Orbital Angular Momentum-enhanced Measurement Of Rotation Vibration Using A Sagnac Interferometer

Laser has been a powerful tool for optical measurement since its discovery.Gaussian mode laser has been well investigated and understood by the scientific researchers.Now,they are more interested in high-order laser modes,for example,orbital angular momentum(OAM)-carrying mode.In comparison to the fundamental Gaussian laser mode,such high-order laser modes provide unique advantages in optical measurements,which could lead an innovation in the field of precision measurement.Especially,the vortex wave-front of an OAM mode makes it feasible to measure a rotation signal or to perform the micromanipulation.Because the modes with different indices are orthogonal,OAM modes can significantly extend the signal channels for classical and quantum communication.Rotation measurement based on OAM modes is one important topic in recent years.One can utilize the unique vortex phase distribution on the cross section of an OAM mode or apply the rotational Doppler effect to measure a rotation.In addition,researchers are making efforts to enhance the signal-to-noise ratio of measurement by using improved detection method.This thesis mainly focuses on an OAM-enhanced measurement of rotation vibration in low frequency by using a Sagnac interferometer.The details are listed as follows:1.We built a Sagnac interferometer for OAM modes.The rotation signal is introduced by a Dove prism.The signal amplitude will be doubled in comparison to the case using an M-Z interferometer.We experimentally measured the static rotation angles of the Dove prism when inputting different OAM lights.The results proved a stable experimental system.2.We used a PZT to drive the Dove prism and measured the vibration signal by using the OAM-based Sagnac interferometer.According to frequency response curve of the system,we chose the response peak as input signal frequency.The experimental results presented a clearly-enhanced rotation signal.3.By inputting different OAM modes to measure the rotation signal,we found that the amplitude of the signal was positively correlated to the mode index.Obviously,one can input higher-order OAM mode to further enhance the signal.Since the noise in low frequency can be considered as a constant under a short measurement time,the SNR of the measurement was also enhanced.