Abstract

The most widely used method for determining the refractive index of optical materials is the minimum deviation method; it is the basis of the divided circle prism spectrometer.¹ Another method is the Brewster angle reflection method. Both methods require the use of a rotating mechanical mount. Thus, these methods can be considered to be optomechanical. To overcome this mechanical and other limitations we have reconsidered the measurement of the refractive index in which there are no moving parts. We show that this is possible for an optical beam which is incident at 45° with respect to the normal.² The optical surface is represented by its Mueller matrix from which a simple expression for the refractive index is found. We then present an experimental configuration for determining the refractive index. Because the measurement is done with a digital voltmeter we call this method digital spectrometry and it can be considered to be an optoelectronic measurement. Finally, we discuss the accuracy and the extension to measuring the extinction coefficient.

© 1985 Optical Society of America