Phase Characterization And Sensing Techniques Based On Weak Measurement In Frequency Domain

Weak measurement technique in frequency domain is a method of constructing weak interaction in frequency domain and using weak value amplification technique to detect small physical quantities.It utilizes the relative time delay or phase delay between the vertical and horizontal components of a light beam as a carrier to achieve high-precision detection of small physical quantities.Compared with weak measurement schemes based on spatial domains,the frequency domain weak measurement technique has higher measurement precision and sensitivity.However,there are still challenges in demonstrating the precision advantage of the frequency domain weak measurement technique in practical applications for characterizing small parameters.In order to address this issue,this dissertation focuses on the study of frequency domain weak measurement techniques and has achieved the following research results in characterizing ultra-small physical quantities using the frequency of classical light as the measurement pointer:1.Chirality has a significant impact on the biological function and pharmacological effects of molecules.However,the high cost and long reaction time of traditional chiral sensing techniques have become urgent issues that need to be addressed.In this work,a novel frequency-domain optical differential detector is proposed,which detects changes in the optical signal induced by chirality-induced optical rotation through weak measurement,achieving real-time high-precision chiral sensing.For example,in the case of a sample of proline,the highest theoretical accuracy of concentration change measured when a chiral solution is introduced and the polarization angle is rotated is 6.25 × 10-6 g/mL.Through experiments,the feasibility of the frequency-domain bias differential detector applied to chiral sensing has been demonstrated,and a combination of optical simulation and sensing technology is provided as an effective approach for high-precision sensing and detection.2.In quantum weak measurements,weak values are quantities related to the pointer displacement of the measuring device,which is typically determined by pre-and post-selecting states.For traditional weak measurements,a single weak value model has already provided good solutions for precise time delay measurement,but this model has certain limitations on the spectral width of the input source.To further improve measurement accuracy,a broadband light source is required.It can be found that due to the occurrence of post-selected state correction,a single weak value model is no longer valid.In this chapter,a multiple weak value model is established by introducing post-selected state correction into time delay estimation.For a broadband light source with a 50 nm spectral width,the multiple weak value scheme enables us to achieve a high resolution of 1.6 × 10-4 as.The multiple weak value amplification scheme proposed in this dissertation has important implications for further improving the measurement accuracy of existing experiments,and maintains important applications in various fields involving precise time delay measurement in the future.3.Accurate measurement of thin film thickness is critical for the study of thin film materials and the development of thin film devices.Here,a unique application of weak measurement is proposed for sub-nanometer resolution thickness characterization.In this scheme,frequency spectrum shift is used as the measurement probe,and weak interaction provided by non-uniform thickness with small time delay is utilized for characterization.As the pointer related to weak value amplification is highly sensitive to time delay,the proposed characterization scheme can achieve an ultra-high measurement resolution of 5 × 10-19 s.This method can achieve a thickness detection accuracy of 0.1 nm,which is significantly improved compared to traditional thin film thickness measurement techniques.The idea proposed in this study may provide support for precision enhancement in advanced material sensing and microfabrication.4.The detection of tiny birefringence is an important and challenging problem in optical research and applications,and weak value amplification has been widely used in weak measurements for accurate estimation of time delay.In this chapter,it is demonstrated that linear amplification in weak measurements has the potential to surpass standard weak value amplification and can be applied to characterization of ultra-small parameters.This approach utilizes the higher measurement precision in linear amplification,enabling the scheme to measure stress-induced birefringence at a high resolution of 5 × 10-10.Compared to existing methods,weak measurement-based birefringence detection offers an improvement in precision by two orders of magnitude.The proposed weak value amplification scheme has important applications in various fields involving precise measurements of time delay or birefringence.