Lossless non-interferometric electro-optic III-V index-guided-wave switches and switching arrays

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION To understand the operation of our active switches, it is important to know the current-controlled spectra of gain and loss, both in bulk heterostructure material and MQW material.
We shall assume that the active material is located in the intrinsic or lightly doped region of an p-i-n or p+-n.
sup.
- -n+diode.
The number of layers, the layer thicknesses, and the doping of the layers is much like that in a laser diode, except there are no reflectors at the ends.
The III-V active material will be injected or depleted depending upon the polarity of voltage applied to the diode.
If we consider the case of a multi-quantum-well material with about 100 angstrom GaAs wells and about 100 angstrom AlGaAs barriers, we find the result shown in FIG.
3, which is a composite drawing of experimental curves taken from the literature.
See D.
A.
B.
Miller, D.
S.
Chemla, T.
C.
Damen, A.
C.
Gossard, W.
Wiegmann, T.
H.
Wood, and C.
A.
Burrus, "Electric-field dependence of optical absorption near the band gap of quantum well structures", Physical Review B, 32, p.
1043 (15 July 1985); D.
A.
B.
Miller, J.
S.
Weiner, and D.
S.
Chemla, "Electric-field dependence of linear optical properties in quantum-well structures", IEEE J.
of Quantum Electronics, QE-22, p.
1816 (September 1986); A.
Tomita and A.
Suzuki, "Carrier-induced lasing wavelength shift for quantum well laser diodes", IEEE J.
of Quantum Electronics, QE-23, p.
1155 (July 1987).
We have identified two wavelengths .
lambda.
.
sub.
1 and .
lambda.
.
sub.
2 that are useful for device operation.
The spectral curves for bulk heterostructures are roughly similar to those in FIG.
3.
The ordinate expressed in cm.
sup.
-1, is the so-called bulk quantum-well gain.
FIG.
1 illustrates a 1.
times.
2 channel waveguide structure for the traveling-wave amplifiers, the ends being anti-reflection coated.
The etching profile, the doping, the active-region composition and the cladding-layer composition are chosen so that the waveguide is strongly index-guided, rather than gain-guided