| 1. |
- Aktas, Ozan, et al.
(författare)
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Interfacing telecom fibers and silicon core fibers with nano-spikes for in-fiber silicon devices
- 2018
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Ingår i: 2018 Optical Fiber Communications Conference and Exposition, OFC 2018 - Proceedings. - : Institute of Electrical and Electronics Engineers Inc. (IEEE). ; , s. 1-3
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Konferensbidrag (refereegranskat)abstract
- We report fabrication of tapered silicon core fibers with nano-spikes enabling efficient optical coupling into the core, as well as their seamless integration with single mode fibers. A proof-of-concept integrated in-fiber silicon device is demonstrated.
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| 2. |
- Frey, B. N., et al.
(författare)
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Cooling Yb-Doped Silica Fibers and Fiber Lasers with Anti-Stokes Pumping
- 2023
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. - 9781510659797
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Konferensbidrag (refereegranskat)abstract
- Optical cooling in Yb-doped silica fibers using anti-Stokes fluorescence has become a subject of great interest in the fiber laser community. This paper provides an update on the development of silica fibers designed specifically to enhance their cooling properties. This growing list includes a new, nearly single-mode fiber with a borophosphosilicate core that produced –65 mK of cooling with only 260 mW of 1040-nm pump power. The silica compositions that have now been successfully cooled at atmospheric pressure by anti-Stokes fluorescence by our team include aluminosilicate, aluminofluorosilicate, borophosphosilicate, and aluminosilicate doped with one of three different alkali-earth nanoparticles (Ba, Sr, and Ca). By fitting the measured temperature dependence of the cooled fiber on pump power, two key parameters that control the degree of cooling are inferred, namely the critical quenching concentration and the absorptive loss due to impurities. The inferred values compiled for the fibers that cooled indicate that the extracted heat is highest when the Yb concentration is 2 wt.% or more (to maximize heat extraction), the Al concentration is ~0.8 wt.% or greater (to reduce quenching), and the absorptive loss is below approximately 15 dB/km, and ideally below 5 dB/km (to minimize heating due to pump absorption). Only two of the reported fibers, an LaF3-doped and an LuF3-doped nanoparticle fiber, did not cool, because their Yb and Al concentrations were not sufficiently high. This analysis shows that through careful composition control (especially the Al and Yb concentrations) and minimization of the OH contamination, a new generation of Yb-doped silica fibers is emerging with higher Yb concentrations, greater resistance to quenching, and lower residual loss than commercial Yb-doped fibers. They can be expected to have a significant impact not only on optically cooled devices but also on a much broader range of fiber lasers and amplifiers.
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| 3. |
- Knall, J., et al.
(författare)
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Radiation-balanced silica fiber laser
- 2021
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Ingår i: Optica. - 2334-2536. ; 8:6, s. 830-833
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Tidskriftsartikel (refereegranskat)abstract
- In optically pumped lasers, heat generated by the quantum defect causes detrimental fluctuations in the output mode, frequency, and power. Common heat-mitigation techniques use bulky mechanical coolers that introduce vibrations, leading to laser frequency and amplitude noise. Here, we present a radiation-balanced fiber laser, optically cooled by anti-Stokes fluorescence (ASF). The gain medium is a silica fiber with a 21-µm-diameter core doped with 2.06 wt. % Yb3+ and co-doped with Al2O3 and F- to reduce concentration quenching. The laser was core-pumped at 1040 nm to create both gain at 1065 nm and ASF cooling at atmospheric pressure. We demonstrate a maximum output power of 114 mW with a slope efficiency of 41% while maintaining near-zero average temperature change. This result could enable the development of fiber lasers with unprecedented coherence and stability.
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| 4. |
- Ren, H., et al.
(författare)
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Low-loss silicon core fibre platform for mid-infrared nonlinear photonics
- 2019
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Ingår i: Light. - : Springer Nature. - 2095-5545 .- 2047-7538. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Broadband mid-infrared light sources are highly desired for wide-ranging applications that span free-space communications to spectroscopy. In recent years, silicon has attracted great interest as a platform for nonlinear optical wavelength conversion in this region, owing to its low losses (linear and nonlinear) and high stability. However, most research in this area has made use of small core waveguides fabricated from silicon-on-insulator platforms, which suffer from high absorption losses of the use of silica cladding, limiting their ability to generate light beyond 3 µm. Here, we design and demonstrate a compact silicon core, silica-clad waveguide platform that has low losses across the entire silicon transparency window. The waveguides are fabricated from a silicon core fibre that is tapered to engineer mode properties to ensure efficient nonlinear propagation in the core with minimal interaction of the mid-infrared light with the cladding. These waveguides exhibit many of the benefits of fibre platforms, such as a high coupling efficiency and power handling capability, allowing for the generation of mid-infrared supercontinuum spectra with high brightness and coherence spanning almost two octaves (1.6–5.3 µm).
