JP4138321B2 - Light separation method, light synthesis method, light separation / synthesis optical element, and light separation coupling device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light separation method, a light synthesis method, a light separation / synthesis optical element, and a light separation coupling device.
[0002]
[Prior art]
In the field of communication and information processing by computers, signal transmission by light has become commonplace, and light having a plurality of wavelength components is used as light for signal transmission, and different information is transmitted for each wavelength. In such signal transmission using a plurality of lights having different wavelengths, light having a plurality of wavelength components is separated into light of each wavelength component (light separation), or conversely, a plurality of lights having different wavelengths from each other, It is necessary to synthesize these into a single light having a wavelength component (photosynthesis).
[0003]
[Problems to be solved by the invention]
An object of the present invention is to realize a novel light separation method, a light synthesis method, and a light separation / synthesis optical element having a simple configuration for realizing the light separation method and the light synthesis method.
Another object of the present invention is to realize a light separation coupling device using a light separation / synthesis optical element.
[0004]
[Means for Solving the Problems]
The light separation method of the present invention is “a method for separating input light including light of a plurality of predetermined wavelengths as components for each light having component wavelengths”, and has the following characteristics.
[0005]
  That is, input light is incident on a “light separating / synthesizing optical element formed with a reflective diffraction grating on one of a pair of planes facing each other through the thickness of a plate-like transparent body”, and the incident input light is reflected. The light is internally reflected and diffracted by the diffraction grating, and the traveling direction of the light of each component wavelength is varied depending on the difference in diffraction angle for each component wavelength.The incident light is a parallel light beam. The parallel light flux is not a strict parallel light flux but can be a “weakly divergent mosque is a weakly convergent light flux” that can be regarded as a substantially parallel light flux.
[0006]
  The component wavelength light diffracted by the reflective diffraction grating is sequentially internally reflected by a pair of planes of the light separating / combining optical element a plurality of times, and then the “flat end surface of the plate-like transparent body (ThicknessThe light is emitted from a separated light exit surface formed as a flat end surface (claim 1).Since the input light is a parallel light beam and the internal reflection is a reflection on a flat surface, the light of each component wavelength that is separated and emitted is also a parallel light beam and is separated radially.
[0007]
2. The light separating method according to claim 1, wherein the input light is made incident at a predetermined incident angle from one of a pair of planes facing each other through the thickness of the light separating / combining optical element, and reflected through the thickness. Can be made incident on (claim 2). Of course, the input light may be incident from an end surface (different from the above-described separated light exit surface) that forms the thickness of the light separating / combining optical element.
[0008]
The light separating / combining optical element of the present invention is a “light separating / combining optical element used for carrying out the light separating method according to claim 1”, and has the following characteristics.
[0009]
That is, the light separating / combining optical element is “formed as a plate-like transparent body, and a reflection diffraction grating is formed at a predetermined position in one of a pair of planes facing each other through the thickness of the plate-like transparent body. The separated light exit surface from which the light separated every time is emitted is formed as a flat end surface that obliquely intersects at least one of the pair of planes ”(claim 3).
[0010]
The reflective diffraction grating of the light separating / combining optical element according to claim 3 can be formed as a “blazed diffraction grating” (claim 4).
The “one pair of planes facing each other through the thickness” of the light separating / combining optical element according to claim 3 or 4 may be non-parallel to each other and form an angle. "Parallel to each other" (claim 5).
[0011]
In the light separating / combining optical element according to claim 3, 4 or 5, the "incident position of input light" can be set to one of a pair of planes (claim 6). The incident position of the input light can also be set at an end surface (different from the separated light exit surface) that forms the thickness of the light separating / combining optical element.
[0012]
The light separating / combining optical element according to claim 3 or 4 or 5 or 6 is also provided: "A reflection film is provided at a site where the diffracted light internally reflected by the reflective diffraction grating is internally reflected in the optical path toward the separated light exit surface". (Claim 7).
[0013]
The photosynthesis method of the present invention is “a method of synthesizing a plurality of lights having predetermined wavelengths different from each other as a single output light by using the light separating and synthesizing optical element according to any one of claims 3 to 7”. Thus, it has the following characteristics (claim 8).
[0014]
  That is, a plurality of lights having predetermined wavelengths different from each other are respectively incident on the separated light exit surface of the light separating / combining optical element at a predetermined incident angle.As parallel light fluxIncidence and sequentially internally reflected a plurality of times on a pair of planes of the light separating / combining optical element, then incident on substantially the same part of the reflective diffraction grating and internally reflected, and each wavelength depending on the difference in diffraction angle for each wavelength Align the light traveling direction of theParallel luminous fluxIt is emitted as output light.
[0015]
In other words, the light synthesizing method of the present invention uses the light separating / synthesizing optical element with “the light traveling direction is opposite to the direction of light separation”.
[0016]
To supplement a little, in general, the wavelengths of light components having a plurality of wavelength components used for signal transmission are often close to each other, and when such light is diffracted by a diffraction grating, The diffraction angle of light is also close. Therefore, even if light separation is performed simply by using diffraction, the separation angle in the traveling direction of each diffracted light is small, and it is difficult to increase the efficiency of light separation. Therefore, the separation angle can be effectively increased by the refractive index of the plate-like transparent body.
[0017]
In addition, the component light separated in the traveling direction by diffraction is reflected a plurality of times inside the light separation / combination optical element, so that the optical path length to the separation light exit surface can be increased, and the well-separated component light can be extracted. Can do.
[0018]
The light separation coupling device according to the present invention is described as follows. “Input light including a plurality of light components having a predetermined wavelength is separated into light components having component wavelengths, and the component light components are spatially separated. An optical separation coupling device that makes each component light and the light receiving portion incident in a 1: 1 ratio to a plurality of light receiving portions arranged in the manner described above. By using a “light separating / combining optical element”, input light including a plurality of light components having a predetermined wavelength is separated into light components having component wavelengths (claim 9).
[0019]
  The light separation coupling device of the present invention comprises:Should be light-separatedWhen the input light is given as a non-parallel light beam, a collimating optical system is provided in front of the light separating / combining optical element to make this non-parallel light beam a parallel light beam.The light that has been converted into a parallel light beam is referred to as “input light to the light-separating and combining optical element”.(Claim 10). The collimating optical system can be configured as a lens system, a mirror system, or a combination system of a mirror and a lens. When the input light is a divergent light beam, the collimating optical system has a positive power, and when the input light is a focused light, the collimating optical system has a negative power.
[0020]
The light separation coupling device according to claim 11 is the light separation coupling device according to claim 9, wherein the collimating optical system is a “collimating lens” (claim 11).
[0021]
  The light separation coupling device according to claim 9, 10, or 11 is also “split spatially separated by a light separation / synthesis optical element”.Parallel luminous fluxIt can have a condensing means for condensing each component light toward the corresponding light receiving section (claim 12). This condensing means can be suitably configured as “a microlens array in which condensing microlenses are arranged according to each component light” (claim 13).
[0022]
The light separation coupling device according to claim 13 includes a collimator lens, a light separation / synthesis optical element, and a microlens array, and separates the input light emitted from the optical fiber into component lights, and each component light is separated. It can be configured as a device for coupling to the incident end of the corresponding waveguide.
[0023]
The “collimating lens” converts the input light emitted from the optical fiber into a parallel beam. The “light separating / combining optical element” receives input light that has been converted into a parallel light beam by a collimating lens and separates it into component light.
The “microlens array” condenses each component light emitted from the light separating / combining optical element toward a waveguide incident end which is a corresponding light receiving unit.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments will be described.
The light separating / combining optical element 10 shown in FIG. 1 is formed as a plate-like transparent body, and is placed at a predetermined position on the plane 10B which is one of a pair of planes 10A and 10B facing each other through the thickness of the plate-like transparent body. A reflection diffraction grating 10C is formed, and a separated light exit surface 10F from which light separated for each component wavelength is emitted is formed as a flat end surface that obliquely intersects the pair of planes 10A and 10B. 3).
[0025]
The planes 10A and 10B of the light separating / combining optical element 10 facing each other through the thickness are parallel to each other (Claim 5). The incident position of the input light is set to a plane 10A which is one of a pair of planes (Claim 6).
[0026]
Reflective films 10D and 10E are provided at portions where the diffracted light internally reflected by the reflective diffraction grating 10C is internally reflected in the optical path toward the separated light exit surface 10F.
[0027]
The light separating / combining optical element 20 shown in FIG. 2 is formed as a plate-like transparent body, and is located at a predetermined position on the plane 20B which is one of a pair of planes 20A and 20B facing each other through the thickness of the plate-like transparent body. A reflection type diffraction grating 20C is formed, and a separated light exit surface 20F from which light separated for each component wavelength is emitted is formed as a flat end surface that obliquely intersects the pair of planes 20A and 20B. 3).
[0028]
The planes 20A and 20B opposed to each other through the thickness of the light separating / combining optical element 20 are not parallel to each other. The incident position of the input light is set to a plane 20A which is one of a pair of planes (Claim 6). Further, reflection films 20D and 20E are provided at portions where the diffracted light internally reflected by the reflection type diffraction grating 20C is internally reflected in the optical path toward the separated light exit surface 20F.
[0029]
FIG. 3 shows a characteristic part of a modification of the above embodiment.
The light separating / combining optical element 10 ′ shown in FIG. 3A is of the same type as the light separating / combining optical element 10 shown in FIG. 1, and the plane 10A ′ is cut out at the portion where the input light is incident. It is characterized in that the incident surface 10a is tapered with respect to '.
[0030]
The light separating / combining optical element 20 ′ shown in FIG. 3B is of the same type as the light separating / combining optical element 20 shown in FIG. 2, and the plane 20A ′ is cut out at the portion where the input light is incident. It is characterized in that the incident surface 20a is tapered with respect to 20A ′. Reference numerals 10C 'and 20C' denote reflective diffraction gratings.
[0031]
Hereinafter, “light separation” will be described. The description of light separation is common to the light separation / combination optical element 10 in FIG. 2 and the light separation / combination optical element 20 in FIG. In the description of the portion, the description will be made with reference to the reference numerals of the light separating / combining optical element 10, and the reference numerals relating to the light separating / combining optical element 20 will be described in parentheses.
[0032]
A method of separating input light including light having a plurality of predetermined wavelengths as components for each light having component wavelengths is performed as follows.
Input to the light separating / combining optical element 10 (20) in which a reflective diffraction grating 10C (20C) is formed on one of a pair of planes 10A, 10B (20A, 20B) facing each other through the thickness of the plate-like transparent body. Make light incident.
[0033]
The input light includes “a plurality of light beams having a predetermined wavelength” as a component, and the light flux form is a parallel light flux or a weakly convergent or weakly divergent light flux. The input light enters from the plane 10A (20A), enters the reflective diffraction grating 10C (20C), is internally reflected, and is diffracted.
[0034]
1 and 2, the symbol L1 represents “light having the shortest wavelength” among the light included in the input light, and the symbol L2 represents “light having the longest wavelength” among the light included in the input light. ing. The same applies to FIG.
[0035]
Considering the light of wavelength: λ included in the input light, the diffraction angle: β of the diffracted light diffracted by the reflective diffraction grating 10C (20C) is incident angle: α, diffraction order: m, wavelength: λ. , Lattice pitch: d, refractive index of the material of the light separating / combining optical element 10 (20): N, and relationship:
sin β = mλ / (N · d) −sin α
Satisfied.
[0036]
In this equation, since the diffraction angle: β on the left side is negative, the incident angle: α, the diffraction order: m, and the grating pitch: d are the same as in the case where diffraction is performed by a reflective diffraction grating placed in the air. A large diffraction angle can be realized. A suitable diffraction order: m can be selected as a design condition. However, by forming the reflective diffraction grating as a blazed diffraction grating (claim 4), the light of the diffracted light of the selected diffraction order is used. The intensity can be effectively increased for other orders of light.
[0037]
When the input light is internally reflected and diffracted by the reflective diffraction grating 10C (20C), the traveling directions of the light beams L1,..., L2 of the respective component wavelengths are different from each other due to the difference in diffraction angle for each component wavelength. The diffracted light components L1,..., L2 are sequentially internally reflected a plurality of times by a pair of planes 10A, 10B (20A, 20B) of the light separating / combining optical element 10 (20), and then separated. The light exits from the light exit surface 10F (20F).
[0038]
The light emitted from the separated light exit surface 10F (20F) has a different traveling direction so that it is emitted from the diffraction position of the reflective diffraction grating 10C (20C), and is separated from each other.
[0039]
In each of the embodiments shown in FIGS. 1 and 2, the diffracted lights L1,..., L2 internally reflected by the reflective diffraction grating are reflected on the reflection films 10D, 10E ( 20D and 20E) are provided, but the reflection at this portion may be total reflection.
[0040]
For this purpose, it is sufficient to increase the diffraction angle and increase the incident angle to the planes 10A and 10B (20A and 20B). However, like the light separating / combining optical element 20 shown in FIG. Is made non-parallel, the incident angle can be increased.
[0041]
In this way, by increasing the incident angle of the diffracted lights L1,..., L2 to the planes 20A and 20B, the reflection films 20A and 20B can be omitted. There is a technical significance of making the “a pair of opposed planes” non-parallel. On the other hand, when the pair of planes are made parallel to each other as in the light separating / combining optical element 10, it can be manufactured simply by forming the separated light emitting surface obliquely on a transparent parallel plate as a material, and thus easy to manufacture. There is a technical advantage.
[0042]
In each of the above embodiments, the input light is incident at a predetermined incident angle from one of a pair of planes 10A (20A) facing each other through the thickness of the light separating / combining optical element 10 (20). Is incident on the reflective diffraction grating 10C (20C) ”.
[0043]
In the above description, the case where the input light is separated into the component lights L1,..., L2 having different wavelengths from each other has been described, but the traveling direction of the light is reversed and the light separation / synthesis optical element 10 (20) is used. A plurality of lights L1,..., L2 having different predetermined wavelengths are respectively incident on the separated light exit surface 10F (20F) of the light separating / combining optical element 10 (20) at a predetermined incident angle (emitted angle in the case of light separation). The light is incident and sequentially internally reflected a plurality of times by a pair of planes 10B and 10A (20B and 20A) of the light separating / combining optical element 10 (20), and then incident on substantially the same part of the reflective diffraction grating 10C (20C). And a light synthesis method in which the traveling direction of light of each wavelength is aligned by the difference in diffraction angle for each wavelength, and is emitted as “single output light” from the light separation / synthesis optical element 10 (20). 8) can be implemented.
[0044]
【Example】
Hereinafter, two specific examples of the light separating / combining optical element will be described. These examples are examples in the case of performing light separation. FIG. 4A shows the same type as the light separating / combining optical element 10 described with reference to FIG. 1, and the same reference numerals as those in FIG. .
[0045]
The dimensions of each part are represented by the following symbols.
That is, the thickness of the light separating / combining optical element 10: T, the length of the plane 10A (in the left-right direction in the figure): LU, the length of the plane 10B (in the left-right direction in the figure): LD, the light separating / combining optical element 10 Distance from the input light incident side (left side) end surface to the left end of the reflective film 10D: LM1, width of the reflective film 10D: LMU, input light incident side (left side) end surface of the light separating / combining optical element 10 to the reflective film 10E Distance to left end: LM2, width of reflective film 10E: LMD, distance from left end face of light separating / combining optical element 10 to left end of reflective diffraction grating 10C: D1, width of reflective diffraction grating 10C: D2 ( The reflection type diffraction grating 10 </ b> C is formed in a square region of one side: D <b> 2), and the distance between the incident position of the central ray of the input light and the left end face of the light separating / combining optical element 10 is IN.
[0046]
Further, the incident angle of the input light on the plane 10A: θ1, the incident angle of the input light incident from the plane 10A on the reflective diffraction grating 10C: θ2, the tilt angle of the separated light exit surface 10F: θ3, the input light reflecting type The distance between the incident position on the diffraction grating 10C (incident position of the central ray) and the left end face of the light separating / combining optical element 10 is D3. In FIG. 2 (a), reference numeral 30 denotes a transmissive body having a wedge-shaped cross section, which is used to align the directions of the component light components separated.
[0047]
The reflective diffraction grating 10C is formed as a blazed diffraction grating as shown in FIG. 4B, and a reflective film (not shown) is formed on the outer surface thereof. The grating pitch in the blazed diffraction grating is “d”, the inclination angle of the groove slope is “η” for the short slope, and “ζ” for the long slope.
[0048]
Example 1
4 types of light having a wavelength difference: 0.02 μm (20 nm), that is, 4 types of light having wavelengths: 1.53 μm, 1.55 μm, 1.57 μm, 1.59 μm as wavelength components, A light separating / synthesizing optical element for separating input light of a parallel light flux at 80 μm into light of each wavelength component was configured as follows.
[0049]
Material: Quartz glass (refractive index in the above-mentioned wavelength region: 1.444402)
Thickness of the light separating / synthesizing optical element 10: T = 1.4 mm
Length of plane 10A: LU = 9.3 mm
Length of plane 10B: LD = 10.4918mm
Distance from the incident side end face to the left end of the reflective film 10D: LM1 = 2.5 mm
Reflective film 10D width: LMU = 4.5 mm
Distance from the incident side end face to the left end of the reflective film 10E: LM2 = 5 mm
Reflective film 10E width: LMD = 5.4918 mm
Distance from left end face to left end of reflective diffraction grating 10C: D1 = 0.41 mm
Distance between input light incident position and left end face of light separating / combining optical element 10: IN = 1 mm
Inclination angle of separated light exit surface 10F: θ3 = 50 degrees
Reflective diffraction grating 10C width: D2 = 1.5 mm
Distance between input light incident on reflection type diffraction grating 10C and left end face of light separating / combining optical element 10: D3 = 1.559 mm
Grating width of the reflective diffraction grating 10C: d = 0.0013 mm
Inclination angle of groove slope: ζ = 30.3378 degrees, η = 60 degrees
Diffraction order: m = 1
Further, the incident state of the input light was set as follows.
[0050]
Angle of incidence of input light on plane 10A: θ1 = 9.2 degrees
Incident angle of input light to reflective diffraction grating 10C: θ2 = 6.3536 degrees
At this time, it was possible to separate the four-component lights having different wavelengths so that their traveling directions are equiangular.
