JPH0743297A - Method and apparatus for measuring refractive index of planar optical waveguide - Google Patents

Abstract

PURPOSE:To provide a method for measuring the refractive index of a planar optical waveguide without immersing the measuring system into a matching oil. CONSTITUTION:Light from a laser light source is condensed through a condenser lens to be focused at the edge of a planar optical waveguide 1. An irradiating light 3 and the waveguide 1 are then shifted relatively and the light leaving the waveguide 1 is measured by a light receiving element 2. A transparent spacer 4 is interposed between the waveguide 1 and the light receiving element 2. The light beam projected to the edge of the waveguide 1 is retracted to enter into the waveguide 1 thence enter through the spacer 4 into the light receiving element 2. Absolute refractive index of the planar optical waveguide 1 can be calculated with reference to a known refractive index of the spacer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a measuring device for measuring the refractive index distribution of an optical plane waveguide.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of an example of an optical plane waveguide. In the figure, 11 is a substrate, 12 is a buffer layer, 13 is a core, and 14 is a clad layer. FIG. 5A shows a slab type, in which a buffer layer 1 is formed on a substrate 11 such as Si or quartz.
2 is formed, the core 13 is provided in a planar shape, and the clad layer 14 is provided thereon. FIG. 5B shows a channel type, similarly, a buffer layer 12 is formed on a substrate such as Si or quartz, a core 13 is linearly provided thereon, and a clad layer 14 is provided thereon. . In each case, the buffer layer 12, the core 13, the clad layer 1 are formed on the substrate 11.
A waveguide portion consisting of 4 is provided. In one example, the thickness of the buffer layer 12 and the clad layer 14 is about 20 μm, the thickness of the slab core is about 8 μm, and the thickness of the channel core is about 8 μm square.

As a method of measuring the refractive index distribution of such an optical plane waveguide, the RNF method (refracted method) is used.
Although a near field technique is known, this method is a method in which a measurement system such as a measurement sample or a light receiving element is immersed in matching oil for measurement.

FIG. 6 is an explanatory view of a conventional method of measuring the refractive index distribution of an optical plane waveguide by the RNF method. In the figure, 1 is an optical plane waveguide, 1a is its substrate portion,
Reference numeral 1b is a waveguide portion thereof, 2 is a light receiving element, and 3 is irradiation light. The irradiation light 3 is obtained by focusing the light from a laser light source (not shown) on the end surface of the optical plane waveguide 1 by using a converging lens and moving the irradiation light 3 and the optical plane waveguide 1 relatively. The light emitted from the optical plane waveguide 1 is measured by the light receiving element 2. In order to prevent the light rays incident on the optical plane waveguide 1 from refracting and scattering when exiting the optical plane waveguide,
The measurement is performed while the optical plane waveguide 1 and the light receiving element 2 are immersed in matching oil.

As described above, when the measuring system is in the matching oil, there is a problem that it takes time to replace the measuring sample. Further, since the matching oil is a liquid, it is unavoidable that the liquid flows during the measurement, and if dust is mixed in the liquid, light is scattered and a measurement error occurs.

When the measurement sample is an optical waveguide formed on a Si substrate, the incident light beam is S
There is also a problem that it is difficult to measure the refractive index distribution because it is reflected on the surface of the i substrate.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a method and a method for measuring the refractive index of an optical planar waveguide which does not require the measurement system to be immersed in matching oil. The purpose is to provide a device.

[0008]

According to a first aspect of the present invention, there is provided a method of measuring a refractive index of an optical plane waveguide, wherein a refractive index distribution of the optical plane waveguide is measured by using an RNF method. The laser light source is focused on the end surface of the optical plane waveguide, and the optical plane waveguide is moved relatively to place the light emitted from the optical plane waveguide on the optical plane waveguide. Through a transparent spacer with a known refractive index,
It is characterized in that the measurement is performed by a photoelectric conversion element placed thereon.

According to a second aspect of the present invention, in the method of measuring the refractive index of the optical planar waveguide according to the first aspect, a light receiving element is used as the photoelectric conversion element, and the amount of light is measured. In the invention according to claim 3, in the method of measuring the refractive index of the optical planar waveguide according to claim 1, a line sensor or a surface sensor is used as the photoelectric conversion element, and a light arrival position, It is characterized by measuring the light intensity.

According to a fourth aspect of the present invention, in the method of measuring the refractive index of the optical plane waveguide according to any one of the first to third aspects, a substrate in the optical plane waveguide is used as the laser light source. A laser light source having a transmitting wavelength is used, and the invention according to claim 5 is the method for measuring the refractive index of the optical planar waveguide according to any one of claims 1 to 4. It is characterized in that the incident angle range of the irradiation light on the substrate in the optical plane waveguide is limited.

According to a sixth aspect of the present invention, in the method of measuring the refractive index of the optical plane waveguide according to any one of the first to fifth aspects, the absolute spacer of the optical plane waveguide is used with the transparent spacer as a reference. It is characterized by measuring the refractive index.

