Abstract:
An optical device includes a first substrate having a first top surface and a first bottom surface, a second substrate having a second top surface and a second bottom surface, and a spacer substrate between substantially planar portions of the second top surface and the first bottom surface. The spacer, first, and second substrates seal an interior space between the second top surface of the second substrate and the first bottom surface of the first substrate. At least two of the first, second, and spacer substrates are aligned and secured on a wafer level. An optoelectronic element is within the interior space. An optical axis of the optical device extends through one of the first top and bottom surfaces and the second top and bottom surfaces. An electrical interconnection extends from the optoelectronic element to outside the interior space.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 12/801,941, filed Jul. 2, 2010, which is a continuation of Ser. No. 12/379,279, filed Feb. 18, 2009, now Pat. No. 7,750,289 B2, which is a continuation of Ser. No. 11/651,525, filed Jan. 10, 2007, abandoned, which in turn is a continuation of Ser. No. 11/127,284, filed May 12, 2005, now Pat. No. 7,375,315 B2, which is a continuation of Ser. No. 10/231,483, filed Aug. 30, 2002, abandoned, which is a continuation of PCT/US01/07053, filed Mar. 6, 2001, which claims priority to provisional application Ser. No. 60/187,034, filed Mar. 6, 2000, and is a continuation-in-part of U.S. patent application Ser. No. 09/418,022 filed Oct. 14, 1999, now Pat. No. 6,374,004, entitled “Optical Subassembly,” and a continuation-in-part of U.S. patent application Ser. No. 09/418,365 filed Oct. 14, 1999, now Pat. No. 6,406,195, entitled “Interface Between Opto-electronic Devices and Fibers,” the entire contents of all of which are hereby incorporated by reference in their entirety for all purposes. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Previous attempts at integrating a transceiver on a chip involved using monolithic integration, in which the active elements are formed in the substrate, and are thus all made of the same material. This does not allow optimum performance to be realized for at least one of the detector array and the light source array. 
         [0003]    Other attempts have placed the active elements, e.g., the light sources and the detectors, on different substrates. However, this increases the complexity of the system due to an increased number of components and alignment difficulty. 
       SUMMARY OF THE INVENTION 
       [0004]    One or more embodiments are directed to an optical device including a first substrate having a first top surface and a first bottom surface, a second substrate having a second top surface and a second bottom surface, a spacer substrate between a substantially planar portion of the second top surface of the second substrate and a substantially planar portion of the first bottom surface of the first substrate, the spacer substrate, the first substrate and the second substrate sealing an interior space between the second top surface of the second substrate and the first bottom surface of the first substrate, at least two of the first substrate, the second substrate, and the spacer substrate being aligned and secured on a wafer level, an optoelectronic element within the interior space, an optical axis of the optical device extending through one of the first top and bottom surfaces and the second top and bottom surfaces, and an electrical interconnection extending from the optoelectronic element to outside the interior space. 
         [0005]    The optoelectronic element may transmit light. 
         [0006]    The optical device may be used in a laser pointer. 
         [0007]    The optical device may be used with a plurality of fibers. 
         [0008]    The optoelectronic element may detect light and output an electrical signal in response thereto. 
         [0009]    The optical device may be used with a plurality of fibers. 
         [0010]    The optoelectronic element may be a transceiver. 
         [0011]    The optical device may be used in an optical head. 
         [0012]    The optical device may be used in a data storage system. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Features will become apparent to those of ordinary skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
           [0014]      FIG. 1  is an elevational exploded top view of an optical transceiver according to an embodiment; 
           [0015]      FIG. 2  is an elevational side view of another optical transceiver according to an embodiment; 
           [0016]      FIG. 3  is a top view of another configuration of the light sources and detectors on the same substrate; 
           [0017]      FIG. 4  is a schematic side view of the creation of multiple transceivers according to an embodiment; and 
           [0018]      FIG. 5  is an exploded elevational perspective view of an interface in conjunction with fibers in a housing and the transceiver according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    In the following description, for purposes of explanation and not limitation, specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known devices and methods are omitted so as not to obscure the description of the present invention with unnecessary details. 
         [0020]    Rather than using monolithic integration, many of the advantages of integration can still be realized by providing the light source array and the detector array on the same surface of a single substrate and providing an optics block having the optical elements for both the light source array and the detector array integrated therein. 
         [0021]    Related, co-pending U.S. Provisional Application Ser. No. 09/690,763 entitled “Fiber Interfaces Including Parallel Arrays, Power Monitoring and/or Differential Mode Delay Compensation” filed on Oct. 18, 2000, describes a laser array and a detector array on the same substrate. In this previous application, the detector array was used for monitoring the power of the lasers, a portion of the output laser beams being directed to the detector. In accordance with the present disclosure, a light source array and a detector array are integrated on the same substrate, but, as shown in  FIGS. 1 and 2  of the present application, these detectors are for receiving a signal from a remote location, not for monitoring the light source array. Of course, an additional array of monitor detectors could be provided for monitoring the output of the light sources. 
         [0022]    In  FIG. 1 , an optical transceiver  100  includes a light source array  102 , here shown as a vertical cavity side emitting laser (VCSEL) array, and a detector array  104  are integrated on a silicon wafer  106 . Silicon interconnect tracks  108  supply power to the active elements  102 ,  106  and pads  110  allow the detector signals to be read out. 
         [0023]    An optics block  120  contains two sets of integrated optics, one set  122  for the light source array  102  and one set  124  for the detector array  104 . The integrated optics  122  for the light source receive light from the light source array  102  and direct the light to a desired application. The integrated optics  124  for the detectors receive light from a desired application and direct the light to the detector array  104 . The optics may be diffractives, refractives or hybrids thereof and may be formed lithographically on the optics block  120 . 
         [0024]    The integrated optics  122 ,  124  for the light source array and the detector array may include optical elements formed on either or both surfaces of the optics block  120 . Since the optics for both the light source array and the detector array are aligned simultaneously, the assembly and alignment steps required for creating a transceiver are reduced. Further, the integration allows the transceiver to be smaller and have fewer parts. Depending upon the material used for the substrate, either the detector array or the light source array may be monolithically integrated therein. 
         [0025]    The transceiver  100  also includes a spacer  130  between the active elements and the optics block  120 . The spacer may be an integrated spacer surrounding the perimeter of the optics block, as shown in  FIG. 1 . The spacer may be a separate element, formed in the optics block or formed in the substrate. The spacer may serve to protect the active elements. 
         [0026]    In  FIG. 2 , the bonded structure of a transceiver  200  is shown. Rather than having a spacer  130  around the perimeter of the optics block  120 , separate spacer elements  230  are positioned at the corners of the optics block. Also, the optics  222  for the light sources  202  are on a different surface of the optics block  220  than the optics  224  for the detectors  204 . The optics for both the light sources and the detectors may have the same design. Again, light sources  202  and detectors  204  are on the same substrate  206 , and one of them may be monolithically integrated therein. Silicon tracks  208  and pads  208  for providing power and signals to and from the active elements are also on the substrate. 
         [0027]      FIG. 3  is a top view of a transceiver  300  in accordance with another embodiment of the present invention. In  FIG. 3 , rather than having the active elements  102 ,  104  arranged in parallel arrays, the active elements form a linear array. In the particular example shown in  FIG. 3 , four light sources  102  and four detectors  104  are in a line. The spacing therebetween reduces cross-talk between the active devices. Corresponding optical elements  122 , 124  are also now in a single line. This configuration allows a standard  1  x  12  fiber array to be connected with the transceiver. This configuration also allows all the required interconnection to be provided on a same side of the substrate  106 , thereby allowing the optics block  120  and the substrate  106  to share a common edge, which may facilitate manufacturing at the wafer level. 
         [0028]    In any of the configurations, the components may be attached using wafer-to-wafer bonding techniques, as set forth, for example, in U.S. Pat. Nos. 6,096,155 and 6,104,690, commonly assigned, which are hereby incorporated by reference in their entirety for all purposes. Both of the above configurations allow the optics for both the transmitter portion and the receiver portion to be aligned simultaneously. As used herein, the term wafer is meant to generally refer to any structure having more than one component which is to be singulated, e.g., diced, for final use. The resultant wafer having a plurality of the transceivers thereon is then singulated, i.e., vertically separated, to form a plurality of transceivers. 
