Semiconductor optical amplifier

Details Semiconductor optical amplifier Semiconductor optical amplifier

1997-10-29

1999-11-09

Moskowitz, Nelson

Optical: systems and elements

Optical amplifier

Particular active medium

257 18, 372 43, H01S 325, H01S 319, H01L 2906

Patent

active

059825316

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention concerns the amplification of optical signals. It typically finds applications in fibre optic telecommunication networks. The signals transmitted by these networks consist of pulses carrying information to be transmitted in binary form. These pulses must be amplified to compensate power losses to which they are subject as they propagate in these networks. Semiconductor amplifiers constitute a compact means of providing such amplification that can be integrated. However, in the absence of particular provisions, their gain is sensitive to the polarisation of the light that they receive, which is referred to for simplicity hereinafter as the polarisation sensitivity of an amplifier. This invention find a more particular application in the situation in which this sensitivity must be eliminated or at least limited. This is frequently the case. It arises when the distance travelled by the optical pulses to be amplified is such that the polarisation of the pulses has been affected greatly and at random during their propagation and when it is preferable for the amplified pulses to have one or more predetermined power levels.
More generally, this invention finds applications when an optical amplifier must have no or limited polarisation sensitivity.
A semiconductor optical amplifier includes a wafer comprising layers of semiconductor materials having respective refractive indices and forming a common crystal lattice. In the absence of mechanical strains, the respective lattices of these materials have characteristic dimensions constituting a respective lattice constant of the material. The layers are in succession in a vertical direction forming a right-angle trihedron with two horizontal directions constituting a longitudinal direction and a transverse direction, these directions being defined relative to this wafer. The latter includes at least the following layers or groups or parts of layers: first type of conductivity. This substrate has a thickness sufficient to impose the lattice constant of the base material on all of the crystal lattice of the wafer. stimulated recombination of charge carriers of both types injected into this material. refractive index higher than that of the surrounding materials. It extends in the longitudinal direction to guide said light in this direction. This stripe has a transverse width and a vertical thickness. second type of conductivity opposite to the first.
This amplifier further includes a bottom electrode and a top electrode respectively formed on the bottom face and the top face of the wafer to enable an electrical current to be passed between these faces to inject said charge carriers of both types into the active material.
The base materials of prior art semiconductor optical amplifiers are of the III-V type. They are typically indium phosphide and gallium arsenide. The active material in typically a ternary or quaternary material comprising the same chemical elements. The width of the stripe that guides the light is generally required to be about one micrometer to facilitate the formation of the stripe by etching and above all to facilitate integration of the amplifier with other optical components on a common semiconductor wafer. The thickness must then be very much less than the width to assure mononodal guidance of the light which typically has a wavelength of 1 310 nm or 1 550 nm. In the absence of specific provisions, it is this rectangular shape of the cross-section of the stripe that gives rise to the polarisation sensitivity previously mentioned.
Various families of prior art amplifiers of this kind are distinguished from each other by the various provisions made therein to render these amplifiers polarisation insensitive.
A first family of prior art amplifiers includes a so-called "ridge" type stripe, i.e. a stripe projecting from the semiconductor wafer. Given that the two lateral faces of a stripe of this kind separate it from a gaseous medium such as air having a refractive index very much lower than that of

REFERENCES:
patent: 5349596 (1994-09-01), Molva et al.
patent: 5521935 (1996-05-01), Irikawa
patent: 5574289 (1996-11-01), Aoki et al.
patent: 5579155 (1996-11-01), Kitamura
Emery et al, RCOC '96, 22nd Europ. Conf. Optic. Comm., vol. 3, pp.165-166; abstract only herewith, Sept. 19, 1996.
Grand et al, European Optic. Commun. Ad Networks, 10th Annun. EFOC/Lan '92, pp. 78-80; abstract only herewith, Jun. 26, 1992.

Affiliated with

Also associated with

Rating

Semiconductor optical amplifier does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Semiconductor optical amplifier, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor optical amplifier will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1464226