JP4656513B2 - Reflective optical device - Google Patents

Description

  The present invention relates to a reflective optical device that controls a polarization direction using a Faraday rotator and controls an optical path shift using birefringence means, and realizes an optical switch function by a ± 45 degree variable Faraday rotator, Or it is related with the reflection type optical device which implement | achieves an optical circulator function with a 45 degree fixed Faraday rotator.

  In an optical communication system or an optical measurement system, an optical device such as an optical switch for switching an optical path or an optical circulator for controlling the optical path is incorporated. An optical switch is an optical device having an optical path switching function that outputs input light from an input port to an arbitrary selected one of output ports. 1 × 2 type (1 input / 2 output) It is the most basic form. The optical circulator is an optical device having a function of cyclically controlling the optical path such that the input light from the first port is output to the second port and the input light from the second port is output to the third port. The 3-port type is the most basic form.

  As an optical device for optical communication, it is important that the optical device is not dependent on polarization, has good compatibility with an optical fiber, and has high reliability. In order to satisfy such requirements, for example, it is necessary by an optical element group in which various optical elements such as a birefringent crystal that controls the optical path according to the polarization plane and a Faraday rotator that controls the rotation angle of the polarization plane are combined and arranged. There is a configuration for realizing an optical function unit.

  In the past, this type of optical device generally has a structure (that is, a transmission type) in which light is input from one end side of the optical element group, travels in one direction in the optical element group, and is output from the other end side. However, in recent years, from the viewpoint of miniaturization of optical devices, etc., an arrayed optical element group and a mirror (reflecting means) are combined, and light input from one end side travels through the optical element group and reaches the mirror. Reflective optical devices have been developed in which the reflected light travels back through the optical element group and is output from one end side, and the light path is switched and controlled while the light travels back and forth through the optical element group. For example, in Patent Document 1, a birefringent crystal, a 45-degree Faraday rotator, a half-wave plate, and a birefringent crystal are arranged in a row, and an input / output unit is provided at one end of the row, and a polarization is provided at the other end. A reflection type optical circulator in which a rotating element and a reflector are arranged is disclosed.

  Such a reflection-type optical device has an advantage that the number of components can be reduced and the length in the optical axis direction can be greatly shortened because light can have a necessary function while reciprocating the optical element group. . However, conventional reflective optical devices have limitations in terms of functions and have limited applications.

  The reflection type optical circulator having the configuration disclosed in Patent Document 1 certainly exhibits a circulator function but is an incomplete circulation type. For example, in the case of a 3-port type, input light from the first port is output to the second port, input light from the second port is output to the third port, but input light from the third port is output to the first port. Cannot be output. In addition, even in the case of four or more ports, the input light from the last port cannot be output to the first port.

  When the structure of the reflection type optical circulator is used and the Faraday rotator is replaced with a variable magnetic field application method from a fixed magnetic field application method to a ± 45 degree variable Faraday rotator, a switching function is obtained. However, it is a 1 × 2 type (1 input · 2 output) or a 2 × 1 type (2 input · 1 output), and a 2 × 2 type (2 inputs · 2 output) cannot be obtained.

In order to solve such a problem, the present inventors have proposed a reflection type optical device having another structure (see Patent Document 2). However, this structure has some points to be improved, such as difficulty in correcting the optical path length difference and complicated mirror shape.
JP 2000-39590 A JP 2004-264368 A

  The problem to be solved by the present invention is that it is easy to correct the optical path length difference while taking advantage of the characteristics of the reflection type that can reduce the number of parts and reduce the size, and the shape of the reflection member can be simplified, thereby improving the quality. It is to make it possible to easily manufacture an optical device at low cost.

  The present invention provides a polarization separation / combination birefringence unit that separates light of the same optical path in which the polarization directions are orthogonal, and combines light of different optical paths, and the polarization direction of the light of different optical paths from orthogonal to parallel or parallel. The polarization rotation control means for converting from the orthogonal to the orthogonal relation and controlling the polarization direction, the optical path control birefringence means for controlling the optical path shift according to the polarization direction, and the polarization plane are rotated 90 degrees in a reciprocating manner. The polarization rotation reflection means for reflecting is arranged in the order along the optical axis, and the polarization rotation reflection means is a reflection of a polarization rotator and prism mirror integrated type that rotates the polarization plane back and forth by 90 degrees. A combination of a structure and a reflecting structure including a prism that returns the light in the optical paths on both outermost sides by reflection twice and a parallel plane mirror that returns the light on the optical paths other than both outermost sides by reflecting once; Reflected light path and mirror that are coupled together through a prism 4 or more ports are arranged in the input / output unit located on the opposite side to the polarization rotation reflection means, and the polarization rotation control means is ± 45 degrees. A reflection type optical device comprising a combination of a variable Faraday rotator and a pair of half-wave plates, and exhibiting an optical switch function by switching the polarization direction by a ± 45 degree variable Faraday rotator. is there.

  Further, the present invention provides a polarization separation / combination birefringence unit that separates light of the same optical path in which the polarization directions are orthogonal, and combines light of different optical paths, and a polarization direction of light of different optical paths from orthogonal to parallel or Polarization rotation control means for converting the parallel to orthogonal relation and controlling the polarization direction, optical path control birefringence means for controlling the optical path shift according to the polarization direction, and the polarization plane are rotated 90 degrees in a reciprocating manner. The polarization rotation reflection means for reflecting the light is reflected along the optical axis in that order, and the polarization rotation reflection means includes a polarization rotator for reciprocating the polarization plane by 90 degrees and a prism mirror integrated type. A combination with a reflecting structure, the reflecting structure comprising a prism that returns the light of the optical paths on both outermost sides by reflecting twice and a parallel plane mirror that returns the light of the optical paths other than both outermost sides by reflecting once And the reflected optical path through the prism and Is a structure that corrects the optical path length difference from the reflected optical path, and four or more ports are arranged in the input / output unit located on the opposite side of the polarization rotation reflection means, and the polarization rotation control means is 45 degrees. A reflection-type optical device comprising a combination of a fixed Faraday rotator and a pair of half-wave plates, and exhibiting an optical circulator function by changing the polarization direction by a 45-degree fixed Faraday rotator. .

  The prism / mirror integrated reflection structure includes, for example, a trapezoidal prism that returns the light in the optical paths on both outermost sides by reflection twice, and forms a reflective film on one end surface to transmit the light in the optical paths other than both outermost parts. A rectangular parallelepiped (including a cube) block that is returned by a single reflection is integrally formed. A structure in which two triangular prisms are combined instead of the trapezoidal prism is also possible.

  Here, the polarization splitting and synthesizing birefringence means divides the polarization splitting and synthesizing birefringent crystal into two parts, and inserts a half-wave plate between them to replace ordinary light and extraordinary light, thereby polarization dispersion. It can be set as the structure which compensated.

  For example, a polarization rotator that rotates the polarization plane back and forth by 90 degrees includes a half-wave plate inserted in one of the optical paths on the outermost side and a quarter wavelength inserted in the optical path excluding both of the outermost parts. The structure is made of a wave plate. Therefore, no wave plate is inserted in the optical path of the other outermost part.

  The input / output unit located on the opposite side of the polarization rotation reflection means has a configuration in which a multi-core ferrule having four or more optical fibers and a coupling lens are arranged. Furthermore, an optical path correcting element or the like can be incorporated as required.

  The present invention is a reflection type optical device configured as described above, and uses an optical path that reciprocates along the optical axis. Therefore, unlike the transmission type in which the input / output unit is present at both ends, the number of components can be reduced and the cost can be reduced. Can be manufactured and can be downsized. Further, the reflecting structure to be incorporated can simplify the structure and can easily correct the optical path length difference, so that a high-quality optical device can be easily manufactured at low cost. Furthermore, since the optical fiber is provided in only one direction, there is an advantage that the device can be easily handled.

  According to the present invention, in the case of a reflective optical switch, a 2 × 2 type (2 inputs / 2 outputs) can be realized. Since it is a magneto-optical system and has no movable part, the operation reliability is extremely high. In the case of a reflection type optical circulator, an n-port complete circulation type can be realized.

  1 shows a typical optical element array structure of a reflective optical device according to the present invention. The optical device body includes a polarization separation / combination birefringence means 10, a polarization rotation control means 12, an optical path control birefringence means 14, and a polarization rotation reflection means 16 in that order along the optical axis. The arrangement is arranged. The input / output unit 18 is disposed facing the optical device body. Light enters and exits parallel to the optical axis. For ease of explanation, the arrangement direction (optical axis) of the optical elements is the z axis, and the two axes orthogonal to the z axis are the x axis (horizontal axis) and the y axis (vertical axis), respectively. Set the coordinate axes. Here, the optical paths are arranged in the y-axis direction (vertical direction), and are referred to as a first optical path, a second optical path,.

  The input / output unit 18 includes a multi-core ferrule 21 having four or more optical fibers 20 and a coupling lens 22 such as a lens array. Although not shown, an optical path correcting element or the like may be provided if further necessary. In FIG. 1, four optical fibers are shown.

  The polarization separation / combination birefringence means 10 separates light of the same optical path whose polarization directions are orthogonal to each other into ordinary light and extraordinary light and synthesizes ordinary light and extraordinary light of different optical paths, and the optical axis is in the xz plane. The first birefringent crystal 24 tilted from the z-axis, the second birefringent crystal 26 whose optical axis is tilted in the opposite direction from the z-axis in the xz plane, and the 1 / It consists of a two-wave plate 28. This combination is for compensating the polarization dispersion generated in the first birefringent crystal 24 by the second birefringent crystal 26, and the optical path length is obtained by exchanging ordinary light and extraordinary light by the half-wave plate 28. Is corrected.

  The polarization rotation control means 12 converts the polarization direction of the light of different optical paths from orthogonal to parallel or from parallel to orthogonal, and is a pair of half-wave plates that are divided from the Faraday rotator 30 to the left and right. It consists of a combination of 32a and 32b. Here, the Faraday rotator 30 includes a Faraday element made of a magneto-optical crystal (for example, a Bi-substituted rare earth iron garnet LPE film) and a magnetic field applying means for applying a magnetic field to the Faraday element from the outside. In the case of functioning as an optical switch, the Faraday rotator is a ± 45 degree variable Faraday rotator, an electromagnet is used as the magnetic field applying means, and the direction of the energization current to the electromagnet is switched to change the Faraday rotation angle to +45 degrees. Or it is set as the structure which can be switched to -45 degree | times. When functioning as an optical circulator, the Faraday rotator is a 45-degree fixed Faraday rotator, and a permanent magnet for applying a fixed magnetic field is used as the magnetic field applying means. The left half-wave plate 32a is tilted +22.5 degrees with respect to the z-axis in the xz plane, and the right half-wave plate 32b is −22 with respect to the z-axis in the xz plane. .Combined to tilt 5 degrees.

  The optical path control birefringence means 14 is made of a single birefringent crystal, and its optical axis is inclined from the z axis in the yz plane.

  The polarization rotation reflection means 16 includes a combination of a polarization rotator 34 that rotates the polarization plane 90 degrees in a reciprocating manner and a prism / mirror integrated reflection structure 36. The polarization rotator 34 includes a half-wave plate 40 inserted in the first optical path (one outermost part), the first optical path, and the nth optical path (n is the last optical path, and in FIG. It consists of a combination with a quarter wave plate 42 inserted in the intermediate optical path except for the optical path. The prism / mirror integrated reflection structure 36 includes a prism 44 that returns the light of the first optical path and the n-th optical path (light passing through both outermost portions) by changing the optical path twice, and the first optical path and the first optical path. An optical path length difference between the reflected optical path passing through the prism 44 and the reflected optical path by the parallel plane mirror 46 is integrally coupled with a parallel plane mirror 46 that returns the light of the intermediate optical path other than the n optical path to the original optical path by a single reflection. It is the structure which corrects. Since the reflected optical path passing through the prism 44 is the longest optical path length, the optical path length difference is corrected by placing the reflecting surface 48 of the parallel flat mirror 46 at a position corresponding to the optical path length. Such an integrated type makes it easy to manufacture and handle.

  An example of a prism / mirror integrated reflection structure is shown in FIG. The example shown in (A) shows a trapezoidal prism 50 that returns the light of the optical paths on both outermost sides by changing the optical path twice by reflection, and an optical path other than both outermost parts by forming a reflection film 48 on one end face. This is a structure in which a rectangular parallelepiped block 54 that returns the light without changing the optical path by reflection once is integrally coupled. The trapezoidal prism 50 has an inclined surface of 45 degrees, a transparent rectangular parallelepiped block 54 is bonded to the short side of the parallel plane, and a surface opposite to the bonded surface is a reflecting surface 48. The reflection surface 48 may be, for example, a metal film or a dielectric multilayer film. The light that has passed through the optical path on one outermost side is totally reflected by one inclined surface of the trapezoidal prism 50 and bent by 90 degrees, and further totally reflected again by the other inclined surface and bent by 90 degrees, and the other outermost part is bent. Go back through the light path. The example shown in (B) is an example in which two triangular prisms 56a and 56b having an inclined surface of 45 degrees are joined symmetrically to the side surface of a transparent rectangular parallelepiped block 58 having a reflection film 48 formed on one end surface. . The light in the optical paths on both outermost sides is reflected by one triangular prism 56a, passes through the rectangular parallelepiped block 58, is reflected by the other triangular prism 56b, and is returned on different optical paths by a total of two reflections.

FIG. 3 and FIG. 4 are explanatory views showing an embodiment of the reflection type optical device according to the present invention, and an optical element arrangement for realizing a 2 × 2 type (2 input / 2 output type) optical switch function. The state (A) and the direction (B) of the polarization plane are shown. FIG. 3 shows a case where light propagates from input 1 (I ₁ ) to output 1 (O ₁ ) and from input 2 (I ₂ ) to output 2 (O ₂ ). In this case, light propagates from input 1 to output 2 and from input 2 to output 1. Here, the input / output ports are such that the position of the first optical path is output 1, the position of the second optical path is input 1, the position of the third optical path is output 2, and the position of the fourth optical path is input 2. It is set. In addition, the polarization rotation direction is counterclockwise on the + side with respect to the z direction (light traveling direction in the forward path). Since the arrangement state of the optical elements is basically the same as that in FIG. 1, the same reference numerals are assigned to the corresponding members except for the Faraday rotator in order to simplify the description. The input / output unit is not shown. As the Faraday rotator, a ± 45 degree variable Faraday rotator 60 is used.

  In FIG. 3, the energization current of the electromagnet is controlled so that the direction of the applied magnetic field of the Faraday rotator faces the z direction. The symbols a,..., H in (B) represent the directions of the polarization planes at the inter-element positions a,.

  The light in the second optical path input from the input 1 is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10. That is, in the first birefringent crystal 24, the ordinary light travels straight and the extraordinary light refracts and travels in the −x direction. In the half-wave plate 28, each polarization plane rotates 90 degrees, and the second birefringent crystal 26 Then, the ordinary light and the extraordinary light are switched, and the ordinary light travels straight and the extraordinary light is refracted in the x direction. In this way, the polarization splitting / combining birefringence means 10 divides the light into two right and left optical paths whose polarization planes are orthogonal to each other. These lights are converted by the polarization rotation control means 12 so that the polarization direction changes from orthogonal to parallel. That is, in the ± 45 degree variable Faraday rotator 60, the +45 degree polarization plane rotates, and in the pair of half-wave plates 32a and 32b divided into the left and right, the light in the left optical path is +45 degrees and the light in the right optical path is − Since the plane of polarization rotates 45 degrees, the plane of polarization is aligned parallel to the x-axis. Both lights pass through the optical path control birefringence means 14, but the birefringent crystal is ordinary light, and thus travels straight. In the next polarization rotator 34, the linearly polarized wave is circularly polarized because it passes through the ¼ wavelength plate 42, and is reflected as it is by the parallel plane mirror 46 of the prism / mirror integrated reflection structure 36. Returned.

  Since the reflected light passes through the ¼ wavelength plate 42 of the polarization rotator 34, the circularly polarized light returns to linearly polarized light. The plane of polarization at this time is parallel to the y-axis, and becomes an extraordinary light with respect to the birefringent crystal of the optical path control birefringence means 14, so that it is refracted in the y direction and shifted to the first optical path. Both lights are converted by the polarization rotation control means 12 from a parallel polarization direction to a perpendicular relationship. That is, in the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path rotates by −45 degrees and the light in the right optical path rotates by +45 degrees, respectively, and +45 in the ± 45 degrees variable Faraday rotator 60. Since the polarization plane rotates, the polarization plane of the light in the left optical path is parallel to the y axis, and the polarization plane of the light in the right optical path is parallel to the x axis. These lights are combined by the polarization separation / combination birefringence means 10. That is, in the second birefringent crystal 26, the ordinary light travels straight and the extraordinary light refracts and travels in the −x direction. In the half-wave plate 28, each polarization plane rotates by 90 degrees, and the first birefringent crystal 24 Then, the ordinary light and the extraordinary light are switched, and the ordinary light travels straight and the extraordinary light is refracted in the x direction. In this way, the polarization splitting and synthesizing birefringence means 10 combines the light into one light whose polarization planes are orthogonal to each other, and outputs it from the output 1 of the first optical path.

  The light in the fourth optical path input from the input 2 exhibits the same behavior as the light input from the input 1 and is reflected and output from the output 2 of the third optical path.

  In FIG. 4, the energization current of the electromagnet is switched and controlled so that the applied magnetic field direction of the Faraday rotator is directed in the −z direction. The symbols a,..., H in (B) represent the directions of the polarization planes at the inter-element positions a,.

  The light input from the input 1 is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10 and becomes light in two right and left optical paths whose polarization planes are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 from a perpendicular polarization direction to a parallel relationship. This time, with the ± 45 degree variable Faraday rotator 60, the -45 degree polarization plane rotates, and with the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path is +45 degrees and the light in the right optical path. Are rotated by −45 degrees, so that the planes of polarization are aligned parallel to the y-axis. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the −y direction and shifted to the third optical path. In the next polarization rotator 34, the linearly polarized wave is circularly polarized because it passes through the ¼ wavelength plate 42, and is reflected as it is by the parallel plane mirror 46 of the prism / mirror integrated reflection structure 36. Returned.

  Since the reflected light passes through the ¼ wavelength plate 42 of the polarization rotator 34, the circularly polarized light returns to linearly polarized light. The plane of polarization at this time is parallel to the x-axis, and becomes ordinary light with respect to the birefringent crystal of the birefringent means 14 for controlling the optical path. Both lights are converted by the polarization rotation control means 12 from a parallel polarization direction to a perpendicular relationship. That is, in the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path rotates by −45 degrees, the light in the right optical path rotates by +45 degrees, and in the ± 45 degrees variable Faraday rotator 60, − Since the 45-degree polarization plane rotates, the light in the left optical path has a polarization plane parallel to the y-axis, and the light in the right optical path has a polarization plane parallel to the x-axis. These lights are combined by the polarization separation / combination birefringence means 10 and output from the output 2 as one light whose polarization planes are orthogonal to each other.

  The light input from the input 2 is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10 and separated into two light beams, the polarization planes of which are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 so that the polarization direction changes from orthogonal to parallel, and the planes of polarization are aligned parallel to the y-axis. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the −y direction and shifted to the fifth optical path. Since the next polarization rotator 34 is bypassed and remains linearly polarized, it is reflected twice by the prism 44 of the prism / mirror integrated reflection structure 36, and returns to the first optical path by changing the optical path.

  Since the reflected light passes through the portion of the half-wave plate 40 of the polarization rotator 34, the plane of polarization is rotated by 90 degrees and becomes parallel to the x-axis. Since these lights become ordinary lights for the birefringent crystal of the birefringent means 14 for controlling the optical path, they go straight as they are. Both lights are converted by the polarization rotation control means 12 so that the polarization direction is changed from parallel to orthogonal. The light in the left optical path has a polarization plane parallel to the y axis, and the light in the right optical path has a polarization plane parallel to the x axis. become. These lights are combined by the polarization separation / combination birefringence means 10 and output from the output 1 as one light whose polarization planes are orthogonal to each other.

  In this way, by using the ± 45 degree variable Faraday rotator 60 and switching the direction of the energizing current of the electromagnet that applies a magnetic field to the Faraday element, a 2 × 2 type optical switch can be obtained.

FIG. 5 is an explanatory view showing another embodiment of the reflection type optical device according to the present invention. The optical element arrangement state (A) and the polarization plane direction (B) in the case of realizing the 4-port type optical circulator function. ). Here, the position of the first optical path is set to port 1 (P ₁ ), the position of the second optical path is set to port 2 (P ₂ ),... The Faraday rotator is a 45-degree fixed Faraday rotator 62, and here, a fixed magnetic field by a permanent magnet is applied in the -z direction.

