Patent Publication Number: US-2007110379-A1

Title: Pinch waveguide

Description:
This application claims the benefit of U.S. Provisional Patent Application No. 60/736,202, entitled “Pinch Waveguide” filed on Nov. 14, 2005.  
     CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application makes reference to co-pending U.S. Provisional Patent Application No. 60/736,480, entitled “Semiconductor Device Having A Laterally Injected Active Region” filed on Nov. 14, 2005, and U.S. Provisional Patent Application No. 60/736,201, entitled “Semiconductor Laser” filed on Nov. 14, 2005, the contents of both of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to optical waveguides, and more particularly to an optical waveguide that changes the depth of propagation of the photons in the waveguide.  
      2. Description of the Prior Art  
      Optoelectronic integrated circuits (OEICs) have found significant applications in a number of fields including communications and optical interconnects of computing. However, those concerned with designing OEICs have recognized the meed for developing improved optical interconnects capable of transmitting light between active devices that form these integrated circuits. Conventional OEICs usually employ optical waveguides as device interconnects. Specifically, circuit fabricators have used thin films of various materials to form optical waveguides directly on the surface of OEIC structures.  
      Typically, active devices or electronic logic elements such as those employed in electronic computer systems do not directly interface with optical information processing and communications systems. Therefore, in a typical system interface involving both electronic and optical techniques, photons must be detected and converted to electrical energy of commensurate signal information, the signal processing operations must then be performed electronically, and that procedure followed by reconversion of the electrical signals to photons.  
      Various techniques and fabrication methods have been utilized to construct OEICs that provide control over the in plane direction of the path of photons in an OEIC. For example, waveguide bends, waveguide junctions and directional couplers have been used to assist in controlling the direction of the path of the photons; however, often the current methods are difficult or expensive to fabricate and often result in optical loss or leakage. In addition, these devices do not address out of plane or the depth of optical coupling.  
     SUMMARY OF THE INVENTION  
      Embodiments described herein include a waveguide that will redirect photons propagating in the waveguide in a direction substantially perpendicular to the propagation axis of the waveguide.  
      Various embodiments also provide for inter-planar propagation of a wave front disposed in a waveguide and allow control over the amount of photons directed to select regions of an OEIC.  
      In general, in one aspect, the invention features a waveguide including: a first photon propagating material having a first index of refraction (n 1 ) and having a pinch disposed therein, the pinch having a second index of refraction (n 1 ′); and a second photon propagating material disposed in optical communication with the first photon propagating material and having a third index of refraction (n 2 ); wherein n 1 ′&lt;n 1 , n 1 ′&lt;n 2 , and the pinch redirects at least a portion of the photons from the first photon propagating material to the second photon propagating material.  
      In general, in another aspect, the invention features an optical apparatus including: a first photon propagating material having a first index of refraction (n 1 ) and having a pinch disposed therein, the pinch having a second index of refraction (n 1 ′); and a second photon propagating material disposed in optical communication with the first photon propagating material and the second photon propagating material having a target region disposed therein and the target region having a third index of refraction (n 2 ); wherein n 1 ′&lt;n 1 , n 1 ′&lt;n 2 , and the pinch redirects at least a portion of the photons from the first photon propagating material to the second photon propagating material in at least the target region.  
      In general, in still another aspect, the invention features an optical apparatus including: a first photon propagating material having a first index of refraction (n 1 ) and having a pinch disposed therein, the pinch having a second index of refraction (n 1 ′); a second photon propagating material disposed in direct contact with the first photon propagating material and the second photon propagating material having a target region disposed therein and the target region having a third index of refraction (n 2 ); and a photon source for supplying photons to the first photon propagating material; wherein n 1 ′&lt;n 1 , n 1 ′&lt;n 2 , and the pinch redirects at least a portion of the photons from the first photon propagating material to the second photon propagating material in at least the target region.  
      In general, in still yet another aspect, the invention features a waveguide including: a first photon propagating material having a first index of refraction (n 1 ) and having a first pinch disposed therein, the pinch having a second index of refraction (n 1 ′); and a second photon propagating material disposed in direct contact with the first photon propagating material and having a third index of refraction (n 2 ), the second photon propagating material having a second pinch oriented opposite that of the first pinch in an axial direction; wherein n 1 ′&lt;n 1 , n 1 ′&lt;n 2 , and the first and second pinches redirect at least a portion of the photons from the first photon propagating material to the second photon propagating material.  
      Other objects and features of the invention will be apparent from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention will be described in conjunction with the accompanying drawings, in which:  
       FIG. 1A  is a top view of a waveguide embodying aspects of the invention.  
       FIG. 1B  is a side view of the waveguide of  FIG. 1A .  
       FIG. 2  is a schematic cross-sectional view of a waveguide embodying various aspects of the invention and showing the path of photon propagation.  
       FIG. 3  is a schematic cross-sectional view of a waveguide coupled with a light source and showing the path of photon propagation.  
       FIG. 4  is a schematic cross-sectional view of a waveguide showing the path of photon propagation.  
       FIG. 5  is a top perspective view of a cross-section of another waveguide embodying various aspects of the invention.  
       FIG. 6A  is a top perspective view of another waveguide embodying various aspects of the invention.  
       FIGS. 6B, 6C  and  6 D are cross-sections of the waveguide illustrated in  FIG. 6   a  which illustrate the optical confinement of the wavefront in the waveguide.  
       FIGS. 7, 8 ,  9 ,  10 ,  11 ,  12  and  13  are schematic representations of top views of different waveguides embodying aspects of the present invention.  
       FIG. 14  is a schematic cross-sectional side view of a waveguide embodying various aspects of the present invention.  
       FIGS. 15A, 15B  and  15 C are cross-sectional end views of waveguides embodying various aspects of the present invention.  
       FIGS. 16A, 16B ,  16 C and  16 D are cross-sectional end views of waveguides embodying various aspects of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      A waveguide is provided, comprising a first photon propagating material having a first index of refraction (n 1 ) and having a pinch disposed therein, the pinch having a second index of refraction (n 1 ′); and a second photon propagating material disposed in optical communication with the first photon propagating material and having a third index of refraction (n 2 ); wherein n 1 ′&lt;n 1 , n 1 ′&lt;n 2 , and the pinch redirects at least a portion of the photons from the first photon propagating material to the second photon propagating material.  
      Turning now to  FIG. 1   
      IA, a top view of a waveguide  100  is illustrated. As may be seen, waveguide  100  has three distinct regions. The first region is an upstream region  110 . Next is a pinch region  112 . Finally, there is a downstream region  114 . It should be appreciated that the terms upstream and downstream are utilized to provide axial location with respect to pinch region  112  in the direction of the propagation of light  116  as illustrated by the associated line. As may be seen, waveguide  100  has an axial length L. In the described embodiment, L will be about 20 micrometers or less. The selection of the length L is non-trivial in that prior art inter-planar couplers are on the order of 100 micrometers or more. Thus, prior art waveguides can be a factor of 10 times larger than the currently described embodiment. It should also be understood that waveguides having a length of greater than 20 micrometers are within the scope of the teachings of the present invention.  
      Waveguide  100  has a lateral width of W 1 . In the described embodiment, width W 1  of waveguide  100  is some fraction of the wavelength of light  116  propagating through waveguide  100 . Generally, width W 1  would be defined by the equation: W 1 ≦λ2, where λ is the free space wavelength of light  116  propagating within waveguide  100 . In the described embodiment, W 1  is less than or equal to ½ a micrometer, when λ=1.5 μm. The selection of width W 1  is non-trivial in that prior art waveguides have widths that are on the order of 2λ or greater. Thus, prior art waveguides can be a factor of 4 times wider than the currently described embodiment. It should be appreciated that waveguides  100  having a width of greater than λ/2 are within the scope of the teachings of the present invention.  
      Turning now to  FIG. 1B , a side view of waveguide  100  is illustrated. As may be seen, waveguide  100  comprises at least three layers. The first layer is an optional substrate  118 . In the described embodiment, substrate  118  is glass (SiO 2 ). However, substrate  118  could be formed from a uniform layer of III-V, IV, and/or II-VI semiconductor material selected from the group comprising: GaAs, InP, AlAs, etc, or any combination thereof. In an embodiment in which substrate  118  is at least partially optically transparent it can be made of indium phosphide (InP). In general, the index of refraction (n 3 ) for substrate  118  will be between 1.4 and 3.5 and it will be between 3.18 and 3.41 when InP is utilized, depending on λ. The material utilized in substrate  118  is selected to provide lattice matching with interaction layer  120 . If it is desired to utilize waveguide  100  in an active device, then n 3  will be at an upper portion of the range identified above. If it is desired to utilize waveguide  100  in a passive device, then n 3  will be at a lower portion of the range identified above. It should be appreciated that substrate  118  may be non-uniform with respect to the index of refraction in an axial, lateral, and/or transverse direction. For example, the index of refraction for substrate  118  may be different in regions  110 ,  112 , and/or  114 . For simplicity, we will refer to substrate  118  having an index of refraction n 3 , whether it is uniform or if that is the average or index of refraction for substrate  118 .  
      Disposed above substrate  118  is an interaction layer  120 . In the described embodiment, interaction layer 120 is formed from a uniform layer of III-V, IV, and/or II-VI semiconductor material selected from the group comprising: GaAs, InP, AlAs, etc., or any combination thereof. A portion of interaction layer  120  could comprise an active material and have an active region  124  disposed in target region  128 . It should be appreciated that target region will have an index of refraction n 2 ′ which is different than layer  120  outside of target region  128 , i.e., have an index of refraction n 2 . Typically, n 2 ′&gt;n 2 . In some embodiments, interaction layer  120  will be at least partially optically transparent. The index of refraction (n 2 ′) for target region  128  will be between 3.4 and 3.6 (e.g. 3.5) while n 2  for interaction layer  120  will be between 1 and 3.4. It should be appreciated that interaction layer  120  may be non-uniform with respect to the index of refraction in an axial, lateral, and/or transverse direction outside of target region  128 . For example, the index of refraction for interaction layer  120  may be different in regions  110 ,  112 , and/or  114 . While no intermediate layers are illustrated between substrate  118  and interaction layer  120 , it should be appreciated that the presence or absence of these intermediate layers are within the scope of the teachings of the present invention.  
      It is also contemplated that in various embodiments interaction layer  120  will comprise distinct sub-layers which may or may not be constructed from the same material. It should be appreciated that interaction layer  120  may be non-uniform with respect to the index of refraction in an axial, lateral, and/or transverse direction. For example, the index of refraction for interaction layer  120  may be different in regions  110 ,  112 ,  114 , and/or  128 . For simplicity, we will refer to interaction layer  120  having an index of refraction n 2 , whether it is uniform or if that is the average or index of refraction for interaction layer  120  outside of target region  128 .  
      Disposed above interaction layer  120  is a confinement layer  122 . In the described embodiment, confinement layer  122  is formed from a uniform layer of III-V, IV, and/or II-VI semiconductor material selected from the group comprising: Si, GaAs, InP, AlAs, etc., or any combination thereof. In at least some embodiments, confinement layer  122  will at least partially optically transparent. It should be appreciated that confinement layer  122  may be multimode or single mode. In the described embodiment, the index of refraction (n 1 ) for confinement layer  122  will be between 3.4 and 3.6 (e.g. 3.49). It should be appreciated that confinement layer  122  may be non-uniform with respect to the index of refraction in an axial, lateral, and/or transverse direction. For example, the index of refraction for confinement layer  122  may be axially different in regions  110 ,  112 , and/or  114  as well as laterally different within any of the regions  110 ,  112 , and/or  114 . For simplicity, we will refer to confinement layer  122  having an index of refraction n 1 , whether it is uniform or if that is the average index of refraction for confinement layer  122  in regions  110  and  114 . Confinement layer  122  has an index of refraction n 1 ′, whether it is uniform or if that is the average index of refraction for confinement layer  122  in region  112 . While no intermediate layers are illustrated between interaction layer  120  and confinement layer  122 , it should be appreciated that the presence or absence of these intermediate layers are within the scope of the teachings of the present invention.  
