WO1998038710A1 - Optoelectronic component - Google Patents

Abstract

The invention relates to an optoelectronic component with adjustable space distribution of temperature, comprising an optical waveguide and at least one electrothermal element to mofidy the temperature of said optical waveguide. The electrothermal element is designed and/or mounted in such a way that the temperature generated inside the optical waveguide varies depending on the place.

Description

Optoelectronic component

Technical field

The invention relates to an optoelectronic component with spatially adjustable temperature distribution, which has at least one optical waveguide and at least one electrothermal element for changing the temperature of the optical waveguide.

State of the art

It is from J. O'Gorman, AF Levi, S. Schmitt-Rink, T. Tanbun-Ek, DL Coblentz and RA Logan "On the temperature sensitivity of semiconductor lasers" Appl. Phys. Lett. 60, 157 (1992) discloses that relevant physical quantities and parameters in optoelectronic components depend on the temperature. This thermal effect is used, for example, for wavelength or frequency tuning in optoelectronic components (S. Sakano, T. Tsuchiya, M. Suzuki, S. Kitajima and N.- Chinone "Tunable DFB laser with a striped thin-film heater", IEEE Phot Technol. Lett. 4, 321 (1992). To supply thermal energy, a resistance heater is used which produces a homogeneous temperature field apart from edge effects in the axial waveguide direction (= light propagation direction). With the known resistance heating, however, only a frequency tuning can be carried out without an efficient possibility to influence further parameters of the optoelectronic component and to adapt the component to the respective application conditions. Furthermore, inhomogeneities in the optical waveguide cause, inter alia, that the yield or the efficiency of the component is not satisfactory.

The object of the invention is therefore to provide an optoelectronic component whose properties can be adapted to the respective application conditions, with a high yield or very good efficiency preferably being achieved.

Presentation of the invention

This object is achieved by the optoelectronic component according to the invention in that the electrothermal element is designed and / or arranged in such a way that the temperature change which can be caused in the optical waveguide is location-dependent. This allows the physical component parameters to be optimized using an individually selected temperature field.

The invention is based on the knowledge that various performance features of optoelectronic components are caused by inhomogeneities of the optical waveguide and that a targeted control of the effect of the inhomogeneities is possible by means of location-dependent temperature changes. In particular, the following features of optoelectronic components can be positively influenced by the measures according to the invention: efficiency, optical Output power, line width, side mode suppression, mode stability, wavelength tunability, efficiency of wavelength tuning, beam steering (beam steering), wavelength selection - depending on the type of component, for example a laser, a laser amplifier, a filter, a length wave converter, a multiplexer, a demultiplexer or a detector can be.

The at least one electrothermal element can be designed as a heating element or as a cooling element, for example in the form of a Peltier element.

In order to achieve the location-dependent temperature change, it is provided in advantageous embodiments of the invention that the cross section of the at least one electrothermal element, the specific resistance of the at least one electrothermal element and / or that the distance of the at least one electrothermal element from the optical waveguide is location-dependent.

Significant advantages, in particular the increase in the efficiency and / or the optical output power and the side mode suppression, can be achieved in another advantageous embodiment in that the positional dependence exists predominantly in the longitudinal direction (axial direction) of the optical waveguide.

An alternative or additional location dependency of the temperature distribution in the other directions can, for example, be used advantageously for beam steering.

The optoelectronic component according to the invention has at least one optical waveguide which guides a light field of a defined wavelength range in the axial direction, for example in the x direction. Due to the spatially inhomogeneous Resistance heating can be used to vary physical parameters, for example the refractive index, which are relevant for the component function locally via their temperature dependence.

The optical waveguide is preferably made up of organic or inorganic semiconductors, polymers or glasses. A particularly advantageous embodiment can be seen in an inorganic semiconductor laser. The electrothermal elements preferably consist of one of the following electrically conductive substances: pure metals, metal alloys, ceramics, polymers or electrolytes. As a particularly advantageous embodiment, a metal film can be seen which has a substantially smaller extent in the z direction than in the x and y directions. The material composition of the metal film can additionally vary spatially (in this case preferably in the x and y directions).

The lateral boundaries (lateral directions run in the xy plane) are preferably described by at least two curved functions y1 (x) and y2 (x) if the electrothermal element is simply connected. In the case of regions which are connected several times, further limiting functions yi (x) occur accordingly. The metal film can additionally be curved in the z-directions, that is to say it runs over ribs, for example. The metal body of the electrothermal element is contacted at at least two points, a voltage applied to the contact depending on the change in the electrical resistance in the xyz space causing a correspondingly spatially distributed current density. This results in a location-dependent heating power, so that a variable temperature distribution in the xyz space can be realized in the optical waveguide of the component. If the optoelectronic component is, for example, a semiconductor laser, the variable temperature distribution enables a more stable single-mode oscillation and an increase in yield to be achieved.

