Quest for Compact Blue Lasers for Optical Memories

ABSTRACTA short wavelength laser offers unique opportunities in high density optical recording as well as in laser printing. To achieve a compact blue laser, the current effort worldwide is primarily concentrated on achieving well-conducting p-type ZnSe and fabricating quantum well heterostructures so as to achieve a low threshold laser at room temperature. The recent milestone ‘an injection blue laser below room temperature’ gives us confidence that indeed we are on the right path. In photopumped lasers in various II-VI heterostructures, thresholds at room temperature comparable to the theoretical limit have been reported. This not only reinforces that indeed a room temperature injection laser is possible but when combined with earlier electron-beam pumped laser results, a scanned compact laser is also feasible.In recent years several breakthroughs have demonstrated that an infrared emitting GaAs laser can be used to generate blue light through efficient second harmonic generation (SHG) in certain non-linear optical materials. Recent exciting results on SHG of GaAs lasers in KTP grating waveguides resulted in a blue laser with output power in the range of several milliwatts. Alternative schemes such as upconversion lasers and SHG in III-V quantum wells structures are presented.In summary, various efforts to achieve compact blue lasers and their availability in the near future are presented.