JP2005164820A - Method for controlling optical characteristic of waveguide type optical component, waveguide type optical component, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling optical characteristics of a waveguide type optical component by which the optical characteristics can be controlled while controlling the induction quantity of double refraction in the refractive index control of a waveguide by using light induction type refractive index changes, and to provide the waveguide type optical component controlled in optical characteristics of polarization-independent and polarization-dependent and its manufacturing method. <P>SOLUTION: In the method for controlling optical characteristics of the waveguide type optical component by using light induction type refractive index changes, the waveguide type optical components has a Mach-Zehnder interferometer arranged in an optical circuit and two arms of the Mach-Zehnder interferometer are irradiated with ultraviolet light of polarized waves of different directions. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for adjusting the optical characteristics of a waveguide-type optical component, and effectively adjusts the local birefringence of the optical circuit to improve productivity, and in particular, effectively adjusts the birefringence of the waveguide. The present invention relates to a method for efficiently adjusting the polarization characteristics of an optical circuit.

Conventionally, for example, methods disclosed in the following Patent Documents 1 to 6 have been proposed as methods for adjusting the optical characteristics of a waveguide type optical component.
Patent Document 1 discloses a step of forming a single-mode optical waveguide including a core portion having a light propagation action embedded in a clad layer on a substrate, and irradiating the single-mode optical waveguide with visible or ultraviolet laser light. And a process for adjusting the birefringence value of the core part. In the method described in Patent Document 1, a dopant such as GeO ₂ sensitive to light is added to the optical waveguide in the ultraviolet region, and there is no description regarding the polarization of the ultraviolet light to be irradiated.
Patent Document 2 discloses a step of impregnating an optical waveguide with hydrogen at room temperature in order to adjust the characteristics of an optical circuit composed of an optical waveguide composed of a core and a clad formed on a substrate, and a heat treatment on the optical waveguide. There is described a characteristic adjusting method including a step of performing a step of irradiating visible light or ultraviolet light locally on the optical waveguide. In the method described in Patent Document 2, hydrogen is impregnated in order to increase the ultraviolet light sensitivity of the optical waveguide. This Patent Document 2 does not describe polarization of ultraviolet light to be irradiated.
Patent Document 3 discloses a step of forming a clad layer on a substrate, a step of forming a single mode waveguide including a core portion embedded in the clad layer and having a light propagation action, and the single mode optical waveguide. Describes a method of manufacturing an integrated optical device, which includes a step of forming a stress-applying film on the clad layer that can apply stress due to residual stress to the stress and irreversibly change the stress by trimming.
In Patent Document 4, when an optical circuit composed of a Mach-Zehnder interferometer is manufactured, the irradiation area width differs at two or more different sites with respect to the two arm waveguides of the Mach-Zehnder interferometer. A method for performing characteristic trimming by irradiating light in the ultraviolet or visible region is described. This Patent Document 4 does not describe the polarization of ultraviolet light to be irradiated.
In Patent Document 5, when manufacturing a waveguide type optical device including a directional coupler having two waveguides having a proximity part, at least one optical waveguide in the proximity part is irradiated with ultraviolet light. A method of manufacturing a waveguide type optical device is described which includes a step of adjusting the degree of coupling of two polarization components substantially orthogonal to each other of light passing through the directional coupler. This Patent Document 5 does not describe the polarization of ultraviolet light to be irradiated.
Patent Document 6 describes a method of performing local heating with an ultraviolet or infrared laser device in order to adjust optical characteristics of an optical device including a waveguide. This Patent Document 6 does not describe the polarization of ultraviolet light to be irradiated.
JP-A-6-511145 JP-A-6-308546 Japanese Patent Publication No. 7-18964 JP 2001-264567 A JP 2001-330742 A Japanese translation of PCT publication No. 2002-530689 T. Meyer et al., "Birefringence writing and erasing in ultra-low-birefringence fibers by polarized UV side-exposure: origin and applications", Proc. OFS '96, We5-1, 1996.

Among the above-described conventional techniques, the method described in Patent Document 3 controls birefringence by controlling the residual stress. However, this method requires stacking a Si film or the like to control the residual stress. This is not preferable because the manufacturing cost increases because the work yield increases and the product yield deteriorates.
The other methods described in Patent Documents 1, 2 and 4 to 6 are methods for controlling the birefringence of the waveguide by irradiating ultraviolet light or the like. It is known that the birefringence introduced into the waveguide differs depending on the direction of the angle (see, for example, Non-Patent Document 1).

  According to Non-Patent Document 1, the increase in refractive index induced by ultraviolet irradiation is said to work greatly on incident light in the same direction as the polarization of the irradiated ultraviolet light. However, the above-mentioned conventional technology does not mention the point of adjusting the polarization state and polarization direction of the irradiated ultraviolet light, and the polarization state and polarization of the irradiated ultraviolet light when actually applied to manufacturing. Therefore, it is difficult to adjust the characteristics of the waveguide-type optical component, particularly the polarization characteristics due to birefringence, with good reproducibility.

  FIG. 1 shows a general ultraviolet light (non-polarized light, all-polarized light, circularly-polarized light, elliptically-polarized light, etc.) with respect to a planar optical waveguide 4 configured with a core 2 (waveguide) and a clad 3 on a substrate 1. Anisotropy introduced when irradiating with ultraviolet light that does not control the direction of the waveguide and the direction of polarization of the irradiated ultraviolet light, such as linearly polarized light that is neither parallel nor perpendicular to the propagation direction of the waveguide It is a perspective view which shows property (birefringence). In this figure, symbol A indicates ultraviolet light in which the direction of polarized light applied to the core 2 is not adjusted, and B indicates the direction of birefringence introduced into the waveguide. The birefringence of the direction of B having anisotropy in the direction of polarization of the ultraviolet light A (the direction of the electric field of the ultraviolet light) is introduced. Here, ultraviolet light in an arbitrary polarization state is divided into polarized light having an electric field component parallel to the waveguide (z-polarized light) and polarized light having an electric field component orthogonal to the waveguide (x-polarized light). .

  FIG. 2 shows the anisotropy (birefringence) introduced by the z-polarization of ultraviolet light having a polarization component parallel to the waveguide direction, and the z-polarization of ultraviolet C having an electric field component parallel to the waveguide. Birefringence in the direction of D parallel to the waveguide is introduced. This works equivalently for the x-polarized component and the y-polarized component of the light propagating through the waveguide, and thus the refractive index change due to the polarized component (z-polarized) of the ultraviolet light is the waveguide. It does not have birefringence for light propagating through

  FIG. 3 shows the anisotropy (birefringence) introduced by x-polarization of ultraviolet light having a polarization component in a direction orthogonal to the waveguide direction, and x of ultraviolet light E having an electric field component orthogonal to the waveguide. Due to the polarization, birefringence is introduced in the x direction (F direction) orthogonal to the waveguide. In this case, the refractive index increase for the x polarization propagating through the waveguide is larger than the refractive index increase for the y polarization. That is, a different amount of refractive index change, that is, birefringence is introduced for the x-polarized wave and the y-polarized wave.

In general, the refractive index change introduced by irradiation with ultraviolet light is very small compared to the absolute value of the refractive index. For example, in the case of quartz-based glass, the amount of change in refractive index introduced by ultraviolet light is at most on the order of 10 ⁻³ . Therefore, for adjusting the characteristics of an optical circuit using this, the refractive index change due to ultraviolet light irradiation is not used directly, such as using the phenomenon that the optical confinement in the waveguide differs depending on the refractive index. -In many cases, the optical path length of the arm of the Zehnder interferometer is slightly changed to cause a phase shift to change the interference condition. At this time, when adjusting the optical characteristics of the optical circuit by irradiating “general ultraviolet light”, that is, ultraviolet light A in which the direction of the waveguide and the direction of polarization of the irradiated ultraviolet light are not particularly controlled, FIG. As shown in FIG. 4, different refractive index changes are given to the x-polarized light and the y-polarized light of the guided light on one side or both sides of the waveguide. FIG. 4 is a diagram showing a state in which a waveguide type optical component 5 having a Mach-Zehnder interferometer is manufactured by changing the optical path length with general ultraviolet light according to the prior art. In FIG. Is a core (waveguide), 10 is a first directional coupler, 11 is a second directional coupler, 12 is a first arm, and 13 is a second arm. In the illustration of FIG. 4, the first arm 12 is irradiated with general ultraviolet light, the optical path length of the first arm 12 is slightly changed, and the waveguide type optical component 5 having a Mach-Zehnder interferometer is obtained. I am making it. In such a waveguide-type optical component 5, the optical path length for each of the x-polarized wave and the y-polarized light changes simultaneously at different rates of change, and in other words, the optical characteristics and polarization characteristics of the optical circuit, It has been very difficult to simultaneously control the optical characteristics of x-polarized light and y-polarized light and the difference between them.

  In many cases, a mirror (reflecting mirror) is used in the optical path of ultraviolet light, but the reflectivity of this ultraviolet light may differ for each polarization component, and is used to adjust the characteristics of the waveguide type optical component. It has been difficult to adjust the characteristics of the optical circuit with good reproducibility, for example, the amount of birefringence introduced into the waveguide type optical component may be different for each optical system such as an ultraviolet irradiation device.

  The present invention has been made in view of the above circumstances, and the optical properties of a waveguide-type optical component capable of adjusting the optical characteristics while controlling the amount of birefringence introduced in the adjustment of the refractive index of the waveguide using a light-induced refractive index change. It is an object of the present invention to provide a waveguide type optical component having a characteristic adjustment method, polarization-independent and polarization-dependent optical characteristics, and a method for manufacturing the same.

In order to achieve the above object, the present invention provides a method for adjusting the optical characteristics of a waveguide-type optical component using a light-induced refractive index change, wherein the waveguide-type optical component is included in an optical circuit. An optical characteristic adjusting method for a waveguide type optical component is provided, in which two arms of the Mach-Zehnder interferometer are irradiated with ultraviolet light having different directions of polarization.
In this adjustment method, it is preferable to equalize the amount of ultraviolet light irradiated to the two arms (where the amount of irradiation is the absolute amount of light power × irradiation time regardless of the direction of polarization). .

  The present invention also relates to a waveguide-type optical component having a Mach-Zehnder interferometer, in which the refractive indexes of the two arms of the Mach-Zehnder interferometer are increased by the same amount, and the refractive index of the refractive index increasing region is increased. There is provided a waveguide type optical component characterized in that the direction of anisotropy is different.

  According to the present invention, there is provided a Mach-Zehnder interferometer in the optical circuit by performing the optical characteristic adjusting method, and the refractive indexes of the two arms of the Mach-Zehnder interferometer are increased by the same amount, and Provided is a method for manufacturing a waveguide-type optical component, characterized by manufacturing a waveguide-type optical component having different refractive index anisotropy directions in the refractive index increasing region.

  The present invention also relates to a method for adjusting the optical characteristics of a waveguide-type optical component utilizing a light-induced change in refractive index, wherein the waveguide-type optical component has a Mach-Zehnder interferometer in the optical circuit. -At least one of the two arms of the Zehnder interferometer is irradiated with polarized ultraviolet light in a direction parallel to the longitudinal direction of the waveguide, and at least one of the two arms is polarized in a direction not parallel to the longitudinal direction of the waveguide Provided is a method for adjusting optical characteristics of a waveguide type optical component, characterized by irradiating a wave of ultraviolet light.

  The present invention also relates to a waveguide-type optical component having a Mach-Zehnder interferometer, in which one of the two arms of the Mach-Zehnder interferometer has an anisotropic direction of refractive index increase in the longitudinal direction of the waveguide. And a refractive index increasing region in which the direction of anisotropy of increasing the refractive index is orthogonal to the longitudinal direction of the waveguide is provided.

  The present invention also includes a Mach-Zehnder interferometer in the optical circuit by performing the optical characteristic adjusting method, and anisotropy of an increase in refractive index is provided in one of the two arms of the Mach-Zehnder interferometer. A waveguide type optical component having a refractive index increasing region whose direction is parallel to the longitudinal direction of the waveguide and a refractive index increasing region where the anisotropic direction of the refractive index increase is perpendicular to the longitudinal direction of the waveguide is manufactured. A method for manufacturing a waveguide type optical component is provided.

  The present invention also relates to a method for adjusting the optical characteristics of a waveguide-type optical component utilizing a light-induced change in refractive index, wherein the waveguide-type optical component has a Mach-Zehnder interferometer in the optical circuit. Provided is a method for adjusting the optical characteristics of a waveguide-type optical component, characterized in that ultraviolet light having different polarization directions is irradiated to any two or more of two arms of a Zehnder interferometer.

  The present invention also relates to a waveguide-type optical component having a Mach-Zehnder interferometer, wherein the refractive index anisotropy direction of the refractive index increasing region of the two arms of the Mach-Zehnder interferometer, and the refractive index. There is provided a waveguide type optical component characterized in that at least one of the magnitudes of anisotropy differs between two arms.

  Further, the present invention provides the anisotropy of the refractive index of the refractive index increasing region having the Mach-Zehnder interferometer in the optical circuit by performing the optical characteristic adjusting method and having the two arms of the Mach-Zehnder interferometer. A waveguide-type optical component manufacturing method is provided, in which at least one of the direction and the refractive index anisotropy is different from each other by two arms.

According to the present invention, for a waveguide type optical component having a Mach-Zehnder interferometer in an optical circuit, adjustment of polarization independent optical characteristics using a refractive index change without birefringence, and birefringence Thus, it is possible to simultaneously adjust the optical characteristics corresponding to the polarization dependence, and to efficiently manufacture a high-performance waveguide type optical component.
Further, the amount of birefringence introduced into the waveguide type optical component can be precisely controlled, and the characteristics of the optical circuit can be adjusted with good reproducibility.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 5 is a diagram showing a first example of a method for adjusting optical characteristics of a waveguide type optical component according to the present invention. In this adjustment method, two optical cores 8 and 9 serving as waveguides are provided on a substrate 6 as waveguide-type optical components, and are provided in a meandering state in which two cores approach each other and are substantially parallel to each other. In the waveguide type optical component 20 having the Mach-Zehnder interferometer that is provided with the clad 7 that surrounds the plates 8 and 9 and has a flat plate shape as a whole, the optical characteristic adjustment method of the present invention is illustrated. The waveguide-type optical component 20 includes a first directional coupler 10 and a second directional coupler 11 in which two cores 8 and 9 approach each other on both sides of the central portion, and the central portion. 1 includes a Mach-Zehnder interferometer configured to include a first arm 12 and a second arm 13 formed so that the two cores 8 and 9 are spaced apart and have parallel portions. . This Mach-Zehnder interferometer has two ports at both ends in the longitudinal direction. For example, when the input light 14 is incident on one of the two left ports in FIG. A port output 15 and a cross port output 16 are emitted.

In this waveguide type optical component 20, two cores 8 and 9 (waveguides) constituting a Mach-Zehnder interferometer are provided on a substrate 6, and a clad 7 surrounding these cores 8 and 9 is provided. The refractive index of the core 8, 9 material is higher than the refractive index of the clad material, light is propagated in the core 8, 9 and the core 8, 9 is light-induced, particularly ultraviolet light-induced refractive index change. Any material may be used as long as the material can generate the above-described material, and the material and shape thereof are not particularly limited. Examples of the substrate 6 include a quartz glass plate, a ceramic substrate, and a silicon substrate. The cores 8 and 9 are preferably formed using quartz glass to which GeO ₂ is added. The pattern of the cores 8 and 9 can be formed using a technique such as photolithography. The clad 7 can also be formed using synthetic resin in addition to quartz glass.

  In the optical characteristic adjustment method according to this example, the ultraviolet light source (not shown) that irradiates the ultraviolet light A that is not polarization-adjusted downward, and the different polarization components are received by receiving the ultraviolet light emitted from the ultraviolet light source. A polarization mirror 17 that transmits ultraviolet light G whose polarization direction is parallel to the parallel portions of the arms 12 and 13 and that reflects ultraviolet light I whose polarization direction is orthogonal to the parallel portions of the arms 12 and 13; The adjustment device includes a mirror 18 that further reflects the ultraviolet light I reflected by the polarizing mirror 17 and irradiates the lower arm 13 with the reflected light. The polarizing mirror 17 has a reflecting surface disposed at an angle of 45 ° and irradiates the ultraviolet light A in a vertical direction toward the reflecting surface, so that the polarization direction is parallel to the parallel portions of the arms 12 and 13. The ultraviolet light G and the ultraviolet light I whose polarization direction is orthogonal to the parallel portions of the arms 12 and 13 can be irradiated to the arms 12 and 13 with the same optical power.

  When the waveguide type optical component 20 for adjusting the optical characteristics is set in this adjusting device and the ultraviolet light A is irradiated from the ultraviolet light source, the direction of the polarized light transmitted through the polarizing mirror 17 is the ultraviolet light parallel to the parallel portions of the arms 12 and 13. After the light G is locally irradiated on the first arm 12 and the ultraviolet light I whose polarization direction reflected by the polarizing mirror 17 is orthogonal to the parallel part of the arms 12 and 13 is reflected by the mirror 18, The two arms 13 are irradiated locally.

  When each ultraviolet light G, I is irradiated for a predetermined time, a refractive index increasing region is formed in the first and second arms 12, 13, and the optical path length changes. In this example, the first arm 12 is irradiated with the ultraviolet light G whose polarization direction is parallel to the parallel part of the arms 12 and 13, and the second arm 13 is directed to the parallel part of the arms 12 and 13. The direction of the anisotropy (birefringence) of the refractive index introduced into the arms 12 and 13 is different by irradiating the ultraviolet light I orthogonal to the refractive index formed in the first arm 12. In the ascending region, birefringence in the direction H parallel to the parallel portions of the arms 12 and 13 is introduced, and in the second arm, birefringence in the direction J perpendicular to the longitudinal direction is introduced. This causes a difference in optical path length between the two arms for the x-polarized light of the guided light, while changes in the optical path lengths of the two arms are equal for the y-polarized light of the guided light.

  As a result, in the optical characteristic adjustment method according to this example, before the adjustment, a Mach-Zehnder interferometer having polarization-independent optical characteristics (both x and y polarized waves are output to the crossport) is shown in FIG. As shown in FIG. 5, by irradiating the arms 12 and 13 with ultraviolet light G and I having asymmetrical polarization, the x-polarized light has almost 100% through-port output and the y-polarized light is the same as before the dose. In addition, a polarized beam splitter (PBS; Polarized-Beam Splitter) having a cross-port output of almost 100% can be manufactured.

As the ultraviolet light source, Ar ⁺ second harmonic generation (SHG) laser (oscillation wavelength 244 nm), KrF excimer laser (oscillation wavelength 248 nm), ArF excimer laser (oscillation wavelength 193 nm), XeF excimer laser (oscillation wavelength 351 nm) ), Xe excimer lamp (wavelength 172 nm), KrCl excimer lamp (wavelength 222 nm), XeI excimer lamp (253 nm), I ₂ excimer lamp (wavelength 341 nm), etc., and non-polarized output light from these light sources It is possible to obtain the same effect by obtaining the necessary polarized light by a method such as passing a polarizer through a polarizer and irradiating it with respect to the waveguide.

  In the first embodiment described above, in the waveguide-type optical component having the Mach-Zehnder interferometer in the optical circuit, the irradiation amount (absolute value) of the ultraviolet light applied to both of the two arms is particularly determined. Although the case where the same and the direction of the anisotropy (birefringence) of the refractive index in the refractive index increasing region are different has been described, in order to realize the object of the present invention, as shown in FIGS. Moreover, it is not necessary to make the irradiation amount (absolute value) of the ultraviolet light irradiated to both the two arms the same.

FIG. 8 is a diagram showing a second example of the optical characteristic adjusting method of the present invention. In this example, the second arm 13 of the Mach-Zehnder interferometer is irradiated with polarized ultraviolet light G in a direction parallel to the longitudinal direction of the waveguide, and the first arm 12 is oriented in a direction not parallel to the longitudinal direction of the waveguide. Irradiate polarized ultraviolet light K. The polarized light applied to the first arm 12 may have an optical power different from the ultraviolet light applied to the arm 13. In FIG. 8, symbol H denotes the direction of birefringence introduced into the refractive index increasing region introduced by the ultraviolet light G, and L denotes birefringence introduced into the refractive index increasing region introduced by the ultraviolet light K. The direction.
As a result, the polarization-independent optical characteristics are adjusted by irradiating at least one side of the arms 12 and 13 with polarized ultraviolet light G parallel to the direction of the waveguide, and the waveguide is provided on at least one side of the waveguide. It is possible to adjust the polarization-dependent optical characteristics by irradiating polarized ultraviolet light K in a direction that is not parallel to the direction of light, and this adjustment method also achieves the purpose of adjusting the local birefringence of the optical circuit it can.

FIG. 9 is a diagram showing a third example of the optical characteristic adjusting method of the present invention. In this example, the first arm 12 of the Mach-Zehnder interferometer is irradiated with ultraviolet light G having a polarization parallel to the longitudinal direction of the waveguide, and the other part of the first arm 12 is parallel to the longitudinal direction of the waveguide. The second arm 13 is not irradiated with ultraviolet light.
As a result, at least one side of the arm (waveguide) is irradiated with polarized light parallel to the direction of the waveguide to adjust the polarization-independent optical characteristics, and at least one side of the waveguide has the direction of the waveguide It is possible to adjust polarization-dependent optical characteristics by irradiating polarized light in a non-parallel direction, and this adjustment method can also achieve the purpose of adjusting the local birefringence of the optical circuit.

FIG. 10 is a diagram showing a fourth example of the optical characteristic adjusting method of the present invention. In this example, the first arm 12 of the Mach-Zehnder interferometer is irradiated with ultraviolet light A whose polarization direction is not adjusted, and the second arm 13 is polarized in a direction parallel to the longitudinal direction of the waveguide. Ultraviolet light G is irradiated.
As a result, at least one side of the arm (waveguide) is irradiated with polarized light parallel to the direction of the waveguide to adjust the polarization-independent optical characteristics, and at least one side of the waveguide has the direction of the waveguide It is possible to adjust polarization-dependent optical characteristics by irradiating polarized light in a non-parallel direction, and this adjustment method can also achieve the purpose of adjusting the local birefringence of the optical circuit.

FIG. 11 is a diagram showing a fifth example of the optical property adjusting method of the present invention. In this example, the first arm 12 of the Mach-Zehnder interferometer is irradiated with polarized ultraviolet light G in a direction parallel to the longitudinal direction of the waveguide, and the polarization direction is adjusted to the other part of the first arm 12. Both the ultraviolet light A which has not been irradiated are irradiated, and the second arm 13 is not irradiated with the ultraviolet light.
As a result, at least one side of the arm (waveguide) is irradiated with polarized light parallel to the direction of the waveguide to adjust the polarization-independent optical characteristics, and at least one side of the waveguide has the direction of the waveguide It is possible to adjust polarization-dependent optical characteristics by irradiating polarized light in a non-parallel direction, and this adjustment method can also achieve the purpose of adjusting the local birefringence of the optical circuit.

The polarized wave used in each of the above examples was polarized light having an electric field in a direction perpendicular to the longitudinal direction of the waveguide, or polarized light having an electric field in a direction parallel to the longitudinal direction of the waveguide. However, in order to achieve the object of the present invention, it is sufficient to make a difference in the birefringence given to the two arms, and the invention is not limited to irradiating the arm with polarized waves parallel or orthogonal to the waveguide. .
The magnitude of anisotropy (birefringence) introduced into the waveguide varies depending on the direction of the polarized light to be irradiated. As shown in FIGS. 12 to 17, the polarization parallel to the waveguide has the minimum birefringence, and is introduced as the angle between the waveguide inorganic and the direction of polarization of the ultraviolet light (the direction of the electric field) increases. Birefringence increases, and the birefringence introduced when the waveguide and the direction of polarization are orthogonal is maximized.

  FIG. 12 shows the anisotropy of the refractive index increase region induced by irradiation with ultraviolet light A whose polarization direction is not adjusted, such as non-polarized light or total polarized light, regardless of the direction of the core 12 (waveguide). Indicates. In FIG. 12, the symbol a indicates the direction of polarization of the irradiated ultraviolet light, A indicates the polarization component of the irradiated ultraviolet light, and B indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence B introduced into the waveguide is moderate.

  FIG. 13 shows the anisotropy of the refractive index increase region induced by irradiating polarized ultraviolet light G having an electric field in a direction parallel to the direction of the core 12 (waveguide). In FIG. 13, symbol g indicates the direction of polarization of the irradiated ultraviolet light, G indicates the polarization component of the irradiated ultraviolet light, and H indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence H introduced into the waveguide is minimized.

  FIG. 14 shows the refractive index increase region obtained when the polarized ultraviolet light K1 having an electric field is irradiated in the direction in which the angle θ formed with the direction of the core 12 (waveguide) is in the range of 0 ° <θ <45 °. It is a figure which shows the anisotropy of refractive index. In FIG. 14, symbol k1 indicates the direction of polarization of the irradiated ultraviolet light, K1 indicates the polarization component of the irradiated ultraviolet light, and L1 indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence L1 introduced into the waveguide is small.

  FIG. 15 is a diagram showing the anisotropy of the refractive index in the refractive index increasing region obtained when the ultraviolet light having an electric field is irradiated in the direction in which the angle θ formed with the direction of the core 12 (waveguide) is 45 °. is there. In FIG. 15, symbol k2 indicates the direction of polarization of the irradiated ultraviolet light, K2 indicates the polarization component of the irradiated ultraviolet light, and L2 indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence L2 introduced into the waveguide is moderate.

  FIG. 16 shows the refractive index of the refractive index increasing region obtained when ultraviolet polarized light having an electric field is applied in the direction in which the angle θ formed with the direction of the core 12 (waveguide) is in the range of 45 ° <θ <90 °. It is a figure which shows the anisotropy of. In FIG. 16, symbol k3 indicates the direction of polarization of the irradiated ultraviolet light, K3 indicates the polarization component of the irradiated ultraviolet light, and L3 indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence L3 introduced into the waveguide is large.

  FIG. 17 shows the refractive index anisotropy in the refractive index increasing region obtained when ultraviolet polarized light having an electric field is irradiated in the direction in which the angle θ formed with the direction of the core 12 (waveguide) is in the range of 90 °. FIG. In FIG. 12, symbol i indicates the direction of polarization of the irradiated ultraviolet light, I indicates the polarization component of the irradiated ultraviolet light, and J indicates the direction of birefringence introduced into the waveguide. In this case, the birefringence J introduced into the waveguide is maximized.

Using these polarizations, the polarization characteristics of the Mach-Zehnder interferometer (for each polarization) are changed by making at least one of the polarization direction and the amount of irradiation of the ultraviolet light irradiating the two arms different. It is also possible to adjust the branching ratio of
In the above description, in the Mach-Zehnder interferometer, the optical coupling portions before and after the first and second arms 12 and 13 are the directional couplers 10 and 11 having a branching ratio of 3 dB. Multimode interference as disclosed in Japanese Patent Application Laid-Open No. 2000-162454 “Optical coupler and Mach-Zehnder optical multiplexer / demultiplexer using the same”, Japanese Patent Application Laid-Open No. 2000-221345 “Multimode interference optical device”. An optical coupler (MMI coupler; Multi-Mode Interferometer) may be used.

  In each of the above-described examples, the case of a PLC (Planar Lightwave Circuit) is described as an object of adjusting the optical characteristics by irradiating ultraviolet light. However, an interleaver manufactured using an optical fiber coupler, etc. Similarly, in the adjustment of the optical characteristics of the Mach-Zehnder interferometer used as the optical delay line while irradiating polarized ultraviolet light with an electric field parallel to the waveguide (optical fiber) of the optical delay line, It is possible to minimize the birefringence introduced into the waveguide (optical fiber).

  The optical characteristic adjusting method shown in FIG. 5 was carried out to produce a waveguide type optical component having a Mach-Zehnder interferometer.

<Fabrication of optical circuit>
A waveguide-type optical component having a silica glass waveguide (the optical circuit is a Mach-Zehnder interferometer) was fabricated. A quartz glass plate was used as the substrate of the waveguide type optical component. The lower cladding layer is made of pure silica glass, and the core layer is made of Ge-added quartz glass (including a small amount of B ₂ O ₃ and P ₂ O ₅ ) by CVD (chemical vapor synthesis) method. An unnecessary portion of the core layer was removed to form a core (waveguide) shape, and an upper clad layer was deposited so as to embed the core. The upper clad layer was made of quartz glass to which B ₂ O ₃ and P ₂ O ₅ were added, and the softening point temperature was made slightly lower than that of pure quartz glass while making the refractive index equal to that of pure quartz glass.

After forming the lower clad layer, core, and upper clad layer, the entire waveguide type optical component is once heated to 800 to 1000 ° C. and then slowly cooled to remove defects in the glass formed during the glass film deposition and Processing was performed to remove the stress.
As the waveguide parameters, the core cross-sectional shape was a substantially square shape of 5.5 μm × 5.5 μm, and the GeO ₂ addition amount of the core was adjusted so that the relative refractive index difference (Δ) with the cladding was 1.0%. .
The formed optical circuit has two directional couplers with a branching ratio of 3 dB (measurement wavelength 1.55 μm), and a Mach-Zehnder having two arms having the same optical path length between them. An interferometer was used.

<Ultraviolet light irradiation to waveguide type optical components>
In order to increase the photosensitivity so that the change in refractive index when the waveguide type optical component is irradiated with ultraviolet light is increased, the waveguide type optical component is subjected to H ₂ loading treatment. That is, the waveguide type optical component was infiltrated with H ₂ gas by being exposed in an atmosphere of H ₂ gas at 20 to 60 ° C. and 100 atm for 7 to 14 days. If the waveguide itself has sufficient light sensitivity, this H ₂ loading process is unnecessary.

The waveguide-type optical component after the H ₂ loading process was set in an ultraviolet irradiation device provided with a combination of an ultraviolet light source and a polarizing mirror 17 and a mirror 18 arranged as shown in FIG.
As the ultraviolet light source, an Ar ⁺ second harmonic generation (SHG) laser (oscillation wavelength 244 nm) was used. The laser oscillation condition was CW, and the irradiation power was 200 mW. When the Ar ⁺ SHG laser light is separated at a 45 ° angle with respect to the birefringence axis of the polarizing mirror 17, that is, when the Ar ⁺ SHG laser light is separated into a polarization parallel to the longitudinal direction of the waveguide arm and a polarization orthogonal thereto, Each arm is incident so as to have an equal irradiation amount (here, the irradiation amount is an absolute amount of light power × irradiation time regardless of the direction of polarization) and separated by the polarizing mirror 17, then one arm. 12 is irradiated with polarized ultraviolet light parallel to the longitudinal direction, and the other arm 13 is irradiated with polarized ultraviolet light in a direction perpendicular to the longitudinal direction.

The absolute value of the power of the ultraviolet light applied to the two arms 12 and 13 is made equal, and the refractive index change introduced into the two arms 12 and 13 is
The introduced anisotropy differs between the two arms 12 and 13 in the x direction (that is, there is a difference in the optical path length between the two arms with respect to the x polarization of the guided light),
The introduced anisotropy is equivalent in the two directions for the y direction (that is, the change in the optical path length of the two arms is equal for the y polarization of the guided light),
I did it.

<Changes in optical properties due to ultraviolet light irradiation>
The waveguide type optical component was irradiated with ultraviolet light having different polarizations by the two arms 12 and 13 as shown in FIG. FIGS. 6 and 7 show the branching ratio of the Mach-Zehnder interferometer for each polarization for each irradiation time (dose time) of ultraviolet light.

As can be seen from FIG. 6 and FIG. 7, the asymmetrical ultraviolet light irradiation to the two arms shown in FIG. You can see that In particular, before irradiating with ultraviolet light (when the dose time is 0 second), the output to the cross port is almost 100% for both x and y polarized waves, whereas when the dose time is around 1000 seconds, the x polarization is The wave has a through-port output of almost 100%, and the y-polarized wave has a cross-port output of almost 100% as before the dose.
That is, at first, a Mach-Zehnder interferometer having polarization-independent optical characteristics (100% of both x and y polarizations are output to the crossport) is converted into a polarization beam splitter (PBS) by asymmetric ultraviolet light irradiation. ; Polarized-Beam Splitter).
This experiment demonstrates that the polarization characteristics of an optical circuit can be adjusted over a wide range by irradiating two arms of a Mach-Zehnder interferometer with ultraviolet light having different polarizations.

It is a perspective view of the planar optical waveguide which shows the anisotropy introduce | transduced in a waveguide by general ultraviolet light irradiation. FIG. 5 is a perspective view of a planar optical waveguide showing anisotropy introduced by ultraviolet light having a polarization component in a direction parallel to the longitudinal direction of the waveguide. It is a perspective view of the planar optical waveguide which shows the anisotropy introduced with the ultraviolet light of the polarization component of the direction orthogonal to a waveguide longitudinal direction. It is a perspective view which shows the waveguide type optical component provided with the Mach-Zehnder interferometer for demonstrating the optical path length adjustment method by the general ultraviolet irradiation by the prior art. It is a perspective view showing a waveguide type optical component provided with a Mach-Zehnder interferometer for explaining a first example of an optical characteristic adjusting method according to the present invention. It is a graph which shows the change of the branching ratio of x polarization | polarized-light of the waveguide type optical component produced in the Example which concerns on this invention. It is a graph which shows the change of the branching ratio of y polarization of the waveguide type optical component produced in the example concerning the present invention. It is a perspective view which shows the waveguide type optical component provided with the Mach-Zehnder interferometer for demonstrating the 2nd example of the optical characteristic adjustment method by this invention. It is a perspective view which shows the waveguide type optical component provided with the Mach-Zehnder interferometer for demonstrating the 3rd example of the optical characteristic adjustment method by this invention. It is a perspective view which shows the waveguide type optical component provided with the Mach-Zehnder interferometer for demonstrating the 4th example of the optical characteristic adjustment method by this invention. It is a perspective view which shows the waveguide type optical component provided with the Mach-Zehnder interferometer for demonstrating the 5th example of the optical characteristic adjustment method by this invention. It is a perspective view which shows the anisotropy of the refractive index raise area | region induced by irradiating the ultraviolet light which is not adjusting the direction of polarization to a waveguide. It is a perspective view which shows the anisotropy of the refractive index raise area | region induced by irradiating a waveguide with the ultraviolet light of the direction parallel to the longitudinal direction. FIG. 6 is a perspective view showing anisotropy of a refractive index increasing region induced by irradiating a polarized ultraviolet light having an angle θ of 0 ° <θ <45 ° with a longitudinal direction of the waveguide. It is a perspective view which shows the anisotropy of the refractive index raise area | region induced by irradiating the polarized light with the direction whose angle (theta) which makes with respect to the longitudinal direction to a waveguide is 45 degrees. FIG. 6 is a perspective view showing anisotropy of a refractive index increasing region induced by irradiating a waveguide with polarized ultraviolet light having an angle θ of 45 ° <θ <90 ° with respect to the longitudinal direction of the waveguide. It is a perspective view which shows the anisotropy of the refractive index raise area | region induced by irradiating the polarized light with the polarization | polarized-light whose direction (theta) which makes the longitudinal direction to a waveguide 90 degrees.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,6 ... Board | substrate, 2,8,9 ... Core, 3,7 ... Cladding, 4 ... Planar type optical waveguide, 5 ... Waveguide type | mold optical component, 10 ... 1st directional coupler, 11 ... 2nd Directional coupler, 12 ... first arm, 13 ... second arm, 14 ... input, 15 ... through port output, 16 ... crossport output, 17 ... polarizing mirror, 18 ... mirror, 20 ... waveguide type light parts.

Claims (10)

  A method for adjusting the optical characteristics of a waveguide type optical component utilizing a light-induced change in refractive index, wherein the waveguide type optical component has a Mach-Zehnder interferometer in an optical circuit. A method for adjusting the optical characteristics of a waveguide-type optical component, characterized in that two arms are irradiated with ultraviolet light having different directions of polarization.   2. The irradiation amount of ultraviolet light irradiating two arms (here, the irradiation amount is an absolute amount of light power × irradiation time regardless of the direction of polarization). A method for adjusting the optical characteristics of the waveguide-type optical component according to claim 1.   A waveguide type optical component having a Mach-Zehnder interferometer, in which the refractive indexes of the two arms of the Mach-Zehnder interferometer are increased by the same amount, and the refractive index anisotropy of the refractive index increasing region is increased. A waveguide type optical component characterized by having different directions.   The optical characteristic adjusting method according to claim 1 or 2 is performed, and the optical circuit has a Mach-Zehnder interferometer, and the refractive indexes of the two arms of the Mach-Zehnder interferometer are increased by the same amount. A method for manufacturing a waveguide-type optical component, characterized in that a waveguide-type optical component having different refractive index anisotropy directions in the refractive index increasing region is manufactured.   A method for adjusting the optical characteristics of a waveguide type optical component using a photo-induced refractive index change, wherein the waveguide type optical component has a Mach-Zehnder interferometer in an optical circuit, and the Mach-Zehnder interferometer At least one of the two arms is irradiated with polarized ultraviolet light in a direction parallel to the waveguide longitudinal direction, and at least one of the two arms is irradiated with polarized ultraviolet light in a direction not parallel to the waveguide longitudinal direction. Irradiating a method for adjusting optical characteristics of a waveguide type optical component.   A waveguide-type optical component having a Mach-Zehnder interferometer, in which one of the two arms of the Mach-Zehnder interferometer has a refractive index whose refractive index rise is parallel to the longitudinal direction of the waveguide. A waveguide-type optical component comprising: a rising region; and a refractive index increasing region in which the direction of anisotropy in increasing the refractive index is not parallel to the longitudinal direction of the waveguide.   6. An optical characteristic adjusting method according to claim 5, wherein a Mach-Zehnder interferometer is provided in the optical circuit, and either of the two arms of the Mach-Zehnder interferometer has an anisotropic refractive index increase. Produces a waveguide-type optical component that has a refractive index increasing region in which the orientation is parallel to the waveguide longitudinal direction and a refractive index increasing region in which the anisotropy direction of the refractive index increase is not parallel to the waveguide longitudinal direction A method for manufacturing a waveguide-type optical component.   A method for adjusting the optical characteristics of a waveguide type optical component utilizing a light-induced change in refractive index, wherein the waveguide type optical component has a Mach-Zehnder interferometer in an optical circuit. A method for adjusting optical characteristics of a waveguide-type optical component, wherein ultraviolet light having different polarization directions is irradiated to any two or more of two arms.   A waveguide type optical component having a Mach-Zehnder interferometer, in which the two arms of the Mach-Zehnder interferometer have a refractive index anisotropy direction and a refractive index anisotropy direction. A waveguide type optical component, wherein at least one of the sizes is different from each other by two arms.   An optical characteristic adjustment method according to claim 8, wherein the optical circuit has a Mach-Zehnder interferometer, and the refractive index increases in the refractive index increasing region of the two arms of the Mach-Zehnder interferometer. A waveguide-type optical component manufacturing method, wherein at least one of the direction of the property and the magnitude of anisotropy of the refractive index is different from each other by two arms.

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