II–VI compound semiconductor quantum-well heterostructures were fabricated for use as efficient, narrow-spectrum, photoluminescent color converters to generate green, yellow, or red light when photopumped with blue GaInN light emitting diodes (LEDs). This approach promises high efficiencies in a wide range of wavelengths that includes the green-yellow portion of the spectrum where conventional LEDs offer relatively low efficiency. External quantum conversion efficiencies of 60%–70% and output spectra with full width at half maximum of 15 nm were achieved using CdZnSe–CdMgZnSe quantum wells grown by molecular beam epitaxy on InP substrates.
Micromirrors were fabricated in gallium phosphide by mass transport to provide spatial-mode control of vertical-cavity surface-emitting lasers (VCSEL's). The concave mirrors were used in an external-cavity configuration to provide spatial filtering in the far field. Single-mode cw lasing was demonstrated in 15-microm-diameter VCSEL's with currents as high as 6 times threshold. The fabrication process was extended to micromirrors in gallium arsenide by use of a replication and dry-etch transfer process.
Refractive prismatic and off-axis micro-optical elements have been fabricated in gallium phosphide by mass-transport smoothing of multistep and binary preforms, respectively. A total optical efficiency of greater than 94% was measured for the prism, while diffraction-limited collimation and steering were demonstrated with the off-axis lens. A qualitative discussion of possible errors in binary preform etching and their effects on the surface figure is also included.
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