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Applying light-emitting diodes with narrowband emission features in differential spectroscopy
Holger Sihler1, Christoph Kern, Denis Pöhler
1Institute of Environmental Physics, University of Heidelberg, Im Neuenheimer Feld 229,D-69120 Heidelberg, Germany. holger.sihler@iup.uni-heidelberg.de
Optics Letters
|December 3, 2009
Summary
Light-emitting diodes (LEDs) show potential for differential optical absorption spectroscopy (DOAS). Tilting the LED emitter effectively suppresses spectral structures, enhancing light coupling for improved DOAS measurements.
Area of Science:
- Optics
- Spectroscopy
- Materials Science
Background:
- Light-emitting diodes (LEDs) are increasingly used as light sources in various spectroscopic techniques.
- Differential optical absorption spectroscopy (DOAS) benefits from stable and tunable light sources.
- Spectral variations in LED emission can pose challenges for precise spectroscopic analysis.
Purpose of the Study:
- To investigate the potential of LEDs as light sources for DOAS.
- To address the issue of spectral structures in LED emission.
- To propose a method for improving LED suitability for DOAS applications.
Main Methods:
- Analysis of spectral structures originating from Fabry-Pérot etalon effects in LEDs.
- Development and application of an emitter-tilting technique to modify spectral characteristics.
- Implementation of long-path DOAS measurements using a modified blue LED setup.
Main Results:
- Identified Fabry-Pérot etalon effects as the cause of problematic spectral structures in LEDs.
- Demonstrated that tilting the LED emitter successfully suppresses these periodic structures.
- Showcased an increase in radiant flux coupled into the optical system by tilting the emitter.
- Presented successful long-path DOAS measurements with a blue LED, confirming the effectiveness of the suppression method.
Conclusions:
- Tilting the LED emitter is an effective method to remove undesirable spectral structures for DOAS.
- This technique enhances optical coupling efficiency, improving the overall performance of LED-based DOAS systems.
- LEDs, with this modification, are a viable and improved light source for differential optical absorption spectroscopy.
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