RESUMO
A silver-halide infrared optical fiber is used in a double-beam spectrometer, demonstrating the ability to guide small infrared signals efficiently. We show that a fractional transmission change of less than 1% is easily measured. Use of the fiber may obviate the necessity for the unfriendly optics currently used in spectrometry systems to probe remote sample zones. As a specific example, we were able to guide with high efficiency an infrared signal to and from a sample that was mounted in a cryostat. Using this setup, we measured the photoinduced absorption due to the e1 ? e2 intersubband transition in a GaAs-GaAlAs multiple quantum-well structure.
RESUMO
An unclad silver-halide fiber was coated with a 0.1-microm silver layer and immersed in ethyl alcohol, and the fiber transmission in the range 2-20 microm was measured. The loss, induced by the metallic layer, was used to calculate the extinction coefficient, kappa', and the index of refraction, n', of the layer by fitting the experimental data with the time-independent perturbation theory in the complex region. The dependence of the extinction coefficient on the wavelength was found to be logarithmic, kappa'(lambda) = kappa(0)' exp(a lambda), and not linear, as predicted by others. This simple technique may be used to study the optical constants of thin metallic films.
RESUMO
The effect of a thin adsorbed layer of a foreign material on the modal propagation constant in an optical fiber is calculated by the use of a time-independent perturbation theory. The effect is measured on a straight fiber but is enhanced on a bent fiber because of tunneling, which is analogous to the Zener effect in quantum mechanics. Experimental results obtained with a fiber interferometer are presented.
