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Record 4 of 4887
Fiber Grating Coupled Light Source Capable of Tunable, Single Frequency Operation
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Author and Affiliation:
Krainak, Michael A. [Inventor](NASA Goddard Space Flight Center, Greenbelt, MD United States)
Duerksen, Gary L. [Inventor](NASA Goddard Space Flight Center, Greenbelt, MD United States)
Abstract: Fiber Bragg grating coupled light sources can achieve tunable single-frequency (single axial and lateral spatial mode) operation by correcting for a quadratic phase variation in the lateral dimension using an aperture stop. The output of a quasi-monochromatic light source such as a Fabry Perot laser diode is astigmatic. As a consequence of the astigmatism, coupling geometries that accommodate the transverse numerical aperture of the laser are defocused in the lateral dimension, even for apsherical optics. The mismatch produces the quadratic phase variation in the feedback along the lateral axis at the facet of the laser that excites lateral modes of higher order than the TM(sub 00). Because the instability entails excitation of higher order lateral submodes, single frequency operation also is accomplished by using fiber Bragg gratings whose bandwidth is narrower than the submode spacing. This technique is particularly pertinent to the use of lensed fiber gratings in lieu of discrete coupling optics. Stable device operation requires overall phase match between the fed-back signal and the laser output. The fiber Bragg grating acts as a phase-preserving mirror when the Bragg condition is met precisely. The phase-match condition is maintained throughout the fiber tuning range by matching the Fabry-Perot axial mode wavelength to the passband center wavelength of the Bragg grating.
Publication Date: Feb 13, 2001
Document ID:
(Acquired Jan 04, 2002)
Subject Category: OPTICS
Report/Patent Number: US-Patent-6,188,705, US-Patent-Appl-SN-079383, US-Patent-Appl-SN-044378
Document Type: Patent
Financial Sponsor: NASA Goddard Space Flight Center; Greenbelt, MD United States
Organization Source: NASA Goddard Space Flight Center; Greenbelt, MD United States
Description: 36p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
Miscellaneous Notes: Provisional US-Patent-Appl-SN-044378, filed 16 May 1997
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