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 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.