JP2010127999A - Planar waveguide element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a planer waveguide element regulating an incident position of incident light and reducing dispersion of demultiplexing characteristics. <P>SOLUTION: The planer waveguide element includes: a rectangular substrate; a first laminate part layered on the substrate; and a second laminate part layered on the first laminate part and having the refractive index higher than that of the first laminate part. The second laminate part includes: a plurality of filament waveguides 5; a spot size conversion waveguide 6; and reflection parts 7 and 8. Furthermore, a heater 11 is mounted on one side of the substrate, and a heat sink 12 is mounted on the other side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a planar waveguide that demultiplexes multiplexed signal waves using optical Bloch oscillation and outputs each of the demultiplexed signal waves from a desired port.

  In the photonic network, there is a method in which an optical signal is sent from a single mode fiber to a thin wire waveguide and the light is controlled by a light control device. However, this method has a problem that an incident loss occurs when light is incident from the single mode fiber to the thin wire waveguide. Light transmitted from the single mode fiber is collected by the lens onto the entrance surface of the thin wire waveguide. The spot diameter of the condensed light is 5 μm or more. On the other hand, the width of the thin wire waveguide is generally less than 5 μm. For this reason, a part of the light transmitted from the single mode fiber deviates from the incident surface of the thin wire waveguide and is not effectively extracted from the emission surface. As a prior document disclosing such a spot size conversion waveguide for reducing the incident loss, there is Patent Document 1.

FIG. 19 is a perspective view of a spot size conversion waveguide described in Patent Document 1. FIG. As shown in FIG. 19, the spot size conversion waveguide 101 has a waveguide core 103 having a rectangular cross section formed on the upper surface of the substrate 102, and has a convex cross section that surrounds the periphery of the waveguide core 103. The ridge portion 104 is formed. A single mode fiber is connected to the incident side end face 106, and a thin wire waveguide 105 is connected to the output side end face 107. The waveguide core 103, the ridge 104, and the substrate 102 are covered with an upper clad (not shown) and function as the spot size conversion waveguide 101. The spot size conversion waveguide 101 is a high Δ waveguide. Δ is a relative refractive index difference between the waveguide core 103 and the upper clad. When the refractive index of the waveguide core 103 is n _CR and the refractive index of the upper clad is n _CL , (n _CR −n _CL ) / n _Represented by _CR .

  A method for manufacturing the spot size conversion waveguide 101 will be described. A resist pattern is formed on the waveguide core film formed on the substrate by photolithography or the like. Etching is performed on the substrate on which the resist pattern is formed by reactive ion etching or the like. After the pattern corresponding to the waveguide core 103 is formed by the etching process, the resist pattern is removed. A mask is disposed above the substrate on which the waveguide core 103 is formed with a predetermined distance from the substrate. The mask is arranged such that the substrate 102 and the waveguide core 103 are exposed over a predetermined length from the incident side end face. Film formation is performed by depositing glass through this mask by a CVD (Chemical Vapor Deposition) method or the like. According to this method, the film thickness of the glass formed around the waveguide core 103 can be continuously changed over the light propagation direction. Therefore, it is possible to form the ridge portion 104 whose height and width continuously change in the light propagation direction.

  The spot size conversion waveguide 101 operates as follows. As shown in FIG. 19, the height and width of the spot size conversion waveguide 101 are formed so as to decrease from the incident side end face 106 toward the output side end face 107. The height and width of the incident-side end face 106 of the spot size conversion waveguide 101 are the same as those of the single mode fiber, and the height and width of the exit-side end face 107 coincide with those of the thin-line waveguide 105. By adopting such a structure, light transmitted from the single mode fiber is transmitted to the thin wire waveguide 105 without detaching from the incident side end face 106 of the spot size conversion waveguide 101, so that the incidence loss can be reduced. .

  In a light control device in a photonic network, a planar waveguide element (hereinafter referred to as “OBO”) using optical Bloch Oscillations (hereinafter referred to as “OBO”) as a wavelength multiplexed light spectrometer or switching element. Patent Document 2 is a prior art document disclosing "planar waveguide element". 20 is a plan view of the OBO planar waveguide device described in Patent Document 2, and FIG. 21 is a cross-sectional view taken along XXI-XXI in FIG.

As shown in FIGS. 20 and 21, the OBO planar waveguide device 111 has a silicon oxide (SiO ₂ ) layer 113 having a thickness of about 1 μm and a Si layer sequentially stacked on a silicon (Si) substrate 112 having a thickness of about 100 μm. It is formed using an SOI (Silicon On Insulator) substrate. In the uppermost Si layer of the SOI substrate, a plurality of thin waveguides 114 arranged in parallel for light propagation are formed. The thin wire waveguide 114 is provided with an incident port 115 on one end face and an exit port 116 on the other end face. In order to control the gradient of the temperature distribution on the Si substrate 112 in the direction in which the thin wire waveguides 114 are arranged, a heater 117 is provided on one end face of the Si substrate 112 and a heat sink 118 is provided on the other end face.

