OPTOELECTRONIC DEVICE AND ARRAY THEREOF

Abstract

An optoelectronic device and an array comprising a plurality of the same. The device(s) comprising: an optically active region with an electrode arrangement for applying an electric field across the optically active region; a first curved waveguide, arranged to guide light into the optically active region; and a second curved waveguide, arranged to guide light out of the optically active region; wherein the first curved waveguide and the second curved waveguide are formed of a material having a different band-gap from a band-gap of the optically active region, and wherein the overall guided path formed by the first curved waveguide, the optically active region and the second curved waveguide is U-shaped.

Claims

1. An optoelectronic device comprising: an optically active region with an electrode arrangement for applying an electric field across the optically active region; a first curved waveguide, arranged to guide light into the optically active region; and a second curved waveguide, arranged to guide light out of the optically active region; wherein the first curved waveguide and the second curved waveguide are formed of a material having a different band-gap from a band-gap of the optically active region, and wherein the overall guided path formed by the first curved waveguide, the optically active region and the second curved waveguide is U-shaped.

2. The optoelectronic device of claim 1, wherein the first curved waveguide or the second curved waveguide are formed as regrown waveguide(s).

3. The optoelectronic device of claim 1, wherein a maximum distance between the first curved waveguide and second curved waveguide is no more than 250 m, or, a radius of curvature of the first curved waveguide, or, the second curved waveguide is less than 100 m, or, the first curved waveguide and the second curved waveguide each curve through an angle of 90.

4. The optoelectronic device of claim 1, wherein the electrode arrangement further comprises first and second electrodes, said electrodes being disposed on a first side of the optically active region and electrically connected thereto.

5. The optoelectronic device of claim 4, wherein the first electrode is a signal electrode and the second electrode is a ground electrode.

6. The optoelectronic device of claim 5, further comprising a third electrode which is a second ground electrode.

7. The optoelectronic device of claim 4, configured to operate as an electro-absorption modulator.

8. The optoelectronic device of claim 1, wherein the first curved waveguide and the second curved waveguide are low-loss passive waveguides.

9. The optoelectronic device of claim 1, wherein the first curved waveguide or the second curved waveguide are deep-etched waveguides.

10. The optoelectronic device of claim 9, wherein the deep-etched waveguides are formed of indium phosphide.

11. The optoelectronic device of claim 1, further comprising: an input waveguide coupled to or provided as a continuation of the first curved waveguide; and an output waveguide coupled to or provided as a continuation of the second curved waveguide; wherein each of the input waveguide and the output waveguide have an end adjacent to a first edge of the optoelectronic device.

12. The optoelectronic device of claim 11, wherein the electrode arrangement further comprises first and second electrodes, said electrodes being disposed on a first side of the optically active region and electrically connected thereto, and the first and second electrodes are disposed adjacent to an edge of the optoelectronic device which is different to the first edge.

13. The optoelectronic device of claim 1, further comprising: a distributed feedback laser, coupled to the first curved waveguide; and an output waveguide, coupled to or provided as a continuation of the second curved waveguide; such that the optoelectronic device is an electro-absorption modulated laser.

14. The optoelectronic device of claim 13, wherein the distributed feedback laser is formed of a material having a band-gap which is the same as the band-gap of the optically active region, or, wherein the distributed feedback laser is formed from material having a band-gap which is different from the band-gap of the optically active region and different from the band-gap of the first and second curved waveguides.

15. The optoelectronic device of claim 1, wherein the optically active region is an electro-absorption modulator, or, wherein the first curved waveguide and the second curved waveguide are formed of a material having a band-gap which is lower in wavelength than a band-gap of the optically active region.

16. The optoelectronic device of claim 7, further comprising a semiconductor optical amplifier (SOA).

17. The optoelectronic device of claim 16, wherein the SOA is located between the first curved waveguide and the second curved waveguide, or, wherein the optoelectronic device includes an output waveguide coupled to or provided as a continuation of the second curved waveguide; and wherein the SOA is located at the output waveguide.

18. An array of optoelectronic devices disposed on a chip, wherein: each optoelectronic device is as set out in claim 1; and a distance between optically active regions of adjacent pairs of optoelectronic devices is no more than 250 m.

19. The array of claim 18, wherein each optoelectronic device has: an input waveguide coupled to or provided as a continuation of each first curved waveguide; and an output waveguide coupled to or provided as a continuation of each second curved waveguide; wherein each input waveguide and each output waveguide has a first end distal to its respective optically active region, and adjacent to a same side of the chip.

