JP6566056B2 - Optical waveguide device and polarization adjustment method - Google Patents

Description

  The present invention relates to an optical waveguide element for confirming and adjusting a polarization state of light from an external optical element, and a polarization adjustment method using the same.

  2. Description of the Related Art In recent years, attention has been focused on a technique for forming an optical device such as an optical transceiver by hybridly integrating a compound semiconductor element such as GaAs or InP on an SOI (Silicon On Insulator) substrate on which an optical waveguide functioning as an optical wiring layer is formed. Yes.

  In such an optical device, an end face connection type spot size converter (for example, a non-contact type) is used as an input port for input light sent from an external optical element such as an optical fiber and an output port for output light sent to the external optical element. A patent document 1 or a non-patent document 2) or a planar coupling type grating coupler (for example, see non-patent document 3) is formed.

  The light propagating through the optical fiber includes TM (Transverse Magnetic) polarization and TE (Transverse Electric) polarization. On the other hand, in an optical device using an SOI substrate, an optical waveguide core made of Si (silicon) is a substantial light transmission path. The Si optical waveguide core has polarization dependency.

  For this reason, when inputting the input light sent from the optical fiber to the optical device, it is necessary to adjust the polarization state (for example, set one polarization component to 0) while confirming the polarization state of the input light. .

  Here, conventionally, the polarization state of the input light from the optical fiber has been confirmed and adjusted using a polarizer. In this case, input light from the optical fiber is input to the polarizer. And the polarization state of input light is confirmed by observing the light which permeate | transmitted the polarizer using an infrared camera. Furthermore, the polarization state can be adjusted by rotating the polarization axis of the optical fiber while observing the transmitted light of the polarizer.

15th Microoptics Conference (MOC'09), Tokyo, Japan, Oct. 25-28, 2009 J90 [Simple Spot-Size Converter With Narrow Waveguide ForSilicon Wire Circuits] Electronics Letters 5th December 2002 Vol.38 No.25 p.1669-1670 IEEE Journal of quantum electronics, vol.38, No.7, July 2002 p.949-955

  In a general optical device, an input port and an output port are provided at positions facing each other. Therefore, when an optical device is put into practical use, an optical fiber connected to the input port (input optical fiber) and an optical fiber connected to the output port (output optical fiber) are sandwiched between the optical devices. Place them facing each other. Then, they are optically connected by matching the optical axes of the input optical fiber and the input port and by matching the optical axes of the output optical fiber and the output port.

  Here, when the polarization state of the input light is confirmed and adjusted when the optical device is put to practical use, the method using the above-described polarizer includes the optical device itself and an output optical fiber. The camera cannot be installed. For this reason, when using a method using a polarizer, release the connection between the optical device, the input optical fiber, and the output optical fiber, disconnect the optical device and the output optical fiber, It is necessary to construct a measurement system in which an optical fiber, a polarizer, and an infrared camera are arranged in this order. Therefore, when using a method using a polarizer, it is necessary to rearrange the arrangement of the optical device and the optical fiber in practical use, which is troublesome.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical waveguide device capable of confirming and adjusting the polarization state of input light from an optical fiber more simply than a method using a conventional polarizer, and a polarization using the same. It is to provide an adjustment method.

In order to achieve the above-mentioned object, an optical waveguide device according to the first aspect of the present invention is connected in series with an input port and a polarization separation unit connected in series, and in parallel with each other and in parallel with each other. And an optical waveguide core formed along a horizontal reference plane, and a clad including the optical waveguide core. The input port sends light input from an external optical fiber to the polarization separation unit. The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output port and the other to the second output port. The first output port and the second output port each output light transmitted from the polarization separation unit in a direction intersecting the reference plane. The first output port so that the output direction of the one polarized light output from the first output port with respect to the reference plane is aligned with the output direction of the other polarized light output from the second output port with respect to the reference plane. And the arrangement of the second output port, the direction of input of one polarized light sent from the polarization separator to the first output port, and the second output port of the other polarized light sent from the polarization separator The direction of input is set.
The optical waveguide element includes an input port and a polarization separation unit connected in series, and a first output port and a second output port connected in series with the polarization separation unit and arranged in parallel with each other. And an optical waveguide core formed along a horizontal reference plane, and a clad including the optical waveguide core. The input port sends light input from an external optical fiber to the polarization separation unit. The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output port and the other to the second output port. A polarization rotation unit that converts the other polarization light into one polarization light is further formed between the polarization separation unit and the second output port. The first output port and the second output port respectively output the light transmitted from the polarization separation unit in a direction intersecting the reference plane in a state where the output directions with respect to the reference plane are aligned with each other.

  An optical waveguide device according to a second aspect of the present invention includes an input port and a polarization separation unit connected in series, and a first output connected in series with the polarization separation unit and arranged in parallel with each other. And an optical waveguide core formed along a horizontal reference plane, and a clad including the optical waveguide core. The input port sends light input from an external optical fiber to the polarization separation unit. The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output unit and the other to the second output unit. Each of the first output units includes m (m is an integer of 2 or more) first branch units and first output ports. The m first branch portions are connected in series. One first output port is connected to each first branch section. The k-th (k is an integer of k ≦ m−1) first branching unit splits light n times (n is an integer of 2 or more), and the n-branched single light k + 1st first branching unit To the first output port connected to the k-th first branching unit. The m-th first branching unit branches the light n times, and sends the n-branched light to the first output port connected to the m-th first branching unit. The second output unit includes m second branch units and second output ports, respectively. The m second branch portions are connected in series. One second output port is connected to each second branch section. The k-th second branching unit branches light n times, sends n-branched light to the k + 1-th second branching unit, and connects the other light to the k-th second branching unit. To the second output port. The m-th second branching unit branches light n times, and sends the n-branched light to the second output port connected to the m-th second branching unit. Each first output port outputs light transmitted from the first branching unit in a direction intersecting the reference plane. Each second output port outputs light transmitted from the second branching unit in a direction intersecting the reference plane.

  An optical waveguide device according to a third aspect of the present invention includes an input port and a polarization separation unit connected in series, and a first output connected in series with the polarization separation unit and arranged in parallel with each other. And an optical waveguide core formed along a horizontal reference plane, and a clad including the optical waveguide core. The input port sends light input from an external optical fiber to the polarization separation unit. The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output unit and the other to the second output unit. The first output unit includes a first branching unit connected to the polarization separation unit, and p (p is an integer of 2 or more) first sub-connection waveguide units and first output ports. The first branch unit p-branches the light transmitted from the polarization separation unit, and sends the p-branched light one by one to the first sub-connection waveguide unit. The p first sub-connection waveguide portions are respectively connected in series with the first branch portion and arranged in parallel with each other. One first output port is connected in series to each first sub-connection waveguide section. Each first sub-connection waveguide section sends the light transmitted from the first branch section to the first output port connected to the first sub-connection waveguide section. Impurity regions into which impurities are introduced at different concentrations are formed in the middle of the other first sub-connection waveguide portions except for one of the p first sub-connection waveguide portions. The second output unit includes a second branch unit connected to the polarization separation unit, and p second sub-connection waveguide units and second output ports, respectively. The second branching unit branches the light transmitted from the polarization splitting unit into p branches, and sends the p-branched light one by one to the second sub-connection waveguide section. The p second sub-connection waveguide sections are connected in series with the second branch sections, respectively, and are arranged in parallel with each other. One second output port is connected in series to each second sub-connection waveguide section. Each second sub-connection waveguide section sends light transmitted from the second branch section to a first output port connected to the second sub-connection waveguide section. Impurity regions into which impurities are introduced at different concentrations are formed in the middle of the other second sub-connection waveguide portions except for one of the p second sub-connection waveguide portions. Each first output port outputs light transmitted from the first sub-connection waveguide section in a direction intersecting the reference plane. Each second output port outputs light transmitted from the second sub-connection waveguide section in a direction intersecting the reference plane.

  The polarization adjustment method of the present invention includes a process of inputting an optical signal from an optical fiber to any one of the input ports of the optical waveguide elements according to the first to third aspects described above, and TE polarized light in the polarization separation unit. By observing the light output from the first output port and the light output from the second output port with respect to the optical signal separated into the TM polarized light, the TE polarized light and TM polarized light included in the optical signal are observed. A process of checking the intensity ratio, and a process of adjusting the polarization state of the optical signal by rotating the polarization axis of the optical fiber while checking the intensity ratio of the TE polarized light and the TM polarized light included in the optical signal; including.

  In the optical waveguide device and the polarization adjustment method of the present invention, the optical signal from the optical fiber is input from the direction along the reference plane, and the TE polarized light and the TM polarized light included in the optical signal intersect with the reference plane. Can be output. For this reason, unlike the method using the above-described polarizer, it is not necessary to construct a new measurement system when confirming and adjusting the polarization state, and the polarization state can be easily confirmed and adjusted.

It is a schematic plan view which shows a 1st optical waveguide element. (A) And (B) is a schematic end view which shows a 1st optical waveguide element. It is a schematic plan view which shows the modification of a 1st optical waveguide element. It is a schematic plan view which shows an optical device and a 1st optical waveguide element at the time of producing using a common support substrate. It is a schematic plan view which shows a 2nd optical waveguide element. It is a schematic end view which shows a 2nd optical waveguide element. It is a schematic plan view which shows a 3rd optical waveguide element. It is a schematic plan view which shows a 4th optical waveguide element.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the shape, size, and arrangement relationship of each component are merely schematically shown to the extent that the present invention can be understood. In the following, a preferred configuration example of the present invention will be described. However, the material and numerical conditions of each component are merely preferred examples. Therefore, the present invention is not limited to the following embodiments, and many changes or modifications that can achieve the effects of the present invention can be made without departing from the scope of the configuration of the present invention.

(First optical waveguide element)
The first optical waveguide device of the present invention will be described with reference to FIGS. FIG. 1 is a schematic plan view showing a first optical waveguide element. FIG. 2A is a schematic end view of the first optical waveguide element shown in FIG. 1 taken along the line II. FIG. 2B is a schematic end view of the first optical waveguide element shown in FIG. 1 taken along the line II-II. In FIG. 1, a clad described later is omitted. In FIG. 2, hatching is omitted.

  In the following description, the direction along the light propagation direction is the length direction of each component. The direction along the thickness of the support substrate is the thickness direction. Moreover, let the direction orthogonal to a length direction and a thickness direction be a width direction.

  The first optical waveguide element 100 includes a support substrate 10, a clad 20, and an optical waveguide core 30.

  The support substrate 10 is composed of a flat plate made of, for example, single crystal Si.

The clad 20 is formed on the support substrate 10 so as to cover the upper surface 10 a of the support substrate 10 and to include the optical waveguide core 30. The clad 20 is formed using, for example, SiO ₂ as a material.

  The optical waveguide core 30 is formed along the horizontal reference plane 15. Here, the reference surface 15 is set as a surface parallel to the upper surface 10 a of the support substrate 10. The optical waveguide core 30 is made of, for example, Si having a refractive index higher than that of the clad 20. As a result, the optical waveguide core 30 functions as a substantial light transmission path, and the input light propagates in the propagation direction according to the planar shape of the optical waveguide core 30.

  In order to prevent propagating light from escaping to the support substrate 10, the optical waveguide core 30 is formed, for example, at least 2 μm or more away from the support substrate 10, particularly 3 μm or more apart to avoid radiation loss of TM polarization. It is preferable.

  The optical waveguide core 30 includes an input port 31, a connection waveguide section 32, a polarization separation section 33, a first output section 34, and a second output section 35.

  The input port 31, the connection waveguide section 32, and the polarization separation section 33 are connected in series in this order.

  The first output unit 34 and the second output unit 35 are respectively connected in series with the polarization separation unit 33, and are arranged in parallel with each other with respect to the polarization separation unit 33. The first output part 34 includes a first connection waveguide part 41, a first taper part 42, and a first output port 43 connected in series in this order. The second output part 35 includes a second connection waveguide part 51, a second taper part 52, and a second output port 53 connected in series in this order.

  The input port 31 receives light sent from the input optical fiber. Further, the input port 31 sends light transmitted from the input optical fiber to the connection waveguide section 32.

  The input port 31 is configured as a spot size converter. The input port 31 as a spot size converter is continuous from the other end 31b connected to the connection waveguide section 32 toward one end (input end) 31a (that is, in a direction away from the connection waveguide section 32). The taper shape is reduced in width. The input end 31 a of the input port 31 coincides with the one end face 100 a of the first optical waveguide device 100 in the surface position. In the input port 31, the light confinement effect becomes weaker toward the narrow input end 31a side, and the light confinement effect becomes stronger toward the wide end 31b side. Therefore, the MFD (Mode Field Diameter: mode field diameter) of the light propagating through the input port 31 is enlarged near the input end 31a. Thus, light can be input from the input optical fiber to the input port 31 together with the MDF.

The spot size converter as the input port 31 is not limited to the configuration shown in FIG. The second optical waveguide core made of, for example, SiO _x (x is a real number satisfying 0 <x <2) having a refractive index lower than that of the optical waveguide core 30 and higher than that of the clad 20 is used as the optical waveguide. A double core structure (not shown) that covers the region of the input port 31 of the core 30 may also be used.

  The connection waveguide unit 32 transmits the light transmitted from the input port 31 to the polarization separation unit 33.

  The connection waveguide section 32 is set to a width that achieves a single mode condition, for example. Therefore, the connection waveguide part 32 propagates the light in the fundamental mode.

  The polarization separation unit 33 separates light transmitted from the connection waveguide unit 32 into TE polarized light and TM polarized light. Then, one polarized light is sent to the first connection waveguide section 41 of the first output section 34, and the other polarization light is sent to the second connection waveguide section 51 of the second output section 35. Here, a case where TE polarized light is sent to the first connection waveguide portion 41 and TM polarized light is sent to the second connection waveguide portion 51 will be described.

  As the polarization separation unit 33, for example, a bidirectional coupler, a multimode interference (MMI) coupler, or an optical waveguide device disclosed in Japanese Patent Laid-Open No. 2015-121696 can be used.

  The first connection waveguide section 41 sends TE polarized light sent from the polarization separation section 33 to the first taper section 42. Further, the second connection waveguide part 51 sends the TM polarized light sent from the polarization separation part 33 to the second taper part 52.

  The first connection waveguide section 41 and the second connection waveguide section 51 are each set to a width that achieves a single mode condition, for example. Therefore, the first connection waveguide portion 41 and the second connection waveguide portion 51 each propagate light in the fundamental mode.

  The first taper part 42 sends TE polarized light sent from the first connection waveguide part 41 to the first output port 43. Further, the second taper portion 52 sends TM polarized light sent from the second connection waveguide portion 51 to the second output port 53.

  The first taper portion 42 is formed in a tapered shape whose width continuously increases from one end connected to the first connection waveguide portion 41 to the other end connected to the first output port 43. The second taper portion 52 is formed in a taper shape whose width continuously increases from one end connected to the second connection waveguide portion 51 to the other end connected to the second output port 53. By forming the first taper portion 42 in the previous stage of the first output port 43 to be described later, the light output from the first output port 43 can be expanded to a beam width that is easy to observe.

  The first output port 43 outputs the TE polarized light transmitted from the first taper portion 42 in a direction intersecting the reference plane 15. The first output port 43 is configured as a grating coupler.

  The first output port 43 as a grating coupler has a grating groove 61 formed in the thickness direction along the light propagation direction (the optical axis direction connecting the first taper portion 42 and the first output port 43). A plurality are continuously formed. Each lattice groove 61 has a rectangular cross-sectional shape along the thickness direction. The first output port 43 selectively diffracts TE polarized light having a specific Bragg wavelength by appropriately designing the formation period of the grating grooves 61 and the equivalent refractive index for the input TE polarized light. Here, by setting the Bragg wavelength to be diffracted in accordance with the wavelength of the light transmitted from the input optical fiber, the TE polarized light transmitted from the first taper portion 42 is caused to cross the reference plane 15. Can be output.

  Further, the second output port 53 outputs the TM polarized light transmitted from the second tapered portion 52 in a direction intersecting the reference plane 15. Similar to the first output port 43, the second output port 53 is also configured as a grating coupler.

  The first optical waveguide element 100 is used as an element for confirming and adjusting the polarization state of an optical signal sent from an input optical fiber.

  Here, the optical signal from the input optical fiber is input from one end (input end) 31 a to the input port 31. The input optical signal is sent from the input port 31 to the polarization separation unit 33 via the connection waveguide unit 32. In the polarization separation unit 33, the optical signal is separated into TE polarized light and TM polarized light. The TE polarized light is sent to the first output unit 34. Further, the TM polarized light is sent to the second output unit 35. The TE polarized light is output from the first output port 43 in a direction intersecting the reference plane 15 through the first connection waveguide portion 41 and the first taper portion 42 in order. Further, the TM polarized light is output in a direction intersecting the reference plane 15 from the second output port 53 through the second connection waveguide portion 51 and the second taper portion 52 sequentially.

  In the first optical waveguide device 100, the TE polarized light output from the first output port 43 and the TM polarized light output from the second output port 53 are observed by using, for example, an infrared camera, whereby the TE polarized light is output. Brightness and darkness corresponding to the intensity ratio of wave light and TM polarized light can be confirmed. Thereby, the intensity ratio of the TE polarized light and the TM polarized light included in the optical signal from the input optical fiber can be confirmed.

  Further, in the first optical waveguide device 100, the polarization state can be adjusted by rotating the polarization axis of the input optical fiber while confirming the intensity ratio of the TE polarized light and the TM polarized light. For example, the optical signal from the input optical fiber can be adjusted to be only TE polarized light by rotating the input optical fiber so that the intensity of the observed TM polarized light becomes zero.

  Here, the TE polarized light output from the first output port 43 and the TM polarized light output from the second output port 53 are output at different angles with respect to the reference plane 15. Therefore, a polarization rotation unit (not shown) can be further formed between the polarization separation unit 33 and the second output port 53, that is, in the middle of the second connection waveguide unit 51.

  The polarization rotation unit converts the other polarization light (here, TM polarization light) sent from the polarization separation unit 33 to the second output port 53 into one polarization light (here, TE polarization light). As the polarization rotation unit, a structure in which the mode distribution is decentered in the thickness direction, such as a structure in which optical waveguide cores having different widths are stacked or a structure in which cores having different refractive indexes are stacked, or a grating that couples different polarizations is used. it can.

  When the polarization rotation unit is provided, the light input to the first output port 43 and the second output port 53 can be aligned with one polarized light (here, TE polarized light). For this reason, the light output from the first output port 43 and the second output port 53 is output in a common direction with respect to the reference plane 15. Therefore, it becomes easy to observe using an infrared camera or the like. In addition, since the first output port 43 and the second output port 53 can be formed with a common design, the design is easy.

  As another modification, for example, as shown in FIG. 3, the arrangement of the first output port 43 and the second output port 53 so that the angles of the output TE polarized light and TM polarized light with respect to the reference plane 15 are aligned. Can be set. FIG. 3 is a schematic plan view showing a modification of the first optical waveguide device. In FIG. 3, only the polarization separation unit 33, the first output unit 34, and the second output unit 35 are shown, and other components are omitted.

  In the configuration example shown in FIG. 3, by forming the second connection waveguide portion 51 including a curved waveguide, the output direction of the TM polarized light from the second output port 53 is changed from the first output port 43. The first output port 43 and the second output port 53 are arranged so as to be aligned with the output direction of the TE polarized light.

  As described above, by appropriately setting the arrangement of the first output port 43 and the second output port 53, the light output from the first output port 43 and the second output port 53 can be shared with the reference plane 15. Can be output in the direction. Therefore, it becomes easy to observe using an infrared camera or the like.

  Further, the first optical waveguide element 100 can be manufactured by using a support substrate 10 common to the optical device 150 as shown in FIG. FIG. 4 is a schematic plan view showing the optical device 150 and the first optical waveguide element 100 when manufactured using the common support substrate 10. In FIG. 4, the clad 20 is omitted.

  As shown in FIG. 4, the first optical waveguide element 100 is a surplus area on the support substrate 10 other than the formation area of the optical circuit 130 (the specific configuration is not shown) included in the optical device 150. Formed. In this case, the input port 31 of the first optical waveguide element 100 and the input port 110 connected to the optical circuit 130 included in the optical device 150 are formed with a common design. In addition, the input end of the input port 31 of the first optical waveguide element 100 and the input end of the input port 110 of the optical device 150 are formed with the end faces aligned by common dicing or the like. As a result, the input end of the input port 31 of the first optical waveguide element 100 and the input end of the input port 110 of the optical device 150 can be formed in common physical states.

  Even when the first optical waveguide device 100 is manufactured using the support substrate 10 common to the optical device 150, the polarization state of the optical signal transmitted from the input optical fiber is confirmed and adjusted by the above-described method. Can do. Then, after adjusting the polarization state of the optical signal, the optical device 150 or the input optical fiber is slid along the reference plane 15 to maintain the polarization state of the optical signal, and the input optical fiber and the optical fiber The input port 110 of the device 150 can be connected. Therefore, the polarization axis can be accurately matched between the input optical fiber and the input port 110 of the optical device 150.

  As described above, in the first optical waveguide device 100, the optical signal from the input optical fiber is input from the direction along the reference plane 15, and the TE polarized light and the TM polarized light included in the optical signal are input to the reference plane 15. Can be output in the direction that intersects. For this reason, unlike the method using the above-described polarizer, it is not necessary to construct a new measurement system when confirming and adjusting the polarization state, and the polarization state can be easily confirmed and adjusted.

(Second optical waveguide element)
A second optical waveguide device of the present invention will be described with reference to FIGS. FIG. 4 is a schematic plan view showing the second optical waveguide element. FIG. 6 is a schematic end view of the second optical waveguide element shown in FIG. 5 taken along line III-III. In FIG. 5, the cladding is omitted. In FIG. 6, hatching is omitted. In addition, the same reference numerals are given to components common to the above-described first optical waveguide device 100, and description thereof is omitted.

  In the second optical waveguide element 200, a light shielding body 70 is further formed in addition to the first optical waveguide element 100 described above.

  The light shield 70 is formed on the clad 20 at a position that defines the periphery of the first output port 43 and the periphery of the second output port 53 in a top view.

  The light shield 70 is made of a material that does not transmit light. For example, when an electrode is formed on the optical device 150 (see FIG. 4), it can be formed using the same material as the electrode. In this case, the light blocking body 70 can be formed in the same process as forming the electrodes of the optical device 150.

  In the second optical waveguide element 200, stray light such as a coupling loss component between the input optical fiber and the input port 31 and reflection or scattering loss component of light propagating through the optical waveguide core 30 is blocked by the light shielding body 70. It is done. As a result, in the second optical waveguide device 200, the TE polarized light output from the first output port 43 and the TM polarized light output from the second output port 53 are observed without being buried in stray light.

(Third optical waveguide device)
With reference to FIG. 7, a third optical waveguide device of the present invention will be described. FIG. 7 is a schematic plan view showing a third optical waveguide device. In FIG. 7, each component is connected by a line. This is a schematic illustration of a transmission path through which light propagates. Here, the connection is configured as a part of the optical waveguide core. This is a waveguide.

  Further, in the third optical waveguide element 300, since the configuration other than the first output portion and the second output portion of the optical waveguide core is the same as that of the first optical waveguide device 100 described above, FIG. Only the first output portion and the second output portion of the optical waveguide core are shown, and the same reference numerals are given to common components, and the description thereof is omitted.

  In the third optical waveguide device 300, the first output unit 34 includes the first connection waveguide unit 41, m (m is an integer of 2 or more) first branching units 81-1 to 81-m, and a first taper. Part 82-1 to m and first output ports 83-1 to 83-m.

  The first branch part 81-1 formed in the foremost stage among the first branch parts 81-1 to 81-1m is connected to the first connection waveguide part 41.

  Each first branching unit 81 outputs TE polarized light transmitted from the polarization separation unit 33 (see FIG. 1) via the first connection waveguide unit 41 by n branching (n is an integer of 2 or more). . FIG. 7 shows a configuration in which each first branching unit 81 branches the input TE polarized light into two. Therefore, hereinafter, a configuration in which the first branching units 81-1 to 81-m branch the TE polarized light into two will be described.

