| Whispering-gallery-mode(WGM)optical microresonator is an optical device with the small mode volume and ultra-high quality factor.It has been widely used in many different fields,including sensing,cavity quantum electrodynamics,micro laser and cavity optomechanics.This thesis mainly studies cavity ring-up spectroscopy(CRUS)of WGM microresonator both in theory and experiment.CRUS is a new spectrum proposed in 2015.The time of measuring CRUS is very short,so it can be applied to nanosecond ultrafast sensing.The research content of this thesis includes three parts.Firstly,we extend the basic theory of CRUS.In our theory of CRUS,the intensity of a monochromatic laser changes from a nonzero constant value to another non-zero constant value within a very short time.This change of the laser intensity includes changing from a smaller value to a larger value,and from a larger value to a smaller value.Therefore,when the laser intensity changes periodically between a smaller value and a larger value,according to our theory,two CURS can be obtained in one period.Compared with the original CRUS,our method doubles the sampling rate without any additional cost.Secondly,we experimentally measure CRUS of the WGM microresonator,and verify the theoretical results.In the WGM system with a microsphere,the fiber taper is used to couple the laser with periodic intensity into the microsphere.We experimentally measure the CRUS without modal coupling and with the modal coupling.The influence of the changing of the laser intensity on CRUS is observed experimentally.Finally,we experimentally study the application of CRUS in measuring rapidly changing temperature.In the experiment,a highintensity laser is input into a microsphere,which will absorb part of the laser energy and change its temperature,i.e.,thermal effect.Using the technique of CRUS,we measure the change of the temperature of the microsphere with time. |
