Abstract: An integrated optical switching device for switchably converting a fraction of a first guided mode signal into a second guided mode signal of different order is provided. Added to a passive mode converter (c) provided with a bimodal waveguide, in which the conversion can take place by a periodic coupling in coupling surfaces 1-N as a consequence of a specific geometry (f, g), are electrodes (10, 14) for switchably disrupting the coupling, as a consequence of which the conversion does or does not take place. Preferably, the optical switching device is constructed on semiconductor material and the modification is carried out by charge carrier injection. On/off and directional switches based on this are provided. As a result, the advantages of the present system are very good integrability, short length, no critical parameters in the manufacture, and operation at low control currents.

Abstract: Integrated optical polarization converter provided with a channel-type waveguide (B) defined by a strip-type structure (S.sub.4) supported by a substrate (S) and having a periodic concatenation of two different part strips having side walls which are at different angles with the plane of the substrate. The two part strips have as cross-sections either a trapezium (EFGH with .DELTA..sub.1, .DELTA..sub.2 .noteq.0) and a rectangle (EFGH with .DELTA..sub.1 =.DELTA..sub.2 =0), or both of them a right-angled trapezium with oblique sides situated opposite one another (EFGH with .DELTA..sub.1 0 and .DELTA..sub.2 .noteq.0, and EFGH with .DELTA..sub.1 .noteq.0 and .DELTA..sub.2 =0). Oblique and vertical side walls on such a strip-type structure supported by a substrate are fabricated, in the case of suitable crystal orientation, by means of two mutually complementary mask patterns, using etching steps, employing wet-chemical and dry etchants respectively.

Abstract: An alignment-tolerant fabrication of a waveguide structure having a symmetrical component structure and an asymmetrical component structure such as an asymmetrical X junction, with the aid of the technique of double masking is presented. The entire waveguide structure is defined by two different mask patterns (p.sub.1, p.sub.2) which are applied successively and in a mutually overlapping position. The two mask patterns are aligned with respect to one another according to alignment directions parallel (z-axis) and perpendicular (x-axis) to the axis of symmetry of the symmetrical component structure. Each mask pattern comprises a first asymmetrical component pattern (32;35) and a second asymmetrical component pattern (31,33; 34,36). The first component patterns (32 and 35) each define a separate portion of the asymmetrical component structure.

Abstract: An optical waveguide circuit comprises a mode splitter and an input guide (1/4/6.1) and first and second output guides (6.2/2, 6.3/3), and a mode converter (5) incorporated in the input guide for converting a fraction of an optical signal (I.sub.i), entering via the input waveguide, of a first propagation mode into a second propagation mode having mutually different order. The mode converter (5) has a first waveguiding section (5.1) and a second waveguiding section (5.2), which adjoin each other via a single discontinuity (7). The first and second sections (5.1 and 5.2) have propagation modalities, as a result of which, at the discontinuity, a coupling can take place between two propagation modes of different order, whereas the extent (x) of discontinuity determines the fraction of conversion for obtaining a desired splitting ratio in emitting signals (I.sub.o1, I.sub.o2).

Abstract: In known coherent optical receivers comprising two detectors, optical 90.degree. hybrids have a `throughput` .ltoreq.25%. Theoretical analysis reveals that a higher `throughput` of up to a maximum of approximately 29.3% is possible. The invention provides such a 90.degree. hybrid (30) of the coupler type with the aid of a 2.times.2 port which is based on a loss-free 3.times.3 directional coupler having the maximum throughput ratios between two of the inputs (31/39, 32/40) and two of the outputs (39/34, 40/35) and the 90.degree. phase difference between said two outputs, the third input and the third output not being used. An integrated version employing indium phosphide is described.

Abstract: An integrated optical, polarization-manipulating device, comprises a first waveguiding section (A) with a first guide (21), a second waveguiding section (E) with a second and a third optically decoupled and physically separated guide (26, 27) and an intermediary waveguiding section (C) for an adiabatic coupling between the first and the second sections (A, B). The intermediary section (C) comprises a polarization-sensitive asymmetric Y-branching device, provided with two mutually diverging intermediary guides (24, 25), a monomodal (24) and a bimodal (25), coupled to the guides (26, 27), respectively, of the second section. The guides (21, 27) form, with dummy guides (22, 28), respectively, polarization-insensitive asymmetric Y-junctions which function as mode converters between zeroth- and first-order guided modes. Bimodal coupling sections (B, D) provide for adiabatic couplings between asymmetric Y-junctions and the intermediary section (C).

Abstract: To manufacture a channel-type waveguide pattern (1.1) having Y-shaped branches and a sharp vertex (V) on or in a substrate (1), masks (6 and 7) which partially overlap one another are used for two different etching steps, which successively define a part of the Y-shaped pattern. In this process, use is made of only one auxiliary mask layer (2) made of suitably chosen material which can be etched in the first etching step but is resistant in a second etching step involving dry etching.

Abstract: The invention provides a wavelength division multiplexer and a wavelength division demultiplexer by combining a wavelength-selective mode converter (3) with a wavelength-independent mode splitter (5). The demultiplexer comprises a monomodal input channel (1), an adapter (2) to the bimodal input of a 100%TX.sub.00 -TY.sub.01 (.lambda..sub.1) mode converter (3), a bimodal junction channel (4), and a mode splitter (5) having a first output channel (6) and a second output channel (7), both monomodal, the first output channel (6) having a higher propagation constant than the second. A .lambda..sub.1 component, which propagates with a polarization TX (TE or TM) in an input signal S.sub.i1 (.lambda..sub.1, .lambda..sub.2, .lambda..sub.3 . . . ), will, after conversion in the converter (3), propagate in the intermediate channel (4), in the first-order guided mode having the polarization TY (TE or TM), and subsequently leave the splitter via output channel (7).

Abstract: Controllable polarization transformer comprising a passive mode converter (4), a controllable phase shifter (5) and a controllable Mach-Zehnder interferometer (7). The mode converter (4) converts the first signal component of one polarization (TE or TM) of a light signal entering via an input (1) into a signal component of the other polarization without affecting the second signal component of the other polarization (TM or TE), the conversion taking place to another order of the guided mode. Phase control by means of the phase shifter (5) controls the intensity distribution of the light signal over the two branches (8, 9) of the interferometer (7). Optical wavelength control in the interferometer (7) controls the phase with which the signals through the branches come together in the output (2).

Abstract: Polarization filter for delivering an output signal So containing only one (TE or TM) of the two polarizations (TE and TM) in an input signal Si, comprising an intermediate guide section (5) between an input section (A) and an output section (B). The output section (B) is a mode splitter having a monomodal output channel (3) for the output signal (S.sub.o) and a monomodal dummy channel (4) which recedes beyond the interaction distance (D). The output channel (3) has a lower propagation constant than the dummy channel (4). The input section (A) having an input channel (1) and a dummy channel (2) is an inverse mode splitter which may be the mirror image of the output section (B). The guide section (5) is monomodal for one of the two polarizations and bimodal for the other polarization. Both polarizations of the input signal S.sub.

Abstract: Mode converter for converting a fraction of one guided mode of an optical signal in an incoming optical waveguide section (A) into another guided mode in an outgoing wave-guiding section (C) by means of a periodic coupling between both guided modes in an intermediate optical waveguide section (B). The intermediate section (B) has a periodic geometrical structure as a result of an N-fold periodic sequence of two light-guiding subsections (P, Q) within a period length (L.sub.P +L.sub.Q). The sequence can be obtained by arranging for the waveguide profiles of the subsections to differ from one another, preferably as a result of differences in width. The sequence can also be obtained by offset joining of the two subsections with the same waveguide profiles.