| 摘要 |
An asymmetric Fabry Perot (FP) modulator includes a quantum well structure having wider (approximately 150 ANGSTROM ) than usual (about 100 ANGSTROM ) wells. The FP cavity has a resonance at a wavelength of an excitonic absorption peak of the QW structure. Although the maximum change in absorption under applied bias is less with 150 ANGSTROM wells than with 100 ANGSTROM wells, the characteristics of the electroabsorption are also altered, with the result that the largest change occurs at the wavelength of the band-edge el-hhl exciton at zero bias. Absorption can be reduced by biasing the QW and hence the AFPM can have a normally-off (zero bias, zero reflectivity) characteristic. Such an arrangement makes possible higher contrast modulation and/or lower operating voltages. The FP modulator may be used in SEEDs.
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