Method for forming groove in hybrid optical device, and hybrid optical device

Abstract

A groove having any length is manufactured in a quartz-based waveguide chip without limitation of a chip size. A marker indicating a planned cutting line extending from a connection end surface of a quartz-based waveguide chip in an in-chip plane direction is formed in advance by processing a core layer of the waveguide of the quartz-based waveguide chip, an irradiation position of laser light is aligned with a position of a starting point of the marker in a state where quartz-based waveguide chip is placed on a stage, and a groove is manufactured in the connection end surface of the quartz-based waveguide chip by moving the stage in the extending direction of the marker while irradiating the quartz-based waveguide chip with the laser light from an upper side.

Claims

1. A method of manufacturing a groove in a hybrid optical device, the method comprising: forming a marker indicating a planned cutting line extending from a connection end surface of a quartz-based waveguide chip in an in-chip plane direction by processing a core layer of a waveguide of the quartz-based waveguide chip; aligning an irradiation position of laser light with a position of a starting point of the marker while quartz-based waveguide chip is placed on a stage; and manufacturing the groove on the connection end surface of the quartz-based waveguide chip so as to divide a first region where light propagates through the waveguide from a second region where the light does not propagate by moving the stage in an extending direction of the marker while irradiating the quartz-based waveguide chip with the laser light from an upper side of the quartz-based waveguide chip; wherein the groove is provided on the connection end surface of the quartz-based waveguide chip with a secondary nonlinear waveguide chip having a periodically poled structure to divide the first region from the second region; and wherein the connection end surface of the quartz-based waveguide chip is bonded to a connection end surface of the secondary nonlinear waveguide chip with an adhesive in the second region.

2. The method of manufacturing a groove in a hybrid optical device according to claim 1, wherein: the waveguide is formed on a substrate made of quartz-based glass; the laser light is irradiated from a laser when the groove is manufactured; and an oscillation wavelength of the laser is in a wavelength band corresponding to absorption characteristics of the quartz-based glass.

3. The method of manufacturing a groove in a hybrid optical device according to claim 2, wherein aligning the irradiation position of the laser light with the position of the starting point of the marker includes: irradiating the quartz-based waveguide chip with the laser light while the quartz-based waveguide chip is placed on the stage to form a scratch on a surface of the quartz-based waveguide chip; moving the stage and obtaining coordinates of the starting point of the marker based on a position of the stage at a time when the starting point of the marker comes to a center of a visual field of a microscope installed above the quartz-based waveguide chip; moving the stage and obtaining, based on a position of the stage at a time when a center of the scratch comes to the center of the visual field of the microscope, coordinates of the center of the scratch; and aligning the irradiation position of the laser light with the position of the starting point of the marker by moving the stage based on relative coordinates of the scratch with respect to the starting point of the marker.

4. The method of manufacturing a groove in a hybrid optical device according to claim 1, wherein: the waveguide is made of quartz-based glass on an Si substrate; when the groove is manufactured, laser light is irradiated from a first laser to process the quartz-based glass and laser light is irradiated from a second laser to process the Si substrate; an oscillation wavelength of the first laser is in a wavelength band corresponding to absorption characteristics of the quartz-based glass; and an oscillation wavelength of the second laser is in a wavelength band corresponding to absorption characteristics of Si.

5. The method of manufacturing a groove in a hybrid optical device according to claim 4, wherein aligning the irradiation position of the laser light with the position of the starting point of the marker includes: irradiating the quartz-based waveguide chip with the laser light from the first laser while the quartz-based waveguide chip is placed on the stage to form a scratch on a surface of the quartz-based waveguide chip; moving the stage and obtaining coordinates of the starting point of the marker based on a position of the stage at a time when the starting point of the marker comes to a center of a visual field of a microscope installed above the quartz-based waveguide chip; moving the stage and obtaining, based on a position of the stage at a time when a center of the scratch comes to the center of the visual field of the microscope, coordinates of the center of the scratch; aligning an irradiation position of the laser light from the first laser with the position of the starting point of the marker by moving the stage based on relative coordinates of the scratch with respect to the starting point of the marker; and aligning an irradiation position of the laser light from the second laser with the position of the starting point of the marker by moving the stage based on the relative coordinates of the scratch with respect to the starting point of the marker and known relative coordinates of the irradiation position of the second laser with respect to the irradiation position of the first laser.

6. The method of manufacturing a groove in a hybrid optical device according to claim 1, wherein manufacturing the groove includes blowing off a component vaporized by irradiation of the laser light with an assist gas.

7. A hybrid optical device comprising: a quartz-based waveguide chip including a first waveguide comprising quartz-based glass as a main material; and a secondary nonlinear waveguide chip including a second waveguide comprising a secondary nonlinear optical material having a periodically poled structure; wherein a groove is disposed on a connection end surface of the quartz-based waveguide chip with the secondary nonlinear waveguide chip to divide a first region where light propagates through the first waveguide from a second region where light does not propagate; wherein the connection end surface of the quartz-based waveguide chip is bonded to a connection end surface of the secondary nonlinear waveguide chip with an adhesive provided in the second region; and wherein a marker extending in an in-chip plane direction from an end point of the groove extending in the in-chip plane direction from the connection end surface of the quartz-based waveguide chip is disposed in a core layer of the first waveguide of the quartz-based waveguide chip.

8. The hybrid optical device according to claim 7, wherein the first waveguide is disposed on a quart-based glass substrate.

9. The hybrid optical device according to claim 7, wherein the first waveguide is disposed on a Si substrate.

10. A method of manufacturing a groove in a hybrid optical device, the method comprising: forming a marker indicating a planned cutting line extending from a connection end surface of a quartz-based waveguide chip in an in-chip plane direction by processing a core layer of a waveguide of the quartz-based waveguide chip; aligning an irradiation position of laser light with a position of a starting point of the marker while quartz-based waveguide chip is placed on a stage; and manufacturing the groove on the connection end surface of the quartz-based waveguide chip so as to divide a first region where light propagates through the waveguide from a second region where the light does not propagate by moving the stage in an extending direction of the marker while irradiating the quartz-based waveguide chip with the laser light from an upper side of the quartz-based waveguide chip.

11. The method according to claim 10, wherein the groove is provided on the connection end surface of the quartz-based waveguide chip with a secondary nonlinear waveguide chip having a periodically poled structure to divide the first region from the second region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram for explaining a method of manufacturing a groove in a hybrid optical device according to a first embodiment of the present invention.

(2) FIG. 2 is a flowchart for explaining the method of manufacturing the groove in the hybrid optical device according to the first embodiment of the present invention.

(3) FIG. 3 is an enlarged perspective view of a connection end surface of a quartz-based waveguide chip, in which the groove is manufactured, with a PPLN waveguide chip according to the first embodiment of the present invention.

(4) FIG. 4 is a diagram for explaining a method of manufacturing a groove in a hybrid optical device according to a second embodiment of the present invention.

(5) FIG. 5 is a flowchart for explaining the method of manufacturing the groove in the hybrid optical device according to the second embodiment of the present invention.

(6) FIG. 6 is a schematic diagram showing a configuration of a conventional bulk component type PPLN module.

(7) FIG. 7 is a perspective view showing a configuration of a hybrid optical device in which a PPLN waveguide chip and a quartz-based waveguide chip are integrated.

(8) FIG. 8 is a cross-sectional view showing an example of a process of manufacturing a quartz-based waveguide chip.

(9) FIG. 9 is a plan view showing a configuration of a waveguide of the hybrid optical device shown in FIG. 7.

(10) FIG. 10 is an enlarged perspective view of a connection end surface of the quartz-based waveguide chip with a PPLN waveguide chip.

(11) FIG. 11 is a diagram for explaining a method of manufacturing a groove in the quartz-based waveguide chip by dicing.

(12) FIG. 12 is a diagram showing a method of processing the groove in a state where the quartz-based waveguide chip is placed horizontally on a stage of a dicing saw.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(13) Referring to the drawings, Embodiments of the present invention will be described in detail below.

First Embodiment

(14) FIG. 1 is a diagram for explaining a method of manufacturing a groove in a hybrid optical device according to a first embodiment of the present invention. A quartz-based waveguide chip 104 used herein includes a quartz substrate 101, a quartz-based glass clad 102 deposited on the quartz substrate 101, and a core (only a marker 103 being presented) formed inside the quartz-based glass clad 102.

