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Torsional oscillator, NEMS, Dimpled tapered fibre, Optomechanics

Kim, Paul H.

Supervisor and department: John P. Davis Department of Physics

Examining committee member and department: Hegmann, Frank Department of Physics Meldrum, Al Department of Physics LeBlanc, Lindsay J. Department of Physics Davis, John P. Department of Physics

Department: Department of Physics

Specialization:

Date accepted: 2014-05-08T14:11:25Z

Graduation date: 2014-11

Degree: Master of Science

Degree level: Master's

Abstract: Torsional oscillators are well known for their extensive applications ranging from measuring gravity to detecting angular momentum of light. When these torsional resonators scale down, through advanced nanofabrication techniques, the applications extend to measuring quantum effects such as the super fluidity in helium and Casimir forces. The benefits of torsional resonators will only increase with smaller structures, provided that they are supplied with a sensitive detection mechanism. The popular choice of interferometric scheme, for example, does not scale down well with nanoscale on-chip devices and requires a separate detection platform.Fortunately, there have been recent successes in on-chip cavity optomechanics where the mechanics can be sensitively measured through a high quality optical resonator. By increasing the coupling between the mechanical oscillator and the optical cavity, mechanical detection can be highly enhanced while the device is miniaturized. I have implemented, for the first time, an optomechanical platform using an optical microdisk evanescently coupled to torsional oscillators to demonstrate high torque sensitivities. The results have shown that optomechanics is highly desirable for nanoscale torsion devices opening doors for vast applications: we have achieved angular displacement sensitivity of 4 nrad per root-Hz, displacement sensitivity of 7 fm per root-Hz, and torque sensitivity of 0.8 zNm per root-Hz.To obtain high-quality silicon-on-insulator microdisks with gaps in the order of ~100 nm, we have chosen a commercial foundry to fabricate our sensitive devices which uses state-of-the-art photolithography procedures. The benefit of deep UV optical lithography is that many chips on a single 8-inch wafer are available that are cost-efficient over the electron beam lithography method. This thesis highlights the custom made optomechanical apparatus using a dimpled tapered fibre to sensitively probe commercially fabricated torsional devices, demonstrating the compatibility of optomechanics to nanoscale torsional platforms.

Language: English

DOI: doi:10.7939-R3348GQ5T

Rights: Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.





Autor: Kim, Paul H.

Fuente: https://era.library.ualberta.ca/


Introducción



Nanoscale Torsional Optomechanics by Paul Ho-Choong Kim A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science Department of Physics University of Alberta c Paul Ho-Choong Kim, 2014 Abstract Torsional oscillators are well known for their extensive applications ranging from measuring gravity to detecting angular momentum of light.
When these torsional resonators scale down, through advanced nanofabrication techniques, the applications extend to measuring quantum effects such as the superfluidity in 4 He film and Casimir forces.
The benefits of torsional resonators will only increase with smaller structures, provided that they are supplied with a sensitive detection mechanism.
The popular choice of interferometric scheme, for example, does not scale down well with nanoscale on-chip devices and requires a separate detection platform. Fortunately, there have been recent successes in on-chip cavity optomechanics where the mechanics can be sensitively measured through a high quality optical resonator.
By increasing the coupling between the mechanical oscillator and the optical cavity, mechanical detection can be highly enhanced while the device is miniaturized.
I have implemented, for the first time, an optomechanical platform using an optical microdisk evanescently coupled to torsional oscillators to demonstrate high torque sensitivities.
The results have shown that optomechanics is highly desirable for nanoscale torsion devices opening doors for vast ap√ plications: we have achieved angular displacement sensitivity of 4 nrad- Hz, displacement √ √ sensitivity of 7 fm- Hz, and torque sensitivity of 0.8 zNm- Hz. To obtain high-quality silicon-on-insulator microdisks with gaps in the order of ∼ 100 nm, we have chosen a commercial foundry to fabricate our sensitive devices which uses stateof-the-art photolithography procedures.
The benefit of deep UV optical lithography is that ii many chips on a single 8-inch waf...





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