Abstract
A Faraday isolator is a 45° Faraday rotator placed between two linear polarizers oriented at 45° to each other. An isolator placed between a laser and subsequent optical components prevents the light reflected and/or scattered from these components from returning to the laser. InSb has been used previously for the fabrication of Faraday isolators for use in the IR, particularly in the 10-μm region of the CO2 laser,1 using either the interband contribution in undoped material or the free-carrier plasma contribution to the Faraday rotation in rt type material. The latter contribution is also referred to as the intraband contribution. We have recently shown2 that in n-type InSb at liquid helium temperature there is an additional contribution to the Faraday rotation arising from the spin of the conduction electrons.34׳ This spin contribution is proportional to the spin alignment which saturates at magnetic fields B above ~ 10 kG. In the regime of low magnetic fields, the spin contribution is found to be dominant even for a relatively low conduction electron concentration Ne ~1 X 1014 cm3״ and is large enough to make a low field 10pm Faraday isolator based largely on the spin contribution.
© 1989 Optical Society of America
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