United States of America As Represented by the Secretary of the Air Force

Leanne J Henry

Thomas M Shay

Gerald T Moore

Jacob R Grosek

A desired N-order Stokes output and zeroth-order Stokes pump input are seeded into a rare-earth doped amplifier where the power of the zeroth-order Stokes signal is amplified prior to both signals entering a Raman amplifier comprised of N&#x2212;1 Raman resonators, each uniquely tuned to one of the N&#x2212;1 Stokes orders, in various configurations to include one or more nested and/or in-series Raman resonators. The zeroth-order Stokes signal is converted to the N&#x2212;1-order Stokes wavelength in steps and the power level of the N-order Stokes wavelength is amplified as the two signals propagate through the Raman resonators. Each Raman resonator includes a photosensitive Raman fiber located between a pair of Bragg gratings. The linewidths of the Stokes orders can be controlled by offsetting the reflectivity bandwidths of each pair of Bragg gratings respectively located in the Raman resonators.

Laser generation using dual seeded nested and/or in-series Raman resonators, for telecommunications applications

A third-order Stokes wavelength seed signal at the desired output wavelength of 1240 nm and a zeroth-order Stokes wavelength signal at 1066 nm are input into a Raman amplifier comprised of two Raman resonators in a linear configuration. The first resonator converts the zeroth-order Stokes wavelength signal at 1066 nm into a first-order Stokes wavelength signal at 1118 nm, and also outputs the third-order Stokes wavelength seed signal at 1240 nm. The second resonator then converts the 1118 nm output from the first resonator into a second-order Stokes wavelength signal at 1176 nm, which amplifies the 1240 nm seed signal power level. Each Raman resonator includes a photosensitive Raman fiber communicating with a plurality of high-reflector Bragg gratings. The linewidths of the second and third Stokes orders are controlled by adjusting the resonant bandwidth of the second Raman resonator by offsetting the respective center wavelengths of the high-reflector Bragg gratings.

Seeded Raman amplifier in a linear configuration for generating a 1240 nm laser

A third-order Stokes signal at the desired output wavelength of 1240 nm and a zeroth-order Stokes pump wavelength at 1066 nm are seeded into a Raman amplifier comprised of two nested resonators tuned to the first-order Stokes line at 1118 nm and second-order Stokes line at 1176 nm, respectively. The pump wavelength is first amplified and then sequentially converted into the first and second-order Stokes wavelengths as the light traverses the nested resonators. The desired third-order Stokes output wavelength is then amplified by the second-order Stokes wavelength as it propagates through the outermost resonator. Each Raman resonator includes a photosensitive Raman fiber located between a pair of Bragg gratings. The linewidths of the various Stokes orders can be controlled through adjusting the resonant bandwidths of the Raman resonators by offsetting, through heating, the reflectivity bandwidths of each pair of Bragg gratings respectively located in the Raman resonators.

Seeded Raman amplifier in a nested configuration for generating a 1240 nm laser

A desired N-order Stokes output and corresponding zeroth-order Stokes pump wavelengths are seeded into a Raman amplifier comprised of one or more Raman resonators in series sequentially tuned to the 1, 2, . . . N&#x2212;1Stokes orders. The pump wavelength is amplified and sequentially converted to the 1, 2, . . . N&#x2212;1order Stokes wavelengths as it propagates through the apparatus. The desired N-order Stokes output wavelength is then amplified by the N&#x2212;1Stokes order as it propagates through the final resonator tuned to the N&#x2212;1Stokes order. Each Raman resonator includes a Raman photosensitive Raman fiber located between a pair of Bragg gratings. The linewidths of the various Stokes orders can be controlled through adjusting the resonant bandwidths of the Raman resonators by offsetting, through heating, the reflectivity bandwidths of each pair of Bragg gratings respectively located in the Raman resonators.

Seeded Raman amplifier in linear configuration for laser applications in the 1100-1500 nm spectral range

A broad linewidth, zeroth Stokes order 1069 nm pump and a narrow linewidth second Stokes order 1178 nm seed propagate through a wavelength division multiplexer and then through a rare-earth-doped amplifier. After passing through a 1121 nm long period or tilted Bragg grating, the amplified 1069 nm Stokes signal and the 1178 Stokes signal are injected into a 1121 nm resonator Raman cavity, which includes a pair of highly reflective Bragg gratings having a center wavelength of 1121 nm. The amplified 1069 nm Stokes signal is Raman converted to high power levels of 1121 nm which then, in turn, amplifies the 1178 nm Stokes seed as it traverses the cavity. The linewidth of the amplified 1178 nm Stokes signal can be controlled by offsetting, through heating, the reflectivity bandwidth of the Bragg grating located near the output end of the Raman cavity.

Generating narrow linewidth 1178 NM laser output using a seeded raman amplifier

A method of implementing a high-power coherent laser beam combining system in which the output of a master oscillator laser having a linewidth broader than the Stimulated Brillouin Scattering linewidth of the laser signal is split into N signals and fed into an array of N optical fibers. This is a modification of the self-synchronous LOCSET and self-referenced LOCSET phase matching systems in which the optical path length of each optical fiber is matched to less than the signal coherence length of the master oscillator by using a path length matching signal processor to modulate temperature controlled segments of each optical fiber.

Fiber active path length synchronization

A method of generating high-power laser output in the 1100 to 1500 um spectral region having a controllable linewidth. A Raman amplifier comprised of one or more nested pairs of fiber Bragg grating cavities tuned to the 1, 2, . . . N&#x2212;1order Stokes wavelengths is seeded with both the desired Nth order Stokes output wavelength and the corresponding zeroth-order Stokes pump wavelength. As the pump wavelength propagates through the apparatus, it is sequentially converted to the 1, 2, . . . N&#x2212;1order Stokes wavelengths in the nested fiber Bragg grating cavities. The desired Nth order Stokes output wavelength is then amplified by the N&#x2212;1Stokes order as it propagates through the nested fiber Bragg grating cavities. The linewidths of various Stokes orders can be controlled through adjusting resonant bandwidths of the fiber Bragg grating cavities by offsetting, through heating, the reflectivity bandwidths of each pair of cavity gratings.

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Albuquerque, NM, United States of America

Leanne J Henry