Polymer lenses for mechanical holding in photonic devices

Abstract

Embodiments of this disclosure relate to polymer lenses for mechanical retention in photonic devices. A photonic device includes a PCB having an integrated circuit mounted thereon, the PCB having a cap mounted to the PCB and carrying a lens located on the integrated circuit. The cap is formed of: an outer wall mounted to the PCB, extending upward from the PCB and surrounding a portion of the integrated circuit; a first retaining structure extending inwardly from the outer wall and across the integrated circuit, the first retaining structure having an aperture defined therein; and a second retaining structure having an aperture defined therein, the second retaining structure being secured within the first retaining structure such that the aperture in the second retaining structure is axially aligned with the aperture in the first retaining structure. The lens is mechanically constrained within the cap between the first and second retaining structures.

Description

Technical Field

[0001] This disclosure relates to the field of photonics, and more particularly to a cap for securely holding a lens in place on an integrated circuit die, the secure holding being achieved mechanically. Background Technology

[0002] In the field of photonics, lenses (or multiple stacked lenses) are held in place by caps on their respective associated light sensors or emitters. During device fabrication, the caps are first glued to a printed circuit board (PCB) that carries the associated light sensor or emitter. Then, when the associated light sensor or emitter is used as a positional reference, the lens can be fixed to the cap, thus ensuring optimal optical alignment of the photonic device.

[0003] Such photonic devices can be incorporated into portable electronic devices that may be subjected to varying temperatures and environments during operation. For example, such portable electronic devices may be exposed to prolonged periods of high temperature and high humidity. This can have a weakening effect on the adhesion between the adhesive and the lens, and low adhesive strength immediately after manufacturing may be of particular concern. For example, adhesion to polycarbonate-based lens materials is typically poor. When the adhesion between the adhesive and the lens is weakened, the lens may separate if the portable electronic device is subjected to mechanical stress (e.g., dropped by a user), rendering the photonic device unusable or inaccurate.

[0004] Since this is clearly undesirable, there is a need for new geometries and technologies to secure lenses within their associated caps in order to produce more robust and durable photonic devices. Summary of the Invention

[0005] This document discloses a photonic device comprising: a printed circuit board (PCB) on which an integrated circuit is mounted; and a cap mounted to the PCB and carrying a lens located on the integrated circuit. The cap has: an outer wall mounted to the PCB, extending upward from the PCB and surrounding at least a portion of the integrated circuit; a first retaining structure extending inward from the outer wall and across the integrated circuit, the first retaining structure having an aperture defined therein; and a second retaining structure having an aperture defined therein, the second retaining structure being fixed within the first retaining structure such that the aperture in the second retaining structure is axially aligned with the aperture in the first retaining structure, the lens being mechanically constrained within the cap between the first and second retaining structures, light being transmittable through the cap via the aperture defined in the second retaining structure, the mechanical constraint of the lens aligning the lens with the integrated circuit.

[0006] The outer wall and the first retaining structure can be integrated into a single unit.

[0007] The first retaining structure may include a shelf extending orthogonally from a corresponding portion of the outer wall and a support extending orthogonally to the shelf from the distal end of the shelf in a direction away from the PCB. A lens may be mechanically constrained between the bottom surface of the second retaining structure and the support of the first retaining structure.

[0008] The second retaining structure may include a shaped wall (e.g., annular) extending parallel to the outer wall, a top plate extending across the shaped wall, and the top plate having a hole defined therein.

[0009] The outer wall may surround three sides of the integrated circuit. The cap may also include an inner wall extending between two portions of the outer wall, such that the inner wall extends along a fourth side of the integrated circuit, wherein a first portion of the first retaining structure extends from the outer wall across the integrated circuit. A second portion of the first retaining structure may extend from the inner wall and across the integrated circuit.

[0010] The first and second portions of the first retaining structure can define a shelf, and a support member can extend orthogonally to the shelf from its distal end in a direction away from the PCB. A lens can be mechanically constrained between the bottom surface of the second retaining structure and the support member of the first retaining structure.

[0011] The PCB may have additional integrated circuits mounted thereon. An outer wall may surround three sides of the additional integrated circuit, and an inner wall may extend between two portions of the outer wall such that the inner wall extends along a fourth side of the additional integrated circuit. A third portion of the first retaining structure may extend outward from the outer wall and across the additional integrated circuit. A fourth portion of the first retaining structure may extend outward from the inner wall and across the additional integrated circuit.

[0012] The third and fourth portions of the first retaining structure may define an additional shelf, and an additional support may extend orthogonally to the additional shelf from its distal end in a direction away from the PCB. An additional lens may be mechanically constrained between the bottom surface of the second retaining structure and the additional support of the first retaining structure.

[0013] The first filter can be adhered to the bottom surface of the shelf, and the second filter can be adhered to the bottom surface of the additional shelf.

[0014] The third and fourth portions of the first retaining structure may define an additional shelf, and an additional support may extend orthogonally to the additional shelf from its distal end in a direction away from the PCB. The size of the additional lens may be determined to be press-fitted and mechanically constrained between the outer and inner walls, and the additional lens is supported by the additional support of the first retaining structure.

[0015] The cap may also include a hardened mass block that contacts the perimeter of the additional lens as well as the outer and inner walls.

[0016] The additional lens may have a chamfer defined therein, and the hardened mass block may contact the chamfered surface.

[0017] The portions of the outer and inner walls adjacent to the second lens may be trapezoidal in shape at their distal ends.

[0018] The filter can be bonded to the bottom surface of the first retaining structure.

[0019] The filter can be made of glass, and the lens can be made of polycarbonate.

[0020] This document also discloses a method for forming a photonic device, the method comprising: mounting an integrated circuit on a printed circuit board (PCB); securing a cap to the PCB above the integrated circuit, the cap having an outer wall mounted to a substrate, the outer wall extending upward from the substrate and surrounding at least a portion of the integrated circuit, and a first retaining structure extending inward from the outer wall and across the integrated circuit; press-fitting a lens into a second retaining structure of the cap; positioning the second retaining structure such that the lens is aligned with the integrated circuit; and bonding the second retaining structure to the first retaining structure such that the lens is mechanically constrained within the cap between the first retaining structure and the second retaining structure.

[0021] The method may also include mounting additional integrated circuits on the PCB and press-fitting additional lenses between the outer wall and the inner wall of the cap before fixing the cap to the PCB.

[0022] The method may further include applying a hardenable material around the perimeter of the additional lens and contacting the outer and inner walls such that, when the hardenable material hardens, the additional lens is mechanically constrained between a first portion of a first retaining structure extending from the outer wall across the additional integrated circuit, a second portion of a first retaining structure extending from the inner wall, and the hardened mass block.

[0023] The method may also include bonding the filter to the bottom surface of the first retaining structure before securing the cap to the PCB. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cross-section of the photonic device disclosed in this paper, in which the lens is mechanically trapped inside the cap.

[0025] Figure 1A yes Figure 1 A schematic diagram of the cross-section of a modified photonic device.

[0026] Figure 2A yes Figure 1 Status Figure 1 A schematic top view of a hat.

[0027] Figure 2B yes Figure 1 A schematic top view of a fully assembled photonic device.

[0028] Figure 3 This is a schematic diagram of the cross-section of another photonic device disclosed in this paper, in which lenses are mechanically trapped inside a cap, one lens being mechanically trapped between the main cap structure and the sub-capturing structure, and the other lens being mechanically trapped between the main cap structure and the hardened epoxy resin layer.

[0029] Figure 3A yes Figure 3 A schematic diagram of the cross-section of a modified photonic device. Detailed Implementation

[0030] The following disclosure enables those skilled in the art to make and use the subject matter disclosed herein. The general principles described herein can be applied to embodiments and applications other than those detailed above, without departing from the spirit and scope of this disclosure. This disclosure is not intended to be limited to the embodiments shown, but is consistent with the widest scope of the principles and features disclosed or suggested herein.

[0031] Now for reference Figure 1 and 2A Describe photonic device 10. First refer to Figure 1 In cross-section, the photonic device 10 may be a time-of-flight (TOF) sensor or a light detection and ranging (LIDAR) sensor, and includes a printed circuit board (PCB) 11 having a light sensor 13 (e.g., a reflected light detector) mounted thereon via a non-conductive adhesive 12, and a light emitter 33 (e.g., a laser emitter) mounted thereon via metal pads 32 forming an anode or cathode connection, wherein another connection is formed via wire bonding. However, it should be noted that many bonding techniques exist for attaching the light sensor 13 and the light emitter 33 to the PCB 11, and the examples given in this paragraph are non-limiting.

[0032] In addition, the reference detector 52 is mounted to the PCB via a non-conductive adhesive 51 and is used to detect the timing of the pulses emitted by the light emitter 33, thereby enabling ranging.

[0033] Cap 40 holds receiver lens 20 above PCB 11 such that receiver lens 20 is properly aligned with light sensor 13, and holds transmitter lens 34 above PCB 11 such that transmitter lens 34 is properly aligned with light emitter 33. Cap 40 is secured to PCB 11 by adhesive beads 14 and 21, which are shaped to approximately match the shape of the bottom of cap 40 secured to PCB 11. Both receiver lens 20 and transmitter lens 34 can be polycarbonate lenses. The adhesive can be epoxy resin. Receiver lens 20 and transmitter lens 34 can take any suitable shape, such as circular or rectangular.

[0034] Please note, Figure 1 The cross-sectional view of the photonic device 10 shown is along... Figure 2A The cross-section of the cap 40 is cut by line X-X. Figure 2A It is the assembled Figure 1 The top view of the photonic device 10, and Figure 2B It is a top view of the cap 40b with the retaining structures 19 and 29 (described below) removed.

[0035] The shape of the cap 40 is in Figure 2B The cap 40 (and PCB, though not shown) is rectangular in shape and has an outer peripheral wall 15 defined by opposing sides 15c, 15d and opposing ends 15a, 15b. The dimensions of the sides 15c, 15d along their longitudinal axes are longer than the dimensions of the ends 15a, 15b along their longitudinal axes; in other words, the length of the sides 15c, 15d extending along the X-axis of the photonic device 10 is greater than the length of the ends 15a, 15b extending along the Y-axis of the photonic device 10. An inner wall 22 extending from the sides 15c to the sides 15d divides the outer peripheral wall 15 into two rectangular shapes.

[0036] Shelf 17a extends substantially vertically from the sides 15a, ends 15c and 15d, and corresponding portions of the inner wall 22. Shelf 17a has an opening 26a defined therein, which is substantially aligned with the photosensor 13 when shelf cap 40 is attached to PCB 11. Support 25a extends substantially vertically from the distal end of shelf 17a in a positive Z direction away from PCB 11 and surrounds opening 26a. When viewed from above, opening 26a and support 25a may be annular or rectangular in shape, matching the shape of receiver lens 20. In some cases, opening 26a and support 25a may be polygonal in shape. When viewed from above, the inner perimeter of shelf 17a defined by support 25a conforms to the shape of opening 26a, while the outer perimeter of shelf 17a defined by the sides 15a, ends 15c and 15d, and corresponding portions of inner wall 22 is rectangular in shape.

