JP3148332B2 - Waveguide-type optical device operating characteristics evaluation method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating operating characteristics of a waveguide type optical device, and more particularly to a grating, a lens, and a directional coupling which are indispensable for practical use of an ultra-wideband high-speed optical communication system and an optical information processing system. The present invention relates to a method for evaluating the operating characteristics of a low-loss waveguide type optical device such as a coupler, a branch waveguide, an optical amplifier, an optical wavelength converter, and a wavelength demultiplexer / combiner.

[0002]

2. Description of the Related Art A so-called optical integrated circuit in which optical systems including various optical devices such as lenses, prisms, mirrors, and couplers are formed on a common substrate does not require optical axis alignment, is stable against vibration, is lightweight and compact. , High-speed operation, low power consumption, etc., which were not obtained with conventional bulk type optical systems,
Basic and applied research is being conducted energetically both in Japan and overseas. The basic component of an optical integrated circuit is a so-called dielectric optical waveguide in which a thin film having a thickness of about a wavelength having a higher refractive index than a substrate is formed on a dielectric substrate, and a substrate material used, for example, glass, ferroelectric A device having various functions can be realized by using a ferrimagnetic material, a semiconductor, or the like. Furthermore, by integrating this on a common substrate, a monolithic or hybrid optical integrated circuit is formed.

One of the important basic techniques for realizing such an optical integrated circuit is characteristic evaluation. Since the optical waveguide is formed on a substrate of the order of centimeters, that is, on the substrate of the order of centimeters, the cutback method (input / output characteristics of long fiber, From the input / output characteristics of the fiber,
The method for evaluating the characteristics of the optical fiber cannot be applied, and a method unique to the optical waveguide is required.

Conventionally, the transmission characteristics of an optical waveguide have been evaluated by inputting a light wave to the optical waveguide using a prism coupler, an objective lens, or the like, and measuring the relationship between input and output light.

[0005]

However, this method cannot be applied to the evaluation of the device characteristics and the observation of the operation state at the stage of trial production, and the evaluation of the operation characteristics of a complicated circuit system in which these are integrated.

A method of directly observing the state of propagation through an optical waveguide (called a scattered streak light) using an image pickup tube type camera or the like is also used. Cannot be applied, and there is also a problem of burning of the image pickup tube due to strong incident light.

The present invention has been made in view of such a situation, and an object of the present invention is to make a light wave propagating in a waveguide type optical device observable from the outside by a phosphor or a scatterer loaded on the surface thereof. In particular, it is possible to evaluate the operation of a low-loss waveguide type optical device.

[0008]

In order to achieve the above object, a method for evaluating the operating characteristics of a waveguide type optical device according to the present invention comprises loading a thin transparent layer containing a phosphor on the surface of the waveguide type optical device, and introducing Visualizing the behavior of light waves in a waveguide-type optical device by externally photographing the fluorescent light distribution generated by the leakage of light waves propagating in the waveguide-type optical device and processing the obtained image data. It is a method characterized by the following.

[0009] Instead of loading the thin transparent layer containing the above-described phosphor, a thin transparent layer containing a fine scatterer,
A scatterer surrounded by minute closed curved surfaces that are regularly or randomly arranged and separated from each other, or a transparent plate having regular or random projections formed on one surface may be loaded. When using point-like scatterers spaced apart from each other, the thickness is preferably 0.1 to 0.2 μm, and the number and interval of the loaded scatterers are preferably 10 to 50 per cm.
When a transparent plate having projections is used, it is desirable that the interval between the projections is 100 μm to 1 mm.

