Modeling and Experimental Verification of Longitudinal Modes in Distributed Bragg Reflector Fiber Lasers
NAVAL RESEARCH LAB WASHINGTON DC WASHINGTON United States
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Little, if any, experimental data exists that explores how different design characteristics affect the number of longitudinal modes in extended cavity fiber lasers. To help facilitate the design of distributed Bragg reflector DBR lasers, a numerical model was used to synthesize their response to various design modifications such as grating reflectivity and bandwidth. Lasers were then fabricated, characterized and compared to the computer model. Experiments were also conducted to determine how the longitudinal mode structure changed depending on the amount of gain available in the laser cavity and where the gain medium was placed within the cavity. These experiments determined the optimum combination of a fiber Bragg gratings FBG reflectivitybandwidth and gain necessary to produce a stable DBR fiber laser. Experiments were then conducted to determine the spectral offset through grating strain needed to achieve single longitudinal mode SLM lasing in DBR fiber lasers under a variety of conditions. Simulations were used to confirm and calculate the influence of the FBG coupling strength and length, strain, cavity length, and laser threshold. Analytical expressions using these parameters were derived and used to verify experimental data and predict the performance of subsequent laser designs.
- Fiber Optics and Integrated Optics
- Lasers and Masers