Electrical Engineering in Japan
Optical signal inversion phenomena due to negative nonlinear absorption effect
Yoshinobu Maeda, Seiichi Ikeda, Takao Sakakibara, Masatoshi Migitaka
Abstract
A negative input-output characteristic was obtained in an erbium-doped yttrium aluminum garnet crystal which has multiple-level energy structure: absorption can occur between a ground level and an excited level (4I−4I) and between two other excited levels (4I−2H) in Er3+. It occurred at a wavelength between 786.6 and 788.4 nm by variation of the incident laser intensity in the intensity range of 60 nW/cm2 to 100 W/cm2. It is considered that an enhanced absorption occurs due to the excited-state absorption from 4I to 2H, its spectra matching the wavelength dependence of the incident laser In addition, optical signal inverter phenomenon was observed using a laser diode modulated at 10 MHz. By considering multiple excited-state absorption in detail, active functions such as an optical signal inverter could be derived from the negative nonlinear absorption effect. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(4): 74–80, 1997