Page 1 |
Save page Remove page | Previous | 1 of 202 | Next |
|
small (250x250 max)
medium (500x500 max)
Large (1000x1000 max)
Extra Large
large ( > 500x500)
Full Resolution
All (PDF)
|
This page
All
|
WHISPERING GALLERY MODE RESONATORS FOR FREQUENCY
METROLOGY APPLICATIONS
by
Lukas Baumgartel
A Dissertation Presented to the
FACULTY OF THE USC GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
DOCTOR OF PHILOSOPHY
(PHYSICS)
December 2013
Copyright 2013 Lukas Baumgartel
Object Description
| Title | Whispering gallery mode resonators for frequency metrology applications |
| Author | Baumgartel, Lukas |
| Author email | dukelukas@gmail.com;dukelukas@gmail.com |
| Degree | Doctor of Philosophy |
| Document type | Dissertation |
| Degree program | Physics |
| School | College of Letters, Arts and Sciences |
| Date defended/completed | 2013-10-08 |
| Date submitted | 2013-11-05 |
| Date approved | 2013-11-06 |
| Restricted until | 2013-11-06 |
| Date published | 2013-11-06 |
| Advisor (committee chair) | El-Naggar, Mohamed Y. |
| Advisor (committee member) |
Kim, Eun Sok Haas, Stephan W. Povinelli, Michelle L. Bozler, Hans |
| Abstract | This dissertation describes an investigation into the use of whispering gallery mode (WGM) resonators for applications towards frequency reference and metrology. Laser stabilization and the measurement of optical frequencies have enabled myriad technologies of both academic and commercial interest. A technology which seems to span both motivations is optical atomic clocks. These devices are virtually unimaginable without the ultra stable lasers plus frequency measurement and down-conversion afforded by Fabry Pérot (FP) cavities and model-locked laser combs, respectively. However, WGM resonators can potentially perform both of these tasks while having the distinct advantages of compactness and simplicity. This work represents progress towards understanding and mitigating the performance limitations of WGM cavities for such applications. ❧ A system for laser frequency stabilization to a the cavity via the Pound-Drever-Hall (PDH) method is described. While the laser lock itself is found to perform at the level of several parts in 10¹⁵, a variety of fundamental and technical mechanisms destabilize the WGM frequency itself. ❧ Owing to the relatively large thermal expansion coefficients in optical crystals, environmental temperature drifts set the stability limit at time scales greater than the thermal relaxation time of the crystal. Uncompensated, these drifts pull WGM frequencies about 3 orders of magnitude more than they would in an FP cavity. Thus, two temperature compensation schemes are developed. An active scheme measures and stabilizes the mode volume temperature to the level of several nK, reducing the effective temperature coefficient of the resonator to 1.7 × 10⁻⁷ K⁻¹; simulations suggest that the value could eventually be as low as 3.5 × 10⁻⁸ K⁻¹, on par with the aforementioned FP cavities. A second, passive scheme is also described, which employs a heterogeneous resonator structure that capitalizes on the thermo-mechanical properties of one material and the optical properties of another. Calculations show that a temperature coefficient zero-crossing can be achieved, and encouraging initial experimental results are presented. ❧ At shorter time scales, fundamental thermal and technical noise sources define stability limits. The relative strengths of thermorefractive, thermoelastic, and Brownian motion are outlined, along with the level at which they can expect to be observed and some approaches to minimize them. It is shown that variations in the coupling gap pull the frequency at about 10 Hz/nm. A method for calculating frequency noise density caused by laser amplitude fluctuations is presented. ❧ Frequency comb generation in WGM resonators is also discussed. It is shown that cavity dispersion can be engineered through geometric parameters, yielding a microcomb with initial sidebands at 1 FSR from the pump. Such combs are thought to be coherent. Also described is a microcomb generated by a PDH locked pump laser. The resulting microwave beatnote can be changed from noisy to quiet by changing the offset of this lock. An investigation of optical to microwave down-conversion is conducted. |
| Keyword | whispering gallery mode resonator; micro resonator; microcomb; laser stabilization; temperature stabilization; frequency reference cavity; temperature coefficient; thermal compensation; frequency down-conversion |
| Language | English |
| Format (imt) | application/pdf |
| Part of collection | University of Southern California dissertations and theses |
| Publisher (of the original version) | University of Southern California |
| Place of publication (of the original version) | Los Angeles, California |
| Publisher (of the digital version) | University of Southern California. Libraries |
| Provenance | Electronically uploaded by the author |
| Type | texts |
| Legacy record ID | usctheses-m |
| Contributing entity | University of Southern California |
| Rights | Baumgartel, Lukas |
| Physical access | The author retains rights to his/her dissertation, thesis or other graduate work according to U.S. copyright law. Electronic access is being provided by the USC Libraries in agreement with the author, as the original true and official version of the work, but does not grant the reader permission to use the work if the desired use is covered by copyright. It is the author, as rights holder, who must provide use permission if such use is covered by copyright. The original signature page accompanying the original submission of the work to the USC Libraries is retained by the USC Libraries and a copy of it may be obtained by authorized requesters contacting the repository e-mail address given. |
| Repository name | University of Southern California Digital Library |
| Repository address | USC Digital Library, University of Southern California, University Park Campus MC 7002, 106 University Village, Los Angeles, California 90089-7002, USA |
| Repository email | cisadmin@lib.usc.edu |
| Filename | etd-Baumgartel-2134.pdf |
| Archival file | uscthesesreloadpub_Volume8/etd-Baumgartel-2134.pdf |
Description
| Title | Page 1 |
| Repository email | cisadmin@lib.usc.edu |
| Full text | WHISPERING GALLERY MODE RESONATORS FOR FREQUENCY METROLOGY APPLICATIONS by Lukas Baumgartel A Dissertation Presented to the FACULTY OF THE USC GRADUATE SCHOOL UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY (PHYSICS) December 2013 Copyright 2013 Lukas Baumgartel |
