Abstract:
An optical device includes a surface-mountable optical component with a base member having a recess filled with a transparent filler and a VCSEL element arranged in the recess. A receptacle is attached to the surface-mountable optical component. The receptacle is for receiving an optical fiber to optically connect the VCSEL element to the optical fiber. Accordingly, an inexpensive way of coupling a VCSEL element with an optical fiber is provided. In particular, the surface-mountable component can be produced using a high volume production so that the overall costs of the optical device are reduced, even if the receptacle is produced in lower numbers due to varying requirements in the way that the VCSEL will be coupled to an optical fiber.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an optical device. 
     A Vertical Cavity Surface Emitting Lasers (VCSEL) is a semiconductor microlaser diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer. VCSELs offer significant advantages when compared to the edge-emitting lasers still used in the majority of fiber optic communications devices. To this end, VCSELs are packaged in TO (Transistor Outline) metal housings and mounted in receptacles for coupling with optical fibers. 
     In WO 9931737, which is hereby incorporated by reference, there is described a method for producing a surface-mounted optoelectronic component. The component provides good optical characteristics while being inexpensive. 
     It would be desirable to provide an inexpensive way of coupling VCSELs to optical fibers. The present invention aims to address this desire. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the invention there is provided an optical device comprising: a surface-mountable optical component comprising a base member having a recess filled with a transparent filler, and an VCSEL element arranged in the recess; and a receptacle attached to the surface-mountable optical component, for receiving an optical fiber, thereby to optically connect the VCSEL element with the optical fiber. Accordingly, there is provided an inexpensive way of coupling a VCSEL element with an optical fiber. In particular, the surface-mountable component is suitable for a high volume production so that the overall costs of the optical device are reduced, even if the receptacle is produced in lower numbers due to varying requirements in the way the VCSEL is to be coupled to an optical fiber. 
     Preferably, the surface-mountable optical component further comprises one or more optoelectronic monitor elements arranged in the recess of the base member, for monitoring a predetermined emission parameter of the light emitter. The predetermined emission parameter may be, for example, the light emission power. Thus, the perfomance of the VCSEL can be monitored and any necessary corrections made. 
     In one embodiment of the invention, the optical device further comprises a reflector arranged between the light emitter and a light receiving end of the receptacle, for reflecting a part of the light emitted by the VCSEL onto at least one of the one or more optoelectronic monitor elements. This facilitates the arrangement of the monitor elements. 
     Preferably, the light emitter and the one ore more optoelectronic elements are mounted to a bottom surface of the recess adjacent to one another, and the reflecting surface of the reflector is at an angle relative to the bottom surface of the recess thereby to reflect light emitted from the light emitter onto at least one of the one or more optoelectonic monitor elements. This further simplifies the design of the optical device. 
     In one embodiment of the invention, the surface of the reflector facing the light receiving end of the receptacle is convex. Thereby, light emitted from the VCSEL is focussed onto the light-receiving end surface of an optical fiber received in the receptacle. 
     Preferably, the receptacle comprises an optical coupling element inbetween the optical fiber and the optoelectronic element, for focussing light from the VCSEL element onto the light receiving end surface of an optical fiber received in the receptacle. Thereby, the optical characteristics of the coupling of the VCSEL and the optical fiber are further improved. 
     The optical coupling element comprise a lens. The receptacle may comprise a recess for holding the lens. The lens may be spherical. This provides for a simple design while achieving a reliable optical coupling. 
     Preferably, the optical coupling element is in contact with the filler. This provides for an exact alignment of the VCSEL and the optical coupling element. 
     In one embodiment of the invention, the light receiving end portion of the receptacle is transparent to optically connect the VCSEL element with the optical fiber, wherein part of the surface of the transparent end portion facing the VCSEL, and/or part of the surface of the transparent end portion facing the light receiving end surface of an optical fiber received in the receptacle, is convex, thereby to form the optical coupling element. 
     In one embodiment of the invention, the receptacle comprises an optical coupling element inbetween the optical fiber and the VCSEL element, for focussing light emitted from the VCSEL element onto the light receiving end surface of an optical fiber, wherein the surface of the optical coupling element facing the VCSEL element is reflective to reflect part of the light emitted from the VCSEL element on at least one of the one or more optoelectronic monitor elements. Thus, no separate reflector is required while still allowing a simple arrangement of the monitor elements. 