According to the invention of claim 7, RNF is used.
In the refractive index measuring device of the optical plane waveguide for measuring the refractive index distribution of the optical plane waveguide using the method, a laser light source for irradiating the end face of the optical plane waveguide with a focused light beam,
A moving means for relatively moving the light source and the optical plane waveguide, a transparent spacer having a known refractive index placed on the optical plane waveguide, and a photoelectric conversion element placed on the transparent spacer. It is characterized by that.

According to an eighth aspect of the invention, in the refractive index measuring device of the seventh aspect, a light receiving element is used as the photoelectric conversion element to measure the light quantity. According to the invention described in claim 9, in the refractive index measuring device of the optical planar waveguide according to claim 7, as a photoelectric conversion element, a line sensor or a surface sensor is used to reach the light, It is characterized by measuring the light intensity.

According to a tenth aspect of the present invention, in the refractive index measuring device for an optical plane waveguide according to any one of the seventh to ninth aspects, a substrate in the optical plane waveguide is used as the laser light source. A laser light source having a transmitting wavelength is used, and in the invention according to claim 11, in the refractive index measuring device for an optical plane waveguide according to any one of claims 7 to 10. A slit for limiting an incident angle range of irradiation light on the substrate in the optical plane waveguide is provided.

[0015]

According to the present invention, in the method and apparatus for measuring the refractive index of the optical planar waveguide using the RNF method, by using the spacer between the measurement sample and the photoelectric conversion element, the measurement sample can be easily set. Further, the positioning of the light receiving element and the measurement sample becomes easy. It is not necessary to immerse the measurement sample and the light receiving element in matching oil as in the conventional case.

By using a line sensor or a surface sensor as the photoelectric conversion element to receive the light refracted in the waveguide, the refractive index distribution can be measured from the light arrival position and the light intensity distribution. Further, scratches, dust, etc. on the waveguide surface can be recognized, and the refractive index distribution of the waveguide can be accurately measured.

By using a laser light source having a transmission wavelength of Si, it is possible to prevent the incident light on the Si substrate from being reflected and affecting the measurement.

Further, by making incident light incident on the measurement waveguide through the slit, the incident light on the Si substrate can be reduced, and even if reflected light is generated, it does not affect the photoelectric conversion element. Since the light can be reflected in the direction, accurate measurement can be performed.

Since the refractive index of the spacer can be made known, the absolute refractive index of the measurement waveguide can be measured using this as a reference.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram for explaining an embodiment of the method of measuring the refractive index of an optical plane waveguide and the refractive index measuring device of the present invention. In the figure, 1 is an optical plane waveguide, 1a is its substrate portion, 1b is its waveguide portion, 2 is a light receiving element, 3 is irradiation light, and 4 is a spacer. The irradiation light 3 is obtained by focusing the light from a laser light source (not shown) on the end surface of the optical plane waveguide 1 by using a converging lens and moving the irradiation light 3 and the optical plane waveguide 1 relatively. The light emitted from the optical plane waveguide 1 is measured by the light receiving element 2. A spacer 4 is interposed between the optical plane waveguide 1 and the light receiving element 2. A transparent material is used for the spacer 4, and the refractive index thereof is preferably close to the refractive index of the cladding of the optical planar waveguide 1. The light beam applied to the end surface of the optical plane waveguide 1 is refracted and enters the optical plane waveguide 1, and enters the light receiving element 2 from the optical plane waveguide 1 via the spacer 4. A matching liquid is applied to the contact surface between the optical planar waveguide 1 and the spacer 4.

FIG. 2 is a block diagram for explaining another embodiment of the method and apparatus for measuring the refractive index of the optical planar waveguide of the present invention. In the figure, the same parts as those in FIG. 5 is a CCD camera. In the embodiment described with reference to FIG. 1, the light receiving element 2 is used as the photoelectric conversion device for measuring the emitted light, but C as the surface sensor is used.
When a CD camera or a line sensor is used, the light intensity distribution at the light arrival position can be detected on the detection surface, and the refractive index distribution can be measured.

If there is a component of the light beam entering the optical planar waveguide 1 toward the substrate portion 1a, the substrate portion 1a
Reflection occurs at the boundary surface between the waveguide portion 1b and the waveguide portion 1b, and if this reflected component enters the light receiving element 2 or the CCD camera 5, it causes an error. Therefore, the wavelength of the laser light source is selected so that it passes through the substrate. For example, as the substrate, Si
When a substrate is used, a laser light source with a wavelength of 1.2 to 1.3 μm is used. Accordingly, even if a component directed to the substrate surface is generated, the light ray can be transmitted through the substrate and the reflected component can be suppressed, so that the error can be reduced.