[0051]
When the base 30 is made of silicon having a thickness of 1 mm as the transmission body 30, the inclination angle of the incident side surface is set to 5 degrees, and the distance L0 in the drawing is set to 10 mm, the above four components are formed on the emission side of the transmission body 30. The light could be separated from each other by 125 μm.
[0052]
Accordingly, if four incident end faces of an optical fiber having a diameter of 125 μm are arranged at a pitch of 125 μm on the right side of the transmission body 30, each of the separated component lights can be optically coupled to individual optical fibers. .
[0053]
Example 2
Wavelength difference: 8 kinds of light having 0.02 μm (20 nm), that is, wavelength: 1.49 μm, 1.51 μm, 1.53 μm, 1.55 μm, 1.57 μm, 1.59 μm, 1.61 μm, 1 A light separating / synthesizing optical element for separating input light of a parallel light flux having a light beam diameter of 80 μm into light of each wavelength component was configured as follows.
[0054]
Material: Quartz glass (refractive index in the above-mentioned wavelength region: 1.444402)
Thickness of the light separating / synthesizing optical element 10: T = 1.4 mm
Length of plane 10A: LU = 9.3 mm
Length of plane 10B: LD = 10.4918mm
Distance from the incident side end face to the left end of the reflective film 10D: LM1 = 2.5 mm
Reflective film 10D width: LMU = 4.5 mm
Distance from the incident side end face to the left end of the reflective film 10E: LM2 = 5 mm
Reflective film 10E width: LMD = 5.4918 mm
Distance from the left end surface to the left end portion of the reflective diffraction grating 10C: D1 = 0.66 mm
Distance between input light incident position and left end face of light separating / combining optical element 10: IN = 1 mm
Inclination angle of separated light exit surface 10F: θ3 = 50 degrees
Reflective diffraction grating 10C width: D2 = 1.5 mm
Distance between input light incident on reflection type diffraction grating 10C and left end face of light separating / combining optical element 10: D3 = 1.4107 mm
Grating width of the reflective diffraction grating 10C: d = 0.0001 mm
Inclination angle of groove slope: ζ = 25.0481 degrees, η = 60 degrees
Diffraction order: m = 1
Further, the incident state of the input light was set as follows.
[0055]
Angle of incidence of input light on plane 10A: θ1 = 24 degrees
Incident angle of input light to reflective diffraction grating 10C: θ2 = 16.35 degrees
At this time, it was possible to separate the eight component lights having different wavelengths so that their traveling directions are equiangular.
[0056]
  When silicon having a base thickness of 1 mm is used as the transmissive body 30, the inclination angle of the incident side surface is set to 5 degrees, and the distance L0 in the figure is set to 10 mm, the above-mentioned eight components are formed on the emission side of the transmissive body 30. 125μ light to each othermCould only be separated.
[0057]
Therefore, if eight incident end faces of an optical fiber having a diameter of 125 μm are arranged at a pitch of 125 μm on the right side of the transmission body 30, each component light component can be optically coupled to an individual optical fiber. .
[0058]
In each of the above embodiments, the inclination angles of the incident portions of the separated lights on the incident side surface of the transmissive body are adjusted to be different from each other so that the lights emitted from the transmissive body travel in parallel with each other. Can be.
[0059]
Also, the number of internal reflections of the diffracted light of each wavelength reflected and reflected by the reflection type diffraction grating in the light separating / combining optical element is set to 2 times above, but of course internally reflected three times or more. You may do it.
[0060]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 5 is a diagram showing an embodiment of the light separation coupling device of the present invention.
[0061]
That is, the light separation coupling device separates the input light IL including a plurality of light components having a predetermined wavelength into light components having component wavelengths, and separates the component light beams CL1, CL2,. . , And a plurality of light receiving units 71, 72,. . In addition, a light separation coupling device that makes each component light and a light receiving unit incident in a 1: 1 ratio, and using the light separation / synthesis optical element 10 described above, a plurality of light components having a predetermined wavelength is used as a component. The included input light is separated for each light having a component wavelength.
[0062]
Further, the input light IL is given as a non-parallel light beam, and in order to make this non-parallel light beam a parallel light beam, a collimating optical system 50 is provided in front of the light separating / combining optical element 10 (claim 10). Is a collimating lens.
[0063]
Further, the component lights CL1, CL2,. . , Corresponding light receiving portions 71, 72,. . Condensing means 60 for condensing the light toward the light source (claim 12), the condensing means 60 comprises condensing microlenses 61, 62,. . A microlens array in which are arranged (claim 13).
