Integrated optical element with polarization effect

the Invention relates to an integrated optical component according to the preamble of claim. 1

In many applications, in which optical sensors and optical transmission devices with high transmission rates are used, it is of critical importance, a to have well-defined polarization state of the light wave. beyond , the polarization sensitivity of anisotropic integrated optical Components which for use in optical on / off switches, changeover switches, filters and amplifiers are determined, a large Problem, that by the use of devices that a change the polarization allow dissolved can be.

In The document EP-A-129 463 is an integrated optical polarization device with spatial Polarization splitting described. In this device be interaction areas produced in that a se highly anisotropic substrate by doping or ion exchange specifically changed is. The doping of the interaction regions is carried out such that these Regions have an effective refractive index smaller is greater or as the refractive indices of a transmission waveguide for the first and second polarization direction. In this way, the Component no longer a wave with the second polarization direction forwarded.

at a device of this type is the one of the polarizations corresponding suppressed light and can not be recovered will. Therefore, there is a loss of energy and in some cases a loss of information. With a device of this kind can only divided two polarizations, but in no case a polarization rotation accomplished will.

Of the Invention is the object of an integrated optical component to do with polarization effect in which the polarization state of Light specifically influenced can be, that this polarization state maintained or targeted changed can be. The component has the Realization of any kind of polarizer or performing a polarization rotation enable.

These Object is through a Device according to claim 1 dissolved.

Lateral planar stripe waveguide influence the anisotropy of the transmission waveguide by mechanical stresses and geometrical effects, so that a waveguide produced with high birefringence.

After a first embodiment of the invention comprises the component planar strip waveguides symmetrically arranged on both sides of the transmission waveguide are. The transmission waveguide possesses characteristics for holding of the polarization state in this case with maximum birefringence of the transmission waveguide.

After a second embodiment of the invention comprises the component planar strip waveguides asymmetrically arranged on both sides of the transmission waveguide are. By this asymmetric disturbance of the index profile the own axis or intrinsic axes of the transmission waveguide inclined so that can be produced arrangements with which the polarization state of changing light can be.

Around the losses between the transmission waveguide reduce and the planar channel waveguides, can the planar Strip waveguide at a certain distance of preferably few tenths of a micrometer from the transmission waveguide to be ordered.

to increase the mechanical stresses, the component at least one additional planar comprise waveguide remote from the transmission waveguide Side of an associated planar stripe waveguide, parallel to longitudinal axis the transmission waveguide is arranged.

Several Embodiments of the invention are exemplified in the accompanying drawings illustrated and further in the following description of Advantages and features nearer explained. show case

<figref idrefs="S13">1</figref> to <figref idrefs="S15">3</figref> three particular embodiments of a component according to the invention, in which the disturbances symmetrically to the longitudinal axis the transmission waveguide are formed.

<figref idrefs="S16">4</figref> the change the effective refractive index in the part of <figref idrefs="S15">3</figref>;

<figref idrefs="S17">5</figref> a particular embodiment of the invention, wherein said transmission waveguide is designed as a coupler;

<figref idrefs="S18">6</figref> and <figref idrefs="S19">7</figref> two particular embodiments of the invention with a single planar stripe waveguide;

<figref idrefs="S20">8</figref> and <figref idrefs="S20">9</figref> two particular embodiments of the invention with a plurality of planar Stripes&lt;?page 3?&gt;fenwellenleitern, the alternately arranged on both sides of the transmission waveguide are.

<figref idrefs="S13">1</figref> shows a transmission waveguide <figref>1</figref>. the in integrated optics substrate <figref>2</figref> brought in is. By left and right in<figref idrefs="S13">1</figref> drawn Arrows, the direction of propagation of a light wave in the waveguide <figref>1</figref> displayed. According to a preferred embodiment, the substrate <figref>2</figref> as a glass substrate formed, and the waveguide <figref>1</figref> is in a known manner introduced by ion exchange. effect during ion exchange stresses anisotropic changes in the refractive index in the waveguide, so that the resulting waveguide <figref>1</figref> a waveguide having birefringence is. However, a waveguide of this type has sufficient Birefringence to achieve selective polarization effects.

By Introduction of suitable additional stresses or interference into the waveguide <figref>1</figref> let yourself achieve high birefringence of the conductor.

These additional Tensions or disturbances According to the invention by scored structures that at least one planar strip waveguide <figref>3</figref> include, which laterally to the waveguide <figref>1</figref> is arranged. These Structures that the waveguide <figref>1</figref> with additional Tensions or disturbances apply, simultaneously with the waveguide <figref>1</figref> in the substrate introduced. It must thereby namely only used for the preparation of the waveguide <figref>1</figref> specific mask adjusted are such that one by ion exchange simultaneously the waveguide <figref>1</figref> and the planar waveguide <figref>3</figref> can produce, without requiring an additional Operation would be necessary.

at the embodiment shown is a planar strip waveguide <figref>3</figref> out several lateral waveguides <figref>4</figref> the width I1 and the Length L1, the parallel and perpendicular to the longitudinal axis A of the waveguide <figref>1</figref> arranged and d are separated from each other by a distance.