  As shown in FIGS. 20 and 21, the direction in which the thin wire waveguides 114 are arranged is the X-axis direction, the direction in which each thin wire waveguide 114 extends is the Y-axis direction, and the direction perpendicular to both the X-axis direction and the Y-axis direction. The Z axis direction. In FIG. 20, a path 119 of light propagating through the thin waveguide 114 while oscillating in the X-axis direction by OBO is depicted. In the OBO planar waveguide element 111, a gradient (temperature difference per unit length) is formed in the temperature distribution in the X-axis direction on the Si substrate 112 by the heater 117. In the OBO planar waveguide device 111 having the thin wire waveguide 114 made of Si material, the equivalent refractive index of the thin wire waveguide 114 on the high temperature side Si substrate 112 is the thin wire waveguide on the low temperature side Si substrate 112. It becomes higher than the equivalent refractive index of 114. Therefore, a difference corresponding to the gradient of the substrate temperature distribution is formed in the equivalent refractive index per unit length of the thin wire waveguide 114 in the X-axis direction.

  Hereinafter, the operation of the OBO planar waveguide element and the spot size conversion waveguide will be described. Light is irradiated into the OBO planar waveguide device 111 such that the light intensity peak 120 is positioned at a predetermined incident port 115. The irradiated light leaks from the traveling thin wire waveguide 114 and is coupled to the adjacent thin wire waveguide 114. As a result, the light vibrates in the X-axis direction while traveling in the Y-axis direction. This vibration phenomenon is called OBO. Thus, the light is demultiplexed on the OBO planar waveguide device 111 as shown by the light path 119 by expressing the OBO.

In the OBO planar waveguide device 111, the width of the thin wire waveguide 114 forming the incident port 115 is about 0.5 μm. For this reason, the spot size conversion waveguide is connected to the incident port 115 of the OBO planar waveguide element 111 so that the spot size of the light incident on the thin wire waveguide 114 is matched with that of the thin wire waveguide 114. With such a configuration, the multiplexed signal wave can be demultiplexed while reducing the incident loss in the light control device such as the OBO planar waveguide element 111.
JP 2007-93743 A JP 2007-41142 A

  The OBO planar waveguide element described in Patent Document 2 changes the behavior of light traveling through a thin-line waveguide when the incident position and angle of light on the incident surface of the thin-line waveguide are different. For this reason, when the spot size conversion waveguide is connected to the incident port of the OBO planar waveguide element, if the incident position of the light incident on the incident surface of the spot size conversion waveguide is not constant, the separation of the OBO planar waveguide element. Variations in wave characteristics occur.

  Specifically, when the incident position of the light is partially off the incident surface of the spot size conversion waveguide, the light that is off is incident from the end surface of the thin waveguide other than the incident port, and the fine waveguide is The light travels and is emitted as unnecessary light from an exit port different from the original exit port. The unnecessary light causes variations in the demultiplexing characteristics of the planar waveguide device.

  As described above, light is detected from the exit port both when the incident position of light is positioned on the incident surface of the spot size conversion waveguide and when it is not positioned. Light detection is performed by condensing the light emitted from the emission port onto a photodiode using a lens, and therefore unnecessary light is also detected. For this reason, it is impossible to determine whether or not the incident position of the light deviates from the incident surface of the spot size conversion waveguide only by confirming the detected light intensity. If the incident position of light cannot be grasped, the incident position cannot be adjusted. The spot size conversion waveguide described in Patent Document 1 is also not provided with a structure for adjusting the incident position of incident light.

  The present invention has been made to solve the above-described problems, and provides a planar waveguide device capable of adjusting the incident position of incident light and suppressing variation in demultiplexing characteristics. For the purpose.

  A planar waveguide device according to the present invention includes a rectangular substrate, a first stacked unit stacked on the substrate, and a second stacked layer stacked on the first stacked unit and having a higher refractive index than the first stacked unit. A part. The second laminated portion has a plurality of fine wire waveguides formed so as to be arranged substantially in parallel, and an incident port provided on one end face of at least one or more fine wire waveguides, and a spot size connected to the incident port. A conversion waveguide. Further, the planar waveguide element includes a heater provided on one side surface of the substrate parallel to the thin wire waveguide and a heat sink provided on the other side surface of the substrate. The width of the spot size conversion waveguide is equal to the spot size of the incident light at the incident side end face, and toward the light propagation direction so as to coincide with the width of the incident port of the thin waveguide at the output side end face. The height of the spot size conversion waveguide becomes smaller and coincides with the height of the entrance port of the thin wire waveguide at the exit end face. The second stacked unit is provided on both sides in the width direction of the spot size conversion waveguide in a non-contact state with the spot size conversion waveguide, and has a reflection region on a surface facing the incident direction of incident light. including.

  According to the present invention, by providing the reflection portions on both sides in the width direction of the spot size conversion waveguide, the light whose incident position deviates from the incident side end face of the spot size conversion waveguide is reflected, and the fine wire waveguide The light can be prevented from being emitted from the emission port. In this way, the incident position of light can be grasped, and the incident position of light with respect to the incident side end face of the spot size conversion waveguide can be adjusted to suppress variations in the demultiplexing characteristics of the planar waveguide element. it can.

  Hereinafter, planar waveguide elements according to embodiments of the present invention will be described with reference to the drawings.

Embodiment 1
FIG. 1 is a plan view of a planar waveguide device according to Embodiment 1 of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIGS. 1 and 2, in the planar waveguide device 1, a first Si substrate 2 having a thickness of about 1 μm, which is composed of a SiO ₂ layer having a refractive index lower than Si on the upper surface of a rectangular Si substrate 2. A stacked portion 3 is formed. On the upper surface of the first stacked unit 3, a second stacked unit 4 having a thickness of about 200 nm including a Si layer having a higher refractive index than that of the first stacked unit 3 is formed.

Thus, the planar waveguide device 1 according to the present embodiment is configured using an SOI substrate in which the SiO ₂ layer and the Si layer are sequentially stacked on the Si substrate. Note that Al ₂ O ₃ , InP, AlGaAs, or the like may be used as the first stacked portion 3. Instead of the Si layer of the second stacked unit 4, InGaAsP, GaAs, AlGaAs, InP, or the like that has a higher refractive index than the first stacked unit 3 and can transmit light may be used.

  The second laminated portion 4 includes a thin wire waveguide 5, a spot size conversion waveguide 6, and reflecting portions 7 and 8. The plurality of thin wire waveguides 5 are formed so as to be arranged substantially in parallel. An incident port 9 through which light enters is provided on one end face of at least one or more thin wire waveguides 5. An exit port 10 through which light exits is provided on the other end face of all the thin wire waveguides 5. A spot size conversion waveguide 6 having an emission side end face 14 connected to the incident port 9 is formed in the second laminated portion 4.

  The width of the spot size conversion waveguide 6 is equal to the spot size of the incident light at the incident side end face 13, and the light size of the spot size conversion waveguide 6 coincides with the width of the incident port 9 of the thin wire waveguide 5 at the output side end face 14. It becomes smaller toward the propagation direction. The height of the spot size conversion waveguide 6 coincides with the height of the incident port 9 of the thin-line waveguide 5 at the exit end face 14.

In the present embodiment, for example, the spot size of incident light is 5 μm, and the width of the incident side end face 13 of the spot size conversion waveguide 6 is 6 μm. Further, the width of the thin wire waveguide 5 is 0.5 μm, the height from the upper surface of the SiO ₂ layer is 0.25 μm, the width of the output side end face 14 of the spot size conversion waveguide 6 is 0.5 μm, and the upper surface of the SiO ₂ layer The height from is set to 0.25 μm. The length of the spot size conversion waveguide 6 was 700 μm. The width of the spot size conversion waveguide 6 may change linearly in the light propagation direction.

  Reflecting portions 7 and 8 are provided on both sides in the width direction of the spot size conversion waveguide 6 so as not to contact the spot size conversion waveguide 6. By making the spot size conversion waveguide 6 and the reflection portions 7 and 8 non-contact, it is possible to prevent light incident on the spot size conversion waveguide 6 from leaking to the reflection portions 7 and 8.

  The reflection parts 7 and 8 have a reflection area on the surface facing the incident direction of incident light. In the present embodiment, a mirror is provided in the reflection area of the reflection portions 7 and 8. A heater 11 for controlling the temperature gradient of the substrate is provided on one side surface of the SOI substrate parallel to the thin wire waveguide 5. A heat sink 12 is provided on the other side surface of the SOI substrate. In the present embodiment, the heater 11 and the heat sink 12 are provided on the side surface of the SOI substrate. However, the heater 11 and the heat sink 12 may be provided only on the side surface of the Si substrate 2.

  A method for manufacturing the planar waveguide device 1 according to the embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a plan view showing a state in which a resist is applied to the upper surface of the SOI substrate before the waveguide is formed. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is a plan view showing a state in which a resist is applied to the upper surface of the SOI substrate after the waveguide is formed. 6 is a cross-sectional view taken along the line VI-VI in FIG.

  First, in order to form a waveguide on the SOI substrate, as shown in FIGS. 3 and 4, a resist film is applied on the upper surface of the second stacked portion 4 formed of an Si layer. The resist film is patterned by an electron beam direct writing method, a photolithography method, or the like to form a resist pattern 15 corresponding to the shapes of the desired thin wire waveguide 5 and spot size conversion waveguide 6. For example, in the electron beam direct writing method, patterning may be performed under an irradiation condition in which the electron beam irradiation current is 0.1 nA and the electron beam dose time per dot is 4 μsec. In the photolithography method, the resist pattern 15 may be formed with a transfer time of about 300 msec.

  Next, using the resist pattern 15 as a mask, the SOI substrate is etched using an etching method such as ICP (Inductively Coupled Plasma) etching, reactive ion etching, and reactive ion beam etching. After etching a part of the surface side of the second laminated portion 4, the resist pattern 15 is peeled off. In this manner, the thin wire waveguide 5 and the spot size conversion waveguide 6 can be formed on the substrate. In the present embodiment, for example, reactive ion etching is performed in which a mixed gas of chlorine gas 25 sccm and nitrogen gas 10 sccm is used as an etching gas, the etching pressure is 0.1 Pa, and the RF (Radio Frequency) power is 200 W. It may be used.

  In order to form a mirror on the incident surface of the reflecting portion on the SOI substrate on which the waveguide is formed, as shown in FIGS. 5 and 6, the second laminated portion in which the thin wire waveguide 5 and the spot size conversion waveguide 6 are formed. A resist film is applied on the upper surface of 4. The resist film is patterned by an electron beam direct writing method or a photolithography method to form a resist pattern 16 having openings 7a and 8a corresponding to the desired shape and arrangement of the reflecting portions 7 and 8. In FIG. 5, the thin-line waveguide 5 and the spot size conversion waveguide 6 covered with the resist pattern 16 are indicated by broken lines.

  From the upper surface of the resist pattern 16, the material constituting the reflective portions 7 and 8 is deposited by sputtering or vapor deposition. Thereafter, the resist pattern 16 is peeled off from the substrate, whereby the reflecting portions 7 and 8 are formed. In addition, the material which comprises the reflection parts 7 and 8 should just be a material which reflects the incident light. For example, when light having a wavelength of 1.55 μm is incident, materials such as Al, Zn, Cu, Au, Pt, Pd, Ag, and Rh may be used.

