JP2007225826A - Deflection-type optical path switching method and optical path switching device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical path switching device in which the extinction ratio is high and one input/multiple outputs is feasible, and to provide an optical path switching method. <P>SOLUTION: The optical path switching device has a signal light source to emit signal light 28; a control light source to emit control light 29, of which the wavelength is different from that of the signal light 28; a thermal lens forming optical element containing a light absorption layer 34 which transmits the signal light 28 and selectively absorbs the control light 29; and a condensing means which condenses the control light 29 and the signal light 28 in the light absorption layer 34 with convergent points made different in a direction vertical to the optical axis, wherein the thermal lens forming optical element changes an advancing direction of the signal light 28 by the action of the thermal lens reversibly formed due to temperature rise, caused by the control light 29 and the signal light 28 which converge in the light-advancing directions on an incident plane of the light absorption layer or in the vicinity thereof and subsequently diffuse, and generated in a region of the light absorption layer where the control light 29 is absorbed and in its peripheral region. The optical path switching device is equipped with an extraction means for separating and extracting a signal light 30 with the unchanged advancing direction and signal light 31, with the changed advancing direction according to the advancing directions. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a deflection optical path switching device and an optical path switching method used in the fields of optical communication and optical information processing.

  In order to cope with the explosive increase in network traffic accompanying the spread of the Internet and intranets within a company / home, there is a need for an optical path switching device (optical switch) that does not pass through an electrical signal, that is, an optical-optical direct switch. As an apparatus / method for switching an optical path, that is, an optical fiber, an optical waveguide, or a path of light propagating in space, for example, a space division type that switches an optical path in or between optical waveguides, and a plurality of multiplexed Wavelength-division multiplexing type that switches light of wavelength by dividing it into optical paths according to wavelength, time-division multiplexing type that switches the optical path of light that is time-division multiplexed every certain time, mirror or shutter for the optical path of light propagating in space There are known methods such as a free space type that spatially divides and synthesizes. Each of these methods can be multiplexed or used in combination.

  The space division type optical switch uses a directional coupler, makes a copy of an optical signal with an optical branching device, turns on and off the light with a gate element, and guides the waveguide at the intersection of the intersection or Y branch. Proposals have been made to transmit or reflect light propagating through a waveguide by changing the refractive index, but it is still in the research and development stage. It is said that a thermooptic effect by heating an electric heater is used to change the refractive index of the waveguide of a Mach-Zehnder interferometer type optical waveguide switch, but the response speed is about 1 millisecond. Not only is it slow, it has the disadvantage that an electrical signal must be used to operate the optical switch.

  The free space type optical switch includes a micro electro mechanical system (abbreviated as MEMS), an exciton absorption / reflection switch (abbreviated as Exciton Absorption Reflection Switch; EARS switch), and a multistage. Beam shifter type optical switches, hologram type optical switches, liquid crystal switches, and the like have been studied. These have problems such as the presence of mechanically movable parts and polarization dependence, and it cannot be said that they are still in practical use.

  On the other hand, an all-optical thermal lens forming optical element or light that directly modulates the intensity or frequency of light with light using the change in transmittance or refractive index caused by irradiating the thermal lens forming optical element with light. Research on control methods is actively conducted. The present inventors have used an organic nanoparticle photothermal lens forming element (see Non-Patent Document 1) in which an organic dye aggregate is dispersed in a polymer matrix with the aim of developing a new information processing technique using an all-optical type optical element. I have studied light control systems. Currently, the control light (660 nm and 980 nm) is used to modulate the signal light (780 nm and 1550 nm). The control light and the signal light are coaxially and confocally incident and formed transiently by absorption of the control light. An element with the principle of operation that signal light is refracted by a thermal lens is developed, and a high-speed response of about 20 nanoseconds is achieved. Forming the thermal lens by irradiating control light to a thermal lens forming optical element made of a photoresponsive composition and reversibly changing the transmittance and / or refractive index of signal light in a wavelength band different from the control light An optical control method for performing intensity modulation and / or light flux density modulation of the signal light transmitted through an optical element, wherein the control light and the signal light are converged and irradiated to the thermal lens forming optical element, and Adjusting the optical paths of the control light and the signal light so that regions having the highest photon density in the vicinity (beam waist) of the respective focal points of the control light and the signal light overlap each other in the thermal lens forming optical element. A light control method is disclosed (see Patent Document 1 to Patent Document 7). The thermal lens forming optical element made of a photoresponsive composition is irradiated with control light and signal light having different wavelengths, and the wavelength of the control light is selected from a wavelength band absorbed by the photoresponsive composition, A signal light that reversibly forms a thermal lens based on a density change distribution caused by a temperature rise generated in a region where the photoresponsive composition absorbs the control light and a peripheral region thereof, and transmits the thermal lens. A light control method for performing intensity modulation and / or light beam density modulation is disclosed (see Patent Document 8). For example, a dye / resin film or a dye solution film is used as the thermal lens forming optical element, and the response time of the signal light with respect to the control light irradiation at the control light power of 2 to 25 mW is described as less than 2 microseconds. (See Patent Document 8). These methods are excellent in controlling light with light and can respond at high speed. However, there is a problem in that the shape of the light beam formed at the time of control light irradiation becomes a donut shape, so that the coupling efficiency to the optical fiber is small. .

  Here, the thermal lens effect means that molecules that absorb light in the central part of light absorption convert light into heat, and this heat is propagated to the surroundings, resulting in a temperature distribution. The refractive index of the light changes such that the refractive index changes spherically from the light absorption center to the outside, resulting in a distribution in which the refractive index at the light absorption center is low and the refractive index increases toward the outside, which functions like a concave lens. Indicates. The thermal lens effect has been used for a long time in the field of spectroscopic analysis, and now it is possible to perform ultrasensitive spectroscopic analysis that detects light absorption by a single molecule (Non-Patent Document 2 and Non-Patent Document). 3).