[0064]
Further, the collimating lens 50 converts the divergent input light emitted from the optical fiber 40 into a parallel light beam, and the light separating / combining optical element 10 receives the input light converted into a parallel light beam by the collimating lens 50 and receives the component light CL1, CL2,. . And the microlens array 60 includes component light beams CL1, CL2,. . , Waveguide incident ends 71, 72,. . The light is condensed toward the head (claim 14).
[0065]
【Example】
A specific embodiment of the light separation coupling device shown in FIG. 5 will be given.
The optical fiber 40 that emits the input light IL is a “single mode fiber”, and its core diameter is 10 μm. Input light includes four wavelengths of light with a design wavelength of 1.53 μm, 1.55 μm, 1.57 μm, and 1.59 μm, but each wavelength varies or varies within a range of ± 4.5 nm around the design wavelength. It is assumed that the variation is included.
[0066]
The collimating lens 50 for collimating the input light IL is a single convex lens with the incident side (optical fiber 40 side) being flat and the exit side (light separating / combining optical element 10 side) being aspherical, with a thickness of D = 0. 65 mm, effective diameter: DEF = 0.6 mm, made of silicon (wavelength: refractive index with respect to 1550 nm: N₁₅₅₀= 3.47772).
[0067]
The aspherical surface is a well-known aspherical surface using a coordinate in the optical axis direction: X, a coordinate in the main scanning direction: Y, a paraxial radius of curvature: R, and a conic constant: K.
X = (Y²/ R) / [1 + √ {1- (1 + K) (Y / R)²}
, The paraxial curvature radius: R = −4.582 mm, and the conic constant: K = −4.672.
[0068]
The light separating / combining optical element 10 has been described above as the second embodiment.
In the microlens array 60, four microlenses whose incident side (the light separating / combining optical element 10 side) is aspherical and whose emission side (the light receiving member 70 side) is flat are separated by the light separating / combining optical element 10. The light source is composed of component light CL1 (wavelength: 1.53 μm), LC2 (wavelength: 1.55 μm), LC3 (wavelength: 1.57 μm), and LC4 (wavelength: 1.59 μm). Silicon (refractive index for wavelength: 1550 nm: N₁₅₅₀= 3.47772).
[0069]
The shape of the aspheric surface in each microlens of the microlens array 60 is specified by the paraxial radius of curvature: R = 5 mm, the conic constant: K = −5.515115, and the wall thickness: D = 0.65 mm. Effective diameter: DEF = 0.64 mm. The arrangement pitch of the four microlenses 61 to 64 is 0.68 mm.
[0070]
On the light receiving surface of the light receiving member 70, waveguide incident ends 71 to 74, which are light receiving portions, are arranged so as to receive the component lights CL1 to CL4, respectively. The waveguide entrance end has a square shape with a side length of 20 μm, and NA = 0.18.
[0071]
The relative arrangement of the optical fiber 40, the collimating lens 50, the light separating / combining optical element 10, the microlens array 60, and the light receiving member 70 follows the dimensions shown in FIG. The horizontal distance from the reference line 500 arranged in the left-right direction in FIG. 5 to the microlens 63 in the microlens array 60 is 23.968 mm, and the horizontal distance in the figure from the reference line 500 to the waveguide incident end 71 is also shown. The distance is 26.324 mm.
[0072]
Both the microlens array 60 and the light receiving surface of the light receiving member 70 are tilted by 10 degrees with respect to a perpendicular line standing on the reference surface SS, as shown in the figure. The height of the optical axis position of the microlens 63 from the reference surface SS is 2.881 mm. Since the arrangement of the microlenses 61 to 64 is at equal intervals and the arrangement pitch is 0.68 mm, the height from the reference plane SS to the optical axis positions of the microlenses 61, 62, and 64 is 2.881 + 2 × 0.68 cos10, respectively. The degree is 2.881 + 0.68 cos 10 degrees and 2.881-0.68 cos 10 degrees.
[0073]
The heights of the waveguide entrance ends 71 to 74 from the reference plane SS are 4.784 mm, 4.042 mm, 3.295 mm, and 2.546 mm, respectively.
[0074]
A semiconductor laser is generally used as the light source of each component light that constitutes the input light. However, the semiconductor laser has a wavelength variation due to the well-known “mode hopping”, and the wavelength between individuals is not necessarily as designed. It will not be.
[0075]
Therefore, as described above, the design wavelengths included in the input light: 1.53 μm, 1.55 μm, 1.57 μm, and 1.59 μm have wavelength fluctuations or wavelength variations in the range of ± 4.5 nm centering on the design wavelength. It is assumed that the coupling efficiency of each component light with respect to the wavelength change in this range is as follows.
