US 5,363,398 AGranted

Absorption resonant rare earth-doped micro-cavities

AssigneeAT&T Bell Laboratories

InventorsAlastair M. Glass, Neil E. J. Hunt, John M. Poate, Erdmann F. Schubert, George J. Zydzik

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Abstract

Absorption properties of an optically active medium can be changed drastically by a Fabry-Perot microcavity. Optically active medium of the cavity includes a host material which is not optically active and at least one rare earth ion which provides optical activity to the medium. The Fabry-Perot cavity is designed to be resonant with excitation wavelength of an absorption band of the host material. The excitation is provided by a source of radiation positioned such that the radiation impinges on the cavity at an angle within a range of from zero to less than 90 degrees from the normal to the top surface of the cavity. In one embodiment Er-implanted SiO.sub.2 is used as the optically active medium. SiO.sub.2 :Er has an absorption band at 980 nm and an emission band at 1.55 .mu.m due to 4f intra-atomic transitions of Er.sup.3+ ions. The Fabry-Perot cavity is designed to be resonant with the 980 nm absorption band of SiO.sub.2 :Er. The efficiency of the cavity structure is much higher as compared to a no-cavity structure, while the spectral features of the active SiO.sub.2 :Er emission are unaltered. The structure can be used for optically pumped semiconductor devices, such as optical amplifiers or lasers, which could be operated with a higher overall efficiency.

Claims14

Dependent claims

A light-emitting device which comprises in an ascending order, a substrate, a bottom reflector, an active layer, and a top reflector, said reflectors forming a Fabry-Perot cavity enclosing said active layer, said active layer is doped with a rare earth element selected from lanthanide series elements with numbers 57 through 71, said rare-earth element being selected on basis of its optical transition so as to provide electroluminescence at a desired emission wavelength, wherein

the material of the active layer, the thickness of the active layer, the wavelength of excitation radiation and an angle, .THETA., at which said radiation impinges on the top reflector are selected such that the fundamental mode of the cavity is in resonance with the excitation wavelength, said active layer including a host material selected from materials which either are not capable of spontaneous luminescence or whose luminescence is of such minor intensity as not to be considered emissive at the wavelength of the rare earth element, the thickness of the active layer being a whole number multiple of .lambda./2 wherein .lambda. is the wavelength of excitation radiation divided by the index of refraction of the material of the active layer, said number being one of the numbers ranging from 1 to 5, and the wavelength of excitation radiation of the source of radiation being substantially smaller than said emission wavelength.

Dependencies are inferred from the claim text.