This application claims all benefits accruing under 35 U.S.C. §119 from China Patent Application No. 201010260139.1, filed on Aug. 23, 2010 in the China Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Technical Field
The present disclosure relates to a grating coupler and a package structure incorporating the grating coupler.
2. Description of Related Art
Grating couplers can include an isolation layer, a waveguide layer, a reflector layer, and an under-cladding layer, disposed on a substrate in turns. The reflector layer is disposed between the under-cladding layer and the waveguide layer. The isolation layer defines a hole for receiving an optical fiber. Optical signals through the optical fiber transmit through the isolation layer, and are captured by the grating coupler, and then optically coupled into an integrated optical chip. However, because the reflector layer is disposed between the under-cladding layer and the waveguide layer, the fabrication technology of the grating coupler is not compatible with conventional CMOS (Complementary Metal Oxide Semiconductor) technology and has a high cost, which makes mass production prohibitive.
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references mean at least one.
Referring to
The waveguide layer 120 can be made of silicon, and have a thickness in a range of about 200 nanometers to about 300 nanometers. The refractive index of the waveguide layer 120 is greater than the refractive index of the isolation layer 110 and the refractive index of the under-cladding layer 130. The waveguide layer 120 is disposed on a surface of the under-cladding layer 130, and the under-cladding layer 130 is sandwiched between the waveguide layer 120 and the substrate 140. The waveguide layer 120 is embedded in the isolation layer 110.
The waveguide layer 120 includes a ridge waveguide 122 and a grating 121 connected to the ridge waveguide 122. The grating 121 includes a plurality of substantially parallel grooves with a rib between every two adjacent grooves. The grooves are defined in one surface of the grating 121 away from the under-cladding layer 130. In one embodiment, the grating 121 has a width of about 20 microns and a length of about 20 microns. The grooves have a depth in a range of about 70 nanometers to about 100 nanometers. The grating period of the grating 121, that is, a sum of a width of one groove and a width of an adjacent rib, is in a range of about 300 nanometers to about 600 nanometers.
The isolation layer 110 can be made of silicon dioxide or silicon nitride. The isolation layer 110 has a thickness in a range of about 0.5 microns to about 5 microns.
The reflector layer 100 can be made from one of gold, silver, copper, and aluminum. The reflector layer 100 can have a thickness in a range of about 50 nanometers to about 200 nanometers. The reflector layer 100 is disposed on a surface of the isolation layer 110 and is away from the under-cladding layer 130. The reflector layer 100 can be easily formed through metal evaporation at low cost.
The substrate 140 can be made of silicon and have a thickness in a range of about 300 nanometers to about 500 nanometers. The substrate 140 has a fiber aligned groove 150 defined therein. The fiber aligned groove 150 allows installation of an optical fiber 50 therein. The fiber aligned groove 150 is depressed from the second surface 142 towards the first surface 141. A cross section of the fiber aligned groove 150 along a surface substantially parallel to the second surface 142 can be substantially square, circular, or triangular. In one embodiment, cross sections of the fiber aligned groove 150 along surfaces substantially parallel to the second surface 142 have about the same shape and size. It should be noted that the shape and the size of the cross section of the fiber aligned groove 150 along a surface substantially parallel to the second surface 142 can be adjusted to match the shape and size of the optical fiber 50 installed in the fiber aligned groove 150.
The fiber aligned groove 150 includes an opening 151, an end surface 153, and a lateral surface 152. The opening 151 is defined in the second surface 142. The end surface 153 is opposite to the opening 151. The end surface 153 is away from the first surface 141. The lateral surface 152 extends along a periphery of the end surface 153 to the opening 151. The fiber aligned groove 150 can be fabricated through wet etching or dry deep etching. The fiber aligned groove 150 can be aligned with the grating 121 through double sided lithography, so that a geometric center of the grating 121 is located on an extended line of a center line or an axis of the fiber aligned groove 150. Further, a geometric center of the end surface 153 is also located on the extended line of the center line or the axis of the fiber aligned groove 150. If the optical fiber 50 is installed in the fiber aligned groove 150, the optical fiber 50 will automatically be aligned with the grating 121.
The under-cladding layer 130 can be made of silicon dioxide and have a thickness in a range of about 2 microns to about 5 microns.
Moreover, the grating coupler 10 can include a plurality of overlapping gratings 121. The gratings 121 are connected to the same ridge waveguide 122.
