JPH04157338A - Method and instrument for measuring refractive index of multilayer plane wave guide path - Google Patents

Abstract

PURPOSE:To measure the refractive index of a multilayer plane wave guide path by obtaining a critical angle for each layer from relationship between the incidence angle of light on a prism brought into close contact with the outermost layer of a multilayer plane wave guide path and the intensity of light emitted from the end of the wave guide path of each layer. CONSTITUTION:A prism 4 is brought into close contact with a wave guide path 2b on the outermost layer of a multilayer plane wave guide path 2 by pressing means 10. He-Ne laser light emitted from the light output device 14a of a light source unit 14 fixedly attached to a rotary table 8 is incident on the prism 4. The incidence angle of the laser light on the prism 4 is measured by an incidence angle measuring device 12 wherein a table 8 is used. Further, the intensity of light emitted from the wave guide path ends 2b and 2c of the respective layers of the wave guide path 2 is detected by light power meters 18 and 20 opposed to light input portions 16 and 17, respectively. From relationship between the intensities of light detected by the meters 18 and 20 and the incidence angle onto the prism 4 measured by the measuring device 12, a critical angle and therefore the refractive index of the multilayer plane wave guide path 2 can be obtained.

Description

[Detailed Description of the Invention] Summary The present invention relates to a method and apparatus for measuring the refractive index of a multilayer planar waveguide. Light is introduced into the multilayer planar waveguide through a prism that is in close contact with the waveguide, and the refractive index is measured from the relationship between the intensity of the light emitted from the waveguide end of each layer and the angle of incidence on the prism. The configuration is such that the critical angle for each of the layers is determined, and the refractive index of each layer is calculated from the critical angle.

INDUSTRIAL APPLICATION FIELD The present invention relates to a method and apparatus for measuring the refractive index of a multilayer planar waveguide.

In the field of optical communication or optical transmission, in addition to transmitters, receivers, and transmission lines, various optical devices such as optical switches and optical couplers are used. One type of optical device is a waveguide type. A waveguide type optical device is configured such that an optical waveguide made of quartz glass is provided on a silicon wafer, and a light beam is controlled while being confined within the optical waveguide, and is easy to miniaturize due to its structure. In addition to the advantage that it can be mass-produced using brainer technology or the like, it also has the advantage that electric and magnetic fields can be effectively applied and power consumption can be dramatically reduced. When manufacturing and researching such waveguide type optical devices, accurate measurement of the refractive index of the optical waveguide is required.

2. Description of the Related Art A conventional method for measuring the refractive index of a planar waveguide will be explained with reference to FIG. As shown in FIG. 5(a), a waveguide 2 made of quartz glass or the like is placed on a substrate 2a made of a silicon wafer or the like.
When measuring the film refractive index of the planar waveguide 2 formed by forming the waveguide 2b, first, a prism 4 is brought into close contact with the waveguide 2b, and light is introduced into the waveguide 2b via the prism 4. The light intensity emitted from the end of the waveguide 2b is made to be detectable by the photodetector 6. Then, when the incident angle θ to the prism 4 is gradually increased from 0°, a certain incident angle θ is reached. Since the light intensity detected by the photodetector 6 becomes zero at this angle, this angle of incidence is defined as the critical angle.

The refractive index of the prism 4 is np, and the refractive index of the waveguide 2b is n
. (no < np ), the refractive index of the waveguide is the critical angle θ. It is expressed as follows using .

no = np 5in(αo +π/4)a, =
5irr' (sin oo/np) Problems to be Solved by the Invention By the way, when creating a waveguide type optical device, generally, two layers of Talarado glass and core glass are deposited on a silicon wafer at once, and then patterned and The optical waveguide is etched and a final cladding glass is applied thereon. Therefore, in order to provide high-quality waveguide type optical components, it is required to be able to measure the refractive index of at least two layers of planar waveguides formed on a wafer.

However, when using the conventional method explained with reference to FIG. 5, it is only possible to measure the refractive index of a single-layer planar waveguide, so when this method is applied to a multilayer planar waveguide,
Only the refractive index of the outermost layer of the waveguide can be measured, which is inconvenient.

The present invention was created in view of the above circumstances, and an object of the present invention is to enable measurement of the refractive index of a multilayer planar waveguide.

Means for Solving the Problems The method for measuring the refractive index of a multilayer planar waveguide of the present invention involves introducing light into the multilayer planar waveguide through a prism that is brought into close contact with the outermost layer waveguide, and measuring the refractive index. The critical angle for each layer is determined from the relationship between the intensity of light emitted from the waveguide end of each layer and the angle of incidence on the prism, and
The refractive index of each layer is calculated from the critical angle.

The refractive index measuring device for a multilayer planar waveguide of the present invention includes a table on which the multilayer planar waveguide is placed, a prism that is in close contact with the outermost layer of the multilayer planar waveguide, and a refractive index measuring device for measuring the refractive index of the multilayer planar waveguide through the prism. It is equipped with a light source device for making light incident, an incident angle measuring device for measuring the angle of incidence on the prism, and a monitor device for detecting the light emitted from the waveguide end of each layer whose refractive index is to be measured. It consists of

For production FIG. 1 and FIG. 2 are diagrams explaining the principle of the present invention.

