Nanoscale Torsional Optomechanics

• Author / Creator

  Kim, Paul H.

• 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.

• Subjects / Keywords

  • Dimpled tapered fibre
  • NEMS
  • Optomechanics
  • Torsional oscillator

• Graduation date

  Fall 2014

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3348GQ5T

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.