Research On Key Technologies Of NPE Mode Locked Fiber Laser And Its Optical Frequency Comb

Femtosecond pulse fiber laser has important applications in scientific research,military,industrial,medical and other fields because of its narrow output pulse width,high peak power,good coherence,compact structure,low cost,maintenance-free and other advantages.In particular,since the realization of optical frequency combs,femtosecond mode-locked fiber lasers have been widely used in the generation of optical frequency combs.Because of its stable comb structure and as a "bridge"between optical frequency and radio frequency,the optical frequency comb has promoted the development of optical frequency measurement,precision spectroscopy and other fields.In recent years,optical frequency combs based on femtosecond mode locked fiber lasers have been produced by direct generation and frequency conversion to meet the needs of different waveband applications.This dissertation focuses on the key technologies of narrow pulse width NPE modelocked fiber lasers and near-infrared and mid-infrared optical frequency combs.The main contents and innovation points include:Firstly,the influence of dispersion distribution in the cavity of an erbium doped fiber laser with NPE mode locked dispersion management on its output pulse width and other characteristics is analyzed by numerical simulation.T The analysis results show that when the negative dispersion optical fiber length behind the laser output end is larger than the front end,it is beneficial for the laser to generate a narrower pulse width.Based on simulation analysis,an NPE mode locked fiber laser with a repetition rate of 209 MHz and a pulse width of 55 fs was designed and developed.The changes of the pulse respiration ratio and the output characteristics of the laser with the addition of near zero dispersion optical fibers were simulated and analyzed.The results show that the introduction of near zero dispersion optical fibers can effectively reduce the repetition rate of the laser and have a small impact on the intracavity pulse respiration ratio.An erbium doped fiber laser with a repetition rate of 100 MHz and a pulse width of 39 fs has been designed and developed.Secondly,a near-infrared optical frequency comb development scheme is proposed.Based on a self-made erbium doped fiber laser with a repetition rate of 209 MHz and a pulse width of 55 fs,a chirped pulse amplification technique and supercontinuum spectrum generation technique were used to generate a octave supercontinuum spectrum with a spectral coverage range of 1070-2390 nm.Based on the f-2f scheme,a carrier envelope offset frequency with a signal-to-noise ratio of 32 dB was extracted.And designed a packaging scheme,integrated packaging to achieve instrumentation.The standard deviations of the measured optical comb repeat frequency and carrier envelope offset after frequency locking are 0.64 mHz and 1.76 mHz respectively at a frequency counter with a l s gating time,and the Allan deviations at a 1000 s sampling time are 8.17×10-14 and 5.58×10-12,respectively。Thirdly,a stable broadband and wide tuning DFG mid infrared optical frequency comb construction scheme is proposed.Using a homemade repetition frequency locked 200 MHz,39 fs erbium doped mode locked fiber laser as a pulse source,using fully polarization-maintaining optical fibers to construct a fiber link to ensure system stability,using self-similar optical fiber amplification,soliton compression,and supercontinuum generation and other technologies,the base frenquency pump pulse with central wavelength of 1.57 μm,pulse width of 38 fs,the average power of 338 mW and the fundamental frequency pump pulse and the center wavelength is 1.85 μm,frequency shift soliton fundamental frequency signal pulse with a bandwidth of 250 nm were obtained.By strictly controlling the spatial overlap and time synchronization of bicolor fundamental frequency pulse,and through the DFG process of GaSe non-linear crystal,under the condition of only adjusting the crystal phase matching supporting role angle and adjustable delay line,the comb can be used in the 7-13 μm continuous tuning in the spectral range.Each tuning band bandwidth is greater than 1 μm,with a bandwidth reaches 2.43 μm at 9.5 μm.A prototype of mid-infrared optical comb in DFG was developed by using a photoelectric separation packaging scheme.The research work on narrow pulse width NPE mode-locked fiber lasers in this paper has guiding significance for the design and development of narrow pulse width fiber lasers with different repetition rates that meet applications such as optical combs.In addition,the design and development technology of near and mid infrared optical combs has important reference value for the development of fiber optic optical frequency combs that meet practical applications such as optical frequency metrology,precision spectral analysis,and multicomponent gas detection.