[0010]

According to the present invention, a thin transparent layer or the like containing a fluorescent substance is loaded on the surface of a waveguide type optical device, and the distribution of fluorescent light and the like generated by leaking light of a light wave propagating in the waveguide type optical device. 0.5dB / cm
Even in the following low-loss optical waveguides, scattered light can be increased, and the behavior of light waves in an optical device can be clearly grasped by a high-sensitivity CCD or the like, and the evaluation thereof can be easily performed.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The basic principle of the evaluation method of the present invention is that a phosphor or a scatterer is loaded on the surface of a waveguide-type optical device to partially leak a light wave propagating in the waveguide of the waveguide-type optical device. The purpose is to observe and measure the leakage light using a high-sensitivity CCD camera or the like.

Specifically, as shown in a perspective view in FIG.
A thin transparent layer 4 containing a fluorescent substance or a small scatterer is loaded on the surface of a waveguide type optical device 1 comprising a waveguide layer 3 provided on a substrate 2. As described above, when the loading layer 4 containing a phosphor or a small scatterer is provided on the surface of the waveguide layer 3, evanescent waves generated on the surface by light propagating through the waveguide layer 3 generate phosphors of the loading layer 4. Alternatively, the fluorescent light or the scattered light is absorbed or scattered by the minute scatterer, and the fluorescent light or the scattered light is emitted to the outside of the waveguide type optical device 1. By observing and measuring this with a highly sensitive CCD camera or the like, the waveguide type light is obtained. The behavior of the light wave propagating in the device 1 is visualized, and its operation characteristics can be evaluated.

The refractive index of the loading layer 4 may be larger or smaller than the refractive index of the waveguide layer 3. Exists. In particular, as shown in FIG. 1, when the refractive index of the waveguide layer 3 is smaller than that of the loading layer 4, FIGS.
As shown in (c), the field distribution of the electromagnetic field varies greatly depending on the thickness of the loading layer 4, and in order to evaluate the operation of the waveguide optical device 1 in a form (a) close to the field distribution at the time of no loading, The thickness of the loading layer 4 needs to be about 0.1 μm (b). In order to prevent the light propagating in the waveguide layer 3 from being attenuated, it is necessary to minimize the mixing ratio of the fluorescent substance and the fine scatterer dispersed in the transparent layer 4.

As shown in a perspective view of FIG. 2, a small island-shaped scatterer 7 is regularly or randomly loaded on the surfaces of the waveguides 5 and 6 of the waveguide type optical device 1 to form a waveguide. 5,6
A part of the light propagating in the inside is scattered to the outside by the scatterer 7, and this is observed and measured by a high-sensitivity CCD camera or the like to evaluate the operating characteristics of the waveguide type optical device 1. You can also. In the case of FIG. 2, as an example, the island-shaped scatterer 7 is formed of a photoresist.
The number and spacing of the island-shaped scatterers 7 vary depending on the target waveguide, but may vary from 10 to 5 per cm.
When the number is about 0, the waveguide characteristics are not affected. Further, the thickness is desirably about 0.1 to 0.2 μm.

Further, as shown in the cross section in FIG. 4, projections 9 are formed regularly or randomly on one side of the surface of the glass plate 8 having excellent parallelism, and as shown in FIG. By closely adhering to the waveguide 5 of the optical device 1,
As in the case of FIG. 2, a part of the propagating light is scattered to the outside at the tip of the protrusion 9, and by observing and measuring this, the operating characteristics of the waveguide type optical device 1 can be evaluated. In this case, the interval between the protrusions 9 varies depending on the target waveguide, but if it is set to about 100 μm to 1 mm,
Does not affect waveguide characteristics.

Next, an example of an apparatus for performing the above-described evaluation method will be described. This device includes an optical system shown in FIG. 6 and an image processing system shown in FIG. The optical system includes light sources 10, 1 as shown in FIG.
1, total reflection mirrors 12, 13, half-wave plates 14, 15, dichroic mirror 16, polarizer 17, attenuator 18, half mirror 19, sample stage 20, camera stage 21, input objective lens 22, output objective lens 2.
3. It is composed of CCD cameras 24-26. The waveguide type optical device 1 to be evaluated is set on the sample stage 20. In this case, two types of lasers (He-Ne laser 10 and GaAs semiconductor laser 11) are used as light sources so that evaluation at two wavelengths is possible. Each stage 2
Reference numerals 0 and 21 have a movable accuracy of 0.1 μm, which is sufficient to evaluate a normal single-mode optical waveguide.

In this configuration, three CCD cameras 24 to
Reference numeral 26 is used for focusing the objective lens 22 for incidence, observing light leaked from the waveguide of the waveguide type optical device 1, and observing the near-field image pattern of the emitted light. The CCD cameras 24 to 26 have excellent linearity, do not burn, and relatively easily handle laser light having high density power. Furthermore, it has sufficient sensitivity to the target laser light. The half-wave plates 14 and 15 can rotate the plane of polarization of linearly polarized light by 90 degrees, and are used to effectively excite the polarization mode unique to the optical waveguide. The dichroic mirror 16 is a total reflection mirror for one of the light waves having different wavelengths (the wavelength from the light source 11), and the other (the light source 1).
(Wavelength from 0) operates as a non-reflection mirror.

FIG. 7 shows an example of the configuration of the image processing system.
1, a computer display 32, a video printer 33, a printer 34, and the like. The microcomputer 30 in this configuration incorporates an image capturing board capable of real-time display, can handle images in a realistic time, can perform high-speed processing, and is the heart of the present processing system. As a specific example, a Macintosh IIcx manufactured by Apple Inc. is used, and a cook capture manufactured by Data Translation Inc. is used as an image capturing board.
The magneto-optical recording device 31 is a device capable of storing a large amount of images having a huge data amount. The computer display 32 is used for displaying the captured image data and for displaying the calculation processing result. Video printer 3
Reference numeral 3 is used to output an image displayed on the computer display 32, and the printer 34 is used to output an evaluation result.

FIG. 8 is a flowchart of the image processing software. Image information from CCD cameras 24-26 is Ima
ge, which is taken into the computer 30 by general-purpose image input processing software, performs image processing such as coloring, emphasis, and end point extraction of light intensity distribution and intensity contour distribution in an arbitrary sampling interval, and converts a file in a format called TIFF. Output. Next, using image processing software named Tiff, data is retrieved from a TIFF format file, transmission loss, optical power distribution is calculated, its three-dimensional display is performed, and a tabular file is output. Finally, general-purpose spreadsheet software is used. Graphing, approximation, and file output in PICT format are performed.

Various measurements were carried out using the above-mentioned apparatus. FIG. 9 is a perspective view showing an example of the waveguide type optical device used. The device 40 is formed on a substrate 41. Two linear waveguides 42 having different waveguide widths,
Reference numeral 43 denotes an asymmetric directional coupler that approaches in the order of wavelength. FIG. 10 shows that the device 40 has, as shown in FIG.
A thin transparent layer containing a phosphor is loaded, and a He-Ne laser 10 is applied to one of the linear waveguides 42 (single mode).
The light wave from the light source is incident, processed by the image processing software of FIG. 8, and displayed three-dimensionally, which clearly shows the operation state.

As described above, in the evaluation method of the present invention, scattered light for observation can be increased even in a low-loss optical waveguide of 0.5 dB / cm or less. The behavior of the light wave in the device can be clearly grasped, and the evaluation can be easily performed.

The method for evaluating the operating characteristics of a waveguide type optical device according to the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications are possible.

[0023]

As is clear from the above description, according to the waveguide-type optical device operating characteristic evaluation method of the present invention, a thin-film transparent layer or the like containing a phosphor is loaded on the surface of the waveguide-type optical device. Since the distribution of fluorescent light and the like generated by the leakage light of the light wave propagating in the waveguide type optical device is photographed from the outside, the waveguide loss is extremely small and it is difficult to directly observe with a high sensitivity camera etc. Can be easily evaluated, and a wide range of applications can be expected, such as quality control in optical device manufacturing lines, development and evaluation of new functional optical devices, examination of optimal manufacturing conditions, and operation analysis of optical integrated circuits. .

[Brief description of the drawings]

FIG. 1 is a perspective view for explaining one embodiment of a waveguide type optical device operation characteristic evaluation method of the present invention.

FIG. 2 is a perspective view for explaining another embodiment.

FIG. 3 is a diagram for explaining the relationship between the thickness of a loading layer and the field distribution of an electromagnetic field in FIG.

FIG. 4 is a sectional view of a glass plate used in another embodiment.

FIG. 5 is a perspective view showing a state in which the glass plate of FIG. 4 is adhered to the waveguide type optical device.

FIG. 6 shows an optical system 1 of an apparatus for implementing the evaluation method of the present invention.
It is a figure showing composition of an example.

FIG. 7 is a diagram showing a configuration of an example of an image processing system of an apparatus that performs the evaluation method of the present invention.

FIG. 8 is a flowchart of an example of image processing software.

FIG. 9 is a perspective view showing an example of a waveguide type optical device to be measured.

FIG. 10 is a diagram three-dimensionally illustrating an operation state of the waveguide type optical device of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Waveguide type optical device 2 ... Substrate 3 ... Waveguide layer 4 ... Loading layer 5, 6 ... Waveguide 7 ... Island scatterer 8 ... Glass plate 9 ... Projection 10, 11 ... Light source 12, 13 ... Total reflection mirror 14, 15: half-wave plate 16: dichroic mirror 17: polarizer 18: attenuator 19: half mirror 20: sample stage 21: camera stage 22: incident objective lens 23 ... exit objective lens 24-26: CCD camera 30 Microcomputer 31 ... Magneto-optical recording device 32 ... Computer display 33 ... Video printer 34 ... Printer 40 ... Asymmetric directional coupler 41 ... Substrate 42,43 ... Linear waveguide

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01M 11/00-11/02 G01N 21/84-21/958

Claims (6)

(57) [Claims] 1. A waveguide-type optical device having a thin transparent layer containing a phosphor loaded on the surface thereof, and a fluorescent light distribution generated by leakage light of a light wave propagating in the waveguide-type optical device being photographed from outside. A method for evaluating operating characteristics of a waveguide-type optical device, comprising visualizing the behavior of a light wave in the waveguide-type optical device by performing image processing on the obtained image data. 2. A light-transmitting thin layer containing a small scatterer is loaded on the surface of a waveguide-type optical device, and a distribution of scattered light generated by leakage light of a light wave propagating in the waveguide-type optical device is photographed from outside. A method for evaluating operating characteristics of a waveguide-type optical device, comprising visualizing the behavior of a light wave in the waveguide-type optical device by performing image processing on the obtained image data. Wherein mutually spaced waveguide type optical device surface
The scattered body surrounded by a small closed curved surface is loaded regularly or randomly, and the scattered light distribution generated by the leakage light of the light wave propagating in the waveguide type optical device is photographed from the outside, and the obtained image data is obtained. A method for evaluating operating characteristics of a waveguide-type optical device, characterized by visualizing the behavior of light waves in the waveguide-type optical device by performing image processing. 4. A small closed curved surface spaced apart from each other.
4. The method according to claim 3, wherein the thickness of the enclosed scatterer is 0.1 to 0.2 [mu] m, and the number of loaded scatterers is 10 to 50 per cm. 5. A transparent plate having regular or random projections formed on one side of the surface of a waveguide-type optical device is adhered to the projection surface, and scattering caused by leaked light of a light wave propagating in the waveguide-type optical device. A method for evaluating operating characteristics of a waveguide-type optical device, characterized in that a light distribution is photographed from outside, and the obtained image data is subjected to image processing to visualize the behavior of light waves in the waveguide-type optical device. 6. The distance between the projections is 100 μm to 1 mm.
6. The method for evaluating operating characteristics of a waveguide type optical device according to claim 5, wherein