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| 5. |
- Song, S., et al.
(författare)
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Crystalline GaSb-core optical fibers with room-temperature photoluminescence
- 2018
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Ingår i: Optical Materials Express. - : OPTICAL SOC AMER. - 2159-3930 .- 2159-3930. ; 8:6, s. 1435-1440
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Tidskriftsartikel (refereegranskat)abstract
- Glass-clad, GaSb-core fibers were drawn and subsequently laser annealed. The as-drawn fibers were found to be polycrystalline, possess Sb inclusions, and have oxide contamination concentrations of less than 3 at%. Melting and resolidifying regions in the cores using 10.6 mu m CO2 laser radiation yielded single crystalline zones with enhanced photoluminescence (PL), including the first observation of strong room temperature PL from a crystalline core fiber. Annealed fibers show low values of tensile strain and a bandgap close to that of bulk GaSb.
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| 6. |
- Ballato, J., et al.
(författare)
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Material approaches to thermal management in advanced fiber lasers and amplifiers
- 2023
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Ingår i: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. - 9781510659797
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Konferensbidrag (refereegranskat)abstract
- For as long as light and matter have partnered, impurities have played a role in optical system performance. This remains generally true for photonic heat engines and especially the case for optical refrigeration. Building on the history of light and glass, including the materials development of low loss telecom fibers, this paper briefly discusses the sources of heat generation in materials and all-material means for their reduction. Particularly attention will be paid to active optical fibers and connect thermal management to parasitic optical nonlinearities, both critical to high and low power amplifier and laser systems.
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| 7. |
- Balliu, Enkeleda, PhD student, et al.
(författare)
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High-efficiency radiation-balanced Yb-doped silica fiber laser with 200-mW output
- 2024
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Ingår i: Optics Letters. - : Optica Publishing Group. - 0146-9592 .- 1539-4794. ; 49:8, s. 2021-2024
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Tidskriftsartikel (refereegranskat)abstract
- The focus of this study was the development of a second generation of fiber lasers internally cooled by anti-Stokes fluorescence. The laser consisted of a length of a single-mode fiber spliced to fiber Bragg gratings to form the optical resonator. The fiber was single-moded at the pump (1040 nm) and signal (1064 nm) wavelengths. Its core was heavily doped with Yb, in the initial form of CaF2 nanoparticles, and co-doped with Al to reduce quenching and improve the cooling efficiency. After optimizing the fiber length (4.1 m) and output-coupler reflectivity (3.3%), the fiber laser exhibited a threshold of 160 mW, an optical efficiency of 56.8%, and a radiation-balanced output power (no net heat generation) of 192 mW. On all three metrics, this performance is significantly better than the only previously reported radiation-balanced fiber laser, which is even more meaningful given that the small size of the single-mode fiber core (7.8-µm diameter). At the maximum output power (∼2 W), the average fiber temperature was still barely above room temperature (428 mK). This work demonstrates that with anti-Stokes pumping, it is possible to induce significant gain and energy storage in a small-core Yb-doped fiber while keeping the fiber cool.
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| 8. |
- Balliu, Enkeleda, PhD student, et al.
(författare)
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Improved Closed-Loop Slow-Light Temperature Sensor With Millidegree Resolution for Laser Cooling
- 2023
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Ingår i: Proceedings - 28th International Conference on Optical Fiber Sensors, OFS 2023. - : Optica Publishing Group.
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Konferensbidrag (refereegranskat)abstract
- For applications such as laser cooling of doped fibers, where it is critical to measure accurately the temperature of a cooled fiber that is very close to room temperature, it is paramount to develop a reliable, very short (mm) fiber temperature sensor with millikelvin resolution and very little drift. We report a second generation of a unique slow-light fiber Bragg grating (FBG) temperature sensor that meets these stringent requirements. Experiments and modeling establish that its temperature response depends only on well-known material constants of the silica FBG and the response of the probe laser's wavelength controller. The response is independent of the linewidth of the slow-light resonance, hence different FBGs and/or resonances have the exact same response. Examples of measured cooling in optically pumped Yb-doped fibers show that more reliable thermal contact with the cooled fiber is obtained by wrapping the FBG and the cooled fiber.
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| 9. |
- Gibson, Ursula J., et al.
(författare)
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Future of semiconductor-core optical fibers
- 2018
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- Semiconductor-core optical fibers hold promise for long wavelength transmission systems as well as for nonlinear and active optoelectronic devices. This talk includes a status report on fiber properties and a prospectus of some future directions.
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| 10. |
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