In the planar waveguide 2, 2a is a substrate made of a silicon wafer or the like, and waveguides 20.2b are formed in this order on this substrate 2a. A prism 4 is in close contact with the outermost waveguide 2b, and 6A and 6B are photodetectors that detect the intensity of light emitted from the ends of the waveguides 2b and 2c, respectively.

FIG. 2 shows the relationship between the intensity of light detected by the photodetectors 6A and 6B and the angle of incidence when the angle of incidence θ on the prism 4 is gradually increased from α°. First, at the first critical angle θ, the photodetector 6
The intensity of the light detected by the photodetector 6A becomes zero at the second critical angle θ2, which is larger than θ1. The refractive index of the waveguide 20.2b is nl + n2, respectively.
and the refractive index of the prism 4 is n, then nl +
2 is expressed as follows using np and the critical angle. Each refractive index satisfies n, <1. <np.

nl =np 5in(α+ +π/4)n, =n,
5in (cr, 1π/4) However, α1. α2 satisfies the following formula.

a, = 5irr'(sinθ, /nP)a2=
5irr' (sin θ, /n,) Thus, according to the method of the present invention, the intensity of light emitted from the waveguide end of each layer whose refractive index is to be measured is detected, and the critical angle for each layer is determined. This makes it possible to measure the refractive index of a multilayer planar waveguide.

Example The present invention will be explained in detail below.

3E is an explanatory diagram of a refractive index measuring device for a multilayer planar waveguide showing the first embodiment of the present invention. 8 is a table on which the multilayer planar waveguide 2 is placed, and 10 is a pressing means for bringing the prism 4 into close contact with the outermost layer waveguide 2b of the multilayer planar waveguide 2. Reference numeral 12 denotes an incident angle measuring device for measuring the incident angle to the prism 4, and this measuring device is equipped with a rotary table, and the light output section 14 of the light source device 14 is mounted on the rotary table.
a is fixed. For example, collimated He--Ne laser light is emitted from the light output section 14a, and the angle of incidence of this light on the prism 4 is measured by angle measurement using a rotary table.

In this embodiment, the monitor device that detects the light emitted from the waveguide ends of each layer of the multilayer planar waveguide 2 is provided with optical input sections 16 and 17 facing the waveguide ends of each layer. It is equipped with an optical power meter 18.20. The optical power meter 18° 20 detects the intensity of the light emitted from the end of each waveguide 2b, 2c, and thereby the relationship between the light intensity and the incident angle as shown in FIG. 2 can be determined. Critical angle measurement becomes possible.

FIG. 4 is an explanatory diagram of a refractive index measuring device for a multilayer planar waveguide showing a second embodiment of the present invention. This embodiment differs from the previous embodiment in that the configuration of the monitor device is different.

That is, in this embodiment, the monitor device includes a multilayer planar waveguide 12.
, and an image processing device 26 that detects whether light is emitted from the waveguide end of each layer based on image information from the television camera 22. It consists of 24 is a monitor device for a television camera. According to this embodiment, when the incident angle to the prism is gradually increased from 0°, it is possible to detect the presence or absence of light emitted from each layer by visual inspection or image processing. The angle can be determined, making it possible to measure the refractive index.

For example, np=2+　θ,=3.607°, θ.

=4.027°, the refractive indices of the waveguide 2C corresponding to the cladding and the waveguide 2b corresponding to the core are 1.45'8 and 1.463, respectively.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, the present invention has the effect of making it possible to measure the refractive index of a multilayer planar waveguide.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of the principle of the present invention, FIG. 3 is an explanatory diagram of a refractive index measuring device for a multilayer planar waveguide showing the first embodiment of the present invention, and FIG. 4 is a diagram illustrating the second embodiment of the present invention. FIG. 5 is an explanatory diagram of a refractive index measuring device for a multilayer planar waveguide showing an embodiment. FIG. 5 is an explanatory diagram of a conventional technique. 2... Multilayer planar waveguide, 4... Prism.

Claims (1)

[Claims] 1. A method for measuring the refractive index of a multilayer planar waveguide, which involves introducing light into the multilayer planar waveguide through a prism (4) that is brought into close contact with the outermost layer of the waveguide, and measuring the refractive index. Determine the critical angle for each layer from the relationship between the intensity of the light emitted from the waveguide end of each layer to be measured and the angle of incidence on the prism (4), and calculate the refractive index of each layer from the critical angle. A method for measuring the refractive index of a multilayer planar waveguide, characterized by calculating the refractive index. 2. A table (8) on which the multilayer planar waveguide (2) is placed; a prism (4) that is in close contact with the outermost layer of the multilayer planar waveguide (2); A light source device (14) that makes light enter the waveguide (2), an incident angle measuring device (12) that measures the angle of incidence on the prism (4), and a waveguide of each layer whose refractive index is to be measured. 1. A refractive index measuring device for a multilayer planar waveguide, comprising a monitor device that detects light emitted from each end. 3. The above-mentioned monitoring device is characterized in that the optical input section includes an optical power meter (18, 20) provided facing each waveguide end of each layer whose refractive index is to be measured. 2. The refractive index measuring device for a multilayer planar waveguide according to 2. 4. The monitor device includes a television camera (22) provided opposite to the end of the multilayer planar waveguide, and monitors light from the waveguide end of each layer based on image information from the television camera (22). An image processing device (
26). The refractive index measuring device for a multilayer planar waveguide according to claim 2, comprising: