Optical attenuator and optical attenuator composite

Abstract

To control the intensities of P-polarized light and S-polarized light components using a wavelength plate irrespective of the rotation of the wavelength plate.SOLUTION: An optical attenuator 1 comprises: a light source 10 for emitting linear polarized light; a wavelength plate 12 for passing linear polarized light through and changing a phase difference in linear polarized light between vibration components of electric fields in two directions orthogonal to each other; a polarized light beam splitter 14 for acquiring P-polarized light and S-polarized light components from the linear polarized light having passed through the wavelength plate 12; and a temperature control unit 18 for controlling the temperature of the wavelength plate 12. Since the intensities of the P-polarized light and S-polarized light components acquired by the polarized light beam splitter 14 are controlled by the temperature control unit 18, it is possible to control the intensities of the P-polarized light and S-polarized light components irrespective of the rotation of the wavelength plate 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to controlling the intensity of linearly polarized light. [Background technology]

[0002] Conventionally, there is known an optical system that provides linearly polarized light to a polarizing beam splitter via a wave plate. By shifting the crystal axis by rotating this wave plate, the phase difference between the P-polarized component and the S-polarized component can be changed, and by changing the state and direction of polarization, the intensity of the P-polarized component and the S-polarized component obtained from the polarizing beam splitter can be controlled.

[0003] It is also known to control the temperature in an optical system (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-330518 A [Patent Document 2] Special Publication No. 2010-534861 [Patent Document 3] International Publication No. 2014-020669 Summary of the Invention [Problem to be solved by the invention]

[0005] However, fine adjustment is difficult when rotating the wave plate manually, and automatic rotation requires many mechanical parts such as motors, which poses various problems (e.g., difficulty in miniaturization). In other words, controlling the intensities of the P-polarized and S-polarized components by rotating the wave plate poses various problems.

[0006] Therefore, an object of the present invention is to control the intensities of the P-polarized component and the S-polarized component using a wave plate without rotating the wave plate. [Means for solving the problem]

[0007] The optical attenuator of the present invention comprises a light source that emits linearly polarized light, a wave plate that transmits the linearly polarized light and changes the phase difference between vibration components of the electric field in two mutually perpendicular directions in the linearly polarized light, a polarization component acquisition unit that acquires the P polarization component and the S polarization component from the linearly polarized light that has passed through the wave plate, and a temperature control unit that controls the temperature of the wave plate, and is configured so that the temperature control unit controls the intensity of the P polarization component or the S polarization component acquired by the polarization component acquisition unit.

[0008] In the optical attenuator configured as described above, a light source emits linearly polarized light. A wave plate transmits the linearly polarized light and changes the phase difference between vibration components of an electric field in two directions perpendicular to each other in the linearly polarized light. A polarization component acquisition unit acquires the P polarization component and the S polarization component from the linearly polarized light that has passed through the wave plate. A temperature control unit controls the temperature of the wave plate. The temperature control unit controls the intensity of the P polarization component or the S polarization component acquired by the polarization component acquisition unit.

[0009] In addition, the optical attenuator of the present invention may be configured so that a polarization component measuring unit measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit, and the temperature control unit compares a target value of the other of the P polarization component and the S polarization component with the light output minus the measurement result of the polarization component measuring unit, to control the other.

[0010] In addition, the optical attenuator of the present invention may be configured so that a polarization component measuring unit measures one of the P polarization component and the S polarization component acquired by the polarization component acquisition unit, and the temperature control unit compares a target value of the other of the P polarization component and the S polarization component with a ratio of the one to the other multiplied by the measurement result of the polarization component measuring unit to control the other.

[0011] In the optical attenuator according to the present invention, the ratio between the one and the other may be determined by measuring a ratio between the P-polarized component and the S-polarized component of the linearly polarized light transmitted through the wave plate.

[0012] In addition, the optical attenuator of the present invention may include another waveplate that transmits the linearly polarized light and changes the phase difference between vibration components of the electric field in two mutually perpendicular directions in the linearly polarized light, and is different from the waveplate, and another polarization component acquisition unit that acquires the P polarization component and the S polarization component from the linearly polarized light that has passed through the other waveplate, and the temperature control unit may control the temperature of the waveplate and the temperature of the other waveplate to the same value, so that the relationship between the temperature at the waveplate and the transmitted light intensity is the same as the relationship between the temperature at the other waveplate and the transmitted light intensity.

[0013] In addition, the optical attenuator of the present invention may be configured so that a polarization component measuring unit measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit, and the temperature control unit compares a target value of the other of the P polarization component and the S polarization component with the light output minus the measurement result of the polarization component measuring unit, to control the other.

[0014] In addition, the optical attenuator of the present invention may be configured so that a polarization component measuring unit measures one of the P polarization component and the S polarization component acquired by the polarization component acquisition unit, and the temperature control unit compares a target value of the other of the P polarization component and the S polarization component with a ratio of the one to the other multiplied by the measurement result of the polarization component measuring unit to control the other.

[0015] In the optical attenuator according to the present invention, the temperature control section may be a heater.

[0016] In the optical attenuator according to the present invention, the temperature control section may be a Peltier element.

[0017] The optical attenuator complex according to the present invention includes a plurality of optical attenuators according to the present invention, and is configured such that the optical energies of the P-polarized component or the S-polarized component output from each of the optical attenuators are all equal. [Brief description of the drawings]

[0018] [Figure 1] 1 is a functional block diagram showing a configuration of an optical attenuator 1 according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a functional block diagram showing a configuration of an optical attenuator 1 according to a second embodiment of the present invention. [Diagram 3] FIG. 1 is a functional block diagram showing a configuration of an optical attenuator 1 according to a third embodiment of the present invention. [Figure 4] FIG. 11 is a functional block diagram showing a configuration of an optical attenuator 1 according to a fourth embodiment of the present invention. [Diagram 5] FIG. 11 is a functional block diagram showing a configuration of an optical attenuator 1 according to a fifth embodiment of the present invention. [Figure 6] FIG. 11 is a functional block diagram showing a configuration of an optical attenuator 1 according to a sixth embodiment of the present invention. [Figure 7] FIG. 13 is a functional block diagram showing a configuration of an optical attenuator 1 according to a seventh embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0020] First embodiment 1 is a functional block diagram showing a configuration of an optical attenuator 1 according to a first embodiment of the present invention. The optical attenuator 1 according to the first embodiment of the present invention includes a light source 10, a wave plate 12, a polarizing beam splitter (polarized component acquisition unit) 14, and a temperature control unit 18.

[0021] The light source 10 emits linearly polarized light (for example, laser light).

[0022] The wave plate 12 transmits the linearly polarized light emitted from the light source 10 and changes the phase difference between the vibration components of the electric field in two directions (for example, the X direction and the Y direction) that are orthogonal to each other in the linearly polarized light. For example, the wave plate 12 can be a half-wave plate. In this case, the phase difference between the vibration component of the electric field in the X direction and the vibration component of the electric field in the Y direction (i.e., the difference between the phase of the vibration component of the electric field in the X direction and the phase of the vibration component of the electric field in the Y direction) can be π+2π×(order of the wave plate 12) (n=0, 1, 2, ...) depending on the thickness of the wave plate (half-wave plate) 12. For example, if the order of the wave plate 12 is set to 4th order depending on the thickness of the wave plate (half-wave plate) 12, the phase difference between the vibration component of the electric field in the X direction and the vibration component of the electric field in the Y direction can be 9π.

[0023] Polarizing beam splitter (polarized component acquisition unit) 14 acquires a P polarized component and an S polarized component from the linearly polarized light transmitted through wave plate 12. The output of polarizing beam splitter 14 is set as the output of optical attenuator 1. For example, the P polarized component output by polarizing beam splitter 14 is set as the output of optical attenuator 1.

[0024] The temperature control unit 18 controls the temperature of the wave plate 12. The temperature control unit 18 is, for example, a heater or a Peltier element.

[0025] Temperature control unit 18 controls the intensity of the P-polarized component or S-polarized component acquired by polarizing beam splitter 14. For example, if wave plate 12 is a half-wave plate, the transmitted light intensity ratio (=(intensity of P-polarized component output by polarizing beam splitter 14) / (intensity of light emitted from light source 10)) is 100% at a predetermined temperature (e.g., 25°C). The transmitted light intensity ratio decreases whether wave plate 12 is heated above or below the predetermined temperature. Note that the higher the order of wave plate 12, the greater the decrease in the transmitted light intensity ratio when wave plate 12 is changed from the predetermined temperature. The greater the decrease in the transmitted light intensity ratio, the greater the controllability of the intensity of the P-polarized component to be lower and the intensity of the S-polarized component to be higher.

[0026] Wave plate 12 is a birefringent crystal with an ordinary axis of refractive index no and an extraordinary axis of refractive index ne. A phase difference occurs between the two components due to a difference in speed between the polarized component along the ordinary axis and the polarized component along the extraordinary axis. A plate with a phase difference of 1 / 2 wavelength is called a 1 / 2 wave plate, and a plate with a phase difference of 1 / 4 wavelength is called a 1 / 4 wave plate. Here, the state of polarization is changed by changing the refractive index difference between no and ne with temperature.

[0027] Next, the operation of the first embodiment will be described.

[0028] Linearly polarized light emitted from light source 10 passes through wave plate 12, and a P-polarized component and an S-polarized component are extracted by polarizing beam splitter 14. Here, the temperature of wave plate 12 is controlled by temperature control unit 18 in order to set the intensity of the P-polarized component to a desired value.

[0029] According to the first embodiment, the intensities of the P-polarized component and the S-polarized component can be controlled using the wave plate 12 by controlling the temperature of the wave plate 12, without rotating the wave plate 12.

[0030] Second embodiment The second embodiment differs from the first embodiment in that it includes an S-polarized component measuring unit 16 and a light source output recording unit 17, and a temperature control unit 18 controