High frequency source having heterodyned laser oscillators injection-locked to a mode-locked laser
First Claim
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1. A signal generator, comprising:
- an actively mode-locking modulation signal source having a frequency harmonically related to a desired output frequency;
a laser coupled to said actively mode-locking modulation signal source and having plural optical modes actively mode-locked by said actively mode-locking modulation signal source and characterized by respective mode frequencies, whereby said laser is an actively mode-locked laser;
plural tuned lasers, each of said plural tuned lasers being tuned to a respective optical frequency, corresponding to respective ones of said mode frequencies, wherein a difference in the optical frequencies of different ones of said plural tuned lasers corresponds to a desired output frequency;
means for injection-locking said plural tuned lasers to corresponding ones of said plural optical modes of said mode-locked laser; and
means for combining the optical outputs of said plural tuned lasers whereby to generate at least an output signal having an output frequency equal to said difference in the optical frequencies of different ones of said plural tuned lasers and corresponding to said desired output frequency.
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Abstract
Two independent laser oscillators are injection-locked to different optical modes of a mode-locked laser, then combined and detected to produce the heterodyne output signal in the microwave to submillimeter wave frequency band. Since the phase fluctuations of the mode-locked laser modes are highly correlated, the phase fluctuations of the heterodyne output signal are greatly reduced, providing a low phase-noise oscillator signal. Since the modes of the mode-locked laser can span hundreds of GigaHertz, the oscillator can be employed to generate microwave, millimeter wave or submillimeter wave frequencies.
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Citations
20 Claims
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1. A signal generator, comprising:
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an actively mode-locking modulation signal source having a frequency harmonically related to a desired output frequency; a laser coupled to said actively mode-locking modulation signal source and having plural optical modes actively mode-locked by said actively mode-locking modulation signal source and characterized by respective mode frequencies, whereby said laser is an actively mode-locked laser; plural tuned lasers, each of said plural tuned lasers being tuned to a respective optical frequency, corresponding to respective ones of said mode frequencies, wherein a difference in the optical frequencies of different ones of said plural tuned lasers corresponds to a desired output frequency; means for injection-locking said plural tuned lasers to corresponding ones of said plural optical modes of said mode-locked laser; and means for combining the optical outputs of said plural tuned lasers whereby to generate at least an output signal having an output frequency equal to said difference in the optical frequencies of different ones of said plural tuned lasers and corresponding to said desired output frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. An optical down-converter for down-converting an incoming signal constituting a carrier signal of a particular carrier frequency and a baseband signal, comprising:
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I. a local oscillator comprising; A. a mode-locked laser having plural optical modes characterized by respective mode frequencies, B. plural tuned lasers, each of said plural tuned lasers being tuned to a respective optical frequency, corresponding to respective ones of said mode frequencies, wherein a difference in the optical frequencies of different ones of said plural tuned lasers corresponds to a desired output frequency, C. means for injection-locking said plural tuned lasers to corresponding ones of said plural optical modes of said mode-locked laser, D. means for combining the optical outputs of said plural tuned lasers whereby to generate a local oscillator optical signal having a local oscillator frequency equal to said difference in the optical frequencies of different ones of said plural tuned lasers; II. means for modulating said local oscillator optical signal with said incoming signal so as to produce a mixed signal; and III. means for detecting said baseband signal. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification