EP0001714A1
Expired / Lapsed
EP
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Control apparatus for a semi-conductor laser device
Assignee: British Telecommunications PLC
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Filing: 1978-10-23
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Granted: —
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Expires: 1998-10-23
Abstract
Abstract Control apparatus for a semi-conductor laser device. Apparatus for controlling the emission wavelength and power of a semi-conductor laser device in which the laser driver (5) is connected in a feedback loop comprising a beam-splitter (6), a photodiode (8) and an amplifier (19), which loop controls the driver (5) to maintain the intensity of the laser emission constant. The emission is also sampled by a beam-splitter (7) and photodiode (9), which is made frequency-dependent by a filter (10) interposed in the path of the beam. The outputs of the matched photodiodes (8) and (9) are fed via amplifiers (11) and (13) to the positive and negative inputs of a subtractor amplifier (12), the output of which is therefore dependent only upon the emission wavelength. This output is fed as negative feedback to an amplifier (15) for controlling an operating parameter (such as the temperature) of the laser (1) to maintain the wavelength constant.
Inventors
- 👤 Derek John Malyon
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 02:52
CPC Classifications
H; H01; H01S; H01S3/00; H01S3/10; H01S3/13; H01S3/136; H01S3/139; H01S5/00; H01S5/06; H01S5/068; H01S5/0683; H01S5/0687; H01S3/137; H01S5/06804; H01S5/06837
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
81 words
Apparatus for controlling the emission wavelength and power of a semi-conductor laser device, characterised in that a feedback loop is provided to monitor the emission wavelength of the radiation from the laser device and to maintain the wavelength at a predetermined value by controlling an operating parameter of the laser device; and in that means is provided to monitor the intensity of the constant wavelength radiation and to maintain the monitored intensity at a constant level by controlling the laser current.
Claim 2
Dependent Claim
81 words
Apparatus for controlling the emission wavelength and power of a semi-conductor laser device, characterised in that a feedback loop is provided to monitor the emission wavelength of the radiation from the laser device and to maintain the wavelength at a predetermined value by controlling an operating parameter of the laser device; and in that means is provided to monitor the intensity of the constant wavelength radiation and to maintain the monitored intensity at a constant level by controlling the laser current.
Claim 3
Dependent Claim
72 words
Apparatus as claimed in Claim 1, characterised in that the means to maintain the monitored intensity at a constant level comprises means to apply electrical power to the laser device; means to extract a first sample of the radiation; a detector to provide a signal dependent upon the intensity of said first sample; and means dependent upon the magnitude of said signal to control the output of the electrical power supply means.
Claim 4
Dependent Claim
19 words
Apparatus as claimed in Claim 2, characterised in that the means to extract said first sample comprises a beam-splitter.
Claim 5
Dependent Claim
45 words
Apparatus as claimed in Claim 2 or Claim 3, characterised in that the means to monitor the emission wavelength comprises means to extract a second sample of said radiation, and means to produce a signal dependent only upon the wavelength of said second 4 sample.
Claim 6
Dependent Claim
39 words
Apparatus as claimed in Claim 4, characterised in that the means to produce a signal dependent upon the wavelength comprises a photodiode, and a wavelength- dependent filter interposed between said photodiode and the means to extract said second sample.
Claim 7
Dependent Claim
45 words
Apparatus as claimed in Claim 5, characterised in that the detector to provide a signal dependent upon the intensity comprises a photodiode; and in that said photodiode and the photodiode of the means to produce a signal dependent upon the wavelength are a matched pair.
Claim 8
Dependent Claim
46 words
Apparatus as claimed in Claim 6, characterised in that the outputs of the diodes are fed via respective amplifiers to respective positive and negative inputs of a subtractor amplifier, the output of which is therefore independent of input changes except those dependent upon the emission wavelength.
Claim 9
Dependent Claim
35 words
Apparatus as claimed in Claim 7, characterised in that the wavelength is controlled by feeding the signal output of the subtracting amplifier to a controller for controlling said parameter, in opposition to a reference signal.
Claim 10
Dependent Claim
60 words
Apparatus as claimed in Claim 8, characterised in that the controlled parameter is the operating temperature of the laser device; and in that the operating temperature is controlled by means to heat or cool a heat sink on which the laser device is mounted, the supply of electrical power to said heating or cooling means being determined by said controller.
Claim 11
Dependent Claim
26 words
Apparatus as claimed in any one of Claims 1 to 8, characterised in that the controlled operating parameter is the operating temperature of the laser device.
Claim 12
Dependent Claim
60 words
Apparatus as claimed in any one of Claims 1 to 8, characterised in that there is provided a cavity associated with the laser device and containing a lens arrangement and an optical grating positioned alosg the path of the radiation, and in that the confrolled parameter is the angle of the optical grating relative to the axis of said path.
Claim 13
Dependent Claim
19 words
Apparatus as claimed in Claim 11, characterised in ihat the angle is adjustable by means of a piezo-electric crystal.
Claim 14
Dependent Claim
15 words
An assembly comprising a semi-conductor laser together with apparatus as claimed in any preceding claLm.
References Cited (Backward Citations)
US3641459A
Cited
FR2263623A1
Cited
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