Coherent light source and control method thereof, and display unit and laser display using them
First Claim
Patent Images
1. A coherent light source comprising:
- a semiconductor laser provided with an active region and a distributed Bragg reflection region;
a light wavelength conversion element that is made of non-linear optical crystal and converts a wavelength of a laser beam emitted from the semiconductor laser;
a photo detector that measures a higher harmonic output from the light wavelength conversion element;
current injection means for applying currents independently to the active region and the distributed Bragg reflection region;
current control means for controlling the current injection means on the basis of the higher harmonic output measured in the photo detector to fix an oscillation wavelength of the semiconductor laser to an inclined portion within a phase matching wavelength spectrum of the light wavelength conversion element;
pulse current injection means for applying a pulse current to at least one region selected from the active region and the distributed Bragg reflection region; and
pulse current control means for controlling the pulse current injection means on the basis of the higher harmonic output measured in the photo detector to change the oscillation wavelength of the semiconductor laser to a desired value at the inclined portion within the phase matching wavelength spectrum of the light wavelength conversion element and to change the higher harmonic output.
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Abstract
In a display device that displays a video by scanning coherent light across a screen, modulation at high speeds and gradation are necessary for a coherent light source.
An oscillation wavelength of a semiconductor laser outputting the fundamental wave is changed at high speeds through the plasma effect induced by applying a pulse current to the coherent light source. A change of the wavelength causes the output of a higher harmonic generated in a light wavelength conversion element to change, and gradation is produced using such a change.
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Citations
20 Claims
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1. A coherent light source comprising:
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a semiconductor laser provided with an active region and a distributed Bragg reflection region; a light wavelength conversion element that is made of non-linear optical crystal and converts a wavelength of a laser beam emitted from the semiconductor laser; a photo detector that measures a higher harmonic output from the light wavelength conversion element; current injection means for applying currents independently to the active region and the distributed Bragg reflection region; current control means for controlling the current injection means on the basis of the higher harmonic output measured in the photo detector to fix an oscillation wavelength of the semiconductor laser to an inclined portion within a phase matching wavelength spectrum of the light wavelength conversion element; pulse current injection means for applying a pulse current to at least one region selected from the active region and the distributed Bragg reflection region; and pulse current control means for controlling the pulse current injection means on the basis of the higher harmonic output measured in the photo detector to change the oscillation wavelength of the semiconductor laser to a desired value at the inclined portion within the phase matching wavelength spectrum of the light wavelength conversion element and to change the higher harmonic output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A control method of a coherent light source, said method comprising:
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converting, with a light wavelength conversion element that is made of non-linear optical crystal, a wavelength of a laser beam emitted from a semiconductor laser provided with an active region and a distributed Bragg reflection region; measuring, with a photo detector, a higher harmonic output from the light wavelength conversion element; applying currents independently to the active region and the distributed Bragg reflection region; controlling the currents on the basis of the higher harmonic output measured in the photo detector to fix an oscillation wavelength of the semiconductor laser to an inclined portion within a phase matching wavelength spectrum of the light wavelength conversion element; applying a pulse current to at least one region selected from the active region and the distributed Bragg reflection region; and controlling the applying of the pulse current on the basis of the higher harmonic output measured in the photo detector to change the oscillation wavelength of the semiconductor laser to a desired value at the inclined portion within the phase matching wavelength spectrum of the light wavelength conversion element and to change the higher harmonic output.
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Specification