Using a pseudo-thermal light source to teach spatial coherence

Teaching students spatial coherence constitutes a challenge. On the one hand, discussing it theoretically requires a quite demanding mathematical breadth. On the other hand, discussing it experimentally is hardly possible as coherence usually cannot be directly observed. To solve this problem, we sh...

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Bibliographic Details
Published in:European journal of physics 2018-07, Vol.39 (4), p.45303
Main Authors: Pieper, K, Bergmann, A, Dengler, R, Rockstuhl, C
Format: Article
Language:English
Subjects:
coherence
coherent areas
physics education
pseudo-thermal
rotating diffuser
speckles
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Summary:Teaching students spatial coherence constitutes a challenge. On the one hand, discussing it theoretically requires a quite demanding mathematical breadth. On the other hand, discussing it experimentally is hardly possible as coherence usually cannot be directly observed. To solve this problem, we show, by studying the contrast of interference patterns of a double slit, that speckles of a pseudo-thermal light source, consisting of a laser and a rotating diffuser disc, are equivalent to the spatial extent of coherent areas of a thermal light source. Coherent areas are spatial regions within which light can be considered as coherent. The unique advantage of such pseudo-thermal light source is the opportunity to directly observe the spatial extent of the coherent areas. This renders the phenomena perceptible and accessible by various experiments, as described in this contribution. This opens modern paths to teach spatial coherence to students with a notably reduced order of abstraction.
ISSN:0143-0807
1361-6404
DOI:10.1088/1361-6404/aaba03