Tunable spectroscopic source with power stability and method of operation
First Claim
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1. A tunable laser source having stable output power during wavelength scanning, the source comprising:
- a laser cavity including;
a wavelength selector for scanning a passband over a scan band, and a laser gain chip providing gain to longitudinal modes of the laser cavity within a gain bandwidth provided by the passband; and
wherein the laser cavity is characterized by a cavity longitudinal mode spacing that is more than two times smaller than the gain bandwidth.
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Abstract
A laser system for a spectroscopic catheter system utilizes an overmoded cavity in order to reduce mode hoping induced power fluctuations during wavelength scanning. In the preferred embodiment, a semiconductor gain medium is used to reduce cost. A fiber pigtail is used to define the laser cavity, which has a tight cavity mode spacing of less that 15 Gigahertz. A diffraction grating is used as the tuning element. A cylindrical lens is used to reduce alignment tolerances and thereby increase manufacturability.
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Citations
43 Claims
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1. A tunable laser source having stable output power during wavelength scanning, the source comprising:
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a laser cavity including;
a wavelength selector for scanning a passband over a scan band, and a laser gain chip providing gain to longitudinal modes of the laser cavity within a gain bandwidth provided by the passband; and
wherein the laser cavity is characterized by a cavity longitudinal mode spacing that is more than two times smaller than the gain bandwidth. - 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 spectroscopic catheter system, comprising:
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a catheter for insertion into a patient to transmit light to the patient;
a tunable laser source having a laser cavity including;
a wavelength selector for scanning a passband over a scan band, a laser gain chip providing gain to modes of the laser cavity within a gain bandwidth provided by the passband;
wherein the laser cavity is characterized by a cavity mode spacing that is two or more times smaller than the gain bandwidth, andan output coupler for coupling laser light from laser cavity into the catheter; and
at least one detector for detecting light returning from the patient to perform spectroscopic analysis. - View Dependent Claims (21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41)
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42. A method for providing tunable frequency light to a patient, the method comprising:
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inserting a catheter into a patient;
generating light with a tunable laser;
tuning a frequency of the light across a scan band;
selecting a length of a laser cavity of the tunable laser so that two or more longitudinal modes of the laser cavity are lasing at all times during the step of tuning the frequency of the light across the scan band; and
detecting light returning from the patient to determine a spectral response of tissue within the patient over the scan band. - View Dependent Claims (43)
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Specification