     The optical device may further comprise an attachment element through which the surface-mountable optical component is attached to the receptacle, the attachment element comprising a through hole, wherein the surface-mountable optical component is arranged at one end of the through hole, and the receptacle is arranged at the other end of the through hole, whereby the VCSEL element is optically connected to an optical fiber received in the receptacle. By means of an attachment element, the design of the end portion of the receptacle for attachment with the surface-mountable optical element, and vice versa, is less restricted. Thus, pre-manufactured surface-mountable optical elements and receptacles can be attached to one another without requiring an adaptation of their design. 
     Preferably, the receptacle and the surface-mountable optical component are glued to opposing surfaces of the attachment element, respectively. This further reduces manufacturing costs. 
     In one embodiment, the optical device further comprises a reflector arranged between the VCSEL element and a light receiving end of the receptacle, for reflecting a part of the light emitted by the VCSEL element onto at least one of the one or more optoelectronic monitor elements; and an attachment element through which the surface-mountable optical component is attached to the receptacle, the attachment element comprising a through-hole, wherein the surface-mountable optical compenent is arranged at one end of the through hole, and the receptacle is arranged at the other end of the through hole, whereby the optoelectronic element is optically connected to the optical fiber, and wherein the reflector is held in the through hole. 
     The receptacle may comprise plastic, metal and/or ceramic material. The optical coupling element may comprise transparent plastic and/or glas material. 
     The filler may comprise a hardenable sealing compound. In particular, the filler may comprise epoxy resin. 
     According to another aspect of the invention, there is provided a surface-mountable optical component comprising a base member having a recess filled with a transparent filler, and a VCSEL arranged in the recess. Accordingly, a simple and inexpensive surface-mountable VCSEL component is provided which is suitable for high volume production. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional view of an optical device according to a first embodiment of the invention; 
     FIG. 2 is a sectional view of an optical device according to a second embodiment of the invention; 
     FIG. 3 is a sectional view of an optical device according to a third embodiment of the invention; and 
     FIG. 4 is a sectional view of an optical device according to a fourth embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, there is shown a sectional view of an optical device according to a first embodiment of the invention. The optical device comprises a surface-mountable optical component  1  which is attached to a receptacle  2  by means of an attachment element  3 . 
     The surface-mountable optical component  1  comprises a base portion  4  with a recess  5 . On a bottom surface  6  of the recess  5 , a VCSEL  7  is provided inbetween monitor diodes  8 . The recess is filled with a transparent hardenable filler  9 . A top surface  10  of the hardened filler  9  is concave. 
     The attachment element  3  comprises two bores  11  and  12 . The first bore  11  has a diameter corresponding to the outer diameter of the surface-mountable component  1 . The second bore  12  has a diameter smaller than that of the first bore  11 ,  50  that a step  13  is formed where the two bores  11  and  12  adjoin. The component  1  is received in the first bore  11  and comes to sit on the step  13 . Preferably, the component is glued to the attachment element  3 . The receptacle  2  is glued to the opposing end of the attachment element  3 . 
     The receptacle  2  comprises a through hole  14  consisting of portions  15 - 19 . Portions  15 ,  17  and  18  are cylindrical and have different diameters. Portions  16  and  19  are conical. An optical fiber  20  is embedded in a ferrule  21  which has the same diameter as the cylindrical portion  18 . The ferrule  21  is inserted into the portion  18  and thereby held in the receptacle  2 . The conical portion  19  facilitates insertion of the ferrule  21  into the cylindrical portion  18 . Since the cylindrical portion  17  adjoining the cylindrical portion  18  has a smaller diameter, another step  22  is formed on which the ferrule  21  comes to sit when inserted into the cylindrical portion  18 . 
     A spherical lens  23  is received in the cylindrical portion  15 . The lens  23  of this embodiment is spherical, has the same diameter as the cylindrical portion  15  and abuts on the walls of the spherical portion  16 . The lens  23  is held by the walls of the cylindrical portion  15  but can be glued therto additionally. The lens  23  projects from the lower exit (i.e. the exit facing the component  1 ) into the second bore  12 . 
     As shown, the lens  23  is at a distance from the upper surface of the surface-mountable optical component  1 . A surface  24  of the lens  23  facing the component  1  is reflective so that part of the light emitted from the VCSEL  7  and impinging on the surface  24  is reflected back onto the monitor diodes  8 , as shown by arrows A. The other part of the light passes through the lens  23  and is thereby focussed onto a light-receiving end of the optical fiber  20  which is at a distance from the lens  23 . 