(15) The quartz-based waveguide chip 104 is placed on an XZ stage 105. The XZ stage 105 includes a vacuum chuck (not shown) so that the quartz-based waveguide chip 104 placed on the stage can be attached and fixed. Note that the attaching may be performed not only by the vacuum chuck but also by another method.

(16) The marker 103 indicating a planned cutting line of the quartz-based waveguide chip 104 is formed by processing a core layer in the quartz-based glass clad 102 in a process of manufacturing the quartz-based waveguide chip 104. In FIG. 8, when a core layer 504 is processed by photolithography and reactive ion etching to form a core 504a, if a marker is put in a mask pattern of a photomask used for the photolithography, the core 504a is formed to propagate signal light and a core (not shown in FIG. 8) corresponding to the marker is also formed at the same time. The marker 103 is formed so as to extend in an in-chip plane direction (direction orthogonal to the connection end surface) from a connection end surface of the quartz-based waveguide chip 104 with a PPLN waveguide chip (secondary nonlinear waveguide chip). Since glass constituting the core has a higher refractive index than the quartz-based glass clad 102, the marker 103 formed in the quartz-based glass clad 102 can be recognized with a microscope due to a refractive index contrast.

(17) Advantages of manufacturing the marker 103 in the same layer and with the same material as the core will be described below. A first advantage is that no additional steps are required to manufacture the marker 103. Since a core pattern can be manufactured in a lump by photolithography using a photomask, the core constituting the waveguide, through which light is transmitted, and the marker 103 can be manufactured at the same time. In addition, since the mask pattern of the photomask can be accurately formed with submicron accuracy, there is also an advantage that the marker 103 can be provided at an accurate position on the quartz-based waveguide chip 104.

(18) In the present embodiment, since the quartz substrate 101 and the quartz-based glass clad 102 are made of quartz-based glass, as a laser 111 for processing the quartz-based waveguide chip 104 to form a groove (corresponding to a groove 406 in FIGS. 7, 9, and 10), a laser configured to oscillate a wavelength to be absorbed by the quartz-based glass may be used. For example, a CO2 laser having an oscillation wavelength of 10.6 m is used. In other words, the oscillation wavelength of the CO2 laser is in a wavelength band corresponding to absorption characteristics of the quartz-based glass. The laser 11 may be used for a pulse oscillation or a CW (Continuous Wave) oscillation in the present embodiment.

(19) A beam expander 112 converts the light oscillated from the laser 111 into expanded collimated light. A horizontal/vertical optical path conversion mirror 113 converts a direction of the beam so that the light beam passing through the beam expander 112 is reflected vertically. A condensing lens 114 condenses the light reflected by the horizontal/vertical optical path conversion mirror 113 and narrows a diameter of the beam. Thus, as shown in FIG. 1, the quartz-based waveguide chip 104 is irradiated with the CO2 laser light from above. The CO2 laser light is absorbed by the quartz-based glass, which constitutes the quartz substrate 101 and the quartz-based glass clad 102, and is converted into heat.

(20) The quartz-based glass is melted by an increase in power of the laser 11. Then, an assist gas such as a nitrogen gas is sprayed from a nozzle (not shown) mounted coaxially with the condensed laser light with which the quartz-based waveguide chip 104 is irradiated, thereby a vaporized glass component is blown off. In this way, a groove is formed in the quartz-based waveguide chip 104 when the quartz-based glass is melted with the laser light and the vaporized glass component is blown off with the assist gas. A width of the groove is 100 m to 500 m. When the width of the groove is larger than the size of a spot condensed by the condensing lens 114, the XZ stage 105 moves in an XZ plane to slightly shift an irradiation position of the condensed laser light on the quartz-based waveguide chip 104, the spot condensed on the quartz-based waveguide chip 104 is reciprocated several times, and thus a groove is processed.

(21) A method of aligning the beam position and position of the groove will be described below. FIG. 2 is a flowchart for explaining a groove manufacturing method of the present embodiment.

