Double-Clad Erbium-Ytterbium Co-Doped Fiber Laser Colin Diehl & Connor Pogue

Double-Clad Erbium-Ytterbium Co-Doped Fiber Laser

• Colin Diehl & Connor Pogue

Fiber Lasers

• Advantages

• Compact
• Reliable
• High optical quality
• High output power
• Convenient

Single-Mode Fiber

• Single-Mode Fiber

• 6 µm core / 125 µm cladding

• High Beam Quality

• Low Propagation Loss

• Lower Power Pumping

• Expensive Pumping

Laser light propagates in single-mode core

• Laser light propagates in single-mode core

• Pump light propagates in inner cladding

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

With Two Internal Cavities

With Three Internal Cavities

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