In the <figref idrefs="S13">1</figref> and <figref idrefs="S14">2</figref> intersects the waveguide <figref>1</figref> With the width I2 rectangular and evenly spaced symmetrically on both Sides of the waveguide <figref>1</figref> arranged lateral waveguide <figref>4</figref>, The lateral waveguide <figref>4</figref> increase in the propagation direction of light periodically the lateral component of the waveguide <figref>1</figref> acting Tensions. increase thus periodically the birefringence of the waveguide <figref>1</figref>,

There the lateral waveguide <figref>4</figref> are narrow and formed perpendicular to the axis A of the waveguide <figref>1</figref> extend, there are only slight losses, and through the waveguide <figref>1</figref> guided light is hardly deflected into the lateral waveguide.

By the symmetrical action of the stresses on the waveguide <figref>1</figref> let yourself an anisotropic waveguide <figref>1</figref> with good polarization retaining properties achieve.

to increase of the waveguide <figref>1</figref> acting stresses, additional planar waveguide <figref>5</figref> as shown in <figref idrefs="S14">2</figref> in the substrate are introduced. A waveguide<figref>5</figref> the Width I3 and length L2 is parallel to the longitudinal axis A waveguide <figref>1</figref>On which the waveguide <figref>1</figref> facing away Side of an associated planar strip waveguide <figref>3</figref> arranged. Thus, in <figref idrefs="S14">2</figref> waveguides <figref>5</figref> on both sides of the waveguide <figref>1</figref>, At a distance L1 from the latter to the outside the component arranged. The distance L1 needs to be sufficiently large, losses due to coupling from the waveguide <figref>1</figref> in the waveguides <figref>5</figref> to avoid.

the particular configuration shown in Figure differs from the assembly in <figref idrefs="S14">2</figref> characterized in that the lateral waveguides <figref>4</figref> not with the waveguide <figref>1</figref> in contact standing, but at a distance e from the waveguide <figref>1</figref> are formed. The distance e, which is typically less than a few tenths of a micrometer is, allows the reduction of the residual couplings and thus the losses and an improvement of the light pipe through the waveguide <figref>1</figref>, The through the waveguides <figref>4</figref> to the waveguide <figref>1</figref> acting Voltages are compared with the embodiments according to <figref idrefs="S13">1</figref> and <figref idrefs="S14">2</figref> reduced.

<figref idrefs="S16">4</figref> shows the change the effective refractive indices n TM (solid line) and nTE (dashed Line) for TM and TE polarization.

There the manufacture of waveguides occur simultaneously hang their effective refractive indices essentially on its dimensions from. These are selected so that the effective refractive indices in the planar waveguides less than or equal to the effective refractive indices in the transmission waveguide <figref>1</figref> are thus optical loss radiations be prevented in the direction of the planar strip waveguide. In practice, the effective refractive indices of the waveguide are all the more smaller, the narrower the waveguide.

the Analysis of the change the effective refractive index in <figref idrefs="S16">4</figref> shows when viewing these changes from left to right, that the Indices n TM and n TE in additional waveguides <figref>5</figref> first high values ​​n1TM and n1T exhibit, then on average values ​​and n2TM n2TE in planar strip waveguide <figref>3</figref> sink and then where between the planar strip waveguide <figref>3</figref> and the &lt;?page 4?&gt;waveguides <figref>1</figref> formed area very small values accept n3TM and n3TE before the waveguide <figref>1</figref> again rise to high values ​​and n4TM n4TE. The index changes extend in relation to the waveguides <figref>1</figref> symmetrically. The distance e between the waveguides <figref>1</figref> and <figref>3</figref> improves light line in the waveguide <figref>1</figref>, The effective refractive indices n1TM and the additional n1TE waveguide <figref>5</figref> are larger than the effective refractive indices and n4TM n4TE the waveguide <figref>1</figref>,

Of the size Distance between the additional waveguides <figref>5</figref> and the waveguide <figref>1</figref> prevents any Loss radiation between the two waveguides, although the additional waveguides <figref>5</figref> due to its large surface higher effective refractive indices than the waveguide <figref>1</figref>,

By in the <figref idrefs="S13">1</figref> to <figref idrefs="S15">3</figref> be shown components to waveguides with very high birefringence achieve a the good behavior with respect to the have attitude of the polarization state of light. In particular they may for the Preparation of phase shifters and polarizers are used. The embodiment according to <figref idrefs="S15">3</figref> can because of the TE mode effective tunneling effect particularly for the production of a polarizer be used.

Of the in <figref idrefs="S17">5</figref> Transmission waveguide shown <figref>1</figref> is as a coupler with two parallel waveguides <figref>1a</figref> and <figref>1b</figref> educated. In the illustrated embodiment, the coupling of the light takes place into the component via the input of the waveguide <figref>1a</figref> and the light exit partly out of the waveguide <figref>1a</figref> and by coupling of the waveguide <figref>1b</figref>, The interactions between the two waveguides generally have a tendency of the intrinsic axes of two waveguides <figref>1a</figref> and <figref>1b</figref> result. A Such rotation of the eigen axes however, makes it difficult to determine the polarization state to control the coupler. By using the structures related on <figref idrefs="S13">1</figref> and <figref idrefs="S15">3</figref> described type, this Inclination of the intrinsic axes of the waveguides <figref>1a</figref> and <figref>1b</figref> reduced be compensated or even entirely. In<figref idrefs="S17">5</figref> are two planar strip waveguide <figref>3</figref> symmetrically on both sides consisting of the two waveguides <figref>1a</figref> and <figref>1b</figref> existing Arrangement arranged. As in<figref idrefs="S14">2</figref> is it possible, additional planar waveguide <figref>5</figref> provide, and the waveguide <figref>3</figref> may like in <figref idrefs="S15">3</figref> at a distance E from the respective waveguide <figref>1a</figref> or. <figref>1b</figref> to be ordered.

In <figref idrefs="S17">5</figref> is a planar strip waveguide <figref>6</figref> in between the waveguides <figref>1a</figref> and <figref>1b</figref> formed intermediate region arranged. The planar strip waveguide<figref>6</figref> in this Intermediate region consists of several mutually parallel between waveguides, in the extension the lateral waveguide <figref>4</figref> the planar waveguide <figref>3</figref> arranged are. The width I4 of the waveguide<figref>7</figref> is less than the width I1 of the corresponding waveguide <figref>4</figref>, So will through the lateral planar strip waveguide <figref>3</figref> the Doppelberechung the waveguide <figref>1a</figref> and <figref>1b</figref> periodically elevated and simultaneously compensates for the inclination of their own axes or reduced. The planar strip waveguide<figref>6</figref> in the intermediate region can to achieve a better compensation of the natural axis tilt . omitted

On symmetrical component with interactive waveguides according <figref idrefs="S17">5</figref> can especially for adiabatic or directional Coupler with polarization attitude, for Y-junctions, for polarization splitting also for Star coupler ( "phased array") are used. By suitable choice of the dimensions and the spacing of the waveguide <figref>4</figref> and <figref>7</figref> can they Losses minimized the intrinsic axes of the waveguides <figref>1a</figref> and <figref>1b</figref> aligned and so their polarization retaining properties while maximizing the birefringence of the transmission waveguide be improved.

In <figref idrefs="S18">6</figref> to <figref idrefs="S20">9</figref> are Components shown in which acting on the transmission waveguide Structures are formed asymmetrically. This allows the inclination the intrinsic axes of the transmission waveguide affected and so the polarization of about the conductor run changing optical targeted will.

The in <figref idrefs="S18">6</figref> Component shown corresponds kind comprising the component out <figref idrefs="S14">2</figref>But has only a planar strip waveguide <figref>3</figref> on, the one on one side of the transmission waveguide <figref>1</figref> arranged additional planar waveguide <figref>5</figref> assigned. This asymmetry has due to the geometry and the voltages in the waveguide <figref>1</figref> an asymmetrical Distribution of the index field and a rotation angle ∅ his Own axes with respect to the eigen axes of a symmetrical structure for Sequence in which the axes at right angles or parallel to the surface of the Substrate run. Due to the properties of the planar strip waveguide<figref>3</figref> let yourself the polarization state of the light at the output of the waveguide <figref>1</figref> targeted influence. Corresponds example L3 half beat length of TE and TM modes learns an over the waveguide <figref>1</figref> guided Optical rotation of its linear polarization plane by 2 ∅. When TE and TM-excitation and a rotation angle of ∅ = 45 ° is obtained on Thus, a TE / TM polarization converter. At a rotational angle turns of ∅ = 22.5 ° the plane of polarization by 45 °, what with exclusive TE or TM-exclusive coupling at the entrance of the waveguide an equal light distribution between TE and TM modes corresponding.

&lt;?page 5?&gt;

at a length L3 corresponding to a quarter of the TE / TM-beat length and a rotation angle of ∅ = 45 ° at the end of the waveguide <figref>1</figref>. the end of the planar waveguide <figref>3</figref> assigned, a TE or TM wave converted into a circular shaft. Thus, the desired phase shift is between the polarizations by the length L3 of the planar strip waveguide <figref>3</figref> certainly. The inclination the intrinsic axes of the transmission waveguide <figref>1</figref> depends on the width I1, the length L1 and the distance d between the lateral waveguides <figref>4</figref> of planar strip waveguide <figref>2</figref> from.

As in <figref idrefs="S13">1</figref> can according to also in the component <figref idrefs="S18">6</figref> the additional planar waveguide <figref>5</figref> . omitted The planar strip waveguide<figref>3</figref> can as shown in <figref idrefs="S19">7</figref> in a Distance e from the waveguide <figref>1</figref> be arranged.

at the arrangements of <figref idrefs="S20">8</figref> and <figref idrefs="S20">9</figref> are planar strip waveguide <figref>3</figref> alternately with a period length Lp on both sides of the waveguide <figref>1</figref> arranged. In<figref idrefs="S20">8</figref> to stand the planar strip waveguide <figref>3</figref> as in <figref idrefs="S18">6</figref> in contact with the waveguide <figref>1</figref>While in the arrangement after <figref idrefs="S20">9</figref> like in <figref idrefs="S19">7</figref> at a distance e waveguide <figref>1</figref> are arranged.

On planar strip waveguide <figref>3</figref> effected as in <figref idrefs="S18">6</figref> and <figref idrefs="S19">7</figref> a Rotation of the intrinsic axes of the waveguide <figref>1</figref> to + ∅ or -∅. It can be shown, that with planar waveguides <figref>3</figref> the length L3 corresponding to half the length of the overlay TE and TM modes and at a rotational angle ∅ polarization the incoming wave at the end of the first planar strip waveguide , At the end of which is arranged to +2 ∅ on the opposite side second planar strip waveguide by -4 ∅ and at the end of rotated third planar strip waveguide to +6 ∅ Has. More generally, is after a number of n, in the longitudinal direction alternately on both sides of the waveguide <figref>1</figref> arranged planar waveguides, the rotation of the polarization (-1)ⁿ 2n ∅. In this way, size achieve and accurate rotation angle of the polarization state. By Arrangement of a polarizer at the end of the waveguide <figref>1</figref> is working the assembly as an optical birefringence filter the type SOLC.

By independent change of the rotational angle and the length L3 of each section of the waveguide <figref>1</figref> with sloping own axes may be on a very simple way, any polarization transfer function achieve and realize a band pass filter with a narrow useful band, the in particular optical sensors, and in optical communications can be used.

the in <figref idrefs="S20">8</figref> and <figref idrefs="S20">9</figref> arrangements shown can also be used when, as in <figref idrefs="S17">5</figref> the transmission waveguide of two parallel coupled transmission waveguides <figref>1a</figref> and <figref>1b</figref> consists. In this way the rotation of their own axes can asymmetrically affected be such that Components for changing can be prepared of the polarization of a light wave, with the optical Fibers would be very difficult or impossible to implement.

Planar Strip waveguide can also in asymmetric form, alternately on both sides of a asymmetric coupler are arranged parallel transmission of two waveguides <figref>1a</figref> and <figref>1b</figref> different Width is. You can so compensate for the angle of rotation produced by the asymmetric coupler while the two effective refractive indexes of the two parallel waveguides <figref>1a</figref> and <figref>1b</figref> for one first polarization state (eg TM) Sync and for the other, perpendicular to the first polarization state aligned (TE) will not cause synchronization. In such a case comes it for the synchronized state of polarization (TM) for coupling between the incident wave leading waveguides <figref>1</figref> and the second waveguide <figref>1b</figref> of Coupler while for the unsynchronized state of polarization (TE) no coupling enters. This can be in particular a compact TE / TM polarization splitters produce a low overall length.

All structures described above, which stresses in the transfer waveguide are produced, work passively. For its operation, an external Setting not required. However, by applying a additional planar layer on the entire surface of the component a more accurate Control of the birefringence and the rotation angle of the eigen axes the transmission waveguide be achieved.

beyond can in known manner the phase shift between TE and TM waves and the angle ∅ by thermo-optical, electro-optical, chemo, optical or other effect can be changed, so that in particular controllable optical filter made asymmetric structures, and optionally an axis rotation for symmetric Structures may be produced.

the Invention is not limited to the above described method of ion exchange limited, but rather may well known in association with each other Methods of integrated optics are used. The waveguide can be incorporated in or on the substrate. Dependent on the method used, it may be under&lt;?page 6?&gt;different modes of action the anisotropy in the transfer waveguide causing structures come. The changes in the anisotropy of the waveguide can produced by geometric effect or by mechanical stresses will. In all cases the component can be easily and accurately only by certain geometrical Arrangement of planar waveguides <figref>3</figref> and optionally of additional planar waveguides <figref>5</figref> getting produced.