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Spectral enhancement of quantum well laser diode bars for spectroscopic applications
Sheehy, Brian
Laser diode bars are notoriously poor at delivering narrow linewidth, fully phase coherent, high power laser beams. Over the width of a multiple emitter diode bar, a wavelength shift of several nanometres is normal since, in practice, the central wavelength varies from diode to diode. However, for applications in spectroscopy, emitters with a narrow wavelength band are required so that a particular transition in an atom or molecule can be excited to accurately detect particular gases or particles. This project investigates the possibility of controlling the spectral width of a laser diode bar by controlling the drive current to each individual emitter with the objective of bringing all emitter spectra as close as possible to a defined central output wavelength. Comparing the spectral output obtained by using a single power source for all emitters with that obtained by exercising drive control over each individual emitter, it is shown that the wavelengths of a group of emitters can be made to overlap with each other. It is also observed that by controlling the current inputs to the emitters, multiple wavelengths can be targeted and overlapped in this way. It is also observed that thermal crosstalk between neighbouring emitters has an effect on central wavelength overlapping. This work represents the first step in developing a high power, long range, infrared (IR) laser based spectrometer for applications in remote gas detection, e.g., from smoke stacks, furnaces, power plants, incinerators, landfill sites, etc.
Keyword(s): Optoelectronics; Electronics; Lasers
Publication Date:
2015
Type: Master thesis (research)
Peer-Reviewed: No
Language(s): English
Institution: Dublin City University
Citation(s): Sheehy, Brian (2015) Spectral enhancement of quantum well laser diode bars for spectroscopic applications. Master of Engineering thesis, Dublin City University.
Publisher(s): Dublin City University. School of Electronic Engineering
File Format(s): application/pdf
Supervisor(s): Barry, Liam P.
Costello, John T.
Related Link(s): http://doras.dcu.ie/20769/1/Master_thesis_Brian_Sheehy_-_Final.pdf
First Indexed: 2015-11-26 05:05:18 Last Updated: 2018-05-15 06:07:27