Amplification And Frequency Stabilization Of A Yb-doped Fiber Laser

Optical frequency standard mainly consists of clock laser,ion trap system and optical frequency comb.As our research group is setting up an Al⁺optical clock,my major task is to realize an optical frequency comb system based on former colleagues'works.Optical frequency comb,which is the bridge of radio frequency and optical frequency,can directly measure the laser frequency.An stable optical frequency comb is generated if both the carrier envelope offset frequency f_o and the repetition frequency f_r of a femtosecond fiber laser are locked.My major work is about the amplification a Yb-doped fiber laser,the generation and locking of a stable,high signal to noise ratio,narrow linewidth f_o signal and the noise analysis of our optical frequency comb system.The detailed work in this thesis mainly includes:Set up a fiber amplifier using a double cladding Yb-doped fiber.A 260 mW laser seed is amplified to 2.37 W,meanwhile the laser pulse duration changes from 52 fs to 95 fs.We also find a proper way to solve the striped optical spectrum problem.A f_o signal is generated through f-2f method with a tapered photonic crystal fiber.We estimate the factors that could influence the SNR of f_o signal and improve it from 35 dB to 49 dB,at the same time the linewidth is narrowed down from 1.9 MHz to 650 kHz.After locking,its peak to peak frequency jitter range is about 60 mHz and its Allan deviation@1s reaches 3.2×10^-10.The other parameter f_r signal is about 400?Hz fluctuation and the Allan deviation@1s is 3.4×10^-13.In order to estimate the noise level of our optical frequency comb system,we distribute an ultra-stable laser from another lab through a single mode polarization maintaining fiber.We detect and compare the performance of the beat signal between the CW laser and the optical frequency comb when the f_r of optical frequency comb system is free running or locked.The comb's frequency stability is 5.7×10^-11@1s since the f_o signal is not locked.Besides,we amplify the CW laser and estimate the noise induced from this amplification.