Fabry-perot modulator
First Claim
1. A Fabry-Perot modulator comprising a resonant cavity defined by front and back reflective surfaces of different reflectivities and including within the cavity a multiple quantum well structure having a barrier width sufficient to prevent resonant coupling between wells in the structure, wherein absorption of the quantum well structure at a resonant wavelength of the cavity and at a low bias level is greater than with a higher bias level, whereby reflectivity of the Fabry-Perot modulator at that wavelength increases with an increase in bias level.
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Abstract
An asymmetric Fabry Perot (FP) modulator includes a quantum well structure having wider (approximately 150 Å) than usual (about 100 Å) 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 Å wells than with 100 Å 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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Citations
20 Claims
- 1. A Fabry-Perot modulator comprising a resonant cavity defined by front and back reflective surfaces of different reflectivities and including within the cavity a multiple quantum well structure having a barrier width sufficient to prevent resonant coupling between wells in the structure, wherein absorption of the quantum well structure at a resonant wavelength of the cavity and at a low bias level is greater than with a higher bias level, whereby reflectivity of the Fabry-Perot modulator at that wavelength increases with an increase in bias level.
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19. A Fabry-Perot modulator comprising a resonant cavity defined by front and back reflective surfaces of different reflectivities and including within the cavity a multiple quantum well structure, the quantum well structure having an excitonic peak wherein the wavelength of an excitonic peak of the quantum well structure in an unbiased state coincides with a resonance of the cavity.
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20. A Fabry-Perot modulator comprising a resonant cavity defined by front and back reflective surfaces of different reflectivities, the cavity including a multiple quantum well structure comprised of well regions separated by barriers, wherein the thickness of the barriers is chosen to prevent resonant coupling between the well regions, and wherein the thickness of the well regions and the thickness of the barriers are chosen whereby absorption of the quantum well structure at a resonant wavelength of the cavity and at a low bias level is greater than with a higher bias level, whereby reflectivity of the Fabry-Perot modulator at that wavelength increases with an increase in bias level.
Specification