| 摘要 |
Modulated signal levels in the range of 1 mu V, as is typical for radar returns, can be used to achieve a useful modulated optical signal that can be launched into a fiber optic waveguide for transmission to a remote location for signal processing. The device of the invention achieves such a conversion by suitably integrating a high gain bipolar transistor with an electroluminescent diode, such as a light emitting diode or diode laser, into a compact monolithic structure. In one structural configuration, the bipolar transistor comprises an emitter comprising a layer of doped n-(Al,Ga)As supported on a base comprising a layer of doped p-GaAs, in turn supported on a collector comprising a layer of undoped n-GaAs or n-(Al,Ga)As. The electroluminescent diode in this embodiment comprises a light-emitting diode formed by a p-n junction between the undoped n-GaAs or n-(Al,Ga)As layer and a supporting doped p-GaAs layer, in turn supported on a doped p+-GaAs substrate. Collector contact is made to the backside of the substrate. An electrical signal at the base is amplified by transistor action, resulting in a high gain optical output by the LED, which may be launched into an optical fiber in either a Burrus or edge-emitting configuration. Direct optical amplification of optical radiation may be made by omitting electrical contact to the base and introducing the optical radiation into the emitter.
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