Weak Coupling Strength Measurement between Two Optical Microcavities near a High-order Exceptional Point
Mode-splitting techniques are widely used in optical sensing to measure target parameters.However,the minimum detectable value of the target parameter is limited by both the total loss of the system and the functional dependence between mode-splitting and the target parameter.This means that there is a limit to how small the target parameter can be determined using this method.One way to over-come this limitation is to utilize exceptional points in non-Hermitian systems.Exceptional points are special parameter points where eigen-values and eigenstates merge.By adjusting the system to operate at an exceptional point,it is possible to reduce the lower threshold for detecting the object.In essence,exceptional points allow a more sensitive measurement of the target parameter.This is because the coales-cence of eigenvalues and eigenstates at an exceptional point leads to a greater sensitivity of the system to changes in the target parameter.As a result,the minimum detectable value of the target parameter can be reduced,allowing for more precise measurements.This paper explores the field of whispering-gallery-mode optical microcavities and introduces a method for measuring the weak coupling strength between two microcavities.By manipulating the number of additional optical microcavities involved,we can precisely control the order of the exceptional points.Whispering-gallery-mode optical microcavities can be used for various appli-cations such as high-precision sensors,filters,and lasers.In order to study the interaction between two WGM microcavities,it is crucial to measure the strength of their coupling strength.However,measuring this weak coupling strength is a challenging task due to the small size of the microcavities and the complex nature of their interactions.The proposed method overcomes these challenges by exploiting the properties of high-order exceptional points.To manipulate the order of the exceptional points,we introduce an additional set of optical microcavities into the system.These auxiliary cavities interact with the primary WGM microcavities through evanescent fields,leading to a complex network of coupled modes.By controlling the number of auxiliary cavities,we can selectively tune the system towards different orders of exceptional points.Our findings reveal that when n optical microcavities are incorporated into the system,an nth-order exceptional point can be real-ized.This is a significant development as it allows for greater flexibility in designing and controlling these systems.Furthermore,as the number of microcavities increases,the lowest threshold for detecting the coupling strength between two optical microcavi-ties decreases.This could pave the way for more sensitive and accurate measurements in the future.This paper presents a novel approach to measuring the weak coupling strength between whispering-gallery-mode optical micro-cavities by exploiting high-order exceptional points.By fine-tuning the system near these singularities and manipulating the num-ber of auxiliary cavities,we can achieve precise control over the coupling dynamics and gain valuable insights into the behavior of whispering-gallery-mode microcavity systems.This research is important for improving the performance of optical sensors as it allows us to measure much weaker coupling strengths.By further optimizing the system and exploring other types of optical microcavities,we expect to achieve higher measurement accuracy and a wider range of applications in the future.
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