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Published online by Cambridge University Press: 21 February 2011
A short wavelength laser offers unique opportunities in high density opticalrecording as well as in laser printing. To achieve a compact blue laser, thecurrent effort worldwide is primarily concentrated on achievingwell-conducting p-type ZnSe and fabricating quantum well heterostructures soas to achieve a low threshold laser at room temperature. The recentmilestone ‘an injection blue laser below room temperature’ gives usconfidence that indeed we are on the right path. In photopumped lasers invarious II-VI heterostructures, thresholds at room temperature comparable tothe theoretical limit have been reported. This not only reinforces thatindeed a room temperature injection laser is possible but when combined withearlier electron-beam pumped laser results, a scanned compact laser is alsofeasible.
In recent years several breakthroughs have demonstrated that an infraredemitting GaAs laser can be used to generate blue light through efficientsecond harmonic generation (SHG) in certain non-linear optical materials.Recent exciting results on SHG of GaAs lasers in KTP grating waveguidesresulted in a blue laser with output power in the range of severalmilliwatts. Alternative schemes such as upconversion lasers and SHG in III-Vquantum wells structures are presented.
In summary, various efforts to achieve compact blue lasers and theiravailability in the near future are presented.