Modeling an improved method for double modulation photo reflectance experiments

M. Hernández¹ & R. Ivanov²

¹ Facultad de Física, UH, Cuba. Email: mhernan@ff.oc.uh.cu

² Facultad de Física, UAZ, México. Email: rumen@ahobon.reduaz.mx

Received: November 27^th, 2001.
Accepted October 15^th, 2002.

Abstract

This paper describes an improved method to be used in double modulation photo reflectance experiments, in order to reduce the influence of parasitic effects in the useful signal. The method uses the inner and outer sections of a single chopper disk to modulate the monochromator and the laser beam, eliminating the need of complex electronic filters, and two additional PIN photodiodes for scattered light compensation. The method has been numerically simulated using LabVIEW in order to investigate the influence of the modulator finite switching time and the finite resolution of the digital acquisition system. Results show that a relative error less than 1% can be achieved.

Keywords: Photo reflectance, Double modulation.

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