Spectroscopic applications of pulsed metal vapour lasers
<p>The early part of this thesis reports time-resolved measurements of the transverse coherence of radiation from a copper vapour laser (CVL), and shows the influence of an unstable resonator. Experiments to measure the visibility of fringes from pairs of pinholes with a range of spacings are...
| Main Authors: | , |
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| Format: | Thesis |
| Language: | English |
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1989
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| _version_ | 1797100296773566464 |
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| author | Freegarde, T Freegarde, T. G. M. |
| author2 | Corney, A |
| author_facet | Corney, A Freegarde, T Freegarde, T. G. M. |
| author_sort | Freegarde, T |
| collection | OXFORD |
| description | <p>The early part of this thesis reports time-resolved measurements of the transverse coherence of radiation from a copper vapour laser (CVL), and shows the influence of an unstable resonator. Experiments to measure the visibility of fringes from pairs of pinholes with a range of spacings are described, and their results are shown to be consistent with a simple theory based upon geometrical optics. With a high magnification laser cavity, high transverse coherence can be achieved before the laser pulse has reached appreciable power. The average coherence over a number of pulses is found to be limited, however, because of distortions introduced by currents of warm air in the beam path. Substantial improvements have now been made.</p><p>The importance of the transverse coherence upon second harmonic generation is then investigated. By improving the transverse coherence of the laser beam, second harmonic generation has been demonstrated at efficiencies close to those theoretically predicted for stable Gaussian laser beams, and 200mW of ultraviolet radiation at 255nm has been produced with 10% conversion efficiency using the nonlinear material beta-barium borate (BBO). High birefringence in BBO causes cylindrical symmetry in the geometry for harmonic generation to be lost, and it has been suggested that the use of astigmatic focussing into the crystal might be advantageous. A theoretical analysis has therefore been made, and improvements are indeed predicted. Elliptical focussing is predicted to increase the typical harmonic power only by a factor of 1.3, however, and no experimental verification has been attempted.</p><p>The remainder of this thesis considers the longitudinal coherence of the copper vapour laser, and describes the design and initial performance of a narrow bandwidth dye laser for use with a CVL. Careful construction of a grazing-incidence grating arrangement similar to that of Littman has resulted in a laser which is particularly simple to align and which promises ease of tuning over a wide range. Operation confined to a single longitudinal mode has been demonstrated, corresponding to single shot bandwidths below IGHz, but instabilities caused by vibration and uneven dye flow broaden the time-averaged width to around 3GHz. Suggested improvements have not yet been implemented.</p> |
| first_indexed | 2024-03-07T05:35:34Z |
| format | Thesis |
| id | oxford-uuid:e3c6fbf2-5e85-4025-bd56-83012421353c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T05:35:34Z |
| publishDate | 1989 |
| record_format | dspace |
| spelling | oxford-uuid:e3c6fbf2-5e85-4025-bd56-83012421353c2022-03-27T10:11:38ZSpectroscopic applications of pulsed metal vapour lasersThesishttp://purl.org/coar/resource_type/c_db06uuid:e3c6fbf2-5e85-4025-bd56-83012421353cMetal vapor lasersHigh power lasersEnglishPolonsky Theses Digitisation Project1989Freegarde, TFreegarde, T. G. M.Corney, ACorney, A<p>The early part of this thesis reports time-resolved measurements of the transverse coherence of radiation from a copper vapour laser (CVL), and shows the influence of an unstable resonator. Experiments to measure the visibility of fringes from pairs of pinholes with a range of spacings are described, and their results are shown to be consistent with a simple theory based upon geometrical optics. With a high magnification laser cavity, high transverse coherence can be achieved before the laser pulse has reached appreciable power. The average coherence over a number of pulses is found to be limited, however, because of distortions introduced by currents of warm air in the beam path. Substantial improvements have now been made.</p><p>The importance of the transverse coherence upon second harmonic generation is then investigated. By improving the transverse coherence of the laser beam, second harmonic generation has been demonstrated at efficiencies close to those theoretically predicted for stable Gaussian laser beams, and 200mW of ultraviolet radiation at 255nm has been produced with 10% conversion efficiency using the nonlinear material beta-barium borate (BBO). High birefringence in BBO causes cylindrical symmetry in the geometry for harmonic generation to be lost, and it has been suggested that the use of astigmatic focussing into the crystal might be advantageous. A theoretical analysis has therefore been made, and improvements are indeed predicted. Elliptical focussing is predicted to increase the typical harmonic power only by a factor of 1.3, however, and no experimental verification has been attempted.</p><p>The remainder of this thesis considers the longitudinal coherence of the copper vapour laser, and describes the design and initial performance of a narrow bandwidth dye laser for use with a CVL. Careful construction of a grazing-incidence grating arrangement similar to that of Littman has resulted in a laser which is particularly simple to align and which promises ease of tuning over a wide range. Operation confined to a single longitudinal mode has been demonstrated, corresponding to single shot bandwidths below IGHz, but instabilities caused by vibration and uneven dye flow broaden the time-averaged width to around 3GHz. Suggested improvements have not yet been implemented.</p> |
| spellingShingle | Metal vapor lasers High power lasers Freegarde, T Freegarde, T. G. M. Spectroscopic applications of pulsed metal vapour lasers |
| title | Spectroscopic applications of pulsed metal vapour lasers |
| title_full | Spectroscopic applications of pulsed metal vapour lasers |
| title_fullStr | Spectroscopic applications of pulsed metal vapour lasers |
| title_full_unstemmed | Spectroscopic applications of pulsed metal vapour lasers |
| title_short | Spectroscopic applications of pulsed metal vapour lasers |
| title_sort | spectroscopic applications of pulsed metal vapour lasers |
| topic | Metal vapor lasers High power lasers |
| work_keys_str_mv | AT freegardet spectroscopicapplicationsofpulsedmetalvapourlasers AT freegardetgm spectroscopicapplicationsofpulsedmetalvapourlasers |