     When assembled, the component  1 , the attachment element  3  and the receptacle  2  form an axis  26  which passes through the center of the VCSEL  7 , the center of the lens  23 , and along the optical axis of the optical fiber  20 . 
     FIG. 2 illustrates a second embodiment of the invention. Same reference numbers designate the same elements as shown in FIG. 1 so that a description of these elements is omitted. 
     In this embodiment, the attachment element  3  and the component  1  are received within a cylindrical portion  27  and thereby held in the receptacle  2 . The cylindrical portion  27  has the same diameter as the attachment element  3 . Also, the attachment element  3  and the component  1  have the same longitudinal extension. Preferably, the outer walls of the attachment element  1  are glued to the walls of the cylindrical portion  27 . The axial extension of the cylindrical portion  27  (i.e. the extension along the axis  26 ) corresponds to that of the attachment element  3  and component  1  so that the component  1  is completely received within the cylindrical portion  27 , and the bottom surface (i.e. the surface of the component  1  which is to be mounted to a component receiving surface) of the component  1  and the attachment element  3  forms an even surface with the bottom surface of the receptacle  2 . This is in contrast to the first embodiment, where part of the component  1  projects from the attachment element  3 . 
     In FIG. 2, the lens is at close distance from the concave top surface  10  of the hardened filler  9 . Although not shown, the lens  23  may also be in direct contact with the surface  10  in an alternative embodiment. 
     FIG. 3 illustrates a third embodiment of the invention. Again, a description of elements corresponding to those of the first and second embodiments is omitted. 
     In FIG. 3, the surface-mountable optical component  1  is attached to the receptacle  2  by means of an attachment element  3 . However, in contrast to the first embodiment, the lens  23  is integrated into receptacle  2 . That is, receptacle  2  is formed of a transparent material. Part of the bottom surface of the receptacle (i.e. the surface facing the component  1 ) at the axis  26  is convex. The portions  15  and  16  of the through hole  14  are omitted. The integrated lens  23  has the same function as in the first and second embodiments, that is to focus light emitted from the VCSEL  7  onto the light receiving surface  25  of the optical fiber  20 . 
     In addition, a transparent reflective element  28  is provided within a through hole  29  through the attachment element  3 . The reflective element has a reflective surface  30  facing the component  1 . Of the light emitted from the VCSEL  7 , one part is reflected back onto the monitor diode  8 , while the other part passes through the reflective element  28  to the lens  23 . The reflective element  28  is mounted to steps  31  and  32  within the through hole  29 . The steps  31  and  32  are provided at different positions along the axis  14 . That is, in the orientation of FIG. 3, the step  31  is located higher (closer to the receptacle) than the step  31  (which is closer to the component  1 ). As a consequence, the reflective surface  30  is at an angle relative to the upper surface of the component  1 . Thus, light emitted from the VCSEL  7  and impinging onto the reflective surface  30  is not reflected back onto the VCSEL  7 , but onto the monitor diode  8  located adjacent to the VCSEL  7  on the bottom surface  6  of the recess  5 . Only a single monitor diode  8  is provided, compared to the first and second embodiments. 
     FIG. 4 illustrates a fourth embodiment of the invention. In this embodiment, the through hole  29  is formed by a single bore through the attachment element  3 . The reflective member  28  is attached to the rim of the recess  5 . Part of the reflective member  28 , and in particular part of the reflective surface  30  extends into the filler  9 . The reflective member  28  is shaped such that the reflective surface  30  is at an angle relative to the upper surface of the component  1 . Thus, light emitted from the VCSEL  7  and impinging onto the reflective surface  30  is not reflected back onto the VCSEL  7 , but onto the monitor diode  8  located adjacent to the VCSEL  7  on the bottom surface  6  of the recess  5 . Again, only a single monitor diode  8  is provided. 
     Opposite the reflective surface  30 , the reflective element  28  comprises a convex surface  33 . As a consequence, light from the VCSEL  7  passing through the reflective element  28  is pre-focussed onto the lens  23  when exiting the reflective element  28 . 
     The lens  23  corresponds to that of the first embodiment, although it is arranged further away from the component  1 , closer to the optical fiber  20 . This is achieved by an longitudinal extension of the cylindrical portion  17  and a shortening of the cylindrical portion  15 . The lens  23  thus no longer projects from the lower exit of the through hole  14 .