[0076]
Design wavelength: 1.53 μm component light coupling efficiency
Wavelength (nm) Coupling efficiency:% (in parentheses are dB)
1525.5 65.8 (-1.82)
1527 74.3 (-1.29)
1528.5 77.1 (-1.13)
1530 77.7 (-1.10)
1531.5 77.4 (-1.11)
1533 76.7 (-1.15)
1534.5 65.7 (-1.83).
[0077]
Design wavelength: 1.55 μm component light coupling efficiency
Wavelength (nm) Coupling efficiency:% (in parentheses are dB)
1545.5 68.8 (-1.63)
1547 75.3 (-1.23)
1548.5 76.6 (-1.16)
1550 79.5 (-0.99)
1551.5 78.8 (-1.04)
1553 73.1 (-1.36)
1554.5 67.4 (-1.71).
[0078]
Design wavelength: coupling efficiency of component light of 1.57 μm
Wavelength (nm) Coupling efficiency:% (in parentheses are dB)
1565.5 64.6 (-1.89)
1567 73.4 (-1.43)
1568.5 76.3 (-1.17)
1570 77.0 (-1.13)
1571.5 76.1 (-1.19)
1573 73.9 (-1.32)
1574.5 66.0 (-1.81).
[0079]
Design wavelength: 1.59 μm component light coupling efficiency
Wavelength (nm) Coupling efficiency:% (in parentheses are dB)
1585.5 61.5 (-2.11)
1587 73.6 (-1.33)
1588.5 76.0 (-1.19)
1590 76.9 (-1.14)
1591.5 76.0 (-1.19)
1593 71.2 (-1.47)
1594.5 61.2 (-2.13).
[0080]
FIG. 6 shows the coupling efficiency (dB value) with respect to wavelength variation for each design wavelength. As can be seen from this result, the light separation coupling device of the example has a small change in the coupling efficiency with respect to the wavelength variation of the component light, and has good stability against the wavelength variation.
[0081]
The list of changes in coupling efficiency at each design wavelength with respect to temperature changes is as follows.
[0082]
Change in coupling efficiency (%, dB in parentheses) with temperature change
Temperature (° C.) 1530 nm 1550 nm 1570 nm 1590 nm
0 78.7 (-1.04) 80.8 (-0.93) 78.3 (-1.06) 78.1 (-1.07)
10 78.1 (-1.07) 80.2 (-0.96) 77.8 (-1.09) 77.5 (-1.11)
20 77.7 (-1.10) 79.5 (-0.99) 77.0 (-1.13) 76.9 (-1.14)
30 77.0 (-1.13) 78.7 (-1.04) 76.4 (-1.17) 76.2 (-1.18)
40 76.3 (-1.18) 78.2 (-1.07) 75.6 (-1.22) 75.4 (-1.23)
50 75.7 (-1.21) 74.6 (-1.27) 74.8 (-1.26) 74.6 (-1.27)
60 75.3 (-1.23) 74.0 (-1.31) 74.2 (-1.30) 74.0 (-1.31).
[0083]
The change in coupling efficiency due to this temperature change is shown in FIG. The light separation coupling device of the embodiment achieves extremely stable coupling efficiency in a wide temperature range of 0 to 60 degrees. The change in the coupling efficiency due to the temperature change is caused by the fact that the “refractive index and dimensions” of the materials of the collimating lens 50, the light separating / combining optical element 10, and the microlens array 60 change depending on the temperature. Since the temperature dependence of the refractive index and dimensions of a certain silicon or quartz glass is very low, the coupling efficiency does not substantially change over a wide temperature range as described above.
[0084]
Therefore, the light separation coupling device of the embodiment can be used without requiring temperature adjustment or the like under a normal environment. 5 can be used to synthesize a plurality of lights having different wavelengths as a single output light by reversing the traveling direction of the light.
[0085]
【The invention's effect】
As described above, according to the present invention, a novel light separation method / light synthesis method, light separation / synthesis optical element, and light separation coupling device can be realized. Since the light separation / synthesis optical element of the present invention has an extremely simple structure as described above, it can be manufactured at a low cost. By using this, a light separation method and a light synthesis method capable of realizing good light separation and photosynthesis can be implemented. it can.
[0086]
In addition, by using the light separating / combining optical element of the present invention, it is possible to realize a light separating coupling device that separates input light into component light and couples it to a light receiving unit corresponding to each component light.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of a light separating / combining optical element and a light separating method using the same.
FIG. 2 is a diagram for explaining another embodiment of the light separation / synthesis optical element and a light separation method using the same.
FIG. 3 is a diagram showing only a characteristic part of a modification of the embodiment of the light separating / combining optical element.
FIG. 4 is a diagram for explaining an embodiment;
FIG. 5 is a diagram showing an embodiment of a light separation coupling device.
FIG. 6 is a diagram showing a change in coupling efficiency accompanying a wavelength variation in one embodiment of the light separation coupling device.
