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Double-Clad Erbium-Ytterbium Co-Doped Fiber Laser. Colin Diehl & Connor Pogue. Advantages Compact Reliable High optical quality High output power Convenient. Applications Telecommunications Materials Processing Medicine Directed Energy Weapons. Fiber Lasers.
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Double-Clad Erbium-Ytterbium Co-Doped Fiber Laser Colin Diehl & Connor Pogue
Advantages Compact Reliable High optical quality High output power Convenient Applications Telecommunications Materials Processing Medicine Directed Energy Weapons Fiber Lasers Active fiber doped with rare-earth elements pumped by a laser diode
Single-Mode Fiber 6 µm core / 125 µm cladding High Beam Quality Low Propagation Loss Lower Power Pumping Expensive Pumping Multimode Fiber 50 µm core / 125 µm cladding Higher Power Pumping Inexpensive Pumping Poor Beam Quality High Propagation Loss
Double-Clad Fiber Laser light propagates in single-mode core Pump light propagates in inner cladding
RP Fiber Power • Simulated fiber ring laser using SM-EYDF-6/125-HE fiber to optimize active fiber length • Simulated with uniform pump intensity profile
Implementing Single Longitudinal Mode • Multiple longitudinal modes due to long cavity • ~ 270,000 modes without FBG • ~ 430 modes with FBG • Applied 10 mm Fabry-Perot etalon into cavity • Aligned for 75% transmission • Limited to a few cavity modes • Reduced output power from 1.1 W to 250 mW
Multi-Ring Cavity • Small ring cavities within larger ring cavity • Effective FSR equal to least common multiple of FSR of each cavity • Polarization must match when cavities combine • Free space polarizer with λ/2 plate in fiber bench • Power reduced from 800 mW to 250 mW • In-fiber polarizer with polarization controller
Determining Single Longitudinal Mode • Fabry-Perot Cavity • Periodic single peak signal • Self-Heterodyne Linewidth Measurement • Narrow linewidth
Single Cavity Laser • 900 mW output • FWHM = 0.1 nm = 12.5 GHz • 7.63 mm coherence length
With One Internal Cavity • 351 mW output • FWHM = 1.92 fm = 240 kHz • 398 m coherence length
With Two Internal Cavities • 383 mW output • FWHM = 385 am = 48 kHz • 1.99 km coherence length
With Three Internal Cavities • 302 mW output • FWHM = 88.2 am = 11 kHz • 8.68 km coherence length
Conclusion • Implemented single longitudinal mode operation through multi-ring cavity design • Constructed self-heterodyne interferometer to measure linewidth with resolution of ~10 kHz • Constructed single-mode fiber laser delivering 302 mW at 1550 nm with linewidth of 88.2 am