      Pinch region  112  is illustrated as tapering or “pinching” from a width W 1  to a width W 3  and then expanding to a width W 4 . In the described embodiment, the change in pinch region  112  is uniform and symmetrical. A goal of designing pinch region  112  is to eliminate as many discontinuities as possible and to remove any sharp corners that may adversely effect wave propagation. In the described embodiment, the change in width is also smooth, i.e., the first derivative would be a continuous as illustrated in the numerous embodiments in the figures. The specific goal of the pinch is to reduce waveguide  100  to a width W 3 . Typically, W 3  is be small enough to prevent any modes from existing downstream of the narrowest point  126  of pinch region  112 . Thus, W 3  is between 0 and W 1 , depending on the particular wavefront propagating in waveguide  100 . It should be appreciated that pinch region  112  may have any shape, such as a quadric, cosine, polynomial series, and/or any other shape specifically illustrated in  FIGS. 7 through 13 . While these Figures illustrate specific shapes, these shapes are merely illustrative. In the described embodiment, the index of refraction n 1 ′&lt;n 1  and n 1 ′&lt;n 2 ; in addition, n 1 ′&lt;n 2   1 ′.  
      Pinch region  112  is illustrated as expanding from a width W 3  to a width W 4 , downstream of point  126 . It should be appreciated that width W 4  may be greater than W 1  or may be less than W 3 , i.e., pinch region  112 , downstream of point  126 , may either expand or contract further, depending on the specific downstream result required in region  114 . We will now discuss the specific widths for downstream region  114  with respect to the width W 4 , in the table, below.  
                                                   Relationship of W 4     Downstream Effect in Region 114                          W 4  = 0   No mode will propagate in layer 122, mode               will propagate in layer 120.           W 4  ≦ W 3     No mode will propagate in layer 122,               mode will propagate in layer 120.           W 3  &lt; W 4  ≦ W 1     Mode will propagate in layer 122,               mode may propagate in layer               120. If there are two modes in               waveguide 100, one mode may               propagate in layer 122 and the other               mode may propagate in layer 120.           W 1  ≦ W 4     Mode will propagate in layer 122.                      
 
      It should be appreciated that while pinch region  112  has been illustrated as a two dimensional taper, it may in fact, be desirable to have pinch region  112 , upstream of point  126 , taper in three dimensions, i.e. provide a change in n 1′  in the axial, lateral and transverse directions.  
      Waveguide  100  may be maintained in free space or may be enclosed in a protective material such as glass (SiO 2 ). The enclosing material or free space will have an effective index of refraction of n 0 . In the described embodiment, n 1  is greater than n 0 , e.g. n 1  is 2 times greater than n 0 .  
      While  FIG. 1B  illustrates waveguide  100  as having substrate  118 , it should be appreciated that substrate  118  may be removed. In the event of removing substrate  118 , the protective material may be treated as the substrate. If substrate  118  is not optically transparent, then it may be desirable to remove substrate  118 . This may be accomplished by mechanical polishing, chemical etching, and/or cleaving, or any other method known in the semiconductor material processing art.  
      It should be appreciated that while light  116  is illustrated as penetrating “down” into interaction layer  120  which is disposed below confinement layer  122 , it may be advantageous to have light propagate “up” above confinement layer  122 . To accomplish this, one would have to assure that in some region above confinement layer  122 , the index of refraction for that region would be greater than n 1 ′.  
      While it has been illustrated that regions  112  are in axial alignment, it should be appreciated that the alignment of region  112  in layer  118  is not critical. The alignment of region  112  in layers  120  and  122  has some criticality in that region  112  in layer  122  should have some overlap with region  112  in layer  120 . In the described embodiment, region  112  in layer  122  would start before region  112  starts in layer  120 . Also, typically, region  112  in layer  122  would end after region  112  ends in layer  120 . That would assure photon interaction with target region  124 .  
      The relationship of the index of refraction of confinement layer  122  and interaction layer  120  are important in determining the confinement of light  116  to a particular layer  120 , 122  in regions  110 ,  112 , and  114 , i.e., the creation of a low velocity channel for light  116  to propagate in. The following table illustrates this concept.  
                                               Relation-   Range               ship of   of Index           Index of   Contrast       Region   refraction   ABS(n 1 -n 2 )   Effect on low velocity channel                  110   n 1  &gt; n 2     0.05 to 2.05   Low velocity channel in confinement                   layer 122       110   n 1 ≈n 2      0.0 to 0.1   Low velocity channel in confinement                   layer 122 and interaction layer 120       110   n 1  &lt; n 2     0.05 to 2.05   Low velocity channel in interaction                   layer 120       112   n 1 ′ &lt; n 2 ′   0.05 to 2.5   Low velocity channel in confinement                   layer 122 and interaction layer 120       114   n 1  &lt; n 2     0.05 to 2.05   Low velocity channel in interaction                   layer 120       114   n 1 ≈n 2     0.05 to 2.05   Low velocity channel in confinement                   layer 122 and interaction layer 120       114   n 1  &gt; n 2     0.05 to 2.05   Low velocity channel in confinement                   layer 122                  
 
      Thus, by appropriately designing the width of regions  110 ,  112 , and  114  with the appropriate index relationship, one is able to create a unique set of low velocity channels for light  116  to propagate in waveguide  100 . While the above table provide a desired Δ between n 1  and n 2 , it should be appreciated that this is illustrative.  
       FIG. 2  illustrates the path of photon propagation  210  in a waveguide  200 . Waveguide  200  has three layers. An optional substrate  202 , an interaction layer  204  and a confinement layer  206 . Confinement layer  206  has a region  208  that may comprise a physical pinch or may comprise a material change or alteration to provide a change in the index of refraction along confinement layer  206 . Material changes may be accomplished by, but not limited to, the following techniques: ion implantation, material disordering, etching, etching and regrowth, vacancy induced layer disordering, thermal diffusion doping, and/or annealing, etc. In the described embodiment, the indices of refraction defined by regions n 1 ′ and n 1  have the following relationship n 1 ′&lt;n 1 , where n 1 ′&lt;n 2 . Also, n 1 ′&lt;n 2 ′.  
       FIG. 3  illustrates the path of photon propagation in another waveguide. Photon source  335  transmits photons into confinement layer  306  as illustrated by photon path  340 . Photons propagate along photon path  340  in confinement layer  306 . In the described embodiment, confinement layer  306  is made from Si and has an index of refraction of 3.5. When photons reach pinch  330 , photons are redirected by pinch  345 ; which has a lower index of refraction, i.e., between 3.5 and 1.0, to the target region. It should be appreciated that pinch  330  comprises Si and some other material such as SiO 2  or air. In this embodiment, active layer  320  is the target region and has an index of refraction between 3.0 and 3.5. Active layer is formed from InGaAs or InAlGaAs. Because active layer  320  has a higher index of refraction n 2 ′ compared to dielectric layers  310 , photons are efficiently redirected into active layer  320 . In addition, insulating regions  305  assists in redirecting photons back into waveguide  300 . Typically, insulating regions  305  are formed from SiO2 and have an index of refraction of 1.44. In the described embodiment, substrate  302  is InP.  
      The photon source may be any suitable source for providing photons to a waveguide, such as a laser, optical fiber, etc. In particular, the teachings herein may be combined with the teachings of U.S. Provisional Patent Application No. (T.B.D.), entitled “Semiconductor Laser” filed on Nov. 14, 2005; or U.S. Provisional Patent Application No. (T.B.D).), entitled “Semiconductor Device Having A Laterally Injected Active Region” filed on Nov. 14, 2005, to allow optical propagation in the active layer or region disclosed in these applications.  
