| 1. |
- Knall, Jennifer M., et al.
(author)
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Radiation-Balanced Silica Fiber Amplifier
- 2021
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 127:1
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Journal article (peer-reviewed)abstract
- We report what we believe to be the first radiation-balanced fiber amplifier-a device that provides optical gain while experiencing no temperature rise. The gain medium is a silica fiber with a 21-mu m-diameter core highly doped with Yb3+ (2.52 wt. %) and codoped with 2.00 wt. % Al to reduce concentration quenching. The amplifier is core pumped with 1040-nm light to create anti-Stokes fluorescence cooling and gain in the core at 1064 nm. Using a custom slow-light fiber Bragg grating sensor with mK resolution, temperature measurements are performed at multiple locations along the amplifier fiber. A 4.35-m fiber pumped with 2.62 W produced 17 dB of gain, while the average fiber temperature remained slightly below room temperature. This advancement is a fundamental step toward the creation of ultrastable lasers necessary to many applications, especially low-noise sensing and high-precision metrology.
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| 2. |
- Vigneron, Pierre-Baptiste, et al.
(author)
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8.5-fm resonances in an amplified slow-light fiber Bragg grating for high-precision metrology
- 2020
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In: Optical, Opto-Atomic, and Entanglement-Enhanced Precision Metrology II. - San Fransisco : SPIE - International Society for Optical Engineering.
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Conference paper (peer-reviewed)abstract
- Fiber Bragg gratings (FBGs) with strong apodized index modulations behave like an in-line Fabry-Perot interferometer and exhibit a series of narrow resonances in the short-wavelength portion of their transmission spectrum. These resonances have proven invaluable for detecting extremely small strains (30-femtostrain/√Hz level) or temperature changes (millidegreeC/√Hz level). The sensitivity of these fiber sensors is limited by the linewidth and peak transmission of the resonance used to interrogate the sensor, which are themselves limited by the intrinsic loss of the grating. In this work, significantly narrower and stronger resonances are demonstrated by introducing a small amount of optical gain in the FBG to offset the intrinsic loss and create a resonator with a much smaller net internal loss. The fiber Bragg grating is written in an Er-doped single-mode fiber and optically pumped to provide the required gain. The device reported here is a 6.5-mm grating with an AC index modulation of 1.59×10-3. With only 30 μW of pump power absorbed by the grating (32.6 mW launched), the fundamental resonance of the FBG was observed to narrow from 737 fm in the absence of pump to a record linewidth of 8.5 fm. The measured peak transmission of the resonance improved from ~-37 dB to -0.2 dB. A new model that predicts the slow-light resonance spectrum of a slow-light grating in the presence of optical gain is presented. This model is in good quantitative agreement with the measured evolution of the resonance linewidth as the pump power and the power of the laser that probes the resonance lineshape are varied.
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| 3. |
- Vigneron, Pierre-Baptiste, et al.
(author)
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Anti-Stokes Cooling of Nanoparticle-Doped Silica Fibers
- 2022
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In: PHOTONIC HEAT ENGINES. - : SPIE - International Society for Optical Engineering. - 9781510649088 - 9781510649071
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Conference paper (peer-reviewed)abstract
- The recent reports of laser cooling in Yb-doped aluminosilicate fibers and silica preforms have opened up the field of optical refrigeration and radiation-balanced lasers to the enormous realm of silica fiber lasers and amplifiers. To increase the cooling efficiency achieved in these materials, it is critical to identify host compositions that improve the Yb3+-ion properties in the directions of low concentration quenching, short radiative lifetime, and a long-wavelength absorption tail that extends as far as possible above the zero-phonon line. In this on-going quest, nanoparticle-doped fibers offer a promising technique to modify the chemical environment of the Yb3+ ions and achieve some of these properties. In this work, three fibers in which the Yb3+ ions are initially encapsulated in CaF2, SrF2, or BaF2 nanoparticles were fabricated using a solution-doping technique, and their laser-cooling properties evaluated experimentally and analyzed. The CaF2 fiber and the SrF2 fiber were successfully cooled at atmospheric pressure when pumped with a continuous-wave laser at the near-optimum wavelength of 1040 nm. The measured maximum temperature change from room temperature was -26.2 mK for the CaF2 fiber at a pump power absorption level of 90 mW/m, and -16.7 mK at 66 mW/m for the SrF2 fiber. The BaF2 fiber did not cool, but it warmed only slightly, indicating that it was not far from cooling. Analysis of the measured dependence of the fiber temperature change on pump power with a model enabled extraction of the fiber's critical quenching concentration and residual absorptive loss due to impurities. Comparison of these values to the values reported for an aluminosilicate fiber and fiber preforms that cooled shows that the CaF2 and SrF2 fibers faired as well as the fiber, and better than the preforms, in terms of quenching, but that they had a higher absorptive loss. This study establishes the significant research potential of nanoparticle-doped fibers in the search for efficient laser-cooling silica hosts.
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| 4. |
- Vigneron, Pierre-Baptiste, et al.
(author)
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Anti-Stokes fluorescence cooling of nanoparticle-doped silica fibers
- 2022
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 47:10, s. 2590-2593
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Journal article (peer-reviewed)abstract
- The first observation of cooling by anti-Stokes pumping in nanoparticle-doped silica fibers is reported. Four Yb-doped fibers fabricated using conventional modified chemical vapor deposition (MCVD) techniques were evaluated, namely, an aluminosilicate fiber and three fibers in which the Yb ions were encapsulated in CaF2, SrF2, or BaF2 nanoparticles. The nanoparticles, which oxidize during preform processing, provide a modified chemical environment for the Yb3+ ions that is beneficial to cooling. When pumped at the near-optimum cooling wavelength of 1040 nm at atmospheric pressure, the fibers experienced a maximum measured temperature drop of 20.5 mK (aluminosilicate fiber), 26.2 mK (CaF2 fiber), and 16.7 mK (SrF2 fiber). The BaF2 fiber did not cool but warmed slightly. The three fibers that cooled had a cooling efficiency comparable to that of the best previously reported Yb-doped silica fiber that cooled. Data analysis shows that this efficiency is explained by the fibers' high critical quenching concentration and low residual absorptive loss (linked to sub-ppm OH contamination). This study demonstrates the large untapped potential of nanoparticle doping in the current search for silicate compositions that produce optimum anti-Stokes cooling.
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| 5. |
- Vigneron, Pierre-Baptiste, et al.
(author)
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Loss-compensated slow-light fiber Bragg grating with 22-km/s group velocity
- 2020
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In: Optics Letters. - 0146-9592 .- 1539-4794. ; 45:11, s. 3179-3182
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Journal article (peer-reviewed)abstract
- This Letter reports the behavior of the slow-light resonances of a strong apodized fiber Bragg grating (FBG) in which the intrinsic loss is compensated for by a small internal gain. The 6.5-mm FBG, written with a femtosecond laser in an Er-doped single-mode fiber, was pumped at similar to 4475 nm just below the lasing threshold to offset most of its intrinsic loss, thereby narrowing its resonances. The fundamental slow-light resonance was measured to have a linewidth of 8.5 fm, or a record group velocity of similar to 22 km/s, and a peak transmission near unity (-0.2 dB). The measured dependencies of the linewidth and peak transmission on pump power agree well with a new model that predicts the transmission spectrum of loss-compensated FBGs in the presence of pump and signal saturation.
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