  As another method of forming the reflective portions 7 and 8, when forming the Si layer of the second stacked portion, the reflective portions 7 and 8 other than the reflective region are formed on the Si layer. Thereafter, the material may be deposited on the reflective region by sputtering or vapor deposition. Next, a tantalum nitride film to be the heater 11 is formed on one side surface of the SOI substrate parallel to the thin-line waveguide 5 by using a sputtering method or a vapor deposition method. Further, an aluminum nitride film to be the heat sink 12 is formed on the other side surface of the Si substrate 2 by using a sputtering method or a vapor deposition method.

  In the planar waveguide device 1 according to the present embodiment, OBO of light that propagates through the spot size conversion waveguide 6 and travels through the thin wire waveguide 5 will be described with reference to FIGS. As shown in FIGS. 1 and 2, the direction in which the thin waveguides 5 are arranged is the X-axis direction, the direction from the heat sink 12 to the heater 11 is the + X-axis direction, and the opposite direction to the + X-axis direction is the −X-axis direction. To do. The extending direction of the thin wire waveguide 5 is defined as the Y-axis direction, the direction from the incident port 9 to the exit port 10 is defined as the + Y-axis direction, and the direction opposite to the + Y-axis direction is defined as the -Y-axis direction. Furthermore, a direction perpendicular to both the X-axis direction and the Y-axis direction is taken as a Z-axis direction.

  In the planar waveguide device 1, a gradient is formed in the temperature distribution in the Si substrate 2 by the heater 11 so that the temperature increases toward the + X axis direction. In the planar waveguide device 1 having the thin-line waveguide 5 made of Si material, the equivalent refractive index of the thin-line waveguide 5 located above the high-temperature Si substrate 2 is the fine line located above the low-temperature Si substrate 2. It is higher than the equivalent refractive index of the waveguide 5. For this reason, in the X-axis direction, an equivalent refractive index distribution of the thin wire waveguide 5 corresponding to the temperature distribution of the Si substrate 2 is generated.

  Next, light is irradiated to the planar waveguide device 1 so that the peak of the light intensity distribution 17 is located on the incident side end face 13 of the spot size conversion waveguide 6. The irradiated light propagates through the spot size conversion waveguide 6, travels to the incident port 9, leaks from the traveling thin wire waveguide 5, and is coupled to the adjacent thin wire waveguide 5. As a result, the light vibrates in the X-axis direction while traveling in the + Y-axis direction through the thin wire waveguide 5. Thus, the light is demultiplexed on the planar waveguide device 1 as indicated by the light path 18 by expressing OBO.

  OBO has an oscillating amplitude that increases as the wavelength of light increases. Therefore, since the amplitude of the OBO is different when the wavelength of the incident light is different, the light is coupled to the thin wire waveguide 5 that is different for each wavelength and is demultiplexed as indicated by the light path 18. The demultiplexed light exits from different exit ports 10. Therefore, when wavelength multiplexed light composed of light of a plurality of wavelengths is incident on the planar waveguide element 1, the planar waveguide element 1 has a function as a spectroscope.

  The function of the reflecting portion in the planar waveguide device according to the embodiment of the present invention will be described with reference to FIGS. 1 and 7 to 10. FIG. 7 shows an enlarged view of the vicinity of the reflecting portion in the planar waveguide device according to the present embodiment. As shown in FIG. 7, a reflection part 7 that reflects incident light is provided in the vicinity of the −X axis direction side of the spot size conversion waveguide 6, and a reflection part 8 that reflects incident light is provided in the vicinity of the + X axis direction side. Is provided. The reflectors 7 and 8 and the spot size conversion waveguide 6 are arranged in a non-contact state.

  In the present embodiment, Al is used as the material of the reflecting portions 7 and 8, and the reflecting areas of the reflecting portions 7 and 8 in the Y-axis direction are the incident-side end surface 13 and the emitting-side end surface 14 of the spot size conversion waveguide 6. However, the embodiment of the present invention is not limited to such a configuration. For example, in the Y-axis direction, the reflection regions of the reflecting portions 7 and 8 may be formed in the same row as the incident-side end face 13 of the spot size conversion waveguide 6 or on the −Y-axis direction side. Also in this case, the light irradiated to the region other than the incident side end face 13 of the spot size conversion waveguide 6 out of the light irradiated to the planar waveguide device 1 is reflected so as not to enter the fine wire waveguide 5. Can do.

  Hereinafter, the reflection parts 7 and 8 which can exhibit a function satisfactorily will be described. On the incident side end face 13 of the spot size conversion waveguide 6, the X coordinate in the −X axis direction is defined as S1, and the X coordinate in the + X axis direction is defined as S2. The X coordinate in the + X axis direction most in the reflection region of the reflection portion 7 provided on the −X axis direction side of the spot size conversion waveguide 6 is defined as M1. The X coordinate in the most −X axis direction in the reflection region of the reflection portion 8 provided on the + X axis direction side of the spot size conversion waveguide 6 is defined as M2. In this case, the reflection regions of the reflection portions 7 and 8 are arranged so that S1 ≦ M1 and M2 ≦ S2 are satisfied.