FIG. 7 is a diagram showing a change in coupling efficiency accompanying a temperature change in the above embodiment of the light separation coupling device.
[Explanation of symbols]
10 Optical separation / synthesis optical element
10A plane
10B plane
10C reflective diffraction grating
10D reflective film
10E reflective film
10F Separation light exit surface

Claims (14)

A method of separating input light including light of a plurality of predetermined wavelengths as components for each light having component wavelengths,
Input light is incident as a parallel light beam on a light separating / synthesizing optical element formed with a reflective diffraction grating on one of a pair of planes facing each other through the thickness of a plate-like transparent body. Internally reflected and diffracted by the diffraction grating, the traveling direction of the light of each component wavelength is changed by the difference in diffraction angle for each component wavelength, and the light of each component wavelength diffracted by the reflective diffraction grating is separated and synthesized After internally reflecting a plurality of times sequentially by the pair of planes of the optical element, it is emitted as a parallel light beam that is radially separated from the separated light emitting surface formed as the flat end surface having the thickness of the plate-like transparent body. A method for separating light. The light separation method according to claim 1,
Input light is made incident at a predetermined incident angle from one of a pair of opposing planes through the thickness of a light separating / combining optical element, and is made incident on a reflective diffraction grating through the thickness. Method. A light separating / synthesizing optical element used for carrying out the light separating method according to claim 1,
A reflection-type diffraction grating is formed at a predetermined position on one of a pair of planes facing each other through a thickness of the plate-like transparent body, and light separated for each component wavelength is emitted. A light separating / combining optical element, wherein the separated light exit surface is formed as a flat end surface that obliquely intersects at least one of the pair of planes. The light separating / combining optical element according to claim 3,
A light separating / synthesizing optical element, wherein the reflective diffraction grating is formed as a blazed diffraction grating. The light separation / synthesis optical element according to claim 3 or 4,
Light separation synthesizing optical element, wherein a pair of planes opposing each other via the Thickness are parallel to each other. The light separating / combining optical element according to claim 3, 4 or 5,
A light separating / combining optical element, wherein an incident position of input light is set to one of a pair of planes. The light separating and synthesizing optical element according to claim 3, 4, 5 or 6,
A light separating / combining optical element characterized in that a reflecting film is provided at a site where the diffracted light internally reflected by the reflective diffraction grating is internally reflected in the optical path toward the separated light exit surface. A method for synthesizing a plurality of lights having predetermined wavelengths different from each other as a single output light using the light separating / combining optical element according to any one of claims 3 to 7,
A plurality of parallel light fluxes having different predetermined wavelengths are incident on the separated light exit surface of the light separating / combining optical element at a predetermined incident angle, respectively, and sequentially inside the pair of planes of the light separating / combining optical element a plurality of times. After reflection, the light is incident on substantially the same part of the reflective diffraction grating and internally reflected, and the traveling direction of light of each wavelength is aligned by the difference in diffraction angle for each wavelength. A light synthesizing method, wherein the light is emitted as output light of a parallel light beam . Input light including a plurality of light components having a predetermined wavelength as a component is separated into light components having component wavelengths to obtain component light, and these component lights are spatially separated and arranged in a plurality of light receiving units. A light separation coupling device that makes each component light and a light receiving unit incident in a 1: 1 ratio,
A light separating / synthesizing optical element according to any one of claims 2 to 7, wherein input light including a plurality of light components having a predetermined wavelength is separated into light components having component wavelengths. Optical separation coupling device. The light separation coupling device according to claim 9,
Input light to be light separation is given as a non-parallel light flux, so as to put the non-parallel light flux into a parallel light beam, have a collimating optical system in front of the light separating and synthesizing optical element, light input to the light splitting-combining optical element A light separation coupling device characterized by that. The light separation coupling device according to claim 9,
A light separation coupling device, wherein the collimating optical system is a collimating lens. The light separating coupling device according to claim 9, 10 or 11,
A light separation coupling device, characterized by having condensing means for condensing each component light beam in a parallel luminous flux spatially separated by a light separation / synthesis optical element toward a corresponding light receiving section. The light separating coupling device according to claim 12,
The light separating coupling device, wherein the light condensing means is a microlens array in which condensing microlenses are arranged according to each component light. The light separation coupling device according to claim 13,
A collimating lens that collimates the divergent input light emitted from the optical fiber;
A light separating / synthesizing optical element that receives input light that has been converted into a parallel beam by the collimator lens and separates the input light into component light; and
A light separation coupling device comprising: a microlens array for condensing each component light emitted from the light separation / synthesis optical element toward a waveguide incident end which is a corresponding light receiving portion.

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