20. The array of claim 18, wherein each optoelectronic device has: a distributed feedback laser, coupled to each first curved waveguide; and an output waveguide, coupled to or provided as a continuation of each second curved waveguide; such that the optoelectronic device is an electro-absorption modulated laser; wherein an end of each output waveguide distal to its respective optically active region is adjacent to a same side of the chip.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

[0026] FIGS. 1A-1C each show a variant of an optoelectronic device according to an embodiment of the invention;

[0027] FIG. 2 shows a further optoelectronic device, the device including a distributed feedback laser (DFB);

[0028] FIGS. 3A and 3B each show further optoelectronic devices according to embodiments of the present invention, the optoelectronic devices including a semiconductor optical amplifier (SOA);

[0029] FIGS. 4A and 4B each show yet further optoelectronic devices according to embodiments of the present invention, where these devices also include a semiconductor optical amplifier.

[0030] FIG. 5 shows an array of optoelectronic devices according to an embodiment of the invention; and

[0031] FIG. 6 shows an array of optoelectronic devices according to an embodiment of the invention.

DETAILED DESCRIPTION AND FURTHER OPTIONAL FEATURES

[0032] FIG. 1A shows an optoelectronic device 100. The device is formed on a III-V semiconductor chip or wafer 101 and is made with, for example, InGaAsP/InP or InAlGaAs/InP. The device generally comprises an optically active region 102, formed of a first material structure (for example InGaAsP or InAlGaAs multiple quantum well heterostructure, InGaAsP, or InAlGaAs bulk material) which has an associated band-gap. Adjacent to opposing ends of the optically active region are first 103 and second 104 curved waveguides. The first curved waveguide 103, the optically active region 102 and the second curved waveguide 104 together form a U-bend; a U-shaped guided optical path. The first and second curved waveguides are formed of or adjusted to have a material structure which has a different band-gap from that of the optically active region. The different bandgaps are achieved by either adjusting the atomic ratios of the elements in the InGaAsP or InAlGaAs quaternaries in certain layers, or changing the thicknesses or material interface profile of the quantum wells in the multiple quantum well heterostructures. The band-gap in the waveguides is typically made to be lower in wavelength than that in the optically active region. The band-gap difference may correspond to a wavelength difference of 50-100 nm, and in some examples may correspond to a wavelength difference of up to 200 nm. The first and second curved waveguides are passive devices in that they are not used to actively modulate optical signals being passed therethrough. In the example shown in this figure, the curved waveguides have an effective radius of curvature of 50 m, or around 50 m. The curved waveguides may be regrown so as to change the band-gap of the curved waveguides relative to the optically active region 102. The degree of curvature of the curved waveguides may be described as a tight bend or Euler bend. The degree of curvature in this example is 90.

[0033] Regrowing is a process where a portion of the existing semiconductor optically active material is etched away, and then a second optically active material with a different band-gap wavelength (e.g. with different atomic ratios of elements, or different quantum well thicknesses) are re-grown into the region that was etched away. The regrowth may be epitaxial.

[0034] An input waveguide 105 couples an edge 109 of the chip 101 to one end of the first curved waveguide 103. Similarly, an output waveguide 106 couples the second curved waveguide 104 to the same edge 109 of the chip 101. The input and output waveguides are either distinct waveguides from the first and second curved waveguides or provided as continuations thereof, but have the same band-gap as the curved waveguides 103 and 104. The input and output waveguides may be coupled to tapers or mode converters near the edge 109 of the chip 101.

[0035] The device also includes a signal electrode 107 and ground electrode 108 to electrically drive the optically active region. In this example, both electrodes are disposed adjacent to a second edge 110 of the chip, which is on an opposite side to the edge 109 adjacent to the input and output waveguides. As both electrodes are on the same edge of the chip, this allows flip-chip bonding with short RF traces or wire bonding with short wire bond lengths to an off-chip driver chip. The distance between the input waveguide 105 and the output waveguide 106 in the device may be used to determine an overall width of the optoelectronic device. This width may be less than 250 m, and may be between 100 m and 160 m.

[0036] FIG. 1B shows a variant device which differs from the device of FIG. 1A in that an additional ground electrode 111 is disposed on an opposing side of the source or signal electrode 107 to the first ground electrode 108. Aside from this, the device is identical to that shown in FIG. 1A. Similarly, the device shown in FIG. 1C differs from that shown in FIG. 1A in that the ground electrode 108 and the source or signal electrode 107 have been swapped so that the ground electrode 108 is located proximate the first curved waveguide 103 and the source/signal electrode 107 is located proximate the second curved waveguide 104.

[0037] FIG. 2 shows an alternative device 200, which shares a number of features with the device 100 discussed above. Like features are indicated by like reference numerals. The device 200 in FIG. 2 however contains a distributed feedback laser 201 instead of the input waveguide 105 (as discussed above). The laser is coupled to the first curved waveguide 103, so as to provide laser light to the optically active region 102. The distributed feedback laser 201 may be formed of a material having a band-gap which is the same (or substantially the same) as the optically active region. Alternatively, it can formed of a material having a band-gap which is different from both the optically active region and the passive waveguide regions. Whilst not shown, the electrodes 107 and 108 in the device 200 can have any of the configurations described above in FIGS. 1A-1C.