  The first branch portions 81-1 to 81-1m are connected in series in this order. In addition, each first branch portion 81 is connected to a first taper portion 82 and a first output port 83 one by one in this order. Therefore, the first branch portion 81, the first taper portion 82, and the first output port 83 in the subsequent stage are connected in parallel to the first branch portions 81-1 to m-1.

  Each first branching unit 81 sends one TE polarized light of the two branched TE polarized light to the first branching unit 81 at the subsequent stage. In addition, each first branching unit 81 sends the other two branched TE polarized light beams to the first taper unit 82 and the first output port 83 connected to the first branching unit 81.

  It should be noted that the first branch portion 81 at a later stage is not connected to the first branch portion 81-m formed at the rearmost stage. Accordingly, one of the two branched TE polarized lights is blocked or sent to another path (not shown) and emitted. Then, the other of the two branched TE polarized lights is sent to the first output port 83 via the first taper portion 82.

  That is, the k-th (k is an integer of k ≦ m−1) first branch portion 81 includes a k + 1-th first branch portion 81 and a k-th first taper portion 82 that are arranged in parallel to each other. Are connected in series. Then, the k-th first branching unit 81 sends one branched TE polarized light to the (k + 1) th first branching unit 81, and sends another branched TE polarized light to the k-th first polarized light. The data is sent to the k-th first first output port 83 via the 1 taper portion 82. In addition, a taper portion 82 is connected in series to the m-th first branch portion 81. Then, the m-th first branching unit 81 sends one branched TE polarized light to the m-th first output port 83 via the m-th first taper unit 82.

  In addition, when the 1st branch part 81-1 to m branches TE polarized light into 3 or more (that is, when n ≦ 3), it is sent to the first branch part 81 or the first taper part 82 in the subsequent stage. Other branched light is blocked or emitted.

  Each first branching unit 81 can be configured as, for example, a directional coupler, an MMI coupler, or the like. In particular, when the first branching unit 81 splits the TE polarized light into two, a 3 dB coupler, a Y branch, or the like can be used as the first branching unit 81.

  The first taper portions 82-1 to m and the first output ports 83-1 to m can be configured in the same manner as the first taper portion 42 and the first output port 43 (see FIG. 1) described above. The TE polarized light transmitted to the first output ports 83-1 to 83-1 m is output in a direction intersecting with the reference plane 15 (see FIG. 2).

  In the third optical waveguide device 300, the second output unit 35 includes the second connection waveguide unit 51, m second branching units 91-1 to 91-m, and second taper units 92-1 to 92-1m, respectively. And second output ports 93-1 to 93-m.

  The second branch part 91-1 formed in the foremost stage among the second branch parts 91-1 to 91-m is connected to the second connection waveguide part 51.

  Each second branching unit 91 branches the TM polarized light transmitted from the polarization separation unit 33 (see FIG. 1) through the second connection waveguide unit 51 into n branches and outputs the branched light. FIG. 7 shows a configuration in which each second branching unit 91 branches the input TM polarized light into two. Therefore, hereinafter, a configuration in which the second branching units 91-1 to 91-m branch the TM polarized light into two will be described.

  The second branch portions 91-1 to 91-m are connected in series in this order. Each second branch portion 91 is connected with a second taper portion 92 and a second output port 93 one by one in this order. Therefore, the second branch portion 91, the second taper portion 92, and the second output port 93 in the subsequent stage are connected in parallel to each second branch portion 91.

  In each second branch section 91, one TM polarized light among the two branched TM polarized lights is sent to the second branch section 91 in the subsequent stage. In addition, the other TM polarized light branched into two is sent to the second taper portion 92 and the second output port 93.

  It should be noted that the second branch portion 91 at a later stage is not connected to the second branch portion 91-m formed at the rearmost stage. Accordingly, one of the two branched TM polarized lights is blocked or sent to another path (not shown) and emitted. Then, the other of the two branched TM polarized lights is sent to the second output port 93 via the second tapered portion 92.

  In other words, the k-th (k is an integer of k ≦ m−1) second branch portion 91 includes a k + 1-th second branch portion 91 and a k-th second taper portion 92 arranged in parallel to each other. Are connected in series. Then, the k-th second branching unit 91 sends one branched TM polarized light to the (k + 1) th second branching unit 91, and sends another branched TM polarized light to the k-th second polarized light. It is sent to the second output port 93 through the two taper portions 92. In addition, the mth second tapered portion 92 is connected in series to the mth second branch portion 91. Then, the m-th second branching unit 91 sends one branched TM polarized light to the second output port 93 via the m-th second taper unit 92.

  In addition, when the 2nd branch part 91-1 to m branches TM polarized light into 3 or more (that is, when n ≦ 3), it is sent to the second branch part 91 or the second taper part 92 in the subsequent stage. Other branched light is blocked or emitted.

  Each second branch unit 91 can be configured as, for example, a directional coupler, an MMI coupler, or the like. In particular, when the second branching unit 91 branches the TE polarized light into two, a 3 dB coupler, a Y branch, or the like can be used as the second branching unit 91.

  The 2nd taper part 92-1 to m and the second output port 93-1 to m can be configured similarly to the second taper part 52 and the second output port 53 (see FIG. 1) described above. The TM polarized light transmitted to the second output ports 93-1 to 93-m is output in a direction intersecting with the reference plane 15 (see FIG. 2).

  In the third optical waveguide device 300, the TE polarized light transmitted from the polarization separation unit 33 to the first output unit 34 is branched at a constant ratio by the first branching units 81-1 to 81-m, while the first output unit 34 is propagated. For this reason, the TE polarized light output from each first output port 83 connected to each first branch portion 81 has a lower output intensity as the first output port 83 disposed in the subsequent stage. Similarly, regarding the TM polarized light transmitted from the polarization separation unit 33 to the second output unit 35, the TE polarized light output from each second output port 93 connected to each second branching unit 91 is the latter stage. The output intensity of the second output port 93 arranged at the lower position becomes smaller.

  Here, each 1st branch part 81 and the 2nd branch part 91 are the structures which branch light into two. For this reason, the output intensity from the first output ports 83-1 to 83-m attenuates by 3 dB with respect to the first output port 83 of the previous stage. The output intensity from the second output ports 93-1 to 93-m is attenuated by 3 dB with respect to the second output port 93 of the previous stage.

