JP2004163257A - Method for guiding light to optical waveguide and optical waveguide spectrometric apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for easily guiding light to an optical waveguide at low costs and to provide an optical waveguide spectrometric apparatus capable of easily performing measurement at low costs. <P>SOLUTION: In the method for guiding light to the optical waveguide, the tip (13a) of the optical waveguide (13) for light guidance for guiding light emitted from a light source into an optical waveguide core (11) is inserted in a droplet (12) provided in such a way as to be in contact with the optical waveguide core (11), and the light is guided into the optical waveguide core (11) via the droplet (12). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for introducing light into an optical waveguide and an optical waveguide spectrometer using the same. More specifically, the present invention relates to a method for introducing light into an optical waveguide using small droplets and an optical waveguide spectrometer using the method.
[0002]
[Prior art]
In a spectrometer using an optical waveguide, it is necessary to introduce light serving as probe light into the core of an extremely thin optical waveguide.
Conventionally, in order to introduce light into such a thin layer, a prism having a high refractive index called a coupling prism has been used, or grooves or patterns serving as diffraction gratings (gratings) have been processed or guided on the core surface. It has been necessary to polish light by polishing the end face of the waveguide core so that light can be incident thereon and to process the waveguide itself (for example, see Patent Documents 1 to 3).
[0003]
A light introducing method using a coupling prism will be described with reference to FIG. FIG. 7 is a schematic diagram of a conventional light introducing method using a coupling prism. A coupling prism 72 is arranged so as to be in contact with the optical waveguide core 71, and a coupling liquid 74 is applied between the optical waveguide core 71 and the coupling prism 72. Light emitted from the light source and propagated by the optical fiber 73 is condensed by the condensing lens 75 and introduced into the optical waveguide core 71 via the incident light side coupling prism 72.
[0004]
However, coupling prisms are expensive and fragile, requiring careful use. Further, it is necessary to use a coupling liquid between the coupling prism and the optical waveguide, and there is a problem when the coupling liquid evaporates. In addition, there is a problem that light is absorbed by the coupling prism and the coupling liquid, and measurement in the ultraviolet region is difficult.
[0005]
In the case of using a grating, it is necessary to process the grating on the surface in advance, and a relatively sophisticated technique such as etching is required, so that the processing cost is high. In addition, it has a strong wavelength dependency, and it is difficult to introduce white light, which is important in spectral analysis. When light is incident from the end face of the waveguide, precision processing of the end face is required, so that the processing cost is high. Further, in order to allow light to pass through to the end face, it is necessary to make the light pass through the entire waveguide, which may limit the use of the waveguide.
As described above, the conventional technology has some problems such as ease of use, cost, and wavelength dependency.
[0006]
In a system using an optical fiber as an optical waveguide for introducing light emitted from a light source into an optical waveguide core, it is necessary to condense the light from the optical fiber to an incident point of a cutting prism by a lens or the like. This is disadvantageous in terms of miniaturization and cost of the apparatus.
[0007]
[Patent Document 1]
Patent No. 2802361 [Patent Document 2]
Patent No. 2807777 [Patent Document 3]
Patent No. 3041408 specification
[Problems to be solved by the invention]
An object of the present invention is to provide a method for introducing light into an optical waveguide simply and at low cost. Another object of the present invention is to provide an optical waveguide spectrometer that can perform measurement easily and at low cost.
[0009]
[Means for Solving the Problems]
The present inventors have conducted intensive studies, and as a result, the droplet provided to be in contact with the optical waveguide core has a respective contact angle according to the wettability of the liquid and the interface, but the contact angle is a specific contact angle When in the range, the droplets have been found to work similarly to the coupling prism. The present invention has been made based on such findings.
[0010]
That is, the present invention
(1) The tip of a light introducing optical waveguide for introducing light emitted from a light source into the optical waveguide core is inserted into a droplet provided in contact with the optical waveguide core, and the optical waveguide core is inserted through the droplet. A method of introducing light into an optical waveguide, which comprises introducing light into the inside,
(2) The method for introducing light into an optical waveguide according to the above item (1), wherein the contact angle between the droplet and the optical waveguide core is 20 ° or more and less than 180 ° or 180 °.
(3) The method for introducing light into an optical waveguide according to item (2), wherein the droplet is a droplet of glycerin, a high-refractive-index liquid, a high-concentration salt solution, water, or oil.
(4) An optical waveguide spectral measurement method using the method for introducing light into an optical waveguide according to any one of (1) to (3),
(5) A method for illuminating a microscope using the method for introducing light into an optical waveguide according to any one of (1) to (3), and (6) a light guide having a contact surface with a sample. A waveguide core, a droplet provided so as to be in contact with the optical waveguide core, a light guiding optical waveguide for introducing light emitted from a light source into the optical waveguide core through the droplet, and the optical waveguide core. An object of the present invention is to provide an optical waveguide spectrometer for use in the method according to the above mode (4), further comprising a sample measuring section comprising a light emitting section for emitting light that has been subjected to total internal reflection.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
According to the present invention, as means for introducing light into the optical waveguide core, a droplet is used without using a conventional coupling prism. The method of introducing light via a droplet according to the present invention will be described with reference to FIG. FIG. 1 is a schematic view of a method for introducing light through a droplet according to the present invention. The droplet 12 is arranged so as to be in contact with the optical waveguide core 11, and the tip 13 a of the optical fiber 13 is inserted into the droplet 12. The light emitted from the light source propagates through the optical fiber 13 and is introduced from the optical fiber 13 into the optical waveguide core 11 via the droplet 12.
According to the present invention, there is no need to use an expensive and fragile coupling prism or to process the optical waveguide core. In addition, the use of a liquid droplet makes it possible to directly insert a light introducing optical waveguide (such as an optical fiber) for introducing light emitted from a light source into the optical waveguide core into the liquid droplet, and in particular, to collect light. It is possible to collect light at the point of introduction without using a system. Therefore, light can be easily introduced into the optical waveguide core at low cost, and the size of the device can be reduced.
[0012]
2 and 3 show a preferred embodiment of the present invention. FIG. 2 is a perspective view showing one embodiment of a spectrometer using an optical waveguide. FIG. 3 is a schematic diagram showing one embodiment of a spectrometer using an optical waveguide.
The device is for introducing light emitted from the optical waveguide cores 21 and 31, the liquid droplets 22 and 32, the support substrates 23 and 33, the silicon rubber sheets 24 and 34, and the light source 35 into the optical waveguide cores 21 and 31. It has a sample measuring section composed of optical waveguides 26 and 36, sample cells 27 and 37, and light emitting sections 28 and 38 for emitting light that has been repeatedly subjected to total reflection in the optical waveguide cores 21 and 31.
[0013]
A preferred embodiment of the optical waveguide spectrometer of the present invention will be described with reference to FIG.
In the device, first, a silicon rubber sheet 24 is disposed on a support substrate 23, and the optical waveguide core 21 is disposed on the silicon rubber sheet 24. The sample in the sample cell 27 is placed in contact with the optical waveguide core 21. The droplet 22 is arranged so as to be in contact with the optical waveguide core 21, and the tip 22 a of the light introducing optical waveguide 26 for introducing the light emitted from the light source into the optical waveguide core 21 is inserted into the droplet 22. .
[0014]
The thickness of the optical waveguide core 21 is preferably 1 μm to 1 mm, more preferably 2 μm to 0.5 mm, and still more preferably 10 μm to 0.2 mm. The material of the optical waveguide core 21 may be any material that is transparent and optically stable, such as soda glass, quartz, plastic, and sapphire. The light introduced into the optical waveguide core 21 travels while being totally reflected in the optical waveguide core 21.
[0015]
A light emitting section 28 is provided at an end of the optical waveguide core 21. Note that light is internally reflected within a certain reflection angle range and reaches the opposite end face, and at that time there is light that happens to be facing upward or downward, and the emitted light is as shown in FIG. Divided up and down. This corresponds to those having the number of reflections of 2n and 2n + 1.
[0016]
The support substrate 23 is not particularly necessary when the optical waveguide core 21 itself has sufficient strength, but is preferably used because it functions as a so-called clad. When used, the thickness of the support substrate 23 is preferably 10 mm or less, more preferably 0.1 to 2 mm. Although the size is not particularly limited, for example, an outer shape having a length of 5 to 200 mm and a width of 1 to 30 mm, preferably an outer shape of a length of 30 to 75 mm and a width of 10 to 25 mm can be used.
Further, it is preferable to use a silicon rubber sheet 24. The silicon rubber sheet 24 plays a role in preventing the optical waveguide core 21 from directly adhering to the support substrate 23 or another object, thereby preventing loss of light. At the same time, the optical waveguide core 21 also serves to fix the optical waveguide core 21 from slipping and changing its position.
[0017]
The droplet 22 preferably has a contact angle with the optical waveguide core 21 of less than 180 °, more preferably 150 ° or less. Here, the lower limit of the contact angle is not particularly limited, but can be appropriately determined within a range for the purpose of introducing light into the optical waveguide core 21 through the droplet 22. It is preferably at least 20 °, more preferably at least 30 °.
Specifically, the droplet 22 is preferably a droplet of glycerin, a high-refractive-index liquid, a high-concentration salt solution, a high-concentration saccharide solution, water, oil, or the like. Examples of the high-refractive index liquid include dichloromethane and dibromonaphthalene, and examples of the high-concentration salt solution include a 50% by mass solution of potassium carbonate and a 40% by mass solution of potassium iodide. For example, a 50% by mass sucrose solution and the like can be mentioned.
The diameter of the droplet 22 is preferably 0.05 to 10 mm, more preferably 0.2 to 3 mm.
[0018]
The sample cell 27 can use glass, quartz, polymethyl methacrylate (PMMA), or the like. The thickness is not particularly limited, but is, for example, about 1 to 5 mm. The smaller the sample cell, the smaller the size of the sample, which is preferable. Therefore, the size is not particularly limited. For example, the outer shape is about 5 cm in length, about 3 cm in width, about 1.5 cm in height, and the inner method is about 4 cm in length, about 2 cm in width, and about 1 cm in depth. can do. However, the depth of the inner method is preferably 0.1 mm or more.
[0019]
In the present invention, an incandescent lamp, a light emitting diode, a laser, a diode laser, or the like is used as a light source. When measuring a spectrum or observing a change in color tone, it is preferable to use white light. In this case, white light means light having a certain wavelength width, and does not mean light of white color. By using white light, it is not necessary to use an expensive laser, and the apparatus is simple and inexpensive. In the present invention, ultraviolet light can be used, and measurement in the ultraviolet region is possible.
[0020]
As the light introducing optical waveguide 26 for introducing the light emitted from the light source into the optical waveguide core 21, for example, an optical fiber can be used.
[0021]
The sample to be measured in the present invention may be in any state of gas, liquid or solid. However, the measurement sample needs to be in contact with the optical waveguide core as described later.
That is, by applying the light introduction method of the present invention, by measuring the refractive index of a fluid such as a solution or a gas in contact with the optical waveguide core, the characteristics of the sample, for example, the substance concentration can be measured.
In addition, the surface of the optical waveguide core is coated with a substance that easily binds to a specific substance by physical adsorption or chemical bonding, and a small effective refractive index change caused by the specific substance binding to the surface is detected to detect the surface thin film. It is also possible to measure the properties of the substance and the adsorbed substance, for example, the thickness and the substance concentration.
[0022]
A preferred embodiment of the optical waveguide spectroscopic measurement method of the present invention will be described with reference to FIG.
First, a measurement sample is set in the sample cell 37. The measurement sample is in contact with the surface of the optical waveguide core 31.