  Furthermore, the length in the X-axis direction of the reflection region of the reflection unit 7 is L1, the length of the reflection region of the reflection unit 8 is L2, and the light incident on the spot size conversion waveguide 6 is incident on the spot size conversion waveguide 6 Let Q be the spot diameter when passing through the end face 13. In this case, the reflection regions of the reflection portions 7 and 8 that satisfy L1− (M1−S1) ≧ Q and L2− (S2−M2) ≧ Q are provided. In the present embodiment, the lengths L1 and L2 of the reflection regions of the reflection portions 7 and 8 are 15 μm. Since the light is totally reflected in the reflection regions of the reflecting portions 7 and 8, the light incident on the spot size conversion waveguide 6 is incident when it is out of the region of the incident side end face 13 of the spot size conversion waveguide 6. The light is reflected by the reflection areas of the reflection portions 7 and 8.

  As shown in FIG. 1, the optical axis of the lens 19 and the central axis of the fiber 20 are arranged on a straight line in the Y-axis direction so that light is incident from the incident side end face 13 of the spot size conversion waveguide 6. The lens 19 is a lens for collecting light, and the spot diameter of the light emitted from the fiber 20 is larger than the spot diameter Q of the light incident on the planar waveguide device 1. The spot diameter Q of incident light is determined by the relationship between the optical characteristics such as the focal length of the fiber 20 and the lens 19.

  The light propagated through the spot size conversion waveguide 6 enters the fine wire waveguide 5 and proceeds in the + Y-axis direction while generating OBO in the X-axis direction. The light traveling through the thin wire waveguide 5 is emitted from the emission port 10. Therefore, when incident light is incident from the incident side end face 13 of the spot size conversion waveguide 6, the light is emitted from the emission port 10. The emitted light is detected by a detection device including a lens and a photodiode (not shown).

  8 and 9 are plan views showing a state in which the light irradiation position is relatively shifted with respect to the planar waveguide device according to the present embodiment. As shown in FIG. 8, the positions of the lens 19 and the fiber 20 are moved in the −X axis direction with respect to the incident side end face 13 of the spot size conversion waveguide 6. If the X coordinate of the peak position of the light intensity distribution 17 at this time is F1, the light intensity of the light incident on the spot size conversion waveguide 6 decreases when F1 <S1 with F1 = S1 as a boundary. In this case, the light that is incident outside the region of the incident side end face 13 of the spot size conversion waveguide 6 is reflected by the reflection region of the reflection unit 7. Further, when F1 <S1, light does not enter the fine wire waveguide 5, and light is not detected from the exit port 10 of the fine wire waveguide 5.

  Further, as shown in FIG. 9, the positions of the lens 19 and the fiber 20 are moved in the + X-axis direction with respect to the incident side end face 13 of the spot size conversion waveguide 6. If the X coordinate of the peak position of the light intensity distribution 17 at this time is F2, the light intensity of the light incident on the spot size conversion waveguide 6 decreases when F2> S2 with F2 = S2. In this case, the light incident from the incident side end face 13 of the spot size conversion waveguide 6 is reflected by the reflection region of the reflection unit 8. Furthermore, when F2> S2, light is not detected from the exit port 10 of the thin waveguide 5 because light does not enter the thin waveguide 5.

  As described above, the reflection areas of the reflecting portions 7 and 8 are provided, and the incident position of the incident light is continuously moved from the −X axis direction to the + X axis direction, thereby being detected from the emission port 10 of the thin wire waveguide 5. The irradiation position where the light intensity becomes 0 can be confirmed. Thereby, the influence of unnecessary light emitted from other than the predetermined exit port 10 is eliminated, and the irradiation position at which the light intensity becomes maximum and the center of the spot size conversion waveguide 6 in the X-axis direction is confirmed. Can do.

FIG. 10 is a diagram showing the relationship between the position where the peak of the light intensity distribution is incident and the light intensity detected at the exit port of the thin wire waveguide. In FIG. 10, the incident positions where the light intensity detected at the exit port 10 of the thin wire waveguide 5 is 1 / e ² times the maximum value of the detected light intensity are shown as S3 and S4. By grasping the X coordinates of the incident positions S3 and S4, the light intensity becomes maximum and the center of the spot size conversion waveguide 6 when the X coordinate serving as the intermediate point is (S3 + S4) / 2. Can be confirmed.

  By adjusting the lens 19 and the fiber 20 so that light is irradiated to the irradiation position where the light intensity that is confirmed in this way becomes the maximum, variation in the demultiplexing characteristics of the planar waveguide device 1 is achieved. Can be suppressed. Further, by making the incident position of light the center of the spot size conversion waveguide 6 in the X-axis direction, reflection on the side wall of the spot size conversion waveguide 6 is suppressed, and the spot size conversion waveguide 6 to the thin wire waveguide 5 are suppressed. The light enters smoothly, and the return light reflected and reflected back at the incident port 9 of the thin wire waveguide 5 is reduced.

  In addition, the reflection parts 7 and 8 are not restricted to said structure, Of the incident light, the light irradiated to area | regions other than the incident side end surface 13 of the spot size conversion waveguide 6 to the thin wire | line waveguide 5 What is necessary is just to reflect so that it may not enter. By providing the reflecting portions 7 and 8, the light whose incident position deviates from the incident side end face 13 of the spot size conversion waveguide 6 is reflected and can be prevented from being emitted from the emission port 10. By doing so, the incident position of the light can be grasped, and the incident position with respect to the incident side end face 13 of the spot size conversion waveguide 6 is adjusted to suppress variations in the demultiplexing characteristics of the planar waveguide device 1. Can do.

Embodiment 2
A planar waveguide device according to the second embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a plan view of a planar waveguide device according to the second embodiment of the present invention. 12 is a cross-sectional view taken along the line XII-XII in FIG. As shown in FIGS. 11 and 12, the reflecting portions 27 and 28 of the planar waveguide device 21 according to the present embodiment are configured such that the Si layer and the air layer are in the Y-axis direction on the Si layer constituting the second stacked portion 24. It is comprised with the photonic crystal formed of the multilayer film arranged in order.

  A reflector 27 that reflects incident light is provided near the −X axis direction side of the spot size conversion waveguide 26, and a reflector 28 that reflects incident light is provided near the + X axis direction side. The reflectors 27 and 28 and the spot size conversion waveguide 26 are arranged in a non-contact state. The photonic crystals constituting the reflecting portions 27 and 28 are designed so that the wavelength of incident light is located in the photonic band gap.

  In the present embodiment, the wavelength of incident light is 1.55 μm, and the photonic crystal includes a 0.3 μm thick Si layer and a 0.4 μm thick air layer at a 0.7 μm pitch. It was formed of a multilayer film in which 30 layers were arranged. Moreover, although the reflection parts 27 and 28 are formed between the entrance-side end face 13 and the exit-side end face 14 of the spot size conversion waveguide 6 in the Y-axis direction, the present invention is not limited to this configuration. Since the configuration other than the reflection units 27 and 28 is the same as that of the first embodiment, description thereof is omitted.

  A method for manufacturing the planar waveguide device 21 according to the present embodiment will be described. FIG. 13 is a plan view showing a state in which a resist is applied to the upper surface of the SOI substrate before the waveguide is formed. 14 is a cross-sectional view taken along the line XIV-XIV in FIG. FIG. 15 is a cross-sectional view of an SOI substrate having a waveguide formed by etching.

  First, in order to form a waveguide on the SOI substrate, as shown in FIGS. 13 and 14, a resist film is applied on the upper surface of the second laminated portion 24 formed of an Si layer. The resist film is patterned by an electron beam direct writing method or a photolithography method to form a resist pattern 35 corresponding to the shape of the desired thin wire waveguide 25, spot size conversion waveguide 26, and reflecting portions 27 and 28.

  For example, in the electron beam direct writing method, patterning may be performed under an irradiation condition in which the electron beam irradiation current is 0.1 nA and the electron beam dose time per dot is 4 μsec. In the photolithography method, the resist pattern 15 may be formed with a transfer time of about 300 msec.

  Using this resist pattern 35 as a mask, the SOI substrate is etched using an etching method such as ICP etching, reactive ion etching, and reactive ion beam etching. After etching a part of the surface side of the second laminated portion 24, the resist pattern 35 is peeled off. In this way, the fine wire waveguide 25, the spot size conversion waveguide 26, and the reflection portions 27 and 28 can be formed on the substrate. In the present embodiment, for example, reactive ion etching using a mixed gas of chlorine gas 25 sccm and nitrogen gas 10 sccm as an etching gas, an etching pressure of 0.1 Pa, and an RF power of 200 W may be used. .

  Next, a tantalum nitride film to be the heater 31 is formed on one side surface of the SOI substrate parallel to the thin waveguide 25 using a sputtering method or a vapor deposition method. Further, an aluminum nitride film to be the heat sink 32 is formed on the other side surface of the Si substrate 22 by using a sputtering method or a vapor deposition method. In the present embodiment, unlike the first embodiment, the pattern of the second stacked portion 24 can be formed by one exposure and etching. Therefore, the planar waveguide device 21 can be manufactured in a shorter manufacturing time than in the first embodiment.

  The function of the reflection part in the planar waveguide device according to the embodiment of the present invention will be described with reference to FIGS. 11 and 16 to 18. FIG. 16 shows an enlarged view of the vicinity of the reflecting portion in the planar waveguide device according to the present embodiment.

  As shown in FIG. 16, a reflecting portion 27 that reflects incident light is provided in the vicinity of the −X axis direction side of the spot size conversion waveguide 26, and a reflecting portion 28 that reflects incident light is provided in the vicinity of the + X axis direction side. Is provided. The reflectors 27 and 28 and the spot size conversion waveguide 26 are arranged in a non-contact state.

  In the present embodiment, the reflection regions of the reflection portions 27 and 28 are formed between the incident side end surface 33 and the emission side end surface 34 of the spot size conversion waveguide 26 in the Y-axis direction. Is not limited to such a configuration. For example, in the Y-axis direction, the reflection regions of the reflecting portions 27 and 28 may be formed in the same row as the incident-side end face 33 of the spot size conversion waveguide 26 or on the −Y-axis direction side. Also in this case, the light irradiated to the region other than the incident side end face 33 of the spot size conversion waveguide 26 out of the light irradiated to the planar waveguide element 21 is reflected so as not to enter the thin wire waveguide 25. Can do.

  Hereinafter, the reflection parts 27 and 28 which can exhibit a function satisfactorily will be described. Of the coordinates in the X-axis direction on the incident side end face 33 of the spot size conversion waveguide 26, the X coordinate in the most −X axis direction is defined as S1, and the X coordinate in the most + X axis direction is defined as S2. Among the coordinates in the X-axis direction in the reflection region of the reflecting portion 27 provided on the −X-axis direction side of the spot size conversion waveguide 6, the X coordinate in the + X-axis direction is defined as N1. Of the coordinates in the X-axis direction in the reflection region of the reflector 28 provided on the + X-axis direction side of the spot size conversion waveguide 26, the X-coordinate that is most in the -X-axis direction is defined as N2. In this case, the reflection regions of the reflection portions 27 and 28 are arranged so that S1 ≦ N1 and N2 ≦ S2 are satisfied.

  Further, the length in the X-axis direction of the reflection region of the reflection portion 27 is P1, the length of the reflection region of the reflection portion 28 is P2, and the light incident on the spot size conversion waveguide 26 is incident on the spot size conversion waveguide 26. Let Q be the spot diameter when passing through the end face 33. In this case, the reflection areas of the reflection portions 27 and 28 satisfying P1- (N1-S1) ≧ Q and P2- (S2-N2) ≧ Q are provided. In the present embodiment, the lengths P1 and P2 of the reflection areas of the reflection portions 27 and 28 are 20 μm.

  As shown in FIG. 11, the optical axis of the lens 38 and the central axis of the fiber 39 are arranged on a straight line in the Y-axis direction so that light is incident from the incident side end face 33 of the spot size conversion waveguide 26. The lens 38 is a lens for condensing light, and the spot diameter of the light emitted from the fiber 39 is larger than the spot diameter Q of the light incident on the planar waveguide element 21. The spot diameter Q of incident light is determined by the relationship between the optical characteristics such as the focal length of the fiber 39 and the lens 38.

  The light propagating through the spot size conversion waveguide 26 enters the fine wire waveguide 25 and travels in the + Y-axis direction while generating OBO in the X-axis direction. The light traveling through the thin wire waveguide 5 is emitted from the emission port 30. Therefore, when incident light is incident from the incident side end face 33 of the spot size conversion waveguide 26, the light is emitted from the emission port 30. The emitted light is detected by a detection device including a lens and a photodiode (not shown).

  17 and 18 are plan views showing a state in which the irradiation position of light is relatively shifted with respect to the planar waveguide device according to the present embodiment. As shown in FIG. 17, the positions of the lens 38 and the fiber 39 are moved in the −X-axis direction with respect to the incident side end face 33 of the spot size conversion waveguide 26. Assuming that the X coordinate of the position of the peak 36 of the light intensity at this time is F3, the light intensity of the light incident on the spot size conversion waveguide 26 decreases when F3 <S1 with F3 = S1 as a boundary. In this case, the light incident from the incident side end face 33 of the spot size conversion waveguide 26 is reflected by the reflection region of the reflection unit 27. Further, when F3 <S1, light does not enter the fine wire waveguide 25, and light is not detected from the exit port 30 of the fine wire waveguide 25.

  Further, as shown in FIG. 18, the positions of the lens 38 and the fiber 39 are moved in the + X-axis direction with respect to the incident side end face 33 of the spot size conversion waveguide 26. If the X coordinate of the position of the peak 36 of the light intensity at this time is F4, the light intensity of the light incident on the spot size conversion waveguide 26 decreases when F4> S2 with F4 = S2. In this case, the light incident from the region of the incident side end face 33 of the spot size conversion waveguide 26 is reflected by the reflection region of the reflection unit 28. Further, when F4> S2, since light does not enter the thin wire waveguide 25, light is not detected from the exit port 30 of the thin wire waveguide 25.

  As described above, the reflection regions 27 and 28 are provided, and the incident position of the incident light is continuously moved from the −X axis direction to the + X axis direction, thereby being detected from the emission port 30 of the thin wire waveguide 25. The irradiation position where the light intensity becomes 0 can be confirmed. Thereby, the influence of unnecessary light detected from other than the predetermined exit port 30 is eliminated, and the irradiation position that maximizes the light intensity and is the center in the X-axis direction of the spot size conversion waveguide 26 is confirmed. Can do.

  By adjusting the lens 38 and the fiber 39 so that light is irradiated to the irradiation position where the light intensity that is confirmed in this way becomes the maximum, variation in the demultiplexing characteristics of the planar waveguide device 21 is achieved. Can be suppressed. Further, by making the incident position of light the center in the X-axis direction of the spot size conversion waveguide 26, reflection on the side wall of the spot size conversion waveguide 26 is suppressed, and the spot size conversion waveguide 26 to the thin wire waveguide 25 are suppressed. The light enters smoothly, and the return light reflected and reflected back at the incident port 29 of the thin wire waveguide 25 is reduced.

  In addition, the reflection parts 27 and 28 are not restricted to said structure, Of the incident light, the light irradiated to area | regions other than the incident side end surface 33 of the spot size conversion waveguide 26 injects into the thin wire | line waveguide 25 As long as it is reflected so as not to occur. By providing the reflecting portions 27 and 28, the light whose incident position deviates from the incident side end face 33 of the spot size conversion waveguide 26 can be reflected and not emitted from the emission port 30. By doing so, the incident position of the light can be grasped, and the incident position with respect to the incident side end face 33 of the spot size conversion waveguide 26 is adjusted, thereby suppressing variations in the demultiplexing characteristics of the planar waveguide element 21. Can do.

  In addition, the said embodiment disclosed this time is an illustration in all the points, Comprising: It does not become the basis of limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiment, but is defined based on the description of the scope of claims. Further, all modifications within the meaning and scope equivalent to the scope of the claims are included.

1 is a plan view of a planar waveguide device according to a first embodiment of the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. It is a top view which shows the state which apply | coated the resist to the upper surface of the SOI substrate before forming a waveguide. It is IV-IV sectional drawing of FIG. It is a top view which shows the state which apply | coated the resist to the upper surface of the SOI substrate after forming a waveguide. It is VI-VI sectional drawing of FIG. The enlarged view of the reflection part vicinity in the planar waveguide element which concerns on the same embodiment is shown. It is a top view which shows the state which shifted the irradiation position of light relatively with respect to the planar waveguide element which concerns on the embodiment. It is a top view which shows the state which shifted the irradiation position of light relatively with respect to the planar waveguide element which concerns on the embodiment. It is the figure which showed the relationship between the incident position of light, and the light intensity detected by the output port of a thin wire | line waveguide. It is a top view of the planar waveguide device concerning Embodiment 2 of the present invention. It is XII-XII sectional drawing of FIG. It is a top view which shows the state which apply | coated the resist to the upper surface of the SOI substrate before forming a waveguide. It is XIV-XIV sectional drawing of FIG. It is sectional drawing of the SOI substrate in which the waveguide was formed by the etching. The enlarged view of the reflection part vicinity in the planar waveguide element which concerns on the same embodiment is shown. It is a top view which shows the state which shifted the irradiation position of light relatively with respect to the planar waveguide element which concerns on the embodiment. It is a top view which shows the state which shifted the irradiation position of light relatively with respect to the planar waveguide element which concerns on the embodiment. 1 is a perspective view of a spot size conversion waveguide described in Patent Document 1. FIG. 10 is a plan view of an OBO planar waveguide device described in Patent Document 2. FIG. It is XXI-XXI sectional drawing of FIG.

Explanation of symbols

  1, 2, 111 Planar waveguide element, 2, 22, 102, 112 Substrate, 3, 23, 113 First laminated portion, 4, 24 Second laminated portion, 5, 25, 105, 114 Fine wire waveguide, 6, 26, 101 Spot size conversion waveguide, 7, 8, 27, 28 Reflection part, 9, 29, 115 Incident port, 10, 30, 116 Exit port, 11, 31, 117 Heater, 12, 32, 118 Heat sink, 13 , 33, 106 Incident side end face, 14, 34, 107 Emission side end face, 15, 16, 35 Resist pattern, 17, 36, 120 Light intensity peak, 18, 119 Light path, 19, 38 Lens, 20, 39 Fiber, 103 waveguide core, 104 ridge, 7a, 8a opening.

Claims (5)

A rectangular substrate;
A first laminated portion laminated on the substrate;
A second laminated portion laminated on the first laminated portion and having a higher refractive index than the first laminated portion;
The second laminated portion includes a plurality of thin wire waveguides formed so as to be arranged substantially in parallel, and an incident port is provided on one end face of at least one of the thin wire waveguides, and is connected to the incident port. A spot size conversion waveguide,
A heater provided on one side surface of the substrate parallel to the thin wire waveguide;
A heat sink provided on the other side surface of the substrate,
The width of the spot size conversion waveguide is equal to the spot size of incident light at the incident side end face, and the light propagation direction so as to coincide with the width of the incident port of the thin wire waveguide at the output side end face. Get smaller,
The height of the spot size conversion waveguide coincides with the height of the incident port of the thin wire waveguide at the output side end face,
The second stacked portion is provided on both sides in the width direction of the spot size conversion waveguide in a non-contact state with the spot size conversion waveguide, and has a reflection region on a surface facing the incident direction of the incident light. A planar waveguide device including a reflective portion.   2. The planar light guide according to claim 1, wherein the reflection unit reflects light incident on a region other than an incident side end face of the spot size conversion waveguide out of the incident light so as not to be incident on the thin wire waveguide. Waveguide element. In the direction in which the thin wire waveguide extends, the reflecting portion is formed between the incident side end surface and the emission side end surface of the spot size conversion waveguide,
The direction from the heat sink to the heater parallel to the thin wire waveguide is the + X-axis direction, and the opposite direction to the + X-axis direction is the −X-axis direction, and the X-axis direction on the incident-side end face of the spot size conversion waveguide In the coordinates, the X coordinate in the most -X axis direction is S1, the X coordinate in the most + X axis direction is S2, and the X axis in the reflection region of the reflecting portion provided on the -X axis direction side of the spot size conversion waveguide In the direction coordinate, the X coordinate that is most in the + X-axis direction is M1, and the X-axis direction coordinate is the most in the X-axis direction in the reflection region of the reflection portion provided on the + X-axis direction side of the spot size conversion waveguide. If the X coordinate is defined as M2,
S1 ≦ M1 and M2 ≦ S2,
The length of the reflection region of the reflection part provided on the −X-axis direction side of the spot size conversion waveguide in the X-axis direction is L1, and the length of the reflection part provided on the + X-axis direction side of the spot size conversion waveguide. When the length in the X-axis direction of the reflection region is L2, and the spot diameter when light incident on the spot size conversion waveguide passes through the incident side end face of the spot size conversion waveguide is Q,
L1- (M1-S1) ≧ Q and L2- (S2-M2) ≧ Q.
The planar waveguide device according to claim 1 or 2.   The planar waveguide device according to claim 1, wherein the reflecting portion includes a mirror.   The planar waveguide device according to claim 1, wherein the reflection portion includes a photonic crystal.

Images