Polarized Injection Laser Development.

Abstract : This report is concerned with the successful development of room-temperature arrays of injection lasers with high polarization and with the study of the fundamental causes of polarization. Three types of multi-heterojunction wafers producing strong polarization are described. Arrays from the wafers have polarization ratios ranging from 90 to 98%. The profiles in the junction plane are nominally 20 deg, while in the transverse plane they depend on the internal structure and range from 30 to 80 deg. Tests of one of the arrays at elevated temperature showed good performance at 78 deg C ambient. A reflecting layer added to the reverse facet increased the differential efficiency of the forward beam without spoiling the polarization. Data on the device properties are presented for system analysis, as are recommendations for further device development and performance specification. The current dependence of polarization shows several types of behavior. For devices with low polarization, the ratio drops monotonicallly with drive from a high value near threshold to near unity at full power. This behavior is interpreted in terms of existing theory of the lasing state. The behavior of devices whose polarization ratio is independent of current or increases with drive, which is often the case with strongly polarized units, is not understood theoretically. A new result of technological significance is that lasers with sawed sidewalls have much lower TE polarization than similar lasers with stripe contacts. The polarization control by the lateral walls is very strong, the ratio varying with the nature of the walls by a factor of four. (Author)