Next, the droplet 32 is provided so as to be in contact with the optical waveguide core 31, and the tip 36 a of the optical fiber 36 is inserted into the droplet 32.
Light emitted from the white light source 35 propagates through the optical fiber 36 and is introduced into the optical waveguide core 31 via the droplet 32. The light introduced into the optical waveguide core 31 repeats total reflection and is emitted from the light emitting portion 38 at the end of the optical waveguide core 31. The emitted light is sent to the detector through the light receiving lens 39, and the light intensity is measured. I do. The intensity of the emitted light is measured by a detector and recorded by a recorder. The light intensity can be measured by a conventional method, for example, by using an optical power meter using a photodiode.
Note that it is preferable to use an optical fiber between the white light source 35 and the droplet 32 and between the light receiving lens 39 and the detector. By using this optical fiber, the distance and angle between the light emitting portion and the lens can be easily and finely adjusted.
From the intensity of the emitted light, the change in the refractive index of the sample in contact with the optical waveguide core 31 can be measured with high sensitivity.
[0023]
The light introduction method of the present invention can be used when observing a phenomenon at an interface such as adsorption, performing high-sensitivity analysis using an antigen-antibody reaction or the like using an optical waveguide. That is, the optical waveguide spectrometer of the present invention can analyze the interface, the vicinity of the core, or the core itself by utilizing the absorption and the fluorescent action of light propagating in the optical waveguide core. It can be used as a device and a biological material measuring device.
In addition, the light introduction method of the present invention includes evaluation of thin films, study of pigments such as paints, dyes, and coloring agents, evaluation of surface modification techniques such as etching, solar cells, catalytic reactions, medical analysis, environmental analysis, gas sensors, and surface treatment. It can be applied in fields such as sensors.
[0024]
The light introduction method of the present invention can also be applied to illumination of a microscope. This will be described with reference to FIG. FIG. 4 is a schematic diagram showing one embodiment in which the light introduction method of the present invention is applied to illumination of a microscope.
The apparatus includes an optical waveguide core 41, a droplet 42, a support substrate 43, a silicon rubber sheet 44, a light introduction optical waveguide 46 for introducing light emitted from a light source 45 into the optical waveguide core 41, a sample cell 47, and an optical waveguide. It comprises a microscope 48 arranged above the waveguide core 41.
Light was introduced into the optical waveguide core 41 using the droplet 42, and the evanescent wave generated on the surface of the optical waveguide core 41 was excited by scattered light scattered by a sample disposed on the surface of the optical waveguide core 41 or by evanescent wave. The fluorescence (phosphorescence) of the sample is observed by a microscope observation device 48 arranged above or below the optical waveguide core 41.
The advantage of this method is that the fluorescent lighting device can be made very simple and dark field illumination can be made easily.
[0025]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.
As shown in the schematic diagrams of FIGS. 1 and 2, a thin film glass having a thickness of 50 μm cut into 76 mm × 26 mm is used as an optical waveguide, and a glycerin droplet having a diameter of 1 mm is placed thereon. An optical fiber for guiding light from a light source was inserted, and light was introduced into the optical waveguide core. The light propagating in the optical waveguide core was emitted from a light emitting portion on the end face of the optical waveguide, and was condensed by a light receiving lens and then guided to a photodetector. FIG. 5 shows the light propagation loss at this time. FIG. 5 is a graph showing light propagation loss in the TE mode and the TM mode.
From the results shown in FIG. 5, it was found that both the TE mode and the TM mode have a small light propagation loss, and the present invention can be used without any problem. Specifically, it has been found that there is no concern that the use of the droplets unnecessarily widens the reflection angle and increases the light propagation loss.
[0026]
Also, a 20 nmol aqueous solution of hemoglobin was put into the sample cell, and light was similarly introduced into the optical waveguide core. FIG. 6 shows the light absorption spectrum at this time. FIG. 6 is a graph showing a measurement result of a light absorption spectrum of a 20 nmol aqueous solution of hemoglobin. In FIG. 6, a dotted line represents actual measurement data, and a solid line represents an average (smoothing) of the actual measurement data.
From the results shown in FIG. 6, it was found that the light absorption spectrum of the diluted hemoglobin solution can be measured without any problem. Thus, it has been found that high-sensitivity measurement is possible as in the case where a conventional prism is used or light is incident from the end face of the optical waveguide core.
[0027]
【The invention's effect】
According to the method for introducing light into an optical waveguide of the present invention, light can be introduced into an optical waveguide simply and at low cost. In addition, the optical waveguide spectrometer of the present invention not only does not require an expensive and fragile coupling prism, but also eliminates the need for precise processing of the optical waveguide core, which greatly facilitates the measurement and makes the optical waveguide core as an optical waveguide core. Inexpensive thin-film glass obtained by cutting rectangular glass can be used, and cost reduction can be realized. In addition, the use of a liquid droplet makes it possible to directly insert a light introducing optical waveguide (such as an optical fiber) for introducing light emitted from a light source into the optical waveguide core into the liquid droplet. It is possible to collect light at the point of introduction without using a system. Further, since the present invention can be used for excitation of fluorescence using an optical waveguide, measurement in the ultraviolet region, which was difficult with a method using a conventional coupling prism, is also possible.
[0028]
The light introduction method of the present invention can be used when observing phenomena at an interface such as adsorption, performing high-sensitivity analysis using an antigen-antibody reaction or the like using an optical waveguide, and evaluating thin films, paints, dyes, and the like. It can be applied in the fields of research on dyes such as color formers, evaluation of surface modification technologies such as etching, solar cells, catalytic reactions, medical analysis, environmental analysis, gas sensors, surface sensors, and the like.
[Brief description of the drawings]
FIG. 1 is a schematic view of a method for introducing light through a droplet according to the present invention.
FIG. 2 is a perspective view showing one embodiment of a spectrometer using an optical waveguide.
FIG. 3 is a schematic view showing one embodiment of a spectrometer using an optical waveguide.
FIG. 4 is a schematic view showing an embodiment in which the light introducing method of the present invention is applied to illumination of a microscope.
FIG. 5 is a graph showing light propagation loss in a TE mode and a TM mode.
FIG. 6 is a graph showing a measurement result of a light absorption spectrum of a 20 nmol aqueous solution of hemoglobin.
FIG. 7 is a schematic diagram of a conventional light introducing method using a coupling prism.
[Explanation of symbols]
11, 21, 31, 41, 71 Optical waveguide cores 12, 22, 32, 42 Droplets 13, 26, 36, 43, 73 Optical waveguide for optical introduction (optical fiber)
13a, 26a, 36a, 46a Tips 28, 38 of light guide for light introduction Light outgoing part 48 Microscopic observation device 72 Coupling prism 74 Coupling liquid 75 Condensing lens

Claims (6)

The tip of a light-introducing optical waveguide that introduces light emitted from a light source into the optical waveguide core is inserted into a droplet provided in contact with the optical waveguide core, and light enters the optical waveguide core through the droplet. A method for introducing light into an optical waveguide, characterized by introducing light. 2. The method for introducing light into an optical waveguide according to claim 1, wherein the contact angle between the droplet and the optical waveguide core is 150 [deg.] Or less. The method for introducing light into an optical waveguide according to claim 2, wherein the droplet is a droplet of glycerin, a high refractive index liquid, a high concentration salt solution, water, or oil. An optical waveguide spectral measurement method using the method for introducing light into an optical waveguide according to claim 1. A method for illuminating a microscope, comprising using the method for introducing light into an optical waveguide according to claim 1. An optical waveguide core having a contact surface with a sample, a droplet provided so as to be in contact with the optical waveguide core, and a light guiding light guide for introducing light emitted from a light source into the optical waveguide core through the droplet. 5. An optical waveguide spectrometer for use in the method according to claim 4, further comprising a sample measuring section comprising a wave path and a light emitting section for emitting light that has been subjected to total reflection inside the optical waveguide core.

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