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Electrically Driven Thin Film Structure for Modulating or Refracting Infrared Radiation

IP.com Disclosure Number: IPCOM000076987D
Original Publication Date: 1972-May-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Esaki, L: AUTHOR [+2]

Abstract

When one couples light into a thin epitaxial film utilizing, for example, the structure shown in the IBM Technical Disclosure Bulletin article, "Structure for Optical Coupling to Thin-Semiconductor Layers," pages 3787 and 3788 where film C of Fig. 2 therein corresponds to the active layer of the present Fig. 1, significant changes in the optical properties of such films can be rather easily produced by electrical means. For instance, the dispersion due to free carriers in a semiconductor produces a change in refractive index which is given by the equation: (Image Omitted) where epsilon/infinity/ is the optical dielectric constant, N is the carrier density, m* is the effective mass, and lambda is the wavelength of infrared light.

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Electrically Driven Thin Film Structure for Modulating or Refracting Infrared Radiation

When one couples light into a thin epitaxial film utilizing, for example, the structure shown in the IBM Technical Disclosure Bulletin article, "Structure for Optical Coupling to Thin-Semiconductor Layers," pages 3787 and 3788 where film C of Fig. 2 therein corresponds to the active layer of the present Fig. 1, significant changes in the optical properties of such films can be rather easily produced by electrical means. For instance, the dispersion due to free carriers in a semiconductor produces a change in refractive index which is given by the equation:

(Image Omitted)

where epsilon/infinity/ is the optical dielectric constant, N is the carrier density, m* is the effective mass, and lambda is the wavelength of infrared light.

If the thin layer into which infrared radiation has been coupled forms the base of a heterodiode or a heteroemitter transistor, as shown in Fig. 1, then the application of bias produces the injection of minority carriers which can change N for the region by orders of magnitude. As a result, the change in index of refraction under the emitter contact which may have geometries such as those shown at (A), (B), and (C) in Fig. 2, may be used to refract or diffract a beam in the plane of the layer using geometries (A) and (B), respectively, or the associated free carrier absorption may be utilized to modulate the intensity of the beam utilizing the geometry...