  The light input from the port 1 of the first optical path is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10, and is separated into light on the left and right optical paths whose polarization planes are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 from a perpendicular polarization direction to a parallel relationship. In the 45-degree fixed Faraday rotator, the -45-degree polarization plane is rotated, and in the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path is +45 degrees, the light in the right optical path is -45 degrees, Since each rotates, the plane of polarization is aligned parallel to the y-axis. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the −y direction and shifted to the second optical path. In the next polarization rotator 34, the linearly polarized wave is circularly polarized because it passes through the ¼ wavelength plate 42, and is reflected as it is by the parallel plane mirror 46 of the prism / mirror integrated reflection structure 36. Returned.

  Since the reflected light passes through the ¼ wavelength plate 42 of the polarization rotator 34, the circularly polarized light returns to linearly polarized light. The plane of polarization at this time is parallel to the x-axis, and becomes ordinary light with respect to the birefringent crystal of the birefringent means 14 for controlling the optical path. Both lights are converted by the polarization rotation control means 12 from a parallel polarization direction to a perpendicular relationship. That is, in the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path rotates by −45 degrees and the light in the right optical path rotates by +45 degrees, respectively, and in the 45 degrees fixed Faraday rotator, −45 degrees. Since the plane of polarization rotates, the light in the left optical path has a plane of polarization parallel to the y-axis, and the light in the right optical path has a plane of polarization parallel to the x-axis. These lights are combined by the polarization separation / combination birefringence means 10 and output from the port 2 of the second optical path as one light whose polarization planes are orthogonal to each other.

  Similarly, input light from port 2 is output from port 3, and input light from port 3 is output from port 4.

  The light input from the port 4 of the fourth optical path is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10 and is divided into two light beams, the polarization planes of which are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 from a perpendicular polarization direction to a parallel relationship. In the 45-degree fixed Faraday rotator, the -45-degree polarization plane is rotated, and in the pair of half-wave plates 32a and 32b divided into left and right, the light in the left optical path is +45 degrees, the light in the right optical path is -45 degrees, Since each rotates, the plane of polarization is aligned parallel to the y-axis. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the −y direction and shifted to the fifth optical path. These lights are reflected twice by the prism 44 portion of the prism / mirror integrated reflection structure 36 so as to bypass the next polarization rotator 34 and remain linearly polarized, and change the optical path to the first optical path. To return.

  Since the reflected light passes through the portion of the half-wave plate 40 of the polarization rotator 34, the plane of polarization is rotated by 90 degrees and becomes parallel to the x-axis. Since these lights become ordinary light with respect to the birefringent crystal of the birefringence means 14 for optical path control, they go straight as they are. Both lights are converted by the polarization rotation control means 12 so that the polarization direction is changed from parallel to orthogonal. The light in the left optical path has a polarization plane parallel to the y axis, and the light in the right optical path has a polarization plane parallel to the x axis. become. These lights are combined by the polarization separation / combination birefringence means 10 and output from the port 1 of the first optical path as one light whose polarization planes are orthogonal to each other.

  In this way, a complete circulation type optical circulator of port 1 → port 2, port 2 → port 3, port 3 → port 4, port 4 → port 1 can be realized.

  FIG. 6 is an explanatory view showing still another embodiment of the reflective optical device according to the present invention, in which the optical element arrangement state (A) and the polarization plane direction (when the n-port optical circulator function is realized) B). Also here, the first optical path is set to port 1, the second optical path is set to port 2,... The Faraday rotator is a 45-degree fixed Faraday rotator 62 and applies a fixed magnetic field by a permanent magnet in the −z direction. The polarization rotator 34 has a structure in which a half-wave plate 40 is inserted in the first optical path and a quarter-wave plate 42 is inserted from the second optical path to the n-th optical path. The board is not inserted. In the prism / mirror integrated reflection structure 36, the light in the first optical path and the (n + 1) th optical path is reflected twice by the prism 44, and the light in the nth optical path from the second optical path is reflected by the parallel plane mirror 48. It is the composition which is done.