  As a method of deflecting an optical path by using a thermal lens effect or a refractive index change due to heat, a method of deflecting light by applying heat to a medium with a heating resistor to generate a refractive index distribution in the medium is disclosed ( (See Patent Document 9). However, the above-described method inherently has a problem of “spreading of heat” because heat is generated by the heating resistor and the medium is heated by heat conduction. That is, due to the spread of heat, a fine thermal gradient cannot be given within a wide area, and it is difficult to obtain a desired refractive index distribution. Further, even if the photolithography technique used in the semiconductor integrated circuit is adopted for the fine processing of the heating resistor, there is a certain limit in practice, and the element must be enlarged. As the element becomes larger, the optical system becomes more complicated and larger. In addition, since the medium is heated by heat generation by generating heat with a heat generating resistor, the response is slow and the problem that the frequency of refractive index change cannot be increased is an essential problem.

  The thermal lens forming optical element made of a photoresponsive composition and at least an intensity distribution adjusting means for irradiating the thermal lens forming optical element with a wedge-shaped light intensity distribution. A deflecting element using a thermal lens forming optical element is disclosed, wherein a refractive index distribution is formed in a lens forming optical element, and signal light having a wavelength different from that of the control light is deflected by the refractive index distribution. (See Patent Document 10). This method is excellent in that the light is controlled by light, but the loss of control light is large due to the intensity distribution adjusting means for irradiating the thermal lens forming optical element with a wedge-shaped light intensity distribution. In addition, it is difficult to freely form a wedge-shaped light intensity distribution, and there is a problem that the optical path switching direction cannot be freely set.

  In addition, there has been proposed a method for deflecting laser light by changing the refractive index of the material irradiated with laser light by irradiating the laser light to heat the material (see Patent Document 11 and Patent Document 12). In both methods, the beam diameter is large, and the deflection of the laser beam is very small unless a large power is input. The method of Patent Document 11 is a method in which the irradiation light itself is deflected by heating the irradiation light. When this method is used for light deflection, the irradiation light is absorbed in order to change the refractive index by heating, so that the light transmitted through the substance is greatly reduced in principle.

  The method of Patent Document 12 is an optical switch that takes no electrical or mechanical means, changes the refractive index of the switch material by irradiation of a control beam, and changes the optical path of the signal beam. However, even in this case, neither the control beam nor the signal beam is collected using a lens, and the laser beam that causes the refractive index change requires a large power. In addition, the device becomes large. In addition, since it is not possible to take a means for the refractive change region to expand as the beam progresses as in the present proposal, the deflection angle cannot be increased too much.

  In both Patent Document 11 and Patent Document 12, as described in this proposal, a means for separating and condensing non-deflected light and deflected light, and an optical fiber as a light detecting means, and using the optical fiber for the non-deflected light and deflected light to the optical fiber. No means or the like for performing high-accuracy separation between unpolarized light and deflected light by utilizing the difference in incident angle is not described.

Takashi Hiraga, Norio Tanaka, Kikuko Hayami, Tetsuro Moriya, Creation of dye aggregates / aggregates, structural evaluation, photophysical properties, "Vocabulary of Electronic Technology Research Institute", published by Electronic Technology Research Institute, Ministry of International Trade and Industry 59, No. 2, pp. 29-49 (1994) Takao Fujiwara, Keiichiro Fuwa, Takayoshi Kobayashi, Laser-induced thermal lens effect and its application to colorimetric method, "Chemical", Kagaku Dojin, Vol. 36, No. 6, pp. 432-438 (1981) Takehiko Kitamori, Goro Sawada, Photothermal Conversion Spectroscopy, “Bunseki”, published by the Japan Society for Analytical Chemistry, March 1994, pp. 178-187 JP-A-8-286220 JP-A-8-320535 JP-A-8-320536 Japanese Patent Laid-Open No. 9-329816 Japanese Patent Laid-Open No. 10-90733 JP-A-10-90734 Japanese Patent Laid-Open No. 10-148852 Japanese Patent Laid-Open No. 10-148853 Japanese Patent Laid-Open No. 60-14221 JP-A-11-194373 US Pat. No. 4,776,677 US Pat. No. 4,585,301

  The present invention makes it possible to deflect light without using complicated and expensive electric circuits or mechanically moving parts, so that the light of signal light is extremely low in failure, highly durable, and extremely low in polarization dependence. The optical path can be switched while the intensity distribution is small and the energy distribution in the cross section of the signal light is diffractive optically easy to converge (for example, Gaussian distribution), and optical coupling to the optical fiber in the subsequent stage can be performed with high efficiency. An object of the present invention is to provide a deflection optical path switching device and an optical path switching method capable of one input and multiple outputs with a high extinction ratio.

  The present invention has the following features.

  (1) Control light and signal light are incident on a light absorption layer in a thermal lens forming optical element including at least a light absorption layer, and the presence or absence of irradiation of the control light is selected according to desired information, and the control The light and the signal light are irradiated so as to converge in the light absorption layer, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are different in the direction perpendicular to the optical axis, The wavelength of the control light is different from the wavelength of the signal light, the wavelength of the control light is selected from a wavelength band that is absorbed by the light absorption layer, and the wavelength of the signal light is from a wavelength band that is not absorbed by the light absorption layer. The control light and the signal light are converged at the incident surface of the light absorption layer or in the vicinity thereof in the light traveling direction and then diffused to thereby diffuse the control light in the light absorption layer and The temperature that occurs in the surrounding area Due to the thermal lens formed reversibly due to the rise, the refractive index is changed to change the traveling direction of the signal light, and the control light is not irradiated with the control light, and the control light is not changed. The signal light whose traveling direction is changed by being irradiated is an optical path switching method that is separated and extracted according to each traveling direction.

  (2) The optical path switching method according to (1), wherein the control light and the signal light are converged or condensed on an incident surface of the light absorption layer or in the light absorption layer in a light traveling direction. It is.

  (3) The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light are separated by a mirror (1) Or it is the optical path switching method as described in (2).

  (4) The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light are collected by the lens and incident on the detection means (1) The optical path switching method according to any one of (3) to (3).

  (5) The optical path switching method according to (4), wherein the detection means is an optical fiber that receives signal light collected by a lens.

  (6) The optical path switching method according to (5), wherein the optical axes of the signal light incident on the optical fiber collected by the lens have an angle that is at least twice the maximum incident angle of propagation of the optical fiber. is there.

  (7) A plurality of control lights are applied to the light absorption layer according to the number of optical path switches, the traveling direction of the signal light is changed by a combination of the plurality of control lights, and a plurality of signals according to the number of optical path switches The optical path switching method according to any one of (1) to (6), wherein light is extracted.

  (8) A signal light source that emits signal light having one or more wavelengths, a control light source that emits control light having a wavelength different from that of the signal light, and the signal light is transmitted, and the control light is selectively used. A thermal lens forming optical element including a light absorption layer that absorbs light, and a condensing means for condensing the control light and the signal light on the light absorption layer with different convergence points in a direction perpendicular to the optical axis. And the thermal lens forming optical element diffuses the control light and the signal light after converging at or near the incident surface of the light absorption layer in the light traveling direction. The thermal lens formed reversibly due to the temperature rise occurring in the region where the control light is absorbed in the layer and the surrounding region, the refractive index is changed, the traveling direction of the signal light is changed, Control light is not irradiated and the direction of travel does not change A signal light Tsu, and said control light irradiated signal light traveling direction is changed, an optical path switching device having a take-out means for taking out and separated respectively in response to each direction of travel.

  (9) The light condensing unit is the optical path switching device according to (8), which converges or condenses in an incident surface of the light absorption layer or in the light absorption layer in a light traveling direction.

  (10) The optical path switching device according to (8) or (9), wherein the extraction means is a mirror.

  (11) Further, there is provided a detection means in which the signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light are collected and incident by a lens. The optical path switching device according to any one of (8) to (10) above.

  (12) The optical path switching device according to (11), wherein the detection unit is an optical fiber.

  (13) The optical path switching device according to (12), wherein the optical axes of the signal light incident on the optical fiber collected by the lens have an angle that is at least twice as large as the maximum propagating angle of propagation of the optical fiber. is there.

  (14) The control light source emits a plurality of control lights of two or more according to the number of optical path switching, and the condensing means sets a convergence point of the plurality of control lights in a direction perpendicular to the optical axis. The optical path switching device according to any one of (8) to (13), wherein the optical path switching device is caused to converge or condense on the light absorption layer.

  According to the present invention, the light power density can be locally increased by condensing the control light and irradiating the light absorption layer, and the local temperature of the light absorption layer can be increased with low power. The refractive index of the part and the vicinity can be changed. In addition, by collecting the signal light and making it incident on the light absorption layer near the irradiation position of the control light, the change in the refractive index due to the control light can be used efficiently, and the optical path of the signal light can be switched.

  Furthermore, by converging the control light near the incident surface of the light absorption layer and making it incident, the control light diffuses from the condensing point in the light absorption layer, so that the region where the refractive index changes is expanded and the signal light is deflected. It becomes possible to enlarge. In addition, since the signal light whose optical path has been switched is output from the thermal lens forming optical element in the same shape as the beam cross section before condensing, it is practical even when the signal light whose optical path has been switched is subsequently condensed. Is expensive.

  Furthermore, a plurality of control lights can be incident on the same light absorption layer, and one input can be switched to a plurality of different optical paths.

  In the present invention, the control light and the signal light can be condensed and the light condensing points can be brought close to each other, so that high-speed optical path switching can be performed.

  In addition, since a low-power semiconductor laser can be used, a small and inexpensive optical path switching device can be provided.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration example of a deflection optical path switching apparatus according to a first embodiment of the present invention. The deflection type optical path switching apparatus according to the first embodiment of the present invention includes a signal light incident terminal 1 that is a signal light source and a first light that makes the signal light substantially parallel light, as schematically illustrated in FIG. A collimating lens 2; a control light incident terminal 3 that is a control light source; a second collimating lens 4 that makes the control light substantially parallel; an optical mixer 5 that combines the signal light and the control light; The condensing lens 6 which is a condensing means for condensing the control light on the light absorption layer of the thermal lens forming optical element 7, the thermal lens forming optical element 7, and the light transmitted through the thermal lens forming optical element 7 are substantially parallel. The third collimating lens 8 to be light, the wavelength selective transmission filter 9, the first branch mirror 10 for branching the non-deflected light and the deflected light, and the non-deflected light are condensed on the first detector 12. Second condenser lens 11, first detector 12 for detecting non-deflected light, and deflection The has a third condenser lens 13 for condensing the second detector 14, and a second detector 14 for detecting the deflected light.

  Although not shown, signal light was incident on the signal light incident terminal 1 by an optical fiber. In this embodiment, the signal light wavelength is 1550 nm. The signal light may have any wavelength as long as it transmits the light absorption layer of the thermal lens forming optical element 7. In this embodiment, the signal light is incident through an optical fiber, but a laser that emits signal light may be directly installed at the signal light incident terminal 1.

  The material of the light absorbing layer, the wavelength band of the signal light, and the wavelength band of the control light in the thermal lens forming optical element used in the deflection optical path switching method and the optical path switching apparatus of the present invention are used as a combination thereof. Appropriate combinations can be selected and used according to. As a specific setting procedure, for example, first, the wavelength or wavelength band of signal light is determined according to the purpose of use, and a combination of the material of the light absorption layer film and the wavelength of control light that is optimal for controlling this is selected. It only has to be selected. Alternatively, after determining the combination of the wavelengths of the signal light and the control light according to the purpose of use, a material for the light absorption layer film suitable for this combination may be selected. For example, when an image or a character is to be directly displayed using signal light, visible light having a wavelength of 400 to 800 nm is used as signal light, infrared light having a wavelength of 980 nm is used as control light, and the light absorbing layer material is the above-described material. A material that transmits visible light having a wavelength and absorbs infrared light having the wavelength is used. In addition, for example, when light having a wavelength corresponding to the longest wavelength λ1 of the absorption maximum in the light absorption spectrum of the material of the light absorption layer to be used is used as control light, light having a wavelength longer than λ1 is preferably used as signal light. Can do. Specifically, when perylene is used as the material of the light absorption layer, the control light can be 405 nm, for example, and the signal light can be 540 nm, 660 nm, 780 nm, 830 nm, 980 nm, 1310 nm, or 1550 nm. When a copper phthalocyanine derivative is used as the material of the light absorption layer, the control light can be set to 650 nm, for example, and the signal light can be set to 690 nm, 780 nm, 830 nm, 980 nm, 1310 nm, or 1550 nm, for example.