         [0029]    A particular example of wafer bonding all three substrates together before separating is shown in  FIG. 4 . By creating spaces  340  between the sets of optical elements  122 ,  124  for each transceiver and spaces  342  between the spacers  130  for each transceiver, e.g., by etching in silicon as shown, the individual transceivers may be realized by separating the substrate  106  containing the light sources  102  and detectors  304  at the appropriate points. As shown in  FIG. 4 , the detectors  304  are monolithically integrated into the substrate  106 . Whichever active element to be provided on the substrate has the higher effective yield is preferably the monolithically integrated element, since the monolithically integrated elements will not be able to be substituted out. Further, the metalization required for the electrical connections for both the monolithically integrated element and the additional active element on the substrate are formed using the same mask set as that for forming the monolithically integrated element. This helps insure precise alignment, since the active element to be mounted can use its metalization to provide its alignment, e.g., by solder self-alignment. The active elements that are to be mounted on the substrate may then be tested before being mounted. After mounting, they may be tested again and replaced if required before the wafer bonding. As used herein, bonding may include any type of attachment, including the use of bonding materials, surface tension or directly forming on the same substrate. As used herein, separating or singulating may include any means for realizing individual components, e.g., dicing. 
         [0030]    The alignment of the active elements to the input and output ports corresponding thereto, typically fibers, is particularly important. One configuration for insuring proper alignment between the transceiver and fibers is shown in  FIG. 5 . As can be seen in  FIG. 5 , a plurality of fibers  410  are inserted into a ferrule  412 . The active elements of the present invention, here the linear configuration as shown in  FIG. 3 , which are to be in communication with the fibers  410 , are preferably provided on a silicon bench or sub-mount  416 , corresponding to the common substrate  106  in  FIG. 3 . In turn, this silicon bench  416  is preferably provided on a substrate  418 . An optics block  420  provides at least one optical element between each opto-electronic device on the sub-mount  416  and a corresponding fiber  410 . The optics block  420  is preferably spaced from the opto-electronic devices by a spacer  415 . The optical elements preferably include elements which collimate, focus, homogenize or otherwise couple the light. Since the optics block has two surfaces, two optical elements may be provided thereon. Further, if required, additional optics blocks may be bonded to and spaced from the optics block  420  to provide additional surfaces, as with any of the previous transceiver configurations. 
         [0031]    The spacer  415  is then bonded, e.g., using solder or epoxy, into place on the bench  416 . The bevels which can be seen on the interior surface of the spacer  415  simply arise when using silicon as the spacer and the hole therein is formed by wet etching silicon along its crystalline plane. While wet-etching is a simple way of forming the hole in the spacer, vertical side walls may be more advantageous, e.g., for load bearing. Substantially vertical side walls may be realized by dry etching silicon. Further, other materials such as ceramic, glass, plastic, may be used for the spacer  415 . If the spacer  415  is transparent to wavelengths of interest, the hole therein may not be required. 
         [0032]    Preferably, the alignment and bonding of the spacer  415  and the optics block  420  occur on a wafer level, and then diced to form respective dies which are then aligned to the bench  416 . The alignment of the spacer  415  is not very sensitive, i.e., the spacer just needs to be aligned so that it does not block light between the optics block  420  and the opto-electronic device. While a spacer  415  may be formed directly on the optics block  420  itself, the use of a separate spacer  15  allows larger vertical separation to be achieved. The use of a separate spacer is particularly advantageous when providing optical elements on a bottom surface of the optics block  20 , since the processes for forming the optics and the spacer features interfere with each other. Finally, use of a separate spacer allows the sealing off of the opto-electronic device to be more readily and stably achieved. Such sealing protects the opto-electronic device from environmental factors, such as humidity. 
         [0033]    A mechanical interface  422  aligns the optics block  420 , which is already aligned with the electro-optical devices, with the fibers  410 . This may be achieved by the provision of alignment features on both the mechanical interface  422  and the ferrule  412  housing the fibers  410 . In the particular example shown, these alignment features consist of holes  424  in the ferrule  412 , which are already typically present for aligning the ferrule with other devices, and alignment holes  426  in the mechanical interface  422 . Once these alignment holes  424 ,  426  are aligned, an alignment pin, not shown, may then be inserted therein to maintain the aligned position. Further details of such interfaces may be found, for example, in commonly assigned, co-pending application U.S. Ser. No. 09/418,022, now U.S. Pat. No. 6,374,004, entitled “Optical Subassembly” which is incorporated by reference in its entirety for all purposes. 
         [0034]    While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the present invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility without undue experimentation. Thus, the scope of the invention should be determined by the appended claims and their legal equivalents, rather than by the examples given.