumping unprocessed InGaAsP chips with cleaved mirrors with a 1.06 μm wavelength Nd:YAG laser and detecting the light emitted by the quaternary active layer, various properties such as laser threshold, wavelength, and differential quantum efficiency can be determined. This technique provides a method for screening InGaAsP laser material prior to time-consuming processing. The technique is also applicable to partially processed laser chips, and hence, the effect of each processing step can be evaluated. We find that threshold pumping intensities and
T_{0} (\sim60\deg
C), the parameter characterizing the temperature variation of threshold, are virtually the same for chips without and with a p-n junction or alloyed contact.