  The light input from the port 1 of the first optical path is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10, and is divided into two light beams whose polarization planes are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 from a perpendicular polarization direction to a parallel relationship. In the 45-degree fixed Faraday rotator 62, the polarization plane rotates by -45 degrees, and in the pair of half-wave plates 32a and 33b divided into the left and right, the light in the left optical path is +45 degrees and the light in the right optical path is -45 degrees. The planes of polarization are aligned parallel to the y-axis because they rotate. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the −y direction and shifted to the second optical path. In the next polarization rotator 34, the linearly polarized wave is circularly polarized because it passes through the ¼ wavelength plate 42, and is reflected as it is by the parallel plane mirror 46 of the prism / mirror integrated reflection structure 36. The

  Since the reflected light passes through the ¼ wavelength plate 42 of the polarization rotator 34, the circularly polarized light returns to linearly polarized light. The plane of polarization at this time is parallel to the x-axis, and becomes ordinary light with respect to the birefringent crystal of the birefringent means 14 for controlling the optical path. Both lights are converted by the polarization rotation control means 12 from a parallel polarization direction to a perpendicular relationship. That is, in the pair of half-wave plates 32a and 32b divided into the left and right, the light in the left optical path rotates by −45 degrees, the light in the right optical path rotates by +45 degrees, and by the 45 degrees fixed Faraday rotator 62, −45 degrees. Since the polarization plane rotates, the polarization plane of the light in the left optical path is parallel to the y axis, and the polarization plane of the light in the right optical path is parallel to the x axis. These lights are combined by the polarization separation / combination birefringence means 10 and output from the port 2 of the second optical path as one light whose polarization planes are orthogonal to each other.

  Similarly, input light from port 2 is output from port 3, input light from port 3 is output from port 4,..., Input light from port n-1 is output from port n.

  The light input from the port n of the n-th optical path is separated into ordinary light and extraordinary light by the polarization separation / combination birefringence means 10, and is divided into two light beams whose polarization planes are orthogonal to each other. Both lights are converted by the polarization rotation control means 12 from the orthogonal direction to the parallel relationship. In the 45-degree fixed Faraday rotator 62, the -45-degree polarization plane rotates, and in the pair of half-wave plates 32a and 32b divided into the left and right, the light in the left optical path is +45 degrees and the light in the right optical path is -45 degrees. The planes of polarization are aligned parallel to the y-axis because they rotate. Both lights pass through the optical path control birefringence means 14 but become extraordinary light with respect to the birefringent crystal, so that they are refracted in the -y direction and shifted to the (n + 1) th optical path. These lights are reflected twice by the prism 44 portion of the prism / mirror integrated reflection structure 36 so as to bypass the next polarization rotator 34 and remain linearly polarized, and change the optical path to the first optical path. To return.

  Since the reflected light passes through the portion of the half-wave plate 40 of the polarization rotator 34, the plane of polarization is rotated by 90 degrees and becomes parallel to the x-axis. Since these lights become ordinary lights for the birefringent crystal of the birefringent means 14 for controlling the optical path, they go straight as they are. Both lights are converted by the polarization rotation control means 12 so that the polarization direction is changed from parallel to orthogonal. The light in the left optical path has a polarization plane parallel to the y axis, and the light in the right optical path has a polarization plane parallel to the x axis. become. These lights are combined by the polarization separation / combination birefringence means 10 and output from the port 1 as one light whose polarization planes are orthogonal to each other.

  In this way, an n-port complete circulation type optical circulator of port 1 → port 2, port 2 → port 3,..., Port n → port 1 can be realized. In such an n-port type optical circulator, the combined optical path length of port n → port 1 is the longest. In order to correct the combined optical path length, it is necessary to adjust the y-direction dimension and the z-direction dimension of the prism / mirror integrated reflection structure 36. Other optical elements can be handled only by adjusting the y-direction dimension.

Explanatory drawing which shows the typical structural example of the reflection type optical device which concerns on this invention. Explanatory drawing which shows the example of a reflective structure of prism / mirror integrated type. BRIEF DESCRIPTION OF THE DRAWINGS It is one Example of the reflection type optical device which concerns on this invention, and is explanatory drawing of the polarization plane direction at the time of applying the electromagnet magnetic field to one element arrangement | positioning state which exhibits an optical switch function, and one direction. BRIEF DESCRIPTION OF THE DRAWINGS It is one Example of the reflection type optical device which concerns on this invention, and is explanatory drawing of the polarization plane direction at the time of applying an electromagnet magnetic field to the element arrangement | sequence state which exhibits an optical switch function, and another direction. FIG. 4 is an explanatory diagram of an element arrangement state and a polarization plane direction that exhibit an optical circulator function, which is another embodiment of the reflective optical device according to the present invention. FIG. 10 is an explanatory diagram of an element arrangement state and a polarization plane direction that exhibit an optical circulator function, which is still another embodiment of the reflective optical device according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Polarization separation birefringence means 12 Polarization rotation control means 14 Optical path control birefringence means 16 Polarization rotation reflection means 18 Input / output unit 20 Optical fiber 21 Multi-core ferrule 22 Coupling lens 24 First birefringence crystal 26 Second birefringent crystal 28 1/2 wavelength plate 30 Faraday rotator 32a, 32b 1/2 wavelength plate 34 Polarization rotator 36 Prism-mirror integrated reflection structure 40 1/2 wavelength plate 42 1/4 Wave plate 44 Prism 46 Parallel plane mirror 48 Reflecting surface

Claims (5)

Polarization separation / combination birefringence means that separates the light of the same optical path whose polarization direction is orthogonal and combines the light of different optical paths, and the polarization direction of the light of different optical paths from orthogonal to parallel or from parallel to orthogonal A polarization rotation control means that converts the polarization direction and controls the polarization direction, an optical path control birefringence means that controls the optical path shift according to the polarization direction, and a polarization that is reflected by rotating the polarization plane back and forth by 90 degrees Rotational reflecting means are arranged along the optical axis in that order,
The polarization rotation reflection means is a combination of a polarization rotator that rotates the polarization plane 90 degrees in a reciprocating manner and a prism / mirror integrated reflection structure, and the reflection structure has optical paths on both outermost sides. The optical path length difference between the reflected light path that passes through the prism and the reflected light path by the mirror is integrally coupled with the prism that returns the light of the light by reflection twice and the parallel plane mirror that returns the light of the optical path other than the outermost part by reflection once. Is a structure for correcting
4 ports or more are arranged in the input / output unit located on the opposite side to the polarization rotation reflection means,
The polarization rotation control means comprises a combination of a ± 45 degree variable Faraday rotator and a pair of half-wave plates, and exhibits an optical switch function by switching the polarization direction with the ± 45 degree variable Faraday rotator. Reflective optical device characterized by the above. Polarization separation / combination birefringence means that separates the light of the same optical path whose polarization direction is orthogonal and combines the light of different optical paths, and the polarization direction of the light of different optical paths from orthogonal to parallel or from parallel to orthogonal A polarization rotation control means that converts the polarization direction and controls the polarization direction, an optical path control birefringence means that controls the optical path shift according to the polarization direction, and a polarization that is reflected by rotating the polarization plane back and forth by 90 degrees Rotational reflecting means are arranged along the optical axis in that order,
The polarization rotation reflection means is a combination of a polarization rotator that rotates the polarization plane 90 degrees in a reciprocating manner and a prism / mirror integrated reflection structure, and the reflection structure has optical paths on both outermost sides. The optical path length difference between the reflected light path that passes through the prism and the reflected light path by the mirror is integrally coupled with the prism that returns the light of the light by reflection twice and the parallel plane mirror that returns the light of the optical path other than the outermost part by reflection once. Is a structure for correcting
4 ports or more are arranged in the input / output unit located on the opposite side to the polarization rotation reflection means,
The polarization rotation control means comprises a combination of a 45 degree fixed Faraday rotator and a pair of half-wave plates, and exhibits an optical circulator function by changing the polarization direction by the 45 degree fixed Faraday rotator. Reflective optical device characterized by   The prism / mirror integrated reflection structure has a trapezoidal prism that returns the light in the optical paths on both outermost sides by reflection twice, and forms a reflection film on one end surface to emit the light in the optical paths other than both outermost parts once. The reflective optical device according to claim 1 or 2, wherein a rectangular parallelepiped block returned by reflection is integrally joined.   The polarization separation / combination birefringence means divides the polarization separation / combination birefringence crystal into two parts and inserts a half-wave plate between them to compensate for polarization dispersion by exchanging ordinary light and extraordinary light. The reflective optical device according to claim 1, wherein the reflective optical device has a structure. A polarization rotator that rotates the plane of polarization 90 degrees in a reciprocating manner is composed of a half-wave plate inserted in one of the outermost optical paths and a quarter-wave plate inserted in the optical path excluding both outermost parts. The reflective optical device according to any one of claims 1 to 4.

Images