Optical waveguides – Planar optical waveguide – Thin film optical waveguide
Patent
1997-08-28
1999-08-17
Palmer, Phan T.H.
Optical waveguides
Planar optical waveguide
Thin film optical waveguide
385129, 359246, 437105, 257 95, G02B 610
Patent
active
059405694
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an integrated optical element on a substrate on InP which element comprises a waveguiding layer of a specific, complex refractive index being interposed between two layers of semiconductor material having real refractive indices with one of the two layers being on the substrate, the complex refractive index of the waveguiding is controllable with electric charge carriers and exhibits a real part that is greater than the real refractive index of the two layers so that the light of a specific wavelength can be coupled into the waveguide layer and guided therein and the waveguiding layer exhibits a crystal lattice constant that is less than one percent greater than a specific lattice constant of the InP and the element includes means for controlling the complex refractive index of the waveguiding layer so that the intensity and/or phase of the light being guided in the waveguiding layer is variable.
An integrated optical element of said species is disclosed by the document GB-A-2 207 283 in which five different examples of integrated optical elements on a substrate of InP are described.
What all of these examples have in common is that the layers of ternary material adjoining the waveguiding layer are composed of such a composition that these layers exhibit the same crystal lattice constant as the InP of the substrate.
In two examples, the waveguiding layer is composed of three adjacent, thin layers at which the layers adjacent to the waveguiding layer adjoin. These outer, thin layers each respectively exhibit a crystal lattice constant that gradually increases in the direction toward the central thin layer from the relatively lower crystal lattice constant of the layers adjacent to the waveguiding layer to the relatively higher crystal lattice constant of the central, thin layers.
In one of these two latter examples, the relatively higher crystal lattice constant of the central thin layer is only 0.5% higher than the crystal lattice constant of the InP of the substrate.
An integrated optical element on a substrate of InP composed of refractive index between which the waveguiding layer is arranged, that adjoin the waveguiding layer and whereof one is located between the waveguiding layer and the substrate, whereby electrical charge carriers and exhibits a real part that is respectively greater than the real refractive index of the two layers adjoining the waveguiding layer, whereby and the in-coupled light is guided essentially in the waveguiding layer, and whereby waveguiding layer such that the intensity and/or phase of the light guided in the waveguiding layer is variable, proceeds from the following documents: tensile-strained-barrier MQW structure", IEEE J. Quantum Electr., Vol. Qe-30, No. 3 (1994) pp. 695-702, from optical amplifier with tensile and compressively strained wells for polarization-independent gain", IEEE Photon. Technol. Lett., Vol. PTL-4, No. 4 , 1993, pp. 406-408, from InGaAs (P) quantum-well semiconductor lasers and amplifiers", IEEE J. Quantum elektron. Vol. QE-30, No. 2 (1994), pp. 477-499 from semiconductor optical amplifiers at 1.3 .mu.m wavelength", Yokohama, Japan, Jul. 4-6, 1993, Paper Sub 2-1, pp. 8-11 (1993) or also from laser amplifiers employing both tensile and compressively strained quantum wells in a single active layer" Proc. Europ. Conf. Opt. Commun. '92 (ECOC'92), Pt. 3, Berlin, 1992, pp. 911.
Each of the waveguides described in these documents a) through e) forms a waveguide in the form of a polarization-independent optical amplifier.
In the case of the amplifier described in document a), the wave-guiding layer has quantum well layers in the form of weakly tensile-strained potential wells or potential barriers. Wealky tensile-strained wells require relatively high current because of "valence band mixing". Quantum wells with tensile-strained barriers require large thicknesses, which are difficult to manufacture because of the strain and which move structures into the range of conventional layered structures without a
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Newkirk et al, "1,5 .mu.m Multiquantum-Well Semiconductor Optical Amplifier with Tensile and Compressively Strained Wells for Polarization-Independent Gain", IEEE Photonics Technology Letters, vol. 4, No. 4, Apr. 1993, pp. 406-408.
Thijs et al, "Progress in Long-Wavelength Strained-Layer InGaAs(p) Quantum-Well Semiconductor Lasers and Amplifiers", IEE Journal of Quantum Electronics, vol. 30, No. 2, Feb. 1994, pp. 477-499.
Holtmann et al, "Polarization Insensitive Bulk Ridge-type Semiconductor Optical Amplifiers at 1.3 .mu.m Wavelength", Conference Optical Amplifiers and Their Applications, Yokohama, Japan, Jul. 4-6, 1993, Paper SuB 2-1, pp. 8-11 (1993).
Tiemeijer et al, "High Performance 1300nm Polarization Insensitive Laser Amplifiers Employing both Tensile and Compressively Strained Quantum Wells in a Single Active Layer", Proc. Europ. Conf. Opt. Commun. '92 (ECOC'92), Pt. 3, Berlin, 1992, pp. 911-913.
Palmer Phan T.H.
Siemens Aktiengesellschaft
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