[0037] Shelf 17b extends substantially vertically from the sides 15b, ends 15c and 15d, and corresponding portions of the inner wall 22. Shelf 17b has an opening 26b defined therein, which is substantially aligned with the light emitter 33 when shelf cap 40 is attached to PCB 11. Support 25b extends substantially vertically from the distal end of shelf 17b in a positive Z direction away from PCB 11 and surrounds opening 26b. When viewed from above, opening 26b and support 25b may be annular or rectangular in shape, matching the shape of emitter lens 34. In some cases, opening 26b and support 25b may alternatively be polygonal in shape. When viewed from a top perspective, the inner perimeter of shelf 17b defined by support 25b follows opening 26b, while the outer perimeter of shelf 17b defined by the sides 15b, ends 15c and 15d, and corresponding portions of inner wall 22 is rectangular in shape.

[0038] The receiver lens 20 is mechanically held within the retaining structure 19 (formed by a rectangular sidewall 19a having a top plate 19b extending across it, in which an opening 19c is defined). The sidewall 19a of the retaining structure 19 is secured to the shelf 17a by adhesive beads 18a. This mechanically holds the receiver lens 20 within a cap 40 between the retaining structure 19 and the support 25a, and thus reliably positions and constrains the receiver lens without applying adhesive to it.

[0039] The transmitter lens 34 is mechanically held within a retaining structure 29 (formed by a rectangular sidewall 29a having a top plate 29b extending across it, with an opening 29c defined in the top plate 29b). The sidewall 29a of the retaining structure 29 is secured to the shelf 17b by adhesive beads 18b. This mechanically holds the transmitter lens 34 within a cap 40 between the retaining structure 29 and the support 25b, and thus reliably positions and constrains the receiver lens without applying adhesive to it.

[0040] In the illustrated application, receiver filter 24a is mechanically attached to the underside of shelf 17a via adhesive beads 21a. Similarly, emitter filter 24b is mechanically attached to the underside of shelf 17b via adhesive beads 21b. Note that receiver filter 24a and emitter filter 24b are made of glass, thus allowing adhesive beads 21a and 21b to adhere appropriately to them.

[0041] However, in other applications, instead of integrating it into glass filters 24a and 24b, the filtering function can be integrated into receiver lens 20 and transmitter lens 34, or into light sensor 13 and light emitter 33.

[0042] The formation of the photonic device 10 is now described. A light sensor 13 is mounted to a PCB 11 using a non-conductive adhesive 12. A light emitter 33 is bonded to a metal pad 32 on the PCB 11 using a conductive adhesive. The light sensor 13 and the light emitter are wire-connected to complete their electrical connection to the PCB 11. A cap 40 is inverted such that supports 25a and 25b extend downwards (in the negative Z direction in the cross-section shown), and then receiver filters 24a and emitter filters 24b are bonded to the underside of shelves 17a and 17b. The cap 40 is then flipped back and bonded to its proper position on the PCB 11 using adhesive mass blocks 14a, 14b, and 21.

[0043] The receiver lens 20 is press-fitted into the retaining structure 19, and then the retaining structure 19 is placed on the shelf 17a and glued in place by adhesive beads 18a. Note that the shelf 17a defines an annulus (or rectangle or polygon) between the support 25a and corresponding portions of the ends 15a, sides 15c and 15d, and inner wall 22. The size and shape of the annulus allow adjustment of the retaining structure 19 (with the receiver lens 20 fixed therein) in the X-Y direction so that the optical axis of the lens 20 is aligned with the optical axis of the sensing portion of the light sensor 13, thereby allowing precise horizontal adjustment of the receiver lens 20 relative to the light sensor 13.

[0044] The emitter lens 34 is press-fitted into the retaining structure 29, which is then placed onto the shelf 17b and bonded in place using adhesive beads 18b. Note that the shelf 17b defines an annulus (or rectangle or polygon) between the support 25b and corresponding portions of the end 15b, sides 15c and 15d, and inner wall 22. The size and shape of this annulus allow adjustment of the retaining structure 29 (within which the emitter lens 34 is fixed) in the X-Y direction so that the optical axis of the lens 34 is aligned with the optical axis of the emitting portion of the light emitter 33, thereby allowing precise horizontal adjustment of the emitter lens 34 relative to the light sensor 13.

[0045] Since the receiver lens 20 and the transmitter lens 34 are in physical contact with the supports 25a and 25b, the axial alignment along the Z direction remains as desired if the supports 25a and 25b are formed with sufficient tolerance.

[0046] As an alternative to the reference detector 52 used, a portion of the light sensor 13 may extend below or through the sidewall to perform a reference detection function, such as... Figure 1A As shown in the image.

[0047] Now refer to Figure 3 Another design for the photonic device 10' is described here. (This is related to...) Figure 1The difference in the photonic device 10 is that one of the lenses (here, the emitter lens 34', but could also be the receiver lens 20) is directly press-fitted into the retaining structure 29 and mechanically constrained in place by an applied and hardened mass block 35. Note the chamfer formed along the top edge of the emitter lens 34', and the sides, end 15b', and sides 15c' and 15d' of the inner wall 22' (neither of which are in the same position as the end 15b' and the side 15c' and 15d' of the inner wall 22'). Figure 3 (As shown in the figure) It is trapezoidal in shape toward its far end, in a manner that facilitates the insertion of the emitter lens 34' to form a press fit.

[0048] The formation of the photonic device 10' is now described. The light sensor 13 is mounted to the PCB 11 via a non-conductive adhesive 12, and the light emitter 33 is bonded to the metal pads 32 on the PCB 11 with conductive adhesive. The cap 40' is inverted such that supports 25a and 25b extend downwards (in the negative Z direction in the shown cross-section), and then the receiver filter 24a and emitter filter 24b are bonded to the underside of shelves 17a and 17b. The cap 40' is then flipped back, and the emitter lens 34' is press-fitted to the inner wall 22', end 15b', and sides 15c' and 15d' (both of which are in…) Figure 3 Between (not shown). Then, a mass block 35, such as epoxy resin, is deposited or applied between the chamfer and ends 15b', sides 15c' and 15d', and inner wall 22' of the emitter end 34', and allowed to harden. Then, the cap 40' is aligned on the PCB 11 such that the desired axial alignment of the emitter lens 34' with the light emitter 33' is achieved, and the cap 40' is bonded to the appropriate position on the PCB 11 by adhesive beads 14 and 21.

[0049] The receiver lens 20 is press-fitted into the retaining structure 19, and then the retaining structure 19 is placed on the shelf 17a and glued in place by adhesive beads 18a. Note that the shelf 17a defines an annular space between the support 25a and corresponding portions of the end 15a, sides 15c and 15d, and inner wall 22. The size and shape of the annular space allow the retaining structure 19 (in which the receiver lens 20 is fixed) to be adjusted in the X-Y direction so that the optical axis of the lens 20 is aligned with the optical axis of the sensing portion of the light sensor 13, thereby allowing precise horizontal adjustment of the receiver lens 20 relative to the light sensor 13.

[0050] As described above, it should be understood that instead of press-fitting the transmitter lens 34' into the cap 40' and mechanically constraining it by the hardened block 35, and mechanically constraining the receiver lens 20 within the retaining structure 19, the receiver lens 20 can be press-fitted into the cap 40' and mechanically constrained by the hardened mass block, and the transmitter lens 34 can be mechanically constrained within the retaining structure 29.

[0051] As described in this article, the adhesive used and the hardened mass can be epoxy resin.

[0052] As an alternative to the reference detector 52 used, a portion of the light sensor 13 may extend below or through the sidewall to perform a reference detection function, such as... Figure 3A As shown in the diagram. This does not change the technology used to form the photonic device 10'.

[0053] Although the invention has been described with respect to a limited number of embodiments, those skilled in the art to which this invention pertains will understand that other embodiments may be conceived without departing from the scope of the invention disclosed herein. Therefore, the scope of this disclosure will be limited only by the appended claims.

Claims

1. A photonic device, comprising: A printed circuit board (PCB) has integrated circuits mounted on it; as well as A cap, mounted to the PCB and carrying a lens positioned above the integrated circuit, the cap comprising: An outer wall is mounted to the PCB, the outer wall extends upward from the PCB and surrounds at least a portion of the integrated circuit, and the outer wall is spaced apart from the lens; A first retaining structure extends inwardly from the outer wall and across the integrated circuit, the first retaining structure having a hole defined therein, the hole being surrounded by a support wall in physical contact with the bottom surface of the lens, the bottom surface of the lens facing the PCB; and A second retaining structure has a hole defined in a top plate of the second retaining structure, the top plate being in physical contact with the top surface of the lens, the top surface of the lens being opposite to the bottom surface, the second retaining structure being fixed within the first retaining structure such that the hole in the second retaining structure is axially aligned with the hole in the first retaining structure and such that... The lens is mechanically constrained within the cap between the support wall of the first retaining structure and the top plate of the second retaining structure, wherein light can be transmitted through the lens via a hole defined in the second retaining structure, and the mechanical constraint of the lens aligns the lens with the integrated circuit.

2. The photonic device according to claim 1, wherein the outer wall and the first retaining structure are integrally formed as a monolithic unit.

3. The photonic device of claim 1, wherein the first holding structure comprises a shelf and a support, the shelf extending orthogonally from a corresponding portion of the outer wall, and the support extending orthogonally to the shelf from a distal end of the shelf in a direction away from the PCB; and wherein the lens is mechanically constrained between the bottom surface of the second holding structure and the support of the first holding structure.

4. The photonic device of claim 3, wherein the second holding structure includes a shaped wall extending parallel to the outer wall, wherein a top plate extends across the shaped wall, the top plate having a hole defined therein.

5. The photonic device of claim 1, wherein the outer wall surrounds three sides of the integrated circuit; wherein the cap further includes an additional wall extending between two portions of the outer wall such that the additional wall extends along a fourth side of the integrated circuit; wherein a first portion of the first retaining structure extends from the outer wall and across the integrated circuit; and wherein a second portion of the first retaining structure extends from the additional wall and across the integrated circuit.

6. The photonic device of claim 5, wherein the first and second portions of the first holding structure define a shelf and a support member, the support member extending orthogonally to the shelf from a distal end of the shelf in a direction away from the PCB; wherein the lens is mechanically constrained between the bottom surface of the second holding structure and the support member of the first holding structure.

7. The photonic device of claim 6, wherein the PCB has an additional integrated circuit mounted thereon; wherein the outer wall surrounds three sides of the additional integrated circuit; wherein the additional wall extends between two portions of the outer wall such that the additional wall extends along a fourth side of the additional integrated circuit; wherein a third portion of the first retaining structure extends outward from the outer wall and across the additional integrated circuit; and wherein a fourth portion of the first retaining structure extends outward from the additional wall and across the additional integrated circuit.

8. The photonic device of claim 7, wherein the third and fourth portions of the first holding structure define an additional shelf and an additional support, the additional support extending orthogonally to the additional shelf from a distal end of the additional shelf in a direction away from the PCB; wherein the additional lens is mechanically constrained between the bottom surface of the second holding structure and the additional support of the first holding structure.

9. The photonic device of claim 8, further comprising a first filter bonded to the bottom surface of the shelf, and a second filter bonded to the bottom surface of the additional shelf.

10. The photonic device of claim 7, wherein the third and fourth portions of the first holding structure define an additional shelf and an additional support, the additional support extending orthogonally to the additional shelf from a distal end of the additional shelf in a direction away from the PCB; and further comprising an additional lens sized for press-fitting and mechanically constrained between the outer wall and the additional wall, the additional lens being supported by the additional support of the first holding structure.