  Although not shown, control light is incident on the control light incident terminal 3 by an optical fiber. In this embodiment, the control light wavelength is 980 nm. The control light may be any wavelength as long as it is absorbed by the light absorption layer of the thermal lens forming optical element 7. In the present embodiment, the control light is incident through an optical fiber, but a laser that emits control light may be directly installed at the control light incident terminal 3.

  As the first collimating lens 2, the second collimating lens 4, and the third collimating lens 8, aspherical lenses having a focal length of 8 mm were used. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller deflecting optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight.

  The optical mixer 5 is a dichroic mirror that transmits signal light and reflects control light. Of course, it goes without saying that a dichroic mirror in which the signal light is reflected and the control light is transmitted can be used by switching the positions of the signal light incident terminal and the control light incident terminal.

  As the condenser lens 6, an aspherical lens having a focal length of 8 mm was used. Needless to say, the focal length need not be 8 mm, and a shorter focal length may be used in order to obtain a smaller deflecting optical path switching device. Further, although it is not necessary to use an aspheric lens, an aspheric lens is used to reduce the size and weight.

  The signal light and the control light are converged by the condenser lens 6 on the incident surface of the light absorption layer or in the vicinity thereof in the light traveling direction. When the signal light and the control light are converged (condensed) at the same position in the vicinity of the incident surface of the light absorption layer, the signal light spreads in a donut shape. This situation is shown in FIG. When there is no control light, the signal light which was a round beam as shown in the photograph 1a of FIG. 14A is irradiated with the control light at the same place at the same time, as shown in the photograph 1b of FIG. 14B. become. It is considered that the light-absorbing layer incident surface has a clear and large donut shape. Therefore, in this embodiment, the light absorption layer is referred to as an incident surface where the donut shape is clear and large. Of course, in this embodiment, the signal light and the control light are separated from each other by about 25 to 50 μm at the position of the convergence (condensing), so that a donut shape is not formed, but the signal light and the control light are the same at the time of adjustment. Then, a donut shape is formed, and then the convergence (condensing) points of the signal light and the control light are separated. In addition, when the distance between the convergence points of the signal light and the control light is less than 25 μm, it does not become a round beam as shown in FIG. 14 but becomes a crescent moon beam. When the signal light of the crescent moon beam is subsequently condensed and incident on the optical fiber, the incident efficiency is reduced, which may impair practicality.

  Although the thermal lens forming optical element 7 has a configuration as shown in FIG. 6, in this embodiment, only the light absorption layer is shown for ease of explanation. In FIG. 6, the light absorption layer 34 of the thermal lens forming optical element 35 is used by sealing a pigment in a solvent in a glass container 36. As the dye soluble in the solvent, a known dye having absorption in the wavelength region of the control light to be used and having no absorption in the wavelength region of the signal light to be used can be used. The glass container 36 through which the laser beam 25 is transmitted has a glass thickness of about 500 μm, and the light absorption layer 34 has a thickness of 200 to 1000 μm. Specific examples of the dye include, for example, xanthene dyes such as rhodamine B, rhodamine 6G, eosin and phloxine B, acridine dyes such as acridine orange and acridine red, azo dyes such as ethyl red and methyl red, porphyrin dyes, Phthalocyanine dyes, cyanine dyes such as 3,3′-diethylthiacarbocyanine iodide, 3,3′-diethyloxadicarbocyanine iodide, triarylmethane dyes such as ethyl violet and Victoria Blue R, naphthoquinone A dye, an anthraquinone dye, a naphthalene tetracarboxylic acid diimide dye, a perylene tetracarboxylic acid diimide dye, or the like can be suitably used. Moreover, these pigment | dyes can be used individually or in mixture of 2 or more types. As the solvent, a solvent that dissolves at least the dye to be used can be used. However, the temperature (boiling point) of boiling without being thermally decomposed when the temperature rises during the formation of the thermal lens is 100 ° C. or higher, preferably 200. Those having a temperature of at least ° C, more preferably at least 300 ° C can be suitably used. Specifically, inorganic solvents such as sulfuric acid, halogenated aromatic hydrocarbons such as o-dichlorobenzene, aromatic substituted aliphatics such as 1-phenyl-1-xylylethane or 1-phenyl-1-ethylphenylethane Organic solvents such as hydrocarbons and nitrobenzene derivatives such as nitrobenzene can be suitably used.

  The wavelength selective transmission filter 9 is a dielectric filter that blocks control light that slightly passes through the thermal lens forming optical element 7 and transmits signal light. If the control light is absorbed by the thermal lens forming optical element 7 to the extent that there is no practical problem, the wavelength selective transmission filter 8 need not be used.

  When the control light is absorbed by the light absorption layer of the thermal lens forming optical element 7, the temperature of the light absorption layer rises and the refractive index changes. As the temperature increases, the refractive index generally changes in a decreasing direction. The intensity distribution of laser light emitted from a normal laser light source and laser light emitted from a normal laser light source and transmitted through an optical fiber is a Gaussian distribution. Further, the light obtained by condensing the laser light with a lens or the like has a Gaussian distribution. Therefore, in the refractive index distribution in the light absorption layer irradiated with the control light, the refractive index is the lowest on the optical axis of the control light, and the refractive index is less reduced around the control light. Further, since there is heat conduction, the refractive index changes even in a portion where light is not irradiated.

  FIG. 5 is a diagram illustrating a situation where the signal light is deflected. In order to simplify the explanation, in FIG. 5, light refraction due to the difference in refractive index between the light absorption layer and the medium around the light absorption layer is ignored. In FIG. 5, signal light 30 and control light 29 are irradiated on the light absorption layer 34 of the thermal lens forming optical element, and the signal light 30 transmitted through the thermal lens forming optical element when the control light is not irradiated. The signal light 31 transmitted through the thermal lens forming optical element when irradiated with light is shown. Further, a light intensity distribution 32 of the control light in the vicinity of the incident surface of the light absorption layer 34 of the thermal lens forming optical element and a light intensity distribution 33 in the vicinity of the emission surface of the light absorption layer 34 of the thermal lens forming optical element are shown. Has been.

  FIG. 5a schematically shows the optical path of the laser light when the laser light is not condensed, and FIG. 5b schematically shows the optical path of the laser light when the laser light is condensed as in this embodiment. The intensity distribution region of the laser beam when the laser beam is not condensed does not change between the vicinity of the incident surface and the exit surface of the light absorption layer. This means that the signal light passes through a region where the refractive index changes little as it travels through the light absorption layer 22. On the other hand, when the laser beam is condensed, the intensity distribution region of the laser beam is greatly changed near the incident surface and the exit surface of the light absorption layer, and the region is expanded near the exit surface. This means that the refractive index also gradually increases, and the signal light has an effect of deflecting more as it travels through the light absorption layer. Since the refractive index change changes substantially in proportion to the control light power, the refractive index change becomes smaller as the light absorption layer is advanced.

  In FIG. 5b, the signal light is also converged (condensed) on the incident surface of the light absorption layer 34 of the thermal lens forming optical element, but may be in the vicinity of the incident surface. In particular, the signal light may be converged (condensed) to the light exit surface side of the light absorption layer. Further, the signal light and the control light are made incident on the same surface in the light traveling direction, but they are not necessarily the same surface, and may be slightly shifted.

The deflection angle changes when the following conditions change.
1. 1. Position of light absorption layer of thermal lens forming optical element with respect to convergence (condensation) point of first condenser lens 6 for signal light and control light. 2. Control light power Control light position (distance perpendicular to the optical axis of signal light and control light at the condensing point of the first condenser lens 6)
4). 4. Thickness of light absorption layer of thermal lens forming optical element Control light wavelength and signal light wavelength.
6). In addition to this, the dye concentration of the light absorption layer also varies depending on the material of the light absorption layer, the convergence (condensation) angle of the control light and signal light to the light absorption layer, and the like.

  In this embodiment, the signal light 1550 nm is incident on the signal light incident terminal with a single-mode quartz optical fiber having a core diameter of 9.5 μm, and the control light 980 nm is incident on the control light incident terminal with a single-mode quartz optical fiber having a core diameter of 9.5 μm. The signal light and the control light are made to be substantially parallel light by the first collimating lens and the second collimating lens having a focal length of 8 mm, the light absorption layer has a thickness of 500 μm, and the transmittance of the light absorption layer at a wavelength of 1550 nm is 95%. It converged (condensed) with a lens having a focal length of 8 mm and was incident on a thermal lens forming optical element having a transmittance of 0.2% at 980 nm.

  FIG. 7 shows the light intensity distribution of the signal light measured by moving a photodetector having a slit opening in the in-plane direction perpendicular to the optical axis immediately before the branch mirror 10 of FIG. In FIG. 7, a line 38 (solid line connecting round points) is unpolarized light when the control light is not irradiated, and a line 39 (solid line connecting square points) is the deflection when the control light power is 7.8 mW. The light, line 40 (solid line connecting the dots) shows the light intensity distribution of the deflected light when the control light power of 12.9 mW is applied. In the case of the deflected light 39 irradiated with the control light power of 7.8 mW, it overlaps with the non-deflected light 38 at the bottom of the intensity distribution and is insufficiently separated from each other, but the control light power of 12.9 mW is not sufficient. The polarized light 40 when irradiated is separated from the non-polarized light 38. Therefore, the non-deflected light and the deflected light 40 when the control light power 12.9 mW is irradiated by the branch mirror 10 can be separated. In FIG. 7, the control light position (distance perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6) is 35 μm, and the control light and the signal light absorb light. The layer converged (condensed) at a position advanced by about 30 μm from the light incident surface of the layer, and the thickness of the light absorption layer was 500 μm.

  When the control light is not irradiated, the non-deflected light that has passed without being reflected by the branch mirror 10 is converged (condensed) to the photodetector 12 by the condensing lens 11 having a focal length of 8 mm, and the non-deflected light Is detected. FIG. 8 shows the relationship between the control light power and the deflection angle. As the control light power increases, the deflection angle increases. In FIG. 8, the control light position (distance perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6) is 35 μm, and the control light and the signal light are in the light absorption layer. The light was converged (condensed) at a position about 60 μm from the light incident surface. The deflected light when the control light power with sufficient intensity (in the example of FIG. 8 is 12.9 mW or more) is irradiated is reflected by the branch mirror 10 shown in FIG. Then, the light converges (condenses) on the light detector 14 and detects the deflected light. Although the focal lengths of the condensing lens 11 and the condensing lens 13 are 8 mm, the focal length need not be 8 mm. In the present embodiment, a 9.5 μm single-mode quartz optical fiber is installed at the photodetectors 12 and 14, the signal light is converged (condensed) on the optical fiber, and transmitted after the optical fiber is detected. . Of course, it goes without saying that a photodetector may be installed directly. Further, although the branching mirror 10 reflects the deflected light, it may be installed so that the non-deflected light is reflected and the deflected light passes.

The numerical aperture (hereinafter referred to as NA) of a 9.5 μm single mode quartz optical fiber is generally 0.1. The maximum incident angle θc that can propagate through an optical fiber with NA = 0.1 is given by the following equation and is about 5.7 degrees.
(Formula 1)
θc = Sin ⁻¹ (0.1) ≈5.7 degrees

