DD286883A5

DD286883A5 - METHOD FOR VOTING AND / OR ADJUSTING INTEGRATED OPTICAL WAVELINE STRUCTURES AND COMPONENTS

Info

Publication number: DD286883A5
Application number: DD33127689A
Authority: DD
Inventors: Andreas Rasch; Matthias Rottschalk; Gert Hagner
Original assignee: Friedrich-Schiller-Universitaetet,De
Priority date: 1989-07-31
Filing date: 1989-07-31
Publication date: 1991-02-07

Abstract

Die Erfindung betrifft ein Verfahren zur Abstimmung der Funktion und/oder der Anpassung von Wellenleiterstrukturen und Bauelemente an andere Wellenleiter auf der Basis des Protonenaustausches in Lithiumniobat. Diese Bauelemente sind fuer die elektrooptische Signalbeeinflussung in der optischen Informationstechnik und Sensorik von Interesse. Angestrebt wurden Verfahrensschritte, die eine direkte Funktionsbeeinflussung entsprechendder technischen Einsatzbedingungen und eine optimale Ankopplung protonenausgetauschter Wellenleiter in Lithiumniobat an integriert-optische Systemkomponenten gewaehrleisten. Die Loesung dieser Aufgabe gelingt erfindungsgemaesz dadurch, dasz nach dem Protonenaustausch und der ganzflaechigen thermischen Nachbehandlung durch eine zusaetzliche und lateral begrenzte thermische Nachbehandlung eine gezielte AEnderung des Brechungsindexprofils der Wellenleiterstrukturen zweckgebunden erfolgt. Wesentlicher Vorteil des Verfahrens ist die selektive thermische Nachbehandlung, die eine getrennte und aber auch gleichzeitige Veraenderung der optischen Parameter von Wellenleiterstrukturen und Bauelementen hinsichtlich der funktionsbezogenen Abstimmung als auch der notwendigen Anpassung an andere Wellenleiterparameter garantiert.{Wellenleiterstrukturen; Bauelemente; Signalbeeinflussung; Protonenaustausch; selektive thermische Nachbehandlung; optische Parameter}The invention relates to a method for tuning the function and / or the adaptation of waveguide structures and components to other waveguides based on the proton exchange in lithium niobate. These components are of interest for electro-optical signal influencing in optical information technology and sensor technology. The aim was to provide process steps which ensure direct functional influence according to the technical conditions of use and optimum coupling of proton-exchanged waveguides in lithium niobate to integrated-optical system components. The solution of this object is achieved according to the invention by targeted replacement of the refractive index profile of the waveguide structures after the proton exchange and the full-surface thermal aftertreatment by an additional and laterally limited thermal aftertreatment. An essential advantage of the method is the selective thermal aftertreatment, which guarantees a separate and simultaneous change in the optical parameters of waveguide structures and components with regard to the function-related tuning as well as the necessary adaptation to other waveguide parameters. components; Preemption; Proton exchange; selective thermal aftertreatment; optical parameters}

Description

Das Wesen der Erfindung soll an den Verfahrensschritten zur Optimierung eines integriert-optischen Bauelementes erläutert werden.The essence of the invention will be explained in the method steps for optimizing an integrated-optical component.

Die Zeichnung stellt schematisch einen X-Koppler mit verbreitertem Kreuzungsbereich 1 der optisch einmodigen Streifenwellenleiterkreuzung dar (Appl. Phys. Lett. 31 [1977] p. 266). In dem auf das 1,5fache der Monomodestreifenwellenleiterbreite w verbreitete Kreuzungsbereich kommt es zur Interferenz der hier geführten zwei optischen Moden. Diese Modeninterferenz ist dabei eine Funktion des Brechungsindexprofils. Der durch Protonenaustausch hergestellte und ganzflächig thermisch nachbehandelte X-Koppler soll nun entsprechend einer vorgegebenen Einsatzcharakteristik (z.B. Lichteinkopplung Eingang A und gleichmäßige Aufteilung auf die Ausgänge C und D) bezüglich seiner Funktion nachbehandelt werden. Außerdem sollen die Wellenleiterein- und -ausgänge an eine vorgegebene Monomodelichtleitfaser angepaßt werden. In einem ersten Verfahrensschritt wird erfindungsgemäß durch ein Aufsetzen eines lateral begrenzten und etwa 1 mm breiten Heizelementes der Kreuzungsbereich bei einer Temperatur von 340 ⁰C modifiziert/Durch gleichzeitige Einkopplung von Laserlicht kann das Intensitätsverhältnis der beiden Ausgänge detektiert werden. Danach werden erfindungsgemäß die Wellenleiterein- und -ausgänge durch Aufsetzen zweier lateral begrenzter Heizelemente in gleicherweise modifiziert, bis das ebenfalls während der thermischen Nachbehandlung detektierte optische Modenfeld der Wellenleiter an das Modenfeld einer z. B. vorgegebenen Monomodelichtleitfaser angepaßt wurde. Im Fall eines Wellenleiters, der durch Protonenaustausch in Benzoesäure mit 1 Mol-% Lithiumbenzoatanteil hergestellt wurde, beträgt die optimale Temperatur der thermischen Nachbehandlung 340⁰C. Bei Temperaturen unterhalb 300⁰C bleibt der wellenleitende Bereich relativ unbeeinflußt. Abschätzungen für Lithiumniobat zeigen, daß bei Aufsetzen eines oben genannten lateral begrenzten Heizelementes bereits im Abstand von 2 mm die Temperatur unter 300°C abgesunken ist und damit die erwünschte Selektivität erreicht wird.The drawing schematically illustrates an X-coupler with widened intersection region 1 of the optical single-mode waveguide waveguide (Appl. Phys. Lett. 31 [1977] p.266). In the crossing area spread to 1.5 times the single-mode strip waveguide width w, the two optical modes guided here are subject to interference. This mode interference is a function of the refractive index profile. The X-coupler produced by proton exchange and thermally aftertreated over the entire surface area is now to be aftertreated with respect to its function in accordance with a predetermined operational characteristic (for example, light input A input and uniform distribution to outputs C and D). In addition, the waveguide inputs and outputs are to be adapted to a given Monomodelichtleitfaser. In a first method step, according to the invention, the intersection region is modified at a temperature of 340 ^° C. by placing a laterally delimited and approximately 1 mm wide heating element. By simultaneous coupling of laser light, the intensity ratio of the two outputs can be detected. Thereafter, according to the invention, the waveguide inputs and outputs are modified by placing two laterally limited heating elements in the same way until the also detected during the thermal post-treatment optical mode field of the waveguide to the mode field of a z. B. predetermined single-mode optical fiber has been adapted. In the case of a waveguide, which was prepared by proton exchange in benzoic acid with 1 mol% Lithiumbenzoatanteil, the optimal temperature of the thermal post-treatment 340 ⁰ C. At temperatures below 300 is ⁰ C, the waveguiding region is relatively unaffected. Estimates for lithium niobate show that when a laterally limited heating element is set down, the temperature has dropped below 300 ° C. already at a distance of 2 mm, and thus the desired selectivity is achieved.

Claims

1. A method for tuning and / or adaptation of integrated optical waveguide structures and devices, preferably based on lithium niobate, which were produced by proton exchange and subsequent large-scale thermal aftertreatment, characterized in that laterally limited regions of the waveguide structures subjected to a further thermal aftertreatment become.

2. The method according to claim 1, characterized in that to tune the function of waveguide structures and / or components function-determining areas forÄnderurig the refractive index profile are thermally post-treated.

3. The method according to claim 1, characterized in that for adapting the optical field of the guided optical mode to Monomodelichtleitfasem or other waveguides via a change in the refractive index profile waveguide inputs and outputs are thermally treated.

For this 1 page drawing

Field of application of the invention

The invention relates to a method for tuning and / or adapting integrated-optical waveguide structures and components which have been produced by proton exchange and full-surface thermal aftertreatment in lithium niobate. The selectivity of the laterally limited additional thermal aftertreatment and the associated function-determining tuning and / or possible adaptation of the waveguide structures to other waveguides decisively improves their use in the field of optical information technology and sensor technology.

Characteristic of the known state of the art

Proton exchange as a method of fabricating integrated optical waveguide structures and devices is well known (Ferroelectrics 50 [1983] p.165). Furthermore, it is known that the extraordinary refractive index profile can be modified by thermal full-surface aftertreatment of the proton-exchanged waveguides in lithium niobate (Opt. Lett. 8 [1983] p. In addition, WP G 02 B / 3164390 mentions a necessary condition for full-surface thermal aftertreatment with regard to the possible use of such waveguide structures as electro-optical components. A selective influencing of the waveguide structures and components by a laterally limited thermal aftertreatment is not known.

Object of the invention

The aim of the invention is to provide a method with which both the coordination of proton-exchanged and all-over thermally treated waveguide structures as well as an optimal adaptation of the waveguide structures to other waveguides are guaranteed.

Explanation of the essence of the invention

The object of the invention is to optimize thermally aftertreated waveguide structures or components produced by proton exchange in lithium niobate and with respect to their function and compatibility with other waveguide components. This object is achieved in that the produced by proton exchange and over the entire surface thermally aftertreated waveguide structures (it must lead to a reduction in proton exchange generated change in the extraordinary refractive index Δη, to at least 25% of the original value) selectively and laterally limited thermal aftertreatment. It must be taken into account that function-determining waveguiding regions (eg waveguide intersections, Y-branches) other than, for example, waveguide inputs and outputs must be modified for optimal coupling. Due to the selectivity of the thermal aftertreatment, the refractive index profile is modified on the one hand in function-related areas of the waveguide structure (changes in physical principles such as mode interference, mode locking) until the predetermined mode of operation is set and, on the other hand, the change in the refractive index per λs at the waveguide element. and -ausgängen an optimization with respect to a coupling to predetermined Monomodelichtleit ^f fps or other waveguiding structures guaranteed. The laterally limited thermal aftertreatment is effected by, for example, line-like heating elements which are brought into direct contact with the occasionally conductive crystal surface . A decisive advantage is the possibility of detecting the modification process at the structural or component outputs.