All Polarization-maintaining Er:Fiber Optical Frequency Comb Based On A Figure-nine Laser And Spectral Transferring For Multi-Target Wavelengths

Optical frequency combs have bridged the gap between optical frequency and ra-dio frequency,due to its accuracy and stability in frequency transferring.With rapid development,optical frequency combs have found a broad range of applications,in-cluding time and frequency metrology,microwave photonics,and spectroscopy.Cav-ity ring-down spectroscopy is the widely used techniques of precision laser frequency spectroscopy,the combination of cavity ring-down spectroscopy and optical frequency combs have determined the positions of ro-vibrational transitions of molecules with sub-kHz accuracy.Optical frequency comb based on a nonlinear polarization rota-tion or semiconductor saturable absorption mirror laser isn't the best choice for cavity ring-down spectroscopy and other applications,because it can't combines the reliabil-ity and low noise.The all polarization-maintaining Er:fiber frequency comb based on a figure-nine laser with both high reliability and low noise,compared with other kinds of combs.The developement of the all polarization-maintaining Er:fiber frequency comb based on a figure-nine laser,and the module of the spectral transferring for multi-target wavelengths,is benificial for improving the efficiency of the comb-linked cavity ring-down spectroscopy.Meanwhile,the long-term frequency stabilization of the figure-nine Er:fiber comb is essential to the long-term stable operation of the space comb.What's more,figure-nine Er:fiber laser is prefered for ultra-fast laser precision machining,due to its high reliability,low costing and self mode-lockingThe main research content and achivements introduced in this thesis are as follows1.An all polarization-maintaining Er:fiber laser is realized with a NALM and a nonreciprocal phase bias.The initiation of mode locking is easily achieved with a 50:50 coupler when pumped at?1 W,and the average output power is about 16 mW when oscillator is pumped at power of 450 mW.The full width at half-maximum(FWHM)of output 1 is about 30 nm,and the corresponding Fourier transform-limited pulse duration is about 84 fs.The repetition rate of the oscillator is about 136 MHz,and the estimated net cavity dispersion is about-0.007 ps 2 at 1550 nm.The output power fluctuation was less than 0.5%.2.To get the fceo,we employed standard f-2f interference method.The signal-to-noise ratio(SNR)at resolution bandwidth(RBW)of 300 kHz is 35 dB which is adequately high for the homemade phase-locking system to stabilize the fceo.Since the frequency instability of OFCs is one of the most important parameters,we measured in-loop frequency stability of fceo and frep.we have succeeded in phase-locking fceo and frep for more than 1 week.The in-loop relative frequency stability of fceo is about 5.56 × 10-18 at 1 second and roll down to 10-20 level at 104 second with a slope of(?).The in-loop relative frequency stability of frep is about 1.8 × 10-12 at 1 second and roll down to 10-15 level at 104 second with a slope of(?),it is basically same as the noise floor of the measurement system.Standard deviations for fceo and frep are estimated to be about 22 mHz,and 67 ?Hz respectively.3.Five application ports are individually optimized for applications with different wavelengths(1064 nm,1083 nm,1380 nm,1637 nm and 1750 nm).In addition,we estimated the energy of per mode at five target wavelength regions.The energy of per mode at the target wavelengths are 220 nW/mode,370 nW/mode,630 nW/mode,320 nW/mode,and 730 nW/mode,respectively.The beat-note between the optical frequency comb and continuous laser exhibits signal-to-noise ratio of at least 30 dB at a resolution bandwidth of 100 kHz.In-loop frequency instabilities of the comb are evaluated to be good enough for measurement of rotation-resolved transitions of molecules below 1 kHz resolution.