Speaker
Mr
Pornchai Kopatta
(Department of Physics , Mahidol Wittayanusorn School , Thailand)
Description
In this work, a Michelson Interferometer was applied for the measurement of coherence length of He-Ne laser (632.8 nm), blue diode laser (404.5 nm), green diode laser (532.5 nm) and red diode laser (656.5 nm). The principle of coherence length measurement is based on the formation of interference fringes obtained from Michelson interferometer. The laser beam is expanded by a beam expander and passes into Michelson interferometer. The laser beam is divided into two beams by a beam splitter. The two beams, are reflected at mirror M1 and M2, and then interferes to form interference fringes as can be seen by the eye. The Michelson interferometer can be used to measure coherence length of laser light directly by measuring the maximum path difference over which we still observe the interference fringe. The coherence length of He-Ne laser (632.8 nm), blue diode laser (404.5 nm), green diode laser (532.5 nm) and red diode laser (656.5 nm) are found to be 0.85, 0.18, 0.3 and 0.45 mm, respectively. The results are in good agreement with those of theoretical calculations, i.e. 0.8, 0.16, 0.28 and 0.43 mm.
Primary author
Mr
Pornchai Kopatta
(Department of Physics , Mahidol Wittayanusorn School , Thailand)