       FIG. 4  illustrates the path of photon propagation  412  in another waveguide  400 . Waveguide  400  has three layers. An optional substrate  402 , an interaction layer  404  and a confinement layer  406 . Confinement layer  406  has a region  408  that may comprise a pinch or may comprise a material change or alteration to provide a change in the index of refraction along confinement layer  406 . Interaction layer  404  has a region  410  that may comprise a pinch or may comprise a material change or alteration to provide a change in the index of refraction along interaction layer  404 . Region  408  starts before region  410  in an axial direction. Because of this relationship, photon propagation path  412  is deflected downward as is approaches region  408 . By axially displacing regions  408  and  410 , one assures that photon propagation path  412  enters interaction layer  404 . As photon propagation path  412  approaches region  410 , it begins to rise toward confinement layer  406 .  
      Various specific examples will now be described.  
     EXAMPLE I  
       FIG. 5  illustrates a cross-section of a waveguide of the present invention. Waveguide  500  comprises confinement layer  502  present on insulating layer  505 , dielectric layers  510  and substrate  515 . Between dielectric layers  510  is active layer  520 . Confinement layer  502  has a region  525  that has a substantially uniform transverse cross-section. Confinement layer  502  also has a pinch  530  that redirects photons to a target region via the low velocity channel. Photons propagating along the longitudinal axis of waveguide  500  are squeezed together as the photons travel through pinch  530 . The effective compression of photons in pinch  530  causes the photons to be directed transversely into a target region (not shown), which is typically into another material or layer having an index of refraction greater than pinch  530 .  
     EXAMPLE II  
       FIGS. 6A, 6B ,  6 C, and  6 D illustrates another waveguide. Waveguide  600  comprises confinement layer  602  disposed directly on top dielectric layer  610  and having substrate  615  disposed below bottom dielectric layer  610 . As may be seen, top dielectric layer  610  may have optional pinches  612  and thus form a double dagger with respect to confinement layer  602 . Between dielectric layers  610  is active layer  620 . Confinement layer  602  has a region  625  that has a substantially uniform transverse cross-section. Confinement layer  602  also has a pinch  630  that redirects photons in a direction of the low velocity channel. It is important to note that section  603  is transverse portion confinement layer  602  which is not pinched in a lateral direction in pinch  630 . This is illustrated in  FIG. 6D  and will be discussed in detail below.  
      Turning now to  FIG. 6D , a description of the photons propagating along the longitudinal axis of waveguide  600  will be described. As may be seen, in  FIG. 6B , the photons and respective energy, illustrated by ring  604  is encapsulated by confinement layer  602 . As the photons propagate axially down waveguide  600 , optional pinch  612  begins to pull the photons into pinch  612  due to the close index of refraction between layers  602  and  610 . While pinch  612  is illustrated as being as wide (at its widest point) as layer  610 , it should be appreciated that pinch  612  may be as wide as layer  610  or as narrow as region  625 . As may be seen in  FIG. 6C , photons and respective energy, illustrated by ring  604  are now disposed both in layer  602  and pinch region  612 . It should be appreciated this is direct coupling of the photons between these two layers. This is accomplished by physical contact between the two layers and the close indicies of refraction of these two layers as discussed above, i.e., both layers are part of the low velocity channel for some portion of pinch  612 . This is in direct contrast to prior art devices that utilize evanescent waves to couple two waveguides such as in the case of delta/beta couplers. Evanescence relies on the coupling of the non-propagating or static optical field disposed outside of the waveguides. Other prior art devices which use evanescence include those taught by Takeuchi et al. in the article entitled “A high-power and high-efficiency photodiode with an evanescently coupled graded-index waveguide for 40 Gb/s applications” and Demiguel et al. in an article entitled “Low-cost, polarization insensitive photodiodes integrating spot size converters for 40 Gb/s applications.” Direct coupling and evanescence are two discrete concepts that are distinctly different in approach and application.  