Properties of optoelectronic components are often subject to aging. According to a development of the invention, such aging can be compensated for by changing the voltage applied to the electrothermal element over time.

Different properties of lasers depend on the current injection, for example the tendency to oscillate in certain modes. Such a dependency can be used consciously according to another further development, since with a corresponding design of the electrothermal element, the voltage applied to the electrothermal element can be chosen so large that the location-dependent temperature change is correlated with the spatial distribution of the current injection. This achieves advantageous component properties, such as side mode suppression, position of the emission wavelength and output powers.

In this development, the electrothermal element can either be put into operation before the current is injected into the laser-active zone of the laser component. Alternatively, it is conceivable to increase the heating current in a defined manner to the final value, which is correlated with the increase in the injection current of the laser-active zone over time.

Further advantageous embodiments of the invention result from the remaining subclaims. Brief description of the drawings

Exemplary embodiments of the invention are shown schematically in the drawing with reference to several figures and are explained in more detail in the following description. It shows:

1 shows a semiconductor laser with two heating elements,

2 shows a semiconductor laser with a heating element with a slightly curved edge on one side,

3 and Fig. 4 each have a semiconductor laser with a

Heating element with a strongly curved edge on one side,

5 shows a semiconductor laser with an overall curved heating element,

6 shows a semiconductor laser with a curved optical waveguide,

7 shows a semiconductor laser with a heating element with a constant width over the length, but with changing length-specific resistance,

8 shows a semiconductor laser with a heating element which has cutouts,

9 shows a semiconductor laser with heating elements arranged on the end regions of the optical waveguide,

10 shows a semiconductor laser with two heating elements which are arranged on different sides on each half of the optical waveguide, 11 shows a semiconductor laser with three heating elements, each of which extends over part of the optical waveguide,

12 shows a semiconductor laser with a heating element that is partially bridged several times,

Fig. 13 shows a semiconductor laser with a

Optical fiber crossing heating element,

Fig. 14 is a semiconductor laser with a

Optical fiber double crossing heating element,

15 is a perspective view of a semiconductor laser and

16 shows a semiconductor laser with a parallel heating element.

In connection with the exemplary embodiments, reference has been made to heating elements for the sake of simplicity. However, the exemplary embodiments can also be implemented with cooling elements.

Ways of Carrying Out the Invention

FIG. 1 shows a top view of a semiconductor laser 10 which has the length L and whose waveguide runs in the axial direction (x direction). The basic structure of a semiconductor laser is known, which is why a detailed description is omitted. A strip 1 can be seen in the figure, which represents the contacting layer on the side of the pn-junction of the semiconductor laser facing away from the substrate. The waveguide, not shown in the figure, runs under the Contacting layer 1.

In the xy plane, which corresponds to the plane of the drawing, a film-like metal heating element 2 or 3 is provided on both sides of the strip 1. These elongated heating elements 2, 3, preferably in the form of a metal film, extend like the strip 1 in the x direction over the length L. Both heating elements 2, 3 are delimited in the y direction by edges R1, R2, R3 and R4, which in the xy plane is curved. It can clearly be seen that the width Bij of a heating element 2 or 3 varies for different x values.

At each longitudinal end of a heating element 2, 3, a contact field 4, 5, 6, 7 is electrically connected to the heating element 2, 3. The contacting faces are preferably formed as a thick (approx. 700 nm) gold layer, so that they have the lowest possible electrical resistance. The Kontaktierungsfeider 4 to 7 are used to apply a heating voltage to the heating elements. The voltage is supplied to the contacting feet by means of contacting wires, which are not shown in FIG. 1, however.

As already mentioned, the edges R1, R2, R3 and R4 of the two heating elements 2, 3 are curved. Specifically, the course of an edge in the xy plane can be described as a function y (x) with O≤x≤L. In the present exemplary embodiment, the limiting function y2 (x) for O≤x≤L describes the edge of the heating element 2 for small y values and the limiting function y1 (x) for d≤x≤ (Ld) describes the edge for large y values. The course of the edge of the other heating element 3 describes the limiting function y3 (x) for O≤x≤L with large y values and the limiting function y4 (x) for d≤x≤ (Ld) with small y values. In the x direction, the heating elements end with the component facets shown as vertical lines.

Is now a heating voltage to the

Contacting fields 4 to 7 and thus applied to the heating elements 2, 3, a current flows, the current density being dependent on the resistance of the heating element. Because the width B12 (X) or B34 (x), that is, the difference y1 (x) - y2 (x) or y3 (x) - y4 (x) varies for different x values, the heating element heats up different in the xy plane. By selecting the limiting functions y1 (x) and y2 (x), the temperature distribution in the heating element 2 and in its surroundings can be varied locally. By varying the difference y1 (x) - y2 (x) for different x values and also by varying the distance, for example the geometric center (y1 (x) + y2 (x)) / 2 of the heating element 2 from the waveguide the temperature of the waveguide is varied locally.

In the present example, the influence of the further heating element 3 must also be taken into account. Because the difference y3 (x) - y4 (x) varies in the x direction, the heating element 3 also heats up differently in the xy plane. By choosing the

Limiting functions y3 (x) and y4 (x) and the choice of material for the heating element, the temperature distribution in the heating element 3 and in its surroundings is varied locally. By varying the difference y3 (x) - y4 (x) in the x direction and also by varying the distance, for example the geometric center (y3 (x) + y4 (x)) / 2 of the heating element 3 from the waveguide the heating element 3 contributes to a local variation in the temperature of the waveguide. The resulting spatial temperature field in the waveguide can be calculated on the basis of the current and heat conduction, the following variables being included: The limiting functions y1 (x) to y4 (x), the material-specific electrical ones Resistances, the material-dependent thermal conductivity values as well as the geometric structure of the component and its heat sink.

FIG. 2 shows a second exemplary embodiment of a semiconductor laser 10, which is distinguished from the first exemplary embodiment in that only one heating element 2 is provided. In addition, the lower edge of the heating element defined by the function y2 (x) is not curved. Because the heating element 2 has a smaller width in the central region of the waveguide than in outer regions, higher local temperatures are achieved in the middle. The prerequisite for this is that the layer thickness of the heating element in the z direction, the specific electrical resistance and the assumed heat dissipation are homogeneous.

The two shown in Figures 3 and 4

Exemplary embodiments each comprise a semiconductor laser 10, which each has a heating element 3. In both embodiments, one edge of the heating element 3 is curved (y3 (x) in FIG. 3; y4 (x) in FIG. 4), while the other edge is not curved. In these exemplary embodiments, too, the width, that is to say the difference y3 (x) - y4 (x), varies in the x direction, so that a different temperature distribution can be achieved.

FIG. 5 shows a semiconductor laser 10 which also has a heating element 2. In contrast to the aforementioned exemplary embodiments, the width, that is to say the difference y1 (x) - y2 (x), is constant in the x direction. In order to achieve a varying temperature distribution in the x direction, that is to say in the direction of extension of the waveguide, the distance between the heating element 2 and the contact strip 1 and thus the waveguide below it is varied. Since the distance between heating element 2 <<

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Heating element section 2 'is provided, which is connected by means of metal wires 9.1, 9.2 to the two heating element sections 3', 3 ¹ '. The two metal wires 9 thus connect the three parts 2 ', 3', 3 '' of the heating element to form a coherent area in the mathematical sense. The figure also shows that the width of the two heating element sections 3 ', 3 ^{1 1 is} constant, while the width of the heating element section 2' varies.

In addition, a metal surface 11 is shown in FIG. 11, which is electrically connected to the contact strip 1 and serves as a contact field for the contact strip 1.

In the exemplary embodiment shown in FIG. 12, the local variation of the electrical resistance results from several local potential adjustments, in that a plurality of metal wires 12 are conductively connected to the heating element 2 at different locations.

FIG. 13 shows an embodiment with a non-planar surface. In this case, the curved heating element 2 crosses the contact strip 1, a conductive connection between the heating element 2 and the contact strip 1 being prevented by an electrically insulating layer 13. The heating voltage is applied between the contacting fields 4 and 6.

FIG. 14 shows a modification of the exemplary embodiment shown in FIG. 13. In addition to a curved course of the heating element 2 is also the

Contact strips 1 are curved so that the heating element and contact strips cross twice. A conductive connection between the heating element 2 and the contacting strip 1 is also prevented in this case by an electrically insulating layer 13. The Heating voltage itself is applied between the contact fields 4 and 5.

The exemplary embodiment shown in FIG. 15 shows an arrangement which has some common features with FIGS. 13 and 14. The optical waveguide and the contacting strip 1 run uncurved in the x direction. The contact strip 1 is supplied with current via the metal surface 11. The heating element 2 is curved in three-dimensional space. The heating voltage is applied between the contacting fields 4 and 6. A conductive connection between the heating element 2 and the contacting strip 1 is prevented by an electrically insulating layer 13. The laser light 14 emerging in the axial direction is also schematically indicated.