[0038] FIG. 3A shows an alternative device 300A, which shares a number of features with the device 100 discussed above. Like features are indicated by like reference numerals. The optically active region 102 forms a high speed optoelectronic device such as an electro-absorption modulator EAM. The device 300A differs from the device 100 shown in FIG. 1C in that it further comprises a semiconductor optical amplifier (SOA), the SOA including a further optically active region 112, a further ground electrode 118, and a further source electrode 117. The EAM and SOA are typically formed of the same semiconductor materials but may be different on structure and/or compositions. The EAM and SOA are both located at the base of the U-bend, in-between the first curved waveguide 103 and the second curved waveguide 104.

[0039] FIG. 3B shows an alternative device 300B, which shares a number of features with the device 300A discussed above in relation to FIG. 3A. Again, like features are indicated by like reference numerals. The device differs from that of FIG. 3A in that it includes a distributed feedback laser 201 coupled to the first curved waveguide 103. The device differs from that of FIG. 2 in that it comprises a SOA region located at the base of the U-bend, adjacent the optically active region 102 of the EAM.

[0040] FIGS. 4A and 4B show alternative devices which differ from the devices of FIGS. 3A and 3B respectively in that rather than being located at the base of the U-bend, the SOA is located at the other side of the second curved waveguide 104 from the first optically active region 102 of the EAM. In other words, the SOA is located on the leg of the U-bend, along the output waveguide 106.

[0041] In each of the embodiments described above in relation to FIGS. 3A, 3B, 4A and 4B, the electrode pads 107, 108, 117, 118, could be positioned in other locations and in other configurations. The DFB and SOA pads are DC pads and so may be positioned away from the edge of the die. However, the EAM pads are RF pads and should therefore be located close to the edge of the die.

[0042] FIGS. 3A and 3B show the SOA also at the edge and close to the EAM. Thus there could be a single driver chip (DC and RF), but it is noted that the spacing of the waveguides is quite large. To reduce the spacing, an arrangement such as FIG. 4A and 4B can be used but here the EAM is distant from the SOA and so the RF (high speed) driver may be a separate chip from the DC driver/source.

[0043] In any one of the embodiments described above, the DFB and SOA are forward biased whilst the EAM is reverse biased.

[0044] FIG. 5 shows an array 500 of high speed optoelectronic devices 100a-100n disposed on a single wafer or chip. As can be seen, all of the input and output waveguides are coupled to the same edge of the chip which can facilitate flip-chipping to a host PIC with only one side of the chip requiring precise alignment to the host PIC waveguides, or fiber attachment to only one side of the chip, and installation in an optical network. Of note is the pitch 501 between devices i.e. the distance between like features in adjacent optoelectronic devices 100a-100n. For example, the distance between the input waveguide in optoelectronic device 100a and the respective input waveguide in the optoelectronic device 100b may be referred to as the pitch. The pitch is generally less than 250 m.

[0045] FIG. 6 shows an alternative array 600 of high speed optoelectronic devices 200a-200n disposed on a single wafer or chip. As can be seen, all of the output waveguides are coupled to the same edge of the chip which can facilitate flip-chipping to a host PIC with only one side of the chip requiring precise alignment to the host PIC waveguides, or fiber attachment to only one side of the chip, and installation in an optical network. Of note is the pitch 601 between devices, i.e., the distance between like features in adjacent optoelectronic devices 200a-200n. For example, the distance between the output waveguide in optoelectronic device 200a and the respective output waveguide in the optoelectronic device 200b may be referred to as the pitch. The pitch is generally less than 250 m.

[0046] Whilst not shown, an array of optoelectronic devices as described above may include at least one optoelectronic device according to FIGS. 1A-1C and at least one optoelectronic device according to FIG. 2.

[0047] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention. As used herein, the word or is inclusive, so that, for example, A or B means any one of (i) A, (ii) B, and (iii) A and B.

[0048] All references referred to above are hereby incorporated by reference.

LIST OF FEATURES

[0049] 100, 200 Optoelectronic device

[0050] 101 Wafer/chip

[0051] 102 optically active region

[0052] 103 First curved waveguide

[0053] 104 Second curved waveguide

[0054] 105 Input waveguide

[0055] 106 Output waveguide

[0056] 107, 117 Source/signal electrode

[0057] 108, 118 Ground electrode

[0058] 109 First edge of chip

[0059] 110 Second edge of chip

[0060] 111 Additional ground electrode

[0061] 201 Distributed feedback laser (DFB)

[0062] 300, 400 Array

[0063] 301, 401 Pitch