Research On Key Technologies Of Engineering Ultrastable Laser In Comunication Band And Its Application

Due to high frequency stability,narrow linewidth and low phase noise,the ultrastable lasers was widely used in many fields,such as high resolution spectroscopy,optical atomic clock,gravitational wave detection,low noise microwave source signal generation,optical frequency transmission and so on.At present,the frequency uncertainty and stability of optical atomic clock can reach the order of 10^-19.In order to transfer such high-precision optical frequency signal to other users,the optical frequency transmission via optical fiber is the only way to transfer the optical clock signal.In order to ensure the stability of the optical frequency transfer system,it is necessary to use the ultra-stable laser as the transfer laser source.At present,due to the line-width of commercial communication band laser is only reach 100 Hz,which cannot meet the requirements of high stability and long-distance optical frequency transfer,it is necessary to develop an ultra-stable laser in communication band as the transfer source.To meet the needs of the optical frequency transmission system in the project of the"High precision ground-based time service system",which is taken by the National Time Service Center of the Chinese Academy of Sciences,the engineering research of ultra-stable lasers at communication band laser are carried out.In this dissertation,the key technologies of engineering of the ultra-stable lasers in communication band engineering are studied.The main research results are as follows:First,the two prototypes of ultra-stable laser at 1550nm are developed.Due to there has significant loss on output mirror of optical reference cavity(the fineness of HG₀₀ mode is148000,the coupling efficiency is 11.9%,the residual amplitude noise is greater than is 484000,the coupling efficiency is 11.2%,and the residual amplitude noise is5.6×10^-15@0.1s-100s)。The finesse of the high-order mode of the optical reference cavity is simulated and verified by experiments,and the two results is very consistent.The slope formula of the discrimination signal of the ultra-stable laser is modified and verified by experiments.Through beat frequency comparison,the line-width of two ultra-stable lasers is measured with100 times,the statistical results show that the median line-width is 0.3Hz,the minimum line-width is 0.21Hz,and the frequency stability is less than 1×10^-15@1s-10s,which is very closeSecond,the auto-lock function of the ultra-stable laser is realized,and the locking time is less than 30s.A method of directly locking the ultra-stable laser in the closed-loop condition is proposed,which is developed by combining the analog circuit with the digital circuit.To verify the reliability of the auto-locking ultra-stable laser,it is auto-locked by 157 times,and the success rate of the lock-in is more than 98%.The statistical results show that the median locking time is 16.6 s,and the probability of less than 20 s is more than 86%.Through beat frequency comparison,the line-width of the ultra-stable laser is measured by 1000 times.The statistical results show that the median line-width is 1.1Hz,the minimum line-width is 0.8Hz.The frequency stability of this ultra-stable laser is less than 3×10^-15 within 100s.Third,a miniaturized and transportable ultra-stable laser at 1550nm based on a 5-cm-long optical reference cavity has been developed.To reduce the vibration sensitivity of the optical reference cavity,the optical reference cavity structure is simulated by the finite element software,and the vibration sensitivity is less than 1×10^-11/g after the optimizing.The optical part and the vacuum part of the ultra-stable laser is integrated designed,and the total volume and the mass is460mm×380mm×280mm and 30kg,respectively.Through the preliminary transportable test,the rang of anti-vibration acceleration is more than±1g,which basically meets the conditions of highway transport.The performance of the ultra-stable laser after testing is tested by comparing with another one,the results show that the line-width of 1.5Hz and the frequency stability of lessForth,the ultra-stable laser is applied in the optical frequency transmission via fiber.Using laser source with line-width of 0.3Hz and 50Hz as transmission light source,the influence of laser source on optical fiber frequency transmission with 112km urban optical fiber link is analyzed.When the 0.3Hz laser source is used as the transmission source,the transfer stability is about 2 times higher than that of the 50Hz laser source.At the same time,the long-distance transmission of strontium atomic clock signal is completed via 224km optical fiber link.Finally,the main contents of this dissertation are summarized and prospected.The next step is to systematic test the engineering prototype of the ultra-stable laser system,so that it can meet the conditions of highway transportation.Meanwhile,we will further improve the function of the circuit part.