  Thus, in the third optical waveguide device 300, TE polarized light and TM polarized light can be output from the plurality of first output ports 83 and second output ports 93, respectively. Then, depending on the intensity of the TE polarized light transmitted from the polarization separation unit 33 to the first output unit 34 and the TM polarized light transmitted to the second output unit 35, the first output port 83-1-m or the second output port 93 is used. The number of steps from -1 to m is different.

  By observing TE-polarized light and TM-polarized light output from the plurality of first output ports 83 and second output ports 93, to what number of stages the first output port 83 outputs TE-polarized light. , And up to what level of the second output port 93, the TM polarized light can be confirmed. Based on this result, by comparing the number of first output ports 83-1 to 83-m that output TE polarized light and the number of second output ports 93-1 to 93-m that output TM polarized light, input light is obtained. The approximate polarization extinction ratio of the TE polarized light and TM polarized light included in the optical signal from the fiber can be confirmed. Note that the output ratio of the first output ports 83-1 to 83-m and the second output port 93-depends on how many lights are branched in the first branch units 81-1 to 8m and the second branch units 91-1 to 91-m. The resolution of the output ratio of 1 to m can be set as appropriate.

  Here, also in the third optical waveguide element 300, similarly to the second optical waveguide element 200, a light shielding body 70 (see FIG. 5) can also be provided.

  Similarly to the first optical waveguide device 100, the polarization rotation unit is provided between the polarization separation unit 33 and the second branching unit 91-1 at the foremost stage, that is, in the middle of the second connection waveguide unit 51. Further, the arrangement of each first output port 83 and each second output port 93 is set so that the angle to the reference plane 15 of the configuration (not shown) to be formed or the output TE polarized light and TM polarized light is aligned. A configuration (see FIG. 3) may be employed.

(Fourth optical waveguide element)
With reference to FIG. 8, a fourth optical waveguide device of the present invention will be described. FIG. 8 is a schematic plan view showing a fourth optical waveguide element. In the fourth optical waveguide element, the configuration other than the first output portion and the second output portion of the optical waveguide core is the same as that of the first optical waveguide device 100 described above. Only the first output portion and the second output portion of the waveguide core are shown, and the same reference numerals are given to common components, and the description thereof is omitted.

  In the fourth optical waveguide device 400, the first output unit 34 includes the first connection waveguide unit 41, the first branch unit 85, and p first (p is an integer of 2 or more) first sub connection waveguide units. 86-1p, 1st taper part 87-1 to p, and 1st output port 88-1 to p are comprised.

  The first branch portion 85 is connected to the first connection waveguide portion 41. The first sub-connection waveguide sections 86-1 to 86-p are connected in series with the first branch section 85 and are arranged in parallel with each other with respect to the first branch section 85. In addition, a first taper 87 and a first output port 88 are connected in series in this order one by one to the end of each first sub-connection waveguide section 86 on the side opposite to the first branching section 85. Yes.

  The first branching unit 85 p-branches (p is an integer of 2 or more) and outputs the TE polarized light transmitted from the polarization separation unit 33 (see FIG. 1) via the first connection waveguide unit 41 described above. In the first branching portion 85, the p-branched TE polarized light is sent to the first sub-connection waveguide portions 86-1 to 86-1p one by one.

  The first branching unit 85 can be configured as, for example, a directional coupler, an MMI coupler, or the like.

  Each first sub-connection waveguide section 86 sends the TE polarized light transmitted from the first branching section 85 to the first output port 88 via the first tapered section 87 connected thereto.

  In the middle of other first sub-connection waveguide portions 86 (here, the first sub-connection waveguide portions 86-2 to 86-p) excluding one of the first sub-connection waveguide portions 86-1 to 86-p, An impurity region 89 into which impurities are introduced is formed. Each of these impurity regions 89 is formed by introducing different concentrations of impurities. The impurity concentration of each impurity region 89 is set to increase at a constant ratio, for example, in the order of the first sub-connection waveguide sections 86-2 to 86-p. Note that the impurity region 89 is not formed in the first sub-connection waveguide section 86-1.

  The 1st taper part 87-1 to p and the 1st output port 88-1 to p can be comprised similarly to the 1st taper part 42 and the 1st output port 43 (refer FIG. 1) mentioned above. The TE polarized light transmitted to the first output ports 88-1 to 88-p is output in a direction that intersects the reference plane 15 (see FIG. 2).

  Further, in the fourth optical waveguide device 400, the second output unit 35 includes the second connection waveguide unit 51, the second branch unit 95, and p second (p is an integer of 2 or more) second sub connection conductors. The waveguide portion 96-1 to p, the second taper portion 97-1 to p, and the second output port 98-1 to p are configured.

  The second branch part 95 is connected to the second connection waveguide part 51. The second sub-connection waveguide sections 96-1 to 96-p are connected in series with the second branch section 95 and are arranged in parallel with each other with respect to the second branch section 95. In addition, a second taper portion 97 and a second output port 98 are connected in series in this order one by one to the end of each second sub-connection waveguide portion 96 on the side opposite to the second branch portion 95. Yes.

  The second branching unit 95 p-branches and outputs the TM polarized light transmitted from the polarization separation unit 33 (see FIG. 1) via the second connection waveguide unit 51 described above. In the second branching section 95, the TM polarized light branched in p is sent to the second sub-connection waveguide sections 96-1 to 96-p one by one.

  The second branch unit 95 can be configured as, for example, a directional coupler, an MMI coupler, or the like.

  Each second sub-connection waveguide section 96 sends the TM polarized light transmitted from the second branch section 95 to the second output port 98 via the second taper section 97 connected thereto.

  In the middle of other second sub-connection waveguide sections 96 (here, second sub-connection waveguide sections 96-2 to 96-p) excluding one of the second sub-connection waveguide sections 96-1 to 96-p, An impurity region 99 into which impurities are introduced is formed. Each of these impurity regions 99 is formed by introducing different concentrations of impurities. The impurity concentration of each impurity region 99 is set so as to increase, for example, in the order of the second sub-connection waveguide portions 96-2 to 96-p at a constant ratio common to the impurity region 89 described above. Note that the impurity region 99 is not formed in the second sub-connection waveguide section 96-1.

  The second taper portions 97-1 to 97-p and the second output ports 98-1 to 98-p can be configured in the same manner as the second taper portion 52 and the second output port 53 (see FIG. 1). The TM polarized light transmitted to the second output ports 98-1 to 98-p is output in a direction intersecting with the reference plane 15 (see FIG. 2).

  In the fourth optical waveguide device 400, the TE polarized light branched by the first branching portion 85 is the first subconnection waveguide portion 86 in which the first subconnection waveguide portion 86-1 or the impurity region 89 is formed. The signals are output from the first output ports 88-1 to 88-p via −2 to p. As described above, the impurity regions 89 formed in the first sub-connection waveguide sections 86-2 to 86-p have different impurity concentrations. For this reason, the intensity of TE polarized light transmitted to the first output port 88 through the impurity region 89 having a high impurity concentration is attenuated, and the output from the first output port 88 is reduced. Here, the impurity region 89 is not formed in the first sub-connection waveguide section 86-1, and the impurity concentration of the impurity region 89 is set to increase in the order of the first sub-connection waveguide sections 86-2 to 86-p. Has been. Therefore, the output intensity of the TE polarized light from the first output port 88-1 is maximized, and the output intensity decreases in the order of the first output ports 88-2 to 88-p. Similarly, for TM polarized light p-branched by the second branching unit 95, the output intensity from the second output port 98-1 is maximized, and the output intensity decreases in the order of the second output ports 98-2 to 98-p. Become.

  Thus, in the fourth optical waveguide device 400, TE polarized light and TM polarized light can be output from the plurality of first output ports 88 and second output ports 98, respectively. Then, depending on the intensity of the TE polarized light transmitted from the polarization separation unit 33 to the first output unit 34 and the intensity of the TM polarized light transmitted to the second output unit 35, the first output port 88-1 to p or the second output port 98 is used. The number of output ports from −1 to p is different.

  Then, by observing TE polarized light and TM polarized light output from the plurality of first output ports 88 and second output ports 98, TE polarized light is output from some of the first output ports 88-1 to 88-p. And how many of the second output ports 98-1 to 98-p output TM polarized light. Based on this result, by comparing the number of first output ports 88-1 to 88-m that output TE polarized light with the number of second output ports 98-1 to 98-m that output TM polarized light, input light is obtained. The approximate polarization extinction ratio of the TE polarized light and TM polarized light included in the optical signal from the fiber can be confirmed. The concentration ratio of the impurity regions 89 formed in the first sub-connection waveguide portions 86-2 to 86-p and the concentration of the impurity regions 99 formed in the second sub-connection waveguide portions 96-2 to 96-p. In accordance with the ratio, the resolution of the output ratio of the first output ports 88-1 to 88-p and the output ratio of the second output ports 98-1 to 98-p can be set as appropriate.

  Here, in the fourth optical waveguide element 400 as well, as in the second optical waveguide element 200, a light shielding body 70 (see FIG. 5) can be provided.

  Further, similarly to the first optical waveguide device 100, a polarization rotation unit is further formed between the polarization separation unit 33 and the second branching unit 95 in the foremost stage, that is, in the middle of the second connection waveguide unit 51. Or a configuration in which the arrangement of the first output ports 88 and the second output ports 98 is set so that the angles of the output TE polarized light and TM polarized light with respect to the reference plane 15 are aligned (not shown). (See FIG. 3).

(Production method)
The first optical waveguide element 100, the second optical waveguide element 200, the third optical waveguide element 300, and the fourth optical waveguide element 400 described above can be simplified by using, for example, an SOI (Silicon On Insulator) substrate. Can be manufactured.

That is, first, an SOI substrate is prepared in which a support substrate layer, a SiO ₂ layer, and a Si layer are sequentially stacked. Next, the optical waveguide core 30 is formed by patterning the Si layer using, for example, an etching technique. As a result, it is possible to obtain a structure in which the SiO ₂ layer is laminated on the support substrate layer as the support substrate 10 and the optical waveguide core 30 is formed on the SiO ₂ layer. Next, SiO ₂ is deposited so as to cover the optical waveguide core 30 on the SiO ₂ layer by using, for example, a CVD method. As a result, the optical waveguide core 30 is included by the SiO ₂ clad 20, and the first optical waveguide device 100, the third optical waveguide device 300, or the fourth optical waveguide device 400 can be manufactured. In the case of manufacturing the second optical waveguide element 200, the light shielding body 70 is formed by depositing and patterning a material such as a metal after the cladding 20 is formed.

10: support substrate 15: reference surface 20: clad 30: optical waveguide core 31, 110: input port 32: connection waveguide section 33: polarization separation section 34: first output section 35: second output section 41: first Connection waveguide portions 42, 82, 87: first taper portions 43, 83, 88: first output port 51: second connection waveguide portions 52, 92, 97: second taper portions 53, 93, 98: second Output port 70: light shield 81, 85: first branch portion 86: first sub-connection waveguide portion 89, 99: impurity region 91, 95: second branch portion 96: second sub-connection waveguide portion 100: first Optical waveguide element 130: optical circuit 150: optical device 200: second optical waveguide element 300: third optical waveguide element 400: fourth optical waveguide element

Claims (10)

An input port and a polarization separator connected in series, and a first output port and a second output port connected in series with each of the polarization separators and arranged in parallel with each other; An optical waveguide core formed along;
A clad including the optical waveguide core,
The input port sends light input from an external optical fiber to the polarization separation unit,
The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output port and the other to the second output port,
The first output port and the second output port each output light transmitted from the polarization separation unit in a direction intersecting the reference plane ,
The direction of the output of the one polarized light output from the first output port with respect to the reference plane and the direction of the output of the other polarized light output from the second output port with respect to the reference plane are aligned. The arrangement of the first output port and the second output port, the direction of input of one polarized light sent from the polarization separation unit to the first output port, and the other sent from the polarization separation unit An optical waveguide device , wherein a direction of input of polarized light to the second output port is set . An input port and a polarization separator connected in series, and a first output port and a second output port connected in series with each of the polarization separators and arranged in parallel with each other; An optical waveguide core formed along;
A clad including the optical waveguide core;
With
The input port sends light input from an external optical fiber to the polarization separation unit,
The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output port and the other to the second output port,
A polarization rotation unit that converts the other polarization light into one polarization light is further formed between the polarization separation unit and the second output port ,
The first output port and the second output port respectively output light transmitted from the polarization separation unit in a direction intersecting the reference plane in a state where the output directions with respect to the reference plane are aligned with each other. br /> optical waveguide device you wherein a. An input port and a polarization separation unit connected in series, and a first output unit and a second output unit connected in series with each of the polarization separation units and arranged in parallel with each other; An optical waveguide core formed along;
A clad including the optical waveguide core,
The input port sends light input from an external optical fiber to the polarization separation unit,
The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output unit and the other to the second output unit,
Each of the first output units includes m (m is an integer of 2 or more) first branch units and first output ports,
The m first branch portions are connected in series, and each of the first branch portions is connected to the first output port one by one,
The k-th first branching unit (k is an integer satisfying k ≦ m−1) branches light n times (n is an integer equal to or greater than 2), and the n-branched one light is the k + 1-th first light. Send the other light to the first output port connected to the k-th first branch,
The m-th first branching unit branches light n times, and sends one n-branched light to the first output port connected to the m-th first branching unit,
The second output unit includes m second branch units and second output ports, respectively.
The m second branch portions are connected in series, and each of the second branch portions is connected to the second output port one by one,
The k-th second branching unit branches light n times, sends the n-branched light to the k + 1-th second branching unit, and sends the other light to the k-th second branching unit. To the connected second output port,
The m-th second branching unit branches light n times, and sends one n-branched light to the second output port connected to the m-th second branching unit,
Each of the first output ports outputs light transmitted from the first branch unit in a direction intersecting the reference plane,
Each said 2nd output port outputs the light sent from the said 2nd branch part in the direction which cross | intersects the said reference plane, respectively, The optical waveguide element characterized by the above-mentioned. The polarization rotation unit for converting the other polarization light into one polarization light is further formed between the polarization separation unit and the second branching unit at the frontmost stage. The optical waveguide device described. An input port and a polarization separation unit connected in series, and a first output unit and a second output unit connected in series with each of the polarization separation units and arranged in parallel with each other; An optical waveguide core formed along;
A clad including the optical waveguide core,
The input port sends light input from an external optical fiber to the polarization separation unit,
The polarization separation unit separates light transmitted from the input port into TE polarized light and TM polarized light, and sends one to the first output unit and the other to the second output unit,
The first output unit includes a first branching unit connected to the polarization separation unit, and each of p (p is an integer of 2 or more) first sub-connection waveguide units and first output ports,
The first branching unit p-branches the light transmitted from the polarization separation unit, and sends the p-branched light one by one to the first sub-connection waveguide unit,
The p first sub-connection waveguide portions are respectively connected in series with the first branch portions and arranged in parallel with each other, and each first sub-connection waveguide portion includes the first output port. One by one connected in series,
Each of the first sub-connection waveguide sections sends light transmitted from the first branch section to the first output port connected to the first sub-connection waveguide section,
Impurity regions into which impurities are introduced at different concentrations are formed in the middle of the other first sub-connection waveguide portions except for one of the p first sub-connection waveguide portions. ,
The second output unit includes a second branch unit connected to the polarization separation unit, and p second sub-connection waveguide units and a second output port, respectively.
The second branching unit p-branches the light transmitted from the polarization separation unit, and sends the p-branched light one by one to the second sub-connection waveguide unit,
The p second sub-connection waveguide portions are respectively connected in series with the second branch portions and arranged in parallel with each other, and each second sub-connection waveguide portion includes the second output port. One by one connected in series,
Each of the second sub-connection waveguide sections sends light sent from the second branch section to the second output port connected to the second sub-connection waveguide section,
Impurity regions into which impurities are introduced at different concentrations are formed in the middle of the other second sub-connection waveguide portions except for one of the p second sub-connection waveguide portions. ,
Each of the first output ports outputs light transmitted from the first sub-connection waveguide section in a direction intersecting the reference plane,
Each said 2nd output port outputs the light sent from the said 2nd sub connection waveguide part, respectively in the direction which cross | intersects the said reference plane, The optical waveguide element characterized by the above-mentioned. The polarization rotation unit for converting the other polarization light into one polarization light is further formed between the polarization separation unit and the second branching unit. Optical waveguide element. The light shielding body is additionally formed at a position on the cladding that defines the periphery of the first output port and the periphery of the second output port. The optical waveguide device according to item. The optical waveguide element is formed in a region other than a region where an optical circuit included in the optical device is formed on a support substrate common to the optical device,
The optical waveguide element according to claim 1, wherein the input port is formed with a design common to an input port included in the optical device. A process of inputting an optical signal from the optical fiber to the input port of the optical waveguide device according to any one of claims 1 to 8,
By observing the light output from the first output port and the light output from the second output port for the optical signal separated into TE polarized light and TM polarized light in the polarization separation unit, Confirming the intensity ratio of TE polarized light and TM polarized light included in the optical signal;
And adjusting the polarization state of the optical signal by rotating the polarization axis of the optical fiber while confirming the intensity ratio of the TE polarized light and the TM polarized light included in the optical signal. Polarization adjustment method. Claim 3, 4, 5, and 6, claim 7, citing claim 3, 4, 5, or 6, and claim 3, 4, 5, 6 or claim 3, 4, 5, or 6. A process of inputting an optical signal from the optical fiber to the input port of the optical waveguide device according to any one of claims 8 to 7,
For the optical signal separated into TE-polarized light and TM-polarized light in the polarization separation unit, the light output from the first output port and the light output from the second output port are observed, and the light is Checking the intensity ratio of the TE polarized light and the TM polarized light included in the optical signal by comparing the number of the first output ports that output and the number of the second output ports that output light;
And adjusting the polarization state of the optical signal by rotating the polarization axis of the optical fiber while confirming the intensity ratio of the TE polarized light and the TM polarized light included in the optical signal. Polarization adjustment method.

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