FIG. 3 is an explanatory view of a main part of an embodiment of the light source. In the figure, 6 is incident light, 7 is a slit member, and 8 is a focusing lens. As the slit for limiting the incident angle range of the irradiation light to the optical planar waveguide, a slit having an appropriate shape such as a semicircular shape in the lower half can be used, but a ghost is caused by the diffracted light at the upper edge. , There is a problem of error. In this embodiment, the slit 7 has a slit shape in which the apex is formed in a triangular shape, and is just like a sharpened pencil viewed from the side. Therefore, the upper edge of the slit 7 is oblique, and a ghost due to the diffracted light of this edge is generated in an obliquely upward direction, is not incident on the photoelectric conversion element, and does not cause an error. The light passing through the slit 7 is focused by the focusing lens 8 on the end face of the optical plane waveguide (not shown).

FIG. 4 is an explanatory diagram of the measurement result of the amount of received light with respect to the position of the end surface of the optical plane waveguide on which the irradiation light is focused. As can be seen from FIGS. 1 and 2, the incident light is largely refracted in the portion having a large refractive index, and the amount of incident light on the light receiving element is small. In the waveguide portion, the refractive index of the core portion is larger than that of the buffer layer and the clad layer, so that the amount of received light when the incident light is located in the core portion is small. Since the matching liquid used has a refractive index larger than that of the waveguide, the amount of received light is small when the incident light is located in this portion. When the incident light is positioned on the spacer using the quartz plate, the amount of received light is large. In this example, the refractive index of the spacer is the same as that of the cladding of the optical plane waveguide. The known refractive index of the quartz plate can be used. Since the relationship between the received light amount and the refractive index can be known by using this as a reference, the absolute refractive index of the optical planar waveguide is calculated from the received light amount. be able to.

[0025]

As is apparent from the above description, according to the present invention, it is possible to provide a refractive index measuring method and a measuring apparatus for an optical planar waveguide which does not require the measurement system to be immersed in matching oil. There is an effect.

[Brief description of drawings]

FIG. 1 is a configuration diagram for explaining one embodiment of a method and a device for measuring a refractive index of an optical planar waveguide according to the present invention.

FIG. 2 is a configuration diagram for explaining another embodiment of the method and device for measuring the refractive index of the optical planar waveguide of the present invention.

FIG. 3 is an explanatory diagram of a main part of an embodiment of a light source used in the present invention.

FIG. 4 is an explanatory diagram of a measurement result of a received light amount.

FIG. 5 is a configuration diagram of an example of an optical plane waveguide.

FIG. 6 is an explanatory diagram of a conventional method of measuring the refractive index distribution of an optical plane waveguide by the RNF method.

[Explanation of symbols]

 1 Optical planar waveguide 1a Substrate portion 1b Waveguide portion 2 Light receiving element 3 Irradiation light 4 Spacer 5 CCD camera 6 Incident light 7 Slit member 8 Focusing lens

Claims (11)

[Claims] 1. A method of measuring a refractive index of an optical plane waveguide using an RNF method for measuring a refractive index distribution of the optical plane waveguide, wherein a laser light source is focused on an end face of the optical plane waveguide, and The light emitted from the optical plane waveguide is placed on the optical plane waveguide through a transparent spacer having a known refractive index by relatively moving the optical plane waveguide. A method for measuring the refractive index of an optical planar waveguide, which is characterized in that it is measured by a photoelectric conversion element. 2. The method for measuring the refractive index of an optical planar waveguide according to claim 1, wherein a light receiving element is used as the photoelectric conversion element, and the amount of light is measured. 3. The method of measuring the refractive index of an optical planar waveguide according to claim 1, wherein a line sensor or a surface sensor is used as the photoelectric conversion element, and the light arrival position and the light intensity are measured. 4. The refraction of the optical plane waveguide according to claim 1, wherein a laser light source having a wavelength that transmits a substrate in the optical plane waveguide is used as the laser light source. Rate measurement method. 5. The method for measuring the refractive index of an optical plane waveguide according to claim 1, wherein an incident angle range of irradiation light on the substrate in the optical plane waveguide is limited. . 6. The refractive index measuring method for an optical plane waveguide according to claim 1, wherein the transparent spacer is used as a reference to measure an absolute refractive index of the optical plane waveguide. . 7. A refraction index measuring apparatus for an optical plane waveguide for measuring a refractive index distribution of an optical plane waveguide using an RNF method, wherein a laser light source for irradiating an end face of the optical plane waveguide with a focused light beam. A moving means for relatively moving the light source and the optical planar waveguide, a transparent spacer having a known refractive index placed on the optical planar waveguide, and a photoelectric conversion element placed on the transparent spacer. A refractive index measuring device for an optical planar waveguide, comprising: 8. The refractive index measuring device for an optical planar waveguide according to claim 7, wherein a light receiving element is used as the photoelectric conversion element to measure the amount of light. 9. The refractive index measuring device according to claim 7, wherein a line sensor or a surface sensor is used as the photoelectric conversion element to measure the light arrival position and the light intensity. 10. The refraction of the optical plane waveguide according to claim 7, wherein a laser light source having a wavelength that transmits a substrate in the optical plane waveguide is used as the laser light source. Rate measuring device. 11. The refraction of the optical plane waveguide according to claim 7, further comprising a slit that limits an incident angle range of irradiation light on the substrate in the optical plane waveguide. Rate measuring device.