  In the present embodiment, the third collimating lens 8 shown in FIG. 1, the condensing lens 11, and the condensing lens 13 have the same focal length of 8 mm, so that the deflection angle is not branched by the branch mirror 10. In this case, the angle is formed between the optical axis of the deflected light incident on the optical fiber and the optical axis of the non-deflected light. That is, when the control light power is 7.8 mW, it is about 6.7 degrees, when the control light power is 12.9 mW, it is about 10.1 degrees, and when the control light power is 18 mW, it is about 13.2 degrees. When the deflected light and the non-deflected light cannot be sufficiently branched by the branch mirror 10, the non-deflected light enters the deflected light detection optical fiber and the deflected light enters the non-deflected light detection optical fiber around this angle. . Since the signal light is also incident through a single-mode quartz optical fiber having a core diameter of 9.5 μm, the NA is 0.1, and the convergence (condensation) angle of the signal light itself is about 5.7 degrees. Therefore, the incident efficiency of the first photodetector 12 and the second photodetector 14 to the optical fiber is slightly deteriorated when the control light power is 7.8 mW, but signal light can be incident. However, the incidence of the signal light on the optical fibers of the first detector 12 and the second detector 14 is very small when the control light power is 12.9 mW and does not enter when the control light power is 18 mW. Become. Therefore, even if the degree of separation between the non-deflected light and the deflected light at the branch mirror 10 is somewhat worse, if the control light power is large and the deflection angle is large, the deflected light to the optical fiber of the first photodetector 12 And the non-deflected light are not incident on the optical fiber of the second photodetector 14, and the optical path can be switched with a large extinction ratio.

  FIG. 9 shows the incident position (referred to as “light absorption layer position”) and the deflection angle of the convergence (condensation) point of the signal light and control light to the light absorption layer 34 of the thermal lens forming optical element 7 shown in FIG. Shows the relationship. In FIG. 9, the position of the light absorption layer on the horizontal axis is the position of the light incident surface on the light absorption layer 34 of the thermal lens forming optical element 7 (position with respect to the convergence (condensing) point of the control light and signal light). Point 0 is the position of the convergence (condensing) point of the control light and signal light, which is the state of FIG. The minus direction is the light traveling direction, and the signal light and the control light converge (condense) in the light absorption layer 34 of the thermal lens forming optical element 7 at the plus position. The vertical axis represents the deflection angle. In FIG. 9, the control light power is about 12.9 mW, and the control light position (distance in the direction perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6). Is 35 μm, and the thickness of the light absorption layer is 500 μm. In the case of the condition of FIG. 9, the deflection angle is large when the position of the light absorption layer is about 40 μm or less, the incidence of the deflected light on the optical fiber of the first photodetector 12 and the optical fiber of the second photodetector 14. There will be no incidence of unpolarized light on the surface. Of course, as is apparent from FIG. 8, if the control light power is increased, the position of the light absorption layer may be made larger than 40 μm or about 100 μm.

  Further, even if the non-deflected light and the deflected light are not separated by the branch mirror 10, the non-deflected light and the deflected light can be separated at the position of the photodetector. FIG. 10 shows the incident position (that is, the light absorbing layer position), the unpolarized light, and the deflected light of the signal light and the control light on the light absorbing layer 34 of the thermal lens forming optical element shown in FIG. An example of the measurement data of the separation distance is shown. When the incident position on the light absorption layer is about 60 μm, the separation distance is close to 0, but when the position is shifted from this, the separation distance increases. In FIG. 10, the sign of the separation distance is defined such that the incident point of the signal light is the origin (that is, 0 point) and the deflection direction is positive. The large separation distance means that even if the non-deflected light and the deflected light at the branch mirror 10 are not sufficiently branched, the incident of the deflected light on the optical fiber of the first photodetector 12 shown in FIG. No unpolarized light is incident on the optical fiber of the second photodetector 14. This measurement was performed by moving a detector having a slit opening at the position of the first detector 12. In FIG. 10, the control light power is 15.4 mW, the thickness of the light absorption layer is 1000 μm, and the control light position (in the direction perpendicular to the optical axis of the signal light and the control light at the condensing point of the first condenser lens 6). ) Is 25 μm.

  In the present embodiment, as described above, the non-deflected light and the deflected light are detected by the photodetector. It is possible to detect with sufficient separation by separation at the photodetector position, etc., and to switch the optical path with high accuracy.

  FIG. 11 shows an example of the optical path switching data in the present embodiment. In FIG. 11, since there was no reliability of the value of 0.1 μW or less of the measuring instrument used for the measurement, the values of 0.1 μW or less were all set to 0.1 μW or less including the case of 0 μW, and the extinction ratio was In the calculation, all the cases of 0.1 μW or less are calculated as 0.1 μW. No. Except for the case of 7, the unpolarized light and the deflected light had an extinction ratio of 40 dB or more.

  The deflection angle varies depending on the control light wavelength and the signal light wavelength. The shorter the wavelength, the greater the deflection angle.

(Comparative Example 1)
In the first embodiment, the condensing lens 6 is not used, and the collimated signal light and control light are irradiated to the thermal lens forming optical element 7 without converging, and the third collimating lens 8 is not used. Except for this point, the same experiment as in the first embodiment was performed. However, when the control light power was about 18 mW, no deflection of the signal light was observed even when the control light was irradiated. Therefore, when the control light source is changed to Ti: cypher laser and further irradiated with high power control light (980 nm), the solvent of the dye solution in the thermal lens forming optical element is detected before the deflection of the signal light is detected. Started boiling and it was confirmed that it was difficult to deflect the signal light. Furthermore, the power of the control light was lowered to just before the start of boiling, and the arrangement of the signal light and the control light and the distance between the beams until entering the thermal lens forming optical element were finely adjusted, but the optical path deflection of the signal light was observed. Was not. Furthermore, although the arrangement of the signal light and the control light and the distance between the beams in the light absorption layer in the thermal lens forming optical element were finely adjusted, no optical path deflection of the signal light was observed. That is, it is sufficient to deflect the optical path of the signal light when it is irradiated as a collimated parallel beam without converging the control light so that light absorption occurs while diffusing in the light absorption layer in the thermal lens forming optical element. It was found that no size thermal lens was formed.

(Second Embodiment)
FIG. 2 is a schematic configuration example of a deflection optical path switching apparatus according to the second embodiment of the present invention. In the second embodiment of the present invention, the same optical members as those in the first embodiment are given the same numbers.

  FIG. 2 shows a deflecting optical path switching device having a second signal light incident terminal 15, a second control light incident terminal 16, and a fourth imaging lens 17 having a focal length of 8 mm. Other optical members are the same as those in FIG. Further, the wavelength of the signal light used was 1550 nm, and the wavelength of the control light was 980 nm. However, it goes without saying that the wavelength of the signal light and the wavelength of the control light may be other wavelengths as in the first embodiment. It is the same as in the first embodiment that the deflection amount (deflection angle) changes when the power of the control light is changed.

  The second signal light incident terminal 15 and the second control light incident terminal 16 are provided with the two-core optical fiber ferrule shown in FIG.

The signal light emitting fiber 46 and the control light emitting fiber 45 of the two-core optical fiber ferrule in FIG. 12 were used by etching a 9.5 μm single-mode quartz optical fiber clat layer to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after etching is the following relationship with the distance “χ” perpendicular to the optical axis of the convergence (condensation) of the signal light and control light converged (condensed) on the light absorption layer: I made it.
(Formula 2)
ω = χ / m
Here, m is the imaging magnification of the fourth condenser lens 17. In this example, m was 1. If m is reduced, the thickness of the optical fiber after etching can be increased. If m is increased, the thickness of the optical fiber after etching must be reduced.

  In the present embodiment, m is 1 and ω is 35 μm. As is clear from the first embodiment, when ω is increased, the deflection angle is reduced, so ω is preferably 25 to 50 microns. When the thickness was 25 μm or less, the transmittance of laser light was deteriorated. In particular, the transmission of 980 nm laser light was poor, and the transmittance with a 1 m fiber was 20% to 80%.

  The optical fiber for control light and the optical fiber for signal light were used after being fixed to the hole of the ferrule with a thickness of 2ω + several μm with an adhesive and then polishing the tip.

  In this embodiment, a single mode optical fiber having a core diameter of 9.5 μm is used. However, when changing the wavelength of the laser light, it is necessary to use an optical fiber having a core diameter suitable for it. For example, when the control light is 660 nm, it is better to set the core diameter to 4.5 μm.

  The optical path switching data obtained in this embodiment is almost the same as that in the first embodiment.

(Third embodiment)
FIG. 3 is a schematic configuration example of a deflection optical path switching apparatus according to the third embodiment of the present invention. In the third embodiment of the present invention, the same optical members as those in the first embodiment and the second embodiment are given the same numbers. The third embodiment is an example in which the number of control lights is increased by one from the second embodiment and the optical path to be switched is set to 3. In FIG. 3, a third signal light incident terminal 18, a third control light incident terminal 19, a fourth control light incident terminal 20, a second branch mirror 21, a fifth condenser lens, and a third detector. Except 23, it is the same as FIG. 1 and FIG. Further, the wavelength of the signal light used was 1550 nm, and the wavelength of the control light was 980 nm. However, it goes without saying that the wavelength of the signal light and the wavelength of the control light may be other wavelengths as in the first embodiment and the second embodiment. It is the same as the first embodiment and the second embodiment that the deflection amount (deflection angle) changes when the power of the control light is changed.

  For the third signal light incident terminal 18, the third control light incident terminal 19, and the fourth control light incident terminal 20, the three-core optical fiber ferrule shown in FIG.

  The three-core optical fiber shown in FIG. 13B is an example when the optical path is switched two-dimensionally. Although the embodiment using the three-core optical fiber in FIG. 13b is not described, for example, the second branch mirror in FIG. 3 may be moved and reflected in a direction perpendicular to the paper surface.

The signal light emitting fiber 48 and the control light emitting fiber 47 of the three-core optical fiber ferrule of FIG. 13 were used by etching a 9.5 μm single mode quartz optical fiber clat layer to a desired thickness with hydrofluoric acid. The part to be etched was only a few mm of the tip of the optical fiber. The thickness “ω” of the optical fiber after etching is the following relationship with the distance “χ” perpendicular to the optical axis of the convergence (condensation) of the signal light and control light converged (condensed) on the light absorption layer: I made it.
(Formula 3)
ω = χ / m
Here, m is the imaging magnification of the second condenser lens 12. In this example, m was 1. If m is reduced, the thickness of the optical fiber after etching can be increased. If m is increased, the thickness of the optical fiber after etching must be reduced.

  In the present embodiment, m is 1 and ω is 35 μm. As is clear from the first embodiment, when ω is increased, the deflection angle is reduced, so ω is preferably 25 to 50 microns. When the thickness was 25 μm or less, the transmittance of laser light was deteriorated. In particular, the transmission of 980 nm laser light was poor, and the transmittance with a 1 m fiber was 20% to 80%.

  The optical fiber for control light and the optical fiber for signal light in the case of FIG. 13 (a) were used after being fixed to the hole of the ferrule with a thickness of 3ω + several μm with an adhesive and then polishing the tip. In addition, the optical fiber for control light and the optical fiber for signal light in the case of FIG. 13 (b) are fixed to the hole of the ferrule with a thickness (1 + √2) ω + several μm with an adhesive, and then the tip is fixed. Polished and used.

  In this embodiment, a single mode optical fiber having a core diameter of 9.5 μm is used. However, when changing the wavelength of the laser light, it is necessary to use an optical fiber having a core diameter suitable for it. For example, when the control light is 660 nm, it is better to set the core diameter to 4.5 μm.

  The optical path switching data obtained in this embodiment is almost the same as that in the first embodiment and the second embodiment.

(Fourth embodiment)
FIG. 4 is a schematic configuration example of an optical path switching apparatus according to the fourth embodiment of the present invention. In the fourth embodiment of the present invention, the same optical members as those in the first embodiment, the second embodiment, and the third embodiment are given the same numbers. The fourth embodiment is an example in which the detection unit is changed from the first embodiment. Without using a branch mirror, unpolarized light and deflected light having different traveling directions are converged (condensed) by the lenses 24 and 26 and detected by a photodetector. In FIG. 4, the sixth condenser lens 24 with a focal length of 8 mm converges (condenses) on the fourth detector 25 to detect unpolarized light. Further, the light is converged (condensed) on the fifth detector 27 by the seventh condenser lens 26 having a focal length of 8 mm, and the deflected light is detected.

  Although the condensing lenses 24 and 26 have a focal length of 8 mm, the focal length need not be 8 mm. In the present embodiment, a 9.5 μm single mode quartz optical fiber is installed in the photodetectors 25 and 27, the signal light is converged (condensed) on the optical fiber, and transmitted through the optical fiber to be detected. Of course, it goes without saying that a photodetector may be installed directly.

  The wavelength of the signal light used was 1550 nm, and the wavelength of the control light was 980 nm. However, it goes without saying that the wavelength of the signal light and the wavelength of the control light may be other wavelengths as in the first embodiment, the second embodiment, and the third embodiment.

  The optical path switching data obtained in this embodiment is almost the same as that in the first embodiment, the second embodiment, and the third embodiment.

  The deflection optical path switching method and the optical path switching apparatus according to the present invention can be effectively used in the fields of optical communication and optical information processing.

It is a conceptual diagram of the deflection | deviation type optical path switching device of the 1st Embodiment of this invention. It is a conceptual diagram of the deflection | deviation type optical path switching apparatus of the 2nd Embodiment of this invention. It is a conceptual diagram of the deflection | deviation type optical path switching apparatus of the 3rd Embodiment of this invention. It is a conceptual diagram of the deflection | deviation type optical path switching device of the 4th Embodiment of this invention. It is a figure explaining deflection of signal light. It is a figure explaining deflection of signal light. It is a figure which shows an example of a structure of a thermal lens formation optical element. It is a figure which shows deflection light intensity distribution. It is a graph which shows the relationship between control light power and a deflection angle. It is a graph which shows the relationship between the position of a light absorption layer, and a deflection angle. It is a graph which shows the relationship between the separation distance of non-deflected light and deflected light. It is a figure which shows optical path switching measurement data. It is a conceptual diagram of a 2-core optical fiber ferrule. It is a conceptual diagram of a 3 core optical fiber ferrule. It is a figure which shows the cross section of the output signal beam | light.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Signal light input terminal, 2 1st collimating lens, 3 Control light input terminal, 4 2nd collimating lens, 5 Optical mixer, 6 Condensing lens, 7 Thermal lens formation optical element, 8 3rd collimating lens, 9 wavelength selective transmission filter, 10 first branch mirror, 11 second condenser lens, 12 first detector, 13 third condenser lens, 14 second detector.

Claims (14)

The control light and the signal light are incident on the light absorption layer in the thermal lens forming optical element including at least the light absorption layer,
Select the presence or absence of the control light according to the desired information,
The control light and the signal light are irradiated so as to converge at the light absorption layer, and the control light and the signal light are irradiated such that the positions of the convergence points of the control light and the signal light are different in the direction perpendicular to the optical axis. And
The wavelength of the control light is different from the wavelength of the signal light, the wavelength of the control light is selected from a wavelength band that is absorbed by the light absorption layer, and the wavelength of the signal light is from a wavelength band that is not absorbed by the light absorption layer. Chosen,
The control light and the signal light are diffused after converging at or near the incident surface of the light absorption layer in the light traveling direction, thereby absorbing the control light in the light absorption layer and its peripheral region Due to the thermal lens that is formed reversibly due to the temperature rise that occurs, the refractive index changes, changing the traveling direction of the signal light,
The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed by being irradiated with the control light are separately sorted and extracted according to the respective traveling directions. An optical path switching method.   2. The optical path switching according to claim 1, wherein the control light and the signal light are converged or condensed in an incident surface of the light absorption layer or in the light absorption layer in a light traveling direction. Method.   3. The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed after being irradiated with the control light are separated by a mirror. The optical path switching method described in 1.   The signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed after being irradiated with the control light are condensed by a lens and made incident on a detecting means. The optical path switching method according to any one of claims 1 to 3.   5. The optical path switching method according to claim 4, wherein the detection means is an optical fiber that receives signal light condensed by a lens.   6. The optical path switching method according to claim 5, wherein the optical axes of the signal lights incident on the optical fiber collected by the lens have an angle that is at least twice as large as a maximum incident angle at which the optical fiber can propagate. .   A plurality of control lights are applied to the light absorption layer according to the number of optical path switches, the traveling direction of the signal light is changed by a combination of the plurality of control lights, and a plurality of signal lights according to the number of optical path switches are extracted. The optical path switching method according to any one of claims 1 to 6, wherein: A signal light source that emits signal light of one or more wavelengths;
A control light source that emits control light having a wavelength different from that of the signal light;
A thermal lens forming optical element including a light absorbing layer that transmits the signal light and selectively absorbs the control light;
Condensing means for condensing the control light and the signal light on the light absorption layer with the convergence points different from each other in the direction perpendicular to the optical axis,
The thermal lens forming optical element is configured such that the control light and the signal light are diffused after converging at or near the incident surface of the light absorption layer in the light traveling direction, so that the control light in the light absorption layer is diffused. By the thermal lens that is reversibly formed due to the temperature rise that occurs in the region where the light is absorbed and its peripheral region, the refractive index is changed, and the traveling direction of the signal light is changed,
Further, there is provided extraction means for taking out the signal light whose traveling direction has not been changed without being irradiated with the control light and the signal light whose traveling direction has been changed by being irradiated with the control light separately according to each traveling direction. An optical path switching device comprising:   9. The optical path switching device according to claim 8, wherein the condensing means converges or condenses on an incident surface of the light absorption layer or in the light absorption layer in a light traveling direction.   The optical path switching device according to claim 8 or 9, wherein the extraction means is a mirror.   Furthermore, it has a detection means in which the signal light whose traveling direction is not changed without being irradiated with the control light and the signal light whose traveling direction is changed while being irradiated with the control light are collected and incident by a lens. The optical path switching device according to any one of claims 8 to 10, wherein the optical path switching device is characterized.   The optical path switching device according to claim 11, wherein the detection means is an optical fiber.   13. The optical path switching device according to claim 12, wherein the optical axes of the signal lights incident on the optical fiber collected by the lens have an angle that is at least twice as large as a maximum incident angle of propagation of the optical fiber. . The control light source emits two or more control lights according to the number of optical path switching,
The said condensing means converges or condenses on the said light absorption layer by making the convergence point of these control lights differ in the orthogonal | vertical direction with respect to an optical axis. The optical path switching device according to claim 1.