#### Optical control and sensing of high-quality nonlinear micromechanical resonance and macroscopic displacement = 고품질 비선형 마이크로 역학 공진과 거시적 변위의 광학적 제어 및 측정

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Light can be used for high-precision control and measurement of the properties of physical systems through light-matter interactions, as its intensity, polarization, frequency, and phase can be adjusted and detected with high accuracy. In this dissertation, I present two experimental studies in the context of optical control and sensing. First, I investigate the nonlinear coupling of mechanical modes of a high-quality micromechanical resonator by using optical means. A mechanical mode of a 30-nm-thick 250×250-$\mu$ $m^2$-wide silicon nitride clamped square membrane is excited by intensity-modulated laser light via radiation pressure. Energy transfer from the optically driven mode to others is then observed by spatially-resolved interferometric measurements of the vibration profiles. In sharp contrast to the one-dimensional resonators such as nanobeams and microcantilevers exclusively used in many previous works, the clamped square membrane features almost frequency-commensurate relations among many mechanical modes. This unique frequency relation allows for the high-efficiency nonlinear coupling of multiple mechanical modes – 3 modes with pN-scale optical forces and 5 modes with piezoelectric ones in my case – via mechanical third-harmonic generation and cascaded four-wave mixing arising from third-order mechanical nonlinearity. These results pave a way towards the implementation of a small-footprint massive optomechanical array that may yield enhanced optomechanical coupling. Second, I demonstrate the optical detection of macroscopic displacements much larger than the optical wavelength by employing a combination of a free-space Fabry-Pérot optical cavity and a wedge prism pair. This scheme permits high-sensitivity measurement of large displacements up to 7 mm without $2\pi$ ambiguity, which surpasses the measurable range of conventional interferometers by a factor of 9,000. Moreover, a large-capacity high-resolution optomechanical mass sensor is developed by combining the cavity-based displacement detector and a load cell. By incorporating the null-method-based scheme of mass measurement, I achieve a resolution higher than 5000:1, a capacity beyond 1 kg, and excellent linearity.
Kang, Myeong Sooresearcher강명수researcher
Description
한국과학기술원 :물리학과,
Publisher
한국과학기술원
Issue Date
2020
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 물리학과, 2020.2,[viii, 70 p. :]

Keywords

High-quality micromechanical resonator▼a2-dimensional square micro/nano-membrane▼aThird-order mechanical nonlinearity▼aDuffing nonlinearity▼aCascaded nonlinear mechanical four-wave mixing▼aHigh-finesse free-space Fabry-Pérot optical cavity▼aOptomechanical system▼aOptical-cavity-based mass sensor; 고품질 마이크로 역학 공진기▼a2차원 정사각형 마이크로/나노 멤브레인▼a삼차 역학 비선형성▼a더핑 비선형성▼a계단식 비선형 역학적 4파 혼합▼a고품질 자유공간 파브리-페로 광공진기▼a광역학 시스템▼a광공진기 기반 질량 센서

URI
http://hdl.handle.net/10203/283596