Skip to main content

Frequency stabilised laser diodes and their use in length metrology

Barwood, Geoffrey P. (1992) Frequency stabilised laser diodes and their use in length metrology. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.86149) (KAR id:86149)

Language: English

Click to download this file (8MB) Preview
[thumbnail of DX171587.pdf]
This file may not be suitable for users of assistive technology.
Request an accessible format
Official URL:


This thesis is concerned with the use of indexed-guided GaA1As laser diodes in length metrology. Since these lasers have important differences from more commonly use HeNe lasers in interferometry, the thesis begins with a review and investigation of these differences. A key problem is the relatively large linewidth (typically 30 MHz). This is reduced, by using the optical feedback from a resonant confocal etalon, to less than -10kHz.

Potential spectroscopic frequency references are discussed and the choice made of the rubidium (Rb) D lines at 780nm and 795 nm, using either Doppler-free features or the linear absorptions. The optically narrowed laser is then stabilised to the various hyperfine components. By measuring the reproducibility of the difference frequency between two systems, a relative frequency reproducibility of \(\approx\) 1x10\(^{-10}\) is demonstrated. Laser frequency stabilities are measured for a number of different cases, for example with the lasers free-running and offset locked. for two optically narrowed RB-stabilised laesrs at \(\tau\)=10 s, the relative frequency stability is \(\approx\) fx10\(^{-12}\). The hyperfine intervals of the two Rb lines are also measured for both isotopes (\(^{85}\)Rb and \(^{87}\)Rb), representing the most complete study of Rb-stabilised diode lasers to date. From these results, values for the hyperfine constants and isotope shifts are obtained. Finally, the absolute frequencies of both RB-stabilised laser diodes are measured by interferometric comparison with an iodine stabilised HeNe laser at 633 nm with a relative accuracy of \(\pm\) 1x10\(^{-9}\).

To demonstrate the use of a frequency tunable laser diode in distance measurement, a swept wavelength measurement system was developed with a demonstrated accuracy of a few parts per million. The thesis ends with a discussion of longitudinal mode control in laser diodes and some potential future uses in length and optical frequency metrology.

Item Type: Thesis (Doctor of Philosophy (PhD))
DOI/Identification number: 10.22024/UniKent/01.02.86149
Additional information: This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 09 February 2021 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives ( licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies ( If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at and we will seriously consider your claim under the terms of our Take-Down Policy (
Uncontrolled keywords: Optics; masers; lasers
Subjects: Q Science > QC Physics
SWORD Depositor: SWORD Copy
Depositing User: SWORD Copy
Date Deposited: 29 Oct 2019 16:30 UTC
Last Modified: 22 Nov 2021 09:37 UTC
Resource URI: (The current URI for this page, for reference purposes)
  • Depositors only (login required):

Total unique views for this document in KAR since July 2020. For more details click on the image.