(22) First, the quartz-based waveguide chip 104 is placed on the XZ stage 105 so that a Z-axis direction of the XZ stage 105 is parallel to an in-chip plane extending direction of the groove in the quartz-based waveguide chip 104 (extending direction of the marker 103), and the quartz-based waveguide chip 104 is attached and fixed (step S100 in FIG. 2) as described above. An example of a simple placing method includes a method of previously providing a rectangular parallelepiped projection 106, a side surface of which is parallel to the Z-axis direction, on the XZ stage 105 and pressing the quartz-based waveguide chip 104 against the side surface of the projection 106 to be parallel. Here, a side surface of the quartz-based waveguide chip 104 to be pressed against the side surface of the projection 106 and the in-chip plane extending direction of the groove to be formed in the quartz-based waveguide chip 104 are generally parallel to each other.

(23) After the quartz-based waveguide chip 104 is placed on the XZ stage 105, the quartz-based waveguide chip 104 is irradiated with the CO2 laser light to form a scratch 122 on the surface of the quartz-based waveguide chip 104 (step S101 in FIG. 2). At this time, the laser light is irradiated for a short time so that the scratch 122 is formed only on the surface of the quartz-based waveguide chip 104.

(24) Next, the microscope 121 confirms XZ coordinates (X1, Z1) of a starting point of the marker 103 (step S102 in FIG. 2). Specifically, a position of the XZ stage 105 at a time when the XZ stage 105 moves and the starting point (an intersection of the end surface of the quartz-based waveguide chip 104 and the marker 103) of the marker 103 comes to a center of a visual field of the microscope 121 is recorded as the XZ coordinates (X1, Z1) of the starting point of the marker 103.

(25) Subsequently, the microscope 121 confirms XZ coordinates (X2, Z2) of a center of the scratch 122 as in the starting point of the marker 103 (step S103 in FIG. 2).

(26) In this way, the starting point of the marker 103 and the XZ coordinates of the respective scratches 122 are confirmed, and differences (ΔX=X1−X2 and ΔZ=Z1−Z2) between the XZ coordinates (X1, Z1) of the starting point of the marker 103 and the XZ coordinates (X2, Z2) of the center of the scratch 122 are calculated, so that a relative coordinate of the scratch 122 (=irradiation position of the laser) with respect to the starting point of the marker 103 can be calculated (step S104 in FIG. 2).

(27) Therefore, the XZ stage 105 is moved to set the position of the XY stage 105 to a position (X1+ΔX, Z1+ΔZ) obtained by adding the differences ΔX and ΔZ to the XZ coordinates (X1, Z1) of the starting point of the marker 103, so that the irradiation position of the laser light can be aligned with the position of the starting point of the marker 103 (step S105 in FIG. 2).

(28) After such alignment, the groove is formed in the quartz-based waveguide chip 104 in such a manner that the quartz-based waveguide chip 104 is irradiated with the CO2 laser light and the XZ stage 105 is moved in Z-axis direction (step S106 in FIG. 2). The irradiation of the CO2 laser light from the laser 111 is stopped at the starting point at the time when the groove of a desired length is formed along the marker 103.

(29) Although the groove is formed along the marker 103 by moving the XZ stage 105 in the Z-axis direction, the groove is preferably formed to have a margin in a length of the marker 103 in the in-chip plane direction rather than the desired length of the groove in the in-chip plane direction (Z-axis direction). Although the irradiation of the CO2 laser light is stopped at the time when the groove of the desired length is formed in the quartz-based waveguide chip 104, the marker 103 remains on the quartz-based waveguide chip 104 in the extending direction of the groove at this point of time. In this way, since the marker 103 remains, it is possible to confirm whether the groove is accurately manufactured along the marker 103.

(30) As is clear from the description of FIGS. 7, 9, and 10, since it is necessary to form grooves in two positions of the quartz-based waveguide chip 104, the marker 103 is also formed in two positions. Accordingly, after the process described in FIG. 2 is performed for one marker 103, the processes of steps S102 to S1o6 may be performed again for the other marker 103.

(31) Thus, in the present embodiment, the groove is formed in the quartz-based waveguide chip 104 by laser processing, and thus it is possible to easily manufacture the groove of any length without being restricted by the chip size.

(32) FIG. 3 is an enlarged perspective view of the connection end surface of the quartz-based waveguide chip 104, in which the groove is manufactured, with the PPLN waveguide chip (secondary nonlinear waveguide chip), and the same components as those in FIG. 10 are denoted by the same reference numerals. In FIG. 3, reference numeral 406 indicates the groove manufactured in the quartz-based waveguide chip 104, and reference numeral 701 indicates the connection end surface of the quartz-based waveguide chip 104 with the PPLN waveguide chip. The connection end surface 701 of the quartz-based waveguide chip 104 is divided by two grooves 406 into a region 720 in which a waveguide is formed and light propagates and regions 719, in which light does not propagate, on both sides thereof.

(33) As is clear from the description of FIGS. 7 and 10, it is necessary to form two grooves having the same spacing and the same width as the grooves 406 of the quartz-based waveguide chip 104 on reinforcement glass sheets (corresponding to the reinforcement glass sheets 407 and 408 in FIGS. 7 and 10) attached to upper and lower sides of the quartz-based waveguide chip 104. However, since the reinforcement glass sheet is smaller than the quartz-based waveguide chip 104, the groove can be easily manufactured in the reinforcement glass sheet using a dicing saw.

(34) A method of bonding the quartz-based waveguide chip 104 and the PPLN waveguide chip (secondary nonlinear waveguide chip) is the same as the method described with reference to FIGS. 7 to 10, and thus will not be described.

(35) In the present embodiment, the CO2 laser having the oscillation wavelength of 10.6 m is used for processing the quartz-based glass, but laser light of the wavelength band to be absorbed by the quartz-based glass may be used without being limited thereto.

Second Embodiment

(36) A second embodiment of the present invention will be described below. FIG. 4 is a diagram for explaining a method of manufacturing a groove of a hybrid optical device according to the second embodiment of the present invention. A quartz-based waveguide chip 204 used in the present embodiment includes an Si substrate 201, a quartz-based glass clad 202 deposited on the Si substrate 201, and a core (only a marker 203 being presented) formed inside the quartz-based glass clad 202.

(37) Similarly to the first embodiment, the quartz-based waveguide chip 204 is placed on an XZ stage 205. The XZ stage 205 is configured such that the quartz-based waveguide chip 204 placed on the stage can be attached and fixed. Note that the attaching may be performed not only by the vacuum chuck but also by another method.

(38) Similarly to the marker 103 of the first embodiment, the marker 203 indicating a planned cutting line of the quartz-based waveguide chip 204 is formed of the same material in the same layer as the core in the quartz-based glass clad 202.

(39) In the present embodiment, two types of lasers 211 and 215 are used for processing the groove of the quartz-based waveguide chip 204.

(40) In the first embodiment, since the clad and the substrate are made of the same material as the quartz-based glass, one laser is sufficient for processing the groove. However, in the present embodiment, a CO2 laser is used as the laser 211 for glass processing and an YAG laser is used as the laser 215 for Si processing.

(41) The reason why the YAG laser for Si processing is used separately from the CO2 laser is that an oscillation wavelength of the YAG laser is 1.064 m, which is in the wavelength band corresponding to absorption characteristics of Si and is higher in an absorption coefficient of Si than the CO2 laser having the oscillation wavelength of 10.6 m, so that the groove processing efficiency for Si is improved.

(42) A beam expander 212 converts the light oscillated from the laser 211 into expanded collimated light. A horizontal/vertical optical path conversion mirror 213 converts a direction of the beam so that the light beam passing through the beam expander 212 is reflected vertically. A condensing lens 214 condenses the light reflected by the horizontal/vertical optical path conversion mirror 213 and narrows a diameter of the beam. Thus, as shown in FIG. 4, the quartz-based waveguide chip 204 is irradiated with the CO2 laser light from above.

(43) Similarly, a beam expander 216 converts the light oscillated from the laser 215 into expanded collimated light. A horizontal/vertical optical path conversion mirror 217 converts a direction of the beam so that the light beam passing through the beam expander 216 is reflected vertically. A condensing lens 218 condenses the light reflected by the horizontal/vertical optical path conversion mirror 217 and narrows a diameter of the beam. Thus, the quartz-based waveguide chip 204 is irradiated with YAG laser light from above.

(44) Since the optical systems of the CO2 laser and the YAG laser are disposed so as not to interfere with each other and the respective optical systems are independent of each other, different positions on the XZ stage 205 are irradiated with the laser light. Therefore, as will be described below, since it is necessary to irradiate the same position on the quartz-based waveguide chip 204 with light from two lasers 211 and 215 in order to manufacture the groove, the laser 211 may irradiate CO2 laser light to form a groove in the quartz-based glass clad 202 of the quartz-based waveguide chip 204, and then the XZ stage 205 may be moved to irradiate YAG laser from the laser 215 to form a groove in the Si substrate 201.

(45) FIG. 5 is a flowchart for explaining a groove manufacturing method of the present embodiment.

(46) First, the quartz-based waveguide chip 204 is placed on the XZ stage 205 so that a Z-axis direction of the XZ stage 205 is parallel to an in-chip plane extending direction of the groove in the quartz-based waveguide chip 204 (extending direction of the marker 203), and the quartz-based waveguide chip 204 is attached and fixed (step S200 in FIG. 5). As in the first embodiment, for example, a rectangular parallelepiped projection 206, a side surface of which is parallel to the Z-axis direction is previously provided on the XZ stage 205 and the quartz-based waveguide chip 204 may be pressed against the side surface of the projection 206 to be parallel.

(47) After the quartz-based waveguide chip 204 is placed on the XZ stage 205, the quartz-based waveguide chip 204 is irradiated with the CO2 laser light to form a scratch 222 on the surface of the quartz-based waveguide chip 204 (step S201 in FIG. 5). At this time, the laser light is irradiated for a short time so that the scratch 222 is formed only on the surface of the quartz-based waveguide chip 204.

(48) As in the first embodiment, the microscope 221 confirms XZ coordinates (X1, Z2) of a starting point of the marker 203 (step S202 in FIG. 5), and then confirms XZ coordinates (X2, Z2) of a center of the scratch 222 (step S203 in FIG. 5)

(49) As in the first embodiment, differences (ΔXCO2=X1−X2 and ΔZ CO2=Z1−Z2) between the XZ coordinates (X1, Z1) of the starting point of the marker 203 and the XZ coordinates (X2, Z2) of the center of the scratch 222 are calculated, so that relative coordinates of the scratch 222 (=irradiation position of the CO2 laser) with respect to the starting point of the marker 203 can be calculated (step S204 in FIG. 5).

(50) Further, differences ΔXYAG and ΔZYAG between the XZ coordinates (X1, Z1) of the starting point of the marker 203 and the irradiation position of the YAG laser can be calculated based on the differences ΔXCO2 and ΔZCO2 and the known relative coordinates of the irradiation position of the YAG laser with respect to the irradiation position of the CO2 laser, and the relative coordinates of the irradiation position of the YAG laser with respect to the starting point of the marker 203 can be calculated (step S205 in FIG. 5).

(51) The relative coordinates of the irradiation position of the YAG laser with respect to the irradiation position of the CO2 laser can be obtained in such a manner that thermal paper is placed on the XZ stage 205 before the quartz-based waveguide chip 204 is placed, the thermal paper is simultaneously irradiated with the CO2 laser light and the YAG laser light to change the thermal paper to black, and XZ coordinates (X3, Z3) of a color change position by the CO2 laser light and XZ coordinates (X4, Z4) of a color change position by the YAG laser light are confirmed by a method using the microscope 221 as in steps S102, S103, S202, and S203. In other words, differences (ΔXYAG=X3−X4 and ΔZYAG2=Z3−Z4) between the XZ coordinates (X3, Z3) of the irradiation position of the CO2 laser and the XZ coordinates (X4, Z4) of the irradiation position of the YAG laser are calculated, so that the relative coordinates of the irradiation position of the YAG laser with respect to the irradiation position of the CO2 laser can be obtained in advance.

(52) Next, the XZ stage 205 is moved to set the position of the XY stage 205 to a position (X1+ΔXCO2, Z1+ΔZCO2) obtained by adding the differences ΔXCO2 and ΔZCO2 to the XZ coordinates (X1, Z1) of the starting point of the marker 203, so that the irradiation position of the CO2 laser light can be aligned with the position of the starting point of the marker 203 (step S206 in FIG. 5).

(53) After such alignment, the groove is formed in the quartz-based waveguide chip 204 in such a manner that the quartz-based waveguide chip 204 is irradiated with the CO2 laser light and the XZ stage 205 is moved in Z-axis direction (step S207 in FIG. 5).

(54) As in the first embodiment, a quartz-based glass clad 202 of the quartz-based waveguide chip 204 is melted by an increase in power of the laser 211. Then, an assist gas such as a nitrogen gas is sprayed from a nozzle (not shown) mounted coaxially with the CO2 laser light with which the quartz-based waveguide chip 204 is irradiated, thereby a vaporized glass component is blown off. In this way, a groove is formed in the quartz-based glass clad 202 of the quartz-based waveguide chip 204 when the quartz-based glass is melted with the laser light and the vaporized glass component is blown off with the assist gas. The quartz-based glass clad 202 is removed, so that Si is exposed under the portion.

(55) The irradiation of the CO2 laser light from the laser 211 is stopped at the time when the groove of a desired length is formed along the marker 203, and then the XZ stage 205 is moved to set the position of the XY stage 205 to a position (X+ΔXYAG, Z1+ΔZYAG) obtained by adding the differences ΔXYAG and ΔZYAG to the XZ coordinates (X1, Z1) of the starting point of the marker 203, so that the irradiation position of the YAG laser light can be aligned with the position of the starting point of the marker 203 (step S2o8 in FIG. 5).

(56) After such alignment, the groove is formed in the Si substrate 201 of the quartz-based waveguide chip 204 in such a manner that the quartz-based waveguide chip 204 is irradiated with the YAG laser light and the XZ stage 205 is moved in Z-axis direction (step S209 in FIG. 5).

(57) A wavelength of the YAG laser is 1.064 m, and the YAG laser light absorbed by Si, and is converted into heat. The Si substrate 201 is melted by an increase in power of the laser 215. Then, an assist gas such as a nitrogen gas is sprayed from a nozzle (not shown) mounted coaxially with the YAG laser light with which the quartz-based waveguide chip 204 is irradiated, thereby a vaporized Si is blown off. In this way, a groove is formed in the Si substrate 201 when the Si substrate is melted with the laser light and the vaporized Si is blown off with the assist gas.

(58) The irradiation of the YAG laser light from the laser 215 is stopped at the starting point at the time when the groove of a desired length is formed along the marker 203.

(59) As in the first embodiment, the groove is desirably formed to have a margin in a length of the marker 203 in the in-chip plane direction rather than the desired length of the groove in the in-chip plane direction (Z-axis direction), thereby allowing the marker 203 to remain on the quartz-based waveguide chip 204 in the extending direction of the groove at the time when the irradiation of the YAG laser light is stopped.

(60) As is clear from the description of FIGS. 7, 9, and 10, since it is necessary to form grooves in two positions of the quartz-based waveguide chip 204, the marker 203 is also formed in two positions. Accordingly, after the process described in FIG. 5 is performed for one marker 203, the processes of steps S202 to S209 may be performed again for the other marker 203.

(61) The shape of the quartz-based waveguide chip 204 in which the groove is manufactured is the same as that in FIG. 3, and a bonding method of the quartz-based waveguide chip 204 and the PPLN waveguide chip (secondary nonlinear waveguide chip) are the same as the method described with reference to FIGS. 7 to 10, and will not be presented.

(62) Thus, according to the present embodiment, it is possible to obtain the same effect as that of the first embodiment when the substrate of the quartz-based waveguide chip 204 is made of Si.

(63) In the present embodiment, the fundamental wave of the YAG laser is used for processing Si, but laser light of the wavelength band to be absorbed by Si may be used without being limited thereto.

INDUSTRIAL APPLICABILITY

(64) Embodiments of the present invention are applicable to a technique for bonding a quartz-based waveguide chip and a secondary nonlinear waveguide chip together.

REFERENCE SIGNS LIST

(65) 101 quartz substrate 102, 202 quartz-based glass clad 103, 203 marker 104, 204 quartz-based waveguide chip 105, 205 XZ stage 106, 206 projection 111, 211, 215 laser 112, 212, 216 beam expander 113, 213, 217 horizontal/vertical optical path conversion mirror 114, 214, 218 condensing lens 121, 221 microscope 122, 222 scratch 406 groove.