11. The photonic device of claim 10, wherein the cap further comprises a hardened mass block in contact with the periphery of the additional lens and the outer and inner walls.

12. The photonic device of claim 11, wherein the additional lens has a chamfer defined therein; and wherein the hardened mass block contacts the surface of the chamfer.

13. The photonic device of claim 12, wherein the portions of the outer wall and the additional wall adjacent to the additional lens are trapezoidal at their distal ends.

14. The photonic device of claim 1, further comprising a filter bonded to the bottom surface of the first holding structure.

15. The photonic device of claim 14, wherein the filter is formed of glass; and wherein the lens is formed of polycarbonate.

16. A method for forming a photonic device, the method comprising: Install integrated circuits on a printed circuit board (PCB); A cap is attached to the PCB above the integrated circuit. The cap has an outer wall that is mounted to a substrate, the outer wall extending upward from the substrate and surrounding at least a portion of the integrated circuit, and a first retaining structure that extends inward from the outer wall and across the integrated circuit. The first retaining structure has a hole defined therein, the hole being surrounded by a support wall. The lens is press-fitted into the second retaining structure of the cap, the second retaining structure having a hole defined in a top plate of the second retaining structure, the top plate being in physical contact with the top surface of the lens, the top surface of the lens being opposite to the bottom surface; as well as Position the second retaining structure such that the lens is aligned with the integrated circuit, and bond the second retaining structure to the first retaining structure such that the lens is mechanically constrained within the cap between the support wall of the first retaining structure and the top plate of the second retaining structure, the support wall being in physical contact with the bottom surface of the lens, the bottom surface of the lens facing the PCB.

17. The method of claim 16, further comprising mounting an additional integrated circuit on the PCB, and press-fitting an additional lens between the outer wall of the cap and the inner wall of the cap before securing the cap to the PCB.

18. The method of claim 17, further comprising applying a hardenable material around the perimeter of the additional lens, and the hardenable material contacting the outer wall and the inner wall such that, when the hardenable material hardens, the additional lens is mechanically constrained between a first portion of the first retaining structure extending from the outer wall across the additional integrated circuit, a second portion of the first retaining structure extending from the inner wall, and the hardened material.

19. The method of claim 16, further comprising bonding the filter to the bottom surface of the first retaining structure before securing the cap to the PCB.

20. A photonic device, comprising: integrated circuit; as well as A cap, mounted on the integrated circuit, the cap comprising: The lens is mechanically constrained within the cap; An outer wall surrounding at least a portion of the integrated circuit, the outer wall being spaced apart from the lens; A first retaining structure extends inward from the outer wall and across the integrated circuit, the first retaining structure having a hole defined therein, the hole being surrounded by a support wall in physical contact with the bottom surface of the lens, the bottom surface of the lens facing the integrated circuit; A second retaining structure has a hole defined in a top plate of the second retaining structure, the top plate being in physical contact with the top surface of the lens, the top surface of the lens being opposite to the bottom surface, the second retaining structure being fixed within the first retaining structure such that the hole in the second retaining structure is axially aligned with the hole in the first retaining structure; and The lens is mechanically constrained within the cap between the support wall of the first retaining structure and the top plate of the second retaining structure, and light can be transmitted through the cap via a hole defined in the second retaining structure. The mechanical constraint of the lens aligns the lens with the integrated circuit.

21. The photonic device of claim 20, further comprising a filter bonded to the bottom surface of the first holding structure.

22. The photonic device of claim 21, wherein the filter is formed of glass; and The lens is made of polycarbonate.

23. The photonic device of claim 20, wherein the outer wall and the first retaining structure are integrally formed as a monolithic unit.

24. The photonic device of claim 20, wherein the first holding structure comprises a shelf and a support, the shelf extending orthogonally from a corresponding portion of the outer wall, and the support extending orthogonally from a distal end of the shelf; and wherein the lens is mechanically constrained between the bottom surface of the second holding structure and the support of the first holding structure.

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