      As the photons continue to propagate axially down waveguide  600 , pinch  630  begins to push the photons into layer  610  due to the indicies of refraction between layers  630  and  610 . As may be seen in  FIG. 6D , photons and respective energy, illustrated by ring  604  are now disposed both in layer  610  and section  603 . Not all photons are redirected due to interaction with a pinch. Some photons continue to propagate along the longitudinal axis of waveguide  600  in section  603 . By not providing a taper in section  603  an unexpected result is achieved with regard to lateral confinement of the photons. By this, we mean that the photons are strongly laterally confined as they propagate axially. This is illustrated by ring  604 . This is a highly desired result which prevents optical spread of the beam in a lateral direction.  
      Photons may be made to contact a laser diode either by redirecting photons from a waveguide via interaction with a pinch, or by directing photons that continue to propagate along the longitudinal axis of the waveguide in region  603  into a laser diode or photon source. When contacting the laser diode or photon source, the photons are at or below a threshold level such that the photons will not cause the laser diode or photon source to lase. However, contacting a laser diode or photon source with this level of photons greatly decreases the amount of time necessary for the laser diode or photon source to overcome the threshold such that the laser diode or photon source will lase. Thus, by controlling the level of photons contacting the laser diode or photon source, the laser diode or photon source may be maintained in a state of readiness.  
      A double pinch can be used to control the level of photons entering a laser diode. A top view of an exemplary double pinch arrangement is shown in  FIG. 10 . Photons interacting with a pinch will be redirected at a degree that is dependent upon the magnitude of the pinch and the difference between the effective indices of refraction. Thus, one of ordinary skill in the art could fabricate a variety of pinch waveguides with pinches of varying magnitudes, thicknesses, and/or materials to meet the requirements of particular applications. In a structure having an axially disposed double pinch waveguide, a controlled and predetermined level of photons is allowed to continue along the longitudinal axis of the waveguide to interact with the second pinch. The same degree of control may be exercised at the second pinch, i.e., managing the photons that are redirected and the photons that continue propagating in the waveguide. The waveguide may be fabricated with any number of pinches in any configuration depending on the desired application.  
      Photon redirection may also be controlled by methods, such as layer doping and cladding. For example, the waveguide, including the pinch, may be clad with any suitable cladding material, such as glass, silicon oxynitride or a polymer, to confine photons within the waveguide. The various layers of the OEIC may be doped to achieve desired indices of refraction for each layer.  
      Redirected photons may be directed to any suitable device or layer. For example, photons may be redirected to another waveguide. Redirected photons may also be redirected into a target region. In an embodiment of the present invention, the target region may be active layer  620 . The target region or active layer may, for example, contain a photodiode (photon detector) that interacts with photons to produce current or may be a laser (photon source) and thus form an optical amplifier. The target region or active layer may contain a variety of optoelectronic devices, logic devices, etc.  
     EXAMPLE III  
       FIGS. 7, 8 ,  9 ,  10 ,  11 ,  12  and  13  illustrate exemplary pinch regions of different waveguides. A pinch may be any shape, grade or angle such that photons propagating in the waveguide are forced into a narrow region disrupting the path of photon propagation. Pinch  705  in waveguide  700  is representative of a squared pinch, pinch  805  in waveguide  800  is representative of a curved pinch, and pinch  905  in waveguide  900  is representative of an angled pinch. Irregular pinch  1005  in waveguide  1000  illustrates that a pinch does not have to be uniform. In addition, as illustrated by pinch  1105  in waveguide  1100 , a pinch may be axially offset. In other words, the indentations in the waveguide do not have to be directly across from one another, but may be axially offset. Pinch  1205  in waveguide  1200  illustrates that a pinch does not have to be disposed on both sides of a waveguide, but rather may, in particular embodiments, a pinch may be disposed on only one side of a waveguide. Pinch  1305  and pinch  1310  in waveguide  1300  illustrate that a waveguide may contain multiple pinches along the longitudinal axis of the waveguide.  
      In addition, a pinch may be fabricated in a waveguide in combination with a reduction in the top or upper surface of the waveguide. In other words, a waveguide may be tapered or may contain a vertical or transverse pinch in any shape described above for a lateral pinch. Thus, various combinations of pinches are contemplated within the present invention and may be utilized for various applications by one of ordinary skill in the art based on the present disclosure.  
