Electro-optical device
First Claim
1. In an electro-optical device comprising a Fabry-Perot etalon having a central region of electro-optic material between two mirrors of multilayer construction, and electrical biasing means, connected to the mirrors, for applying a variable bias to the mirrors to vary the refractive index of the central region and thereby the etalon fringe maximum wavelength, the improvement wherein:
- (1) the central region and the mirrors are a heterostructure of successively deposited layers of semiconductor materials,(2) the mirrors are doped to have mutually opposite conductivity type and the central region has lower doping than the mirrors to provide a PIN diode structure in which bias voltage applied by the biasing means appears predominantly across the central region,(3) the etalon has an interference fringe maximum in the vicinity of a central region optical absorption wavelength associated with electric field dependent refractive index, and(4) the biasing means is arranged to reverse bias the PIN diode structure.
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Accused Products
Abstract
An electro-optical device is arranged as a Fabry Perot etalon comprising two mirrors and a central region. The mirrors are multilayer heterostructures of Alx Ga1-x As semiconductor materials where x alternates between 1.0 and 0.3. The central region may be a multiple quantum well structure of Alx Ga1-x As where x alternates between 0 and 0.3. The etalon material doping is non-uniform so that it is electrically a semiconductor device with a biasable central region. The optical path length in the central region is electric field dependent, and the etalon transmission or reflection is accordingly modulatable by varying the central region bias. The mirrors may be heavily doped and of opposite conductivity type with the central region undoped. This provides a PIN diode. Light incident on the etalon executes multiple transits of the central region. It is therefore unnecessary to employ long path lengths and high fields to enhance weak electro-optical effects in order to produce significant modulation, this being necessary in prior art devices.
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Citations
12 Claims
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1. In an electro-optical device comprising a Fabry-Perot etalon having a central region of electro-optic material between two mirrors of multilayer construction, and electrical biasing means, connected to the mirrors, for applying a variable bias to the mirrors to vary the refractive index of the central region and thereby the etalon fringe maximum wavelength, the improvement wherein:
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(1) the central region and the mirrors are a heterostructure of successively deposited layers of semiconductor materials, (2) the mirrors are doped to have mutually opposite conductivity type and the central region has lower doping than the mirrors to provide a PIN diode structure in which bias voltage applied by the biasing means appears predominantly across the central region, (3) the etalon has an interference fringe maximum in the vicinity of a central region optical absorption wavelength associated with electric field dependent refractive index, and (4) the biasing means is arranged to reverse bias the PIN diode structure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. In an electro-optical device comprising a Fabry-Perot etalon having a central region of electro-optic material between two mirrors of multilayer construction, and electrical biasing means, connected to the mirrors, for applying a variable bias to the mirrors to vary the central region refractive index and thereby the etalon fringe maximum wavelength, the improvement wherein:
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(1) the central region and the mirrors are a heterostructure of successively deposited layers of semiconductor materials, (2) the mirrors are doped to have like conductivity type, (3) the central region comprises a heterojunction bipolar transistor having emitter and collector regions of conductivity type equivalent to that of the mirrors but relatively lower doping such that bias voltage applied by the biasing means appears predominantly across the central region, (4) the transistor has a base region formed of a semiconductor material having opposite conductivity type to and lower energy gap than the emitter and collector regions, (5) the base region is absorbing at an etalon interference fringe maximum wavelength but the emitter and collector regions are transport at this wavelength, and (6) the biasing means is arranged to bias the central region to produce phototransistor operation
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Specification