The exemplary embodiment shown in FIG. 16 represents a variant of the exemplary embodiment shown in FIG. 8, wherein the heating element 2 consists of two different types of metal with different specific resistance and the metal 16 fills the cutouts in the metal 15. It is also conceivable that the metal 15 has no recesses, but forms a homogeneous layer. The metal fields 16 are then attached in the z direction on or below this layer. The shape and distribution of the metal fields 16 can now be used to spatially vary the heating current density. A spatial variation of the temperature can also be achieved in this way. Of course, other designs of a heating element 2 and its arrangement relative to the contact strip 1 are also conceivable in order to achieve a desired temperature distribution in the optical waveguide.

Claims

Expectations 1. Optoelectronic component with spatially adjustable temperature distribution, which has at least one optical waveguide and at least one electrothermal element for changing the temperature of the optical waveguide, characterized in that the electrothermal element (2, 3) is designed and / or arranged such that the temperature change which can be caused in the optical waveguide is location-dependent. 2. Optoelectronic component according to claim 1, characterized in that the cross section of the at least one electrothermal element (2, 3) is location-dependent. 3. Optoelectronic component according to one of the claims 1 or 2, characterized in that the distance of the at least one electrothermal element (2, 3) from the optical waveguide is location-dependent. 4. Optoelectronic component according to one of the preceding claims, characterized in that the specific resistance of the at least one electrothermal element (2, 3) is location-dependent. 5. Optoelectronic component according to one of the claims 2 to 4, characterized in that the positional dependence exists in the longitudinal direction of the optical waveguide. 6. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2, 3) has at least one recess (8), so that the electrothermal element (2, 3) represents a spatially multiple area in the mathematical sense. 7. Optoelectronic component according to claim 6, characterized in that the spatial arrangement and / or the geometric shape of the at least one recess (8) are selected such that the location-dependent temperature change occurs in the optical waveguide. 8. Optoelectronic component according to one of the preceding claims, characterized in that in the geometric projection of the electrothermal element (2, 3) in a plane parallel to the surface of the component (xy plane), the local limitation in this plane by limiting function y1 (x ) and y2 (x) is defined. 9. Optoelectronic component according to claim 8, characterized in that at least one of the two limiting functions y1 (x) and y2 (x) is curved. 10. Optoelectronic component according to one of the preceding claims, characterized in that in the projection of the electrothermal element (2, 3) into an x'y 'plane, the local limitation in the x' y 'plane by the limiting functions y'1 (x ') and y'2 (x') can be defined, the x'y 'plane being different from the xy plane. 11. Optoelectronic component according to claim 10, characterized in that at least one of the two limiting functions y'1 (x ') and y'2 (x) is curved. 12. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2, 3) is electrically contacted at at least two points. 13. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2, 3) is constructed from different individual bodies which consist of different metals and / or metal alloys and are electrically connected to one another. 14. Optoelectronic component according to one of claims 1 to 12, characterized in that the electrothermal element (2, 3) consists of a metal alloy, a metal, a ceramic compound or an electrically conductive polymer. 15. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2, 3) has a resistive substance which is an electrolyte or a combination of metal alloys, pure metals, polymers and electrolytes. 16. Optoelectronic component according to one of the preceding claims, characterized in that it is a semiconductor laser, a semiconductor laser amplifier, a filter or a wavelength converter. 17. Optoelectronic component according to one of the preceding claims, characterized in that the voltage applied to the electrothermal element (2) can be changed over time. 18. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2) is a mathematically connected body, at least one section being formed by an electrically conductive bridge (9) extending through the air. 19. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2) represents a body which is connected several times in the mathematical sense, at least one electrically conductive wire bridge (12) being provided, through which points of the electrothermal element which are at a distance from one another are provided get connected . 20. Optoelectronic component according to claim 6, characterized in that the electrothermal element (2) is constructed from two different materials with different resistivities, the first material filling the recess (8) in the second material. 21. Optoelectronic component according to one of the preceding claims, characterized in that the electrothermal element (2) is formed from two different materials with different resistivities, the first material forming a homogeneous layer (15) and the second material in locally limited fields (16) lies below or on the layer and is conductively connected to it. 22. Optoelectronic component according to one of the preceding claims, characterized in that the limiting function y1 (x) and y2 (x) and / or the limiting function y'1 (x ') and y'2 (x') represent sectionally defined functions. 23. Optoelectronic component according to one of the preceding claims, characterized in that at least two electrothermal elements (2, 3) are formed.