     EXAMPLE IV  
       FIG. 14  shows yet another waveguide  1400 . Waveguide  1400  has optional substrate layer  1402 , interaction layer  1404 , and confinement layer  1406 . Layer  1408  represents free space or a material encasing waveguide  1400 . Region  1410  represents an area from which material has been etched from confinement layer  1406  and thus changing the index of refraction in region  1410  from the rest of layer  1406 .  
     EXAMPLE V  
       FIGS. 15A, 15B  and  15 C show cross-sectional views looking down the z-axis of various exemplary waveguides taken in regions  110  and/or  114  of  FIG. 1   a . In  FIGS. 15A, 15B  and  15 C, layers  1502 ,  1502 ′ and  1502 ″ are sufficiently thin such that these layers are unable to support a mode.  FIG. 15A  exemplifies a waveguide  1500  in which confinement layer  1504  is present on top of interaction layer  1502 .  FIG. 15B  exemplifies a waveguide  1500 ′ in which confinement layer  1504 ′ is raised in a pedestal arrangement on interaction layer  1502 ′.  FIG. 15C  exemplifies a waveguide  1500 ″ that incorporates a substrate layer  1506  and a confinement layer  1504 ″ that is at least partially embedded in interaction layer  1502 ″. Interaction layer  1502 ″ also extends at least partially into substrate layer  1506 .  
     EXAMPLE VI  
       FIGS. 16A, 16b ,  16 C and  16 D show cross-sectional views looking down the z-axis or axially along various exemplary waveguides taken in region  112  of  FIG. 1   a . In  FIGS. 16A, 16b ,  16 C and  16 D, layers  1602 ,  1602 ′,  1602 ″ and  1602 ′″ are sufficiently thick such that these layers are able to support a mode.  FIG. 16A  exemplifies a waveguide  1600  in which confinement layer  1604  is present on top of interaction layer  1602 .  FIG. 16   b  exemplifies a waveguide  1600 ′ in which confinement layer  1604 ′ is present on top of interaction layer  1602 ′ and interaction layer  1602 ′ extends downward in the central region beneath confinement layer  1604 ′.  FIG. 16C  exemplifies a waveguide  1600 ″ in which confinement layer  1604 ″ is at least partially embedded in interaction layer  1602 ″.  FIG. 16D  exemplifies a waveguide  1600 ′″ in which there is no confinement layer, but there is an interaction layer  1602 ′″ that extends upward.  
      Waveguides mentioned herein may be of any suitable material. Suitable materials include germanium, silicon, indium-phosphide (InP), gallium-arsenide (GaAs), aluminum-arsenide (AlAs), indium-arsenide (InAs), and/or SiO 2  polymers, etc.  
      Insulating layers mentioned herein may be of any suitable material. Suitable materials include silicon dioxide (SiO 2 ) and/or nitrides, etc.  
      Dielectric layers mentioned herein may be of any suitable material. Suitable materials include SiO 2 , Si 3 N 4 , Al 2 O 3 , CaF 2 , and/or nitrides, etc.  
      Active layers mentioned herein may be of any suitable material. Suitable materials include, but are not limited to, II-V, IV, and/or II-VI, such as INAlGaAs and InGaAsP.  
      Suitable materials for substrates mentioned herein include, but are not limited to, III-V, IV, and/or II-VI, such as InP, GaAs, aluminum-gallium-arsenide (AlGaAs), silicon, SiO 2 , and sapphire.  
      Waveguides mentioned herein may be fabricated by any known method. Suitable methods include thin film deposition, dry etching, wet etching, reactive ion etching, epitaxial techniques such as molecular beam epitaxy, lithography such as photolithography and E-beam lithography.  
      Other suitable fabrication methods and materials are described in U.S. Pat. Nos. 6,051,445; 5,917,967; 5,838,870; 5,559,912; 5,514,885; 5,354,709; 5,163,118; 4,996,575; 4,877,299; and 4,789,642, the entire disclosures of which are hereby incorporated by reference.  
      Other embodiments are within the following claims.