Electro-optic devices
First Claim
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1. An electro-optic device comprising:
- a Burrus-type light emitting diode having an active layer, the light emitting diode being operable to produce primary top emission of light perpendicular to said layer, and relatively low intensity secondary side emission in the plane of said layer;
drive means for applying current to drive the light emitting diode;
monitoring means located in the plane of the active layer for monitoring the secondary side emission and for generating an electrical analog of such monitored secondary side emission; and
feedback means for applying said electrical analog to the drive means whereby to stabilize primary top emission from said light emitting diode.
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Abstract
An electro-optic device for stabilizing the output level of a Burrus-type light emitting diode (LED) utilizes a photodiode to monitor side emission from an active region of the LED. Side emission closely tracks top emission, which is launched into an output fiber. An electrical analog is derived from the monitored side emission and is applied in a feedback loop to control modulation level or bias current to the LED. In this way, peak optical output (for digital systems) or r.m.s. output and linearity (for analog systems) is stabilized. The monitoring photodiode and the LED may be spatially separate or may form a unitary structure.
33 Citations
18 Claims
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1. An electro-optic device comprising:
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a Burrus-type light emitting diode having an active layer, the light emitting diode being operable to produce primary top emission of light perpendicular to said layer, and relatively low intensity secondary side emission in the plane of said layer; drive means for applying current to drive the light emitting diode; monitoring means located in the plane of the active layer for monitoring the secondary side emission and for generating an electrical analog of such monitored secondary side emission; and feedback means for applying said electrical analog to the drive means whereby to stabilize primary top emission from said light emitting diode. - View Dependent Claims (2, 3, 4)
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- 5. A method of stabilizing top emission from a Burrus-type light emitting diode in response to an operating current directed through an active region of the light emitting diode, said method comprising monitoring side emission from the light emitting diode in the plane of the active region, generating an electrical analog of said monitored side emission and utilizing said electrical analog to vary the operating current applied to the light emitting diode and thereby stabilize top emission emitted perpendicularly to the active region.
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9. An electro-optic device comprising an integrated Burrus-type light emitting diode and a detector, the device having:
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a semiconductor chip having a p-n junction layer; the Burrus-type light emitting diode including means for directing an operating current across a first region of the p-n junction to stimulate light emission from said region; the detector including means for reverse biasing another region of the p-n junction electrically isolated from said first region for stimulating a detector current across the second region in response to photon emission from the first region incident on the second region; the device further comprising feedback means for varying the operating current across the first junction region in response to the detector current whereby to stabilize light output of the Burrus-type light emitting diode. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification