Optical Loss Measurement Of Optical Components With CW Fiber Laser Based Cavity Ring-down Technique

With the demand for high-precision and high-performance optical devices in the fields of modern optical communication technology,optical sensing and optical imaging,these applications require the use of low-loss optical components to ensure system performance and efficiency.The loss of optical components is one of the important factors affecting system performance,so it needs to be accurately measured and evaluated.Optical cavity ring down technology has ultra-high measurement accuracy and is widely used in the measurement of parameters such as loss,reflection and transmission of optical components.Therefore,this topic uses optical cavity ring down technology to measure the loss of optical components.The main work has the following aspects:(1)A cavity decay system was built based on the theory of cavity decay.Compared with semiconductor lasers and gas lasers,fiber lasers were selected as the light source for this system according to project requirements.Finally,loss measurement of optical components in the 780 nm wavelength band was achieved,and the standard deviation of the sample loss measurement was only a few ppm.(2)Based on the theory of time attenuation,the measurement principle of optical cavity ring down technology is deeply analyzed,and the expressions for measuring optical element loss,reflection and other parameters are derived.A variety of factors affecting the measurement accuracy are summarized,including the influence of cavity length imbalance,environmental interference and light source stability.In addition,the mode matching between the laser and the resonator is discussed in detail,which is of guiding significance for the construction of the experimental system.Through the research of this paper,we can better understand the measurement principle of optical cavity ring-down technology,and at the same time,we can also understand the working principle of the resonant cavity,which provides a useful reference for further research.(3)This paper studies the problem of air absorption loss when measuring low-loss optical components,and eliminates the influence of air absorption by changing the cavity length.In addition,this paper also discusses the influence of laser excitation of different modes in the resonant cavity on the measurement results,and proposes a new way of tuning the cavity,which is adjusted by simultaneously detecting the signal size and the shape of the transmitted spot,so that the initial cavity only has the basement membrane excitation,the stability and repeatability of the system are better.At the same time,this paper measured the loss of the sample at different positions in the cavity,and found that the measured loss values in different positions are inconsistent,and it is speculated that the composite cavity has affected the measurement results.Finally,this paper completes the instrumentation of the experimental system,including hardware selection,software design and overall debugging.The measurement results show that the instrument has good measurement accuracy and stability.