In assembling the grating coupler 10 and the optical fiber 50, the optical fiber 50 is inserted into the fiber aligned groove 150 through the opening 151, and is then encapsulated or packaged therein. As a result, a grating coupler package structure is formed. In one embodiment, the optical fiber 50 can be encapsulated or packaged in the fiber aligned groove 150 using glue. In one embodiment, the optical fiber 50 has a flat end surface which is substantially perpendicular to an axis of the optical fiber 50. In one embodiment, the flat end surface of the optical fiber 50 can be in close contact with the end surface 153 of the fiber aligned groove 150.
In operation of the grating coupler package structure, the optical fiber 50 can be connected to an external photo-conducting device and receive optical signals from the external photo-conducting device. Optical signals from the optical fiber 50 can be optically coupled into an integrated optical chip through the grating coupler 10.
Referring to
The substrate 240 includes a first surface 241, an opposite second surface 242, a third surface 243, and a fourth surface 244. The third surface 243 and the fourth surface 244 are located at opposite sides of the substrate 240. The third surface 243 and the fourth surface 244 extend between the first surface 241 and the second surface 242. When the substrate 240 is positioned in the position shown in
The substrate 240 includes a fiber aligned groove 250. The fiber aligned groove 250 includes a first opening 2520, a second opening 251, an end surface 253 and two lateral surfaces 252. The first opening 2520 is defined in the second surface 242, and the second opening 251 is defined in the third surface 243. The first opening 2520 and the second opening 251 intersect with each other at a joint of the second surface 242 and the third surface 243. The end surface 253 is substantially parallel to and away from the fourth surface 244. The two lateral surfaces 252 extend from edges of the end surface 253 towards the first opening 2520, and the second opening 251, respectively.
The fiber aligned groove 250 is depressed from the second surface 242 towards the first surface 241, and is away from the first surface 241, as well as being depressed from the third surface 243 towards the fourth surface 244, and away from the third surface 243. A cross section of the fiber aligned groove 250 along a surface substantially parallel to the fourth surface 244 can be square, circular, or a triangular.
In one embodiment, cross sections of the fiber aligned groove 250 along surfaces substantially parallel to the fourth surface 244, are substantially triangular. The first opening 2520 is substantially rectangular. The second opening 251 is substantially triangular. The shape and the size of the cross section of the fiber aligned groove 250 along a surface substantially parallel to the fourth surface 244 can be adjusted to match the shape and size of an optical fiber 60 installed in the fiber aligned groove 250.
As shown in
In assembling the grating coupler 20 and the optical fiber 60, the optical fiber 60 is inserted into the fiber aligned groove 250 through the first and second openings 2520, 251, and is then encapsulated or packaged therein. As a result, a grating coupler package structure is formed. In one embodiment, the optical fiber 60 can be encapsulated or packaged in the fiber aligned groove 250 by coating glue on the lateral surfaces 252.
In one embodiment, the optical fiber 60 has a flat end surface which defines an included angle of about 45 degrees with respect to an axis of the optical fiber 60. The optical fiber 60 is installed in the fiber aligned groove 250 with the flat end surface towards the second surface 242. The flat end surface defines an included angle of about 45 degrees with respect to the second surface 242. A line passing through a geometric center of the flat surface and a geometric center of the grating 221 is substantially perpendicular to the second surface 242.
In operation of the grating coupler package structure shown in
As described above, the reflector layer 100/200 can be disposed on a surface of the isolation layer 110/210 and is away from the first surface 141/241 of the substrate 140/240, the reflector layer 100/200 can be easily formed through metal evaporation at low cost. Further, the fabrication technology of the grating coupler 100/200 can be compatible with conventional CMOS technology and has a low cost, which makes it possible for mass production. Further, because the fiber aligned groove 150/250 is defined in the second surface 142/242 of the substrate 140/240, it is convenient for aligning the optical fiber 50/60 with the grating 121/221.
It is to be understood that the above-described embodiments are intended to illustrate rather than limit the disclosure. Variations may be made to the embodiments without departing from the spirit of the disclosure as claimed. It is understood that any element of any one embodiment is considered to be disclosed to be incorporated with any other embodiment. The above-described embodiments illustrate the scope of the disclosure but do not restrict the scope of the disclosure.
Depending on the embodiment, certain of the steps of methods described may be removed, others may be added, and the sequence of steps may be altered. It is also to be understood that the description and the claims drawn to a method may include some indication in reference to certain steps. However, the indication used is only to be viewed for identification purposes and not as a suggestion as to an order for the steps.
Number | Date | Country | Kind |
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201010260139.1 | Aug 2010 | CN | national |