Integrated Optical Circuits
Semiannual technical summary rept. 1 Jul-31 Dec 1974
MASSACHUSETTS INST OF TECH LEXINGTON LINCOLN LAB
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Detailed measurements of the attenuation of high-purity planar GaAs waveguides have been made over the wavelength range from 0.90 to 1.06 micrometers. The loss, which appears to be primarily due to a band-edge absorption tail, ranges from 3.0 per cm at 0.90 micrometer to 0.3 per cm at 1.06 micrometers and is equal to or less than 1 per cm for lambda greater than 0.909 micrometer. These waveguides are suitable for use with si-doped GaAs-AlGaAs integrated lasers and with integrated electroabsorption detectors and modulators. Integrated structures consisting of Fabry-Perot GaAs-AlGaAs double-heterostructure lasers immersed in high-purity GaAs slab waveguides have been fabricated and characterized. These structures are quite attractive for use as sources in GaAs-based monolithic integrated optical circuits. Threshold current densities at room temperature as low as 7.5 kA per sq cm for 1-micrometer-thick active regions were measured. Measured external differential quantum efficiencies of the laser-waveguide combinations were about 3.5 percent, but appeared to be limited by the presence of internally circulating modes. Over three-orders-of-magnitude reduction of lattice-misfit dislocation densities in heteroepitaxial Pb0.88Sn0.12Te layers grown either by molecular beam or liquid-phase epitaxy has been achieved by growing the layers on nearly lattice-matched PbTe0.952Se0.048 substrates.
- Fiber Optics and Integrated Optics
- Solid State Physics