double-clad erbium-ytterbium co-doped fiber laser colin diehl & connor pogue
TRANSCRIPT
Double-Clad Erbium-Ytterbium Co-Doped Fiber Laser
Colin Diehl & Connor Pogue
Fiber Lasers
Advantages• Compact• Reliable• High optical quality• High output power• Convenient
Applications• Telecommunications• Materials Processing• Medicine• Directed Energy Weapons
Active fiber doped with rare-earth elements pumped by a laser diode
Single-Mode Fiber6 µm core / 125 µm cladding
+ High Beam Quality+ Low Propagation Loss- Lower Power Pumping- Expensive Pumping
Multimode Fiber50 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
Erbium-Ytterbium Co-Doped Fiber
Output Power
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
RP Fiber Power: Output Power
RP: Power vs. Position
RP: Active Fiber Length
RP: Power vs. Position
RP: Output Power with 975 nm Pump
RP: Power vs. Position with 975 nm Pump
RP: Active Fiber Length with 975 nm Pump
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
Self-Heterodyne Linewidth Measurement
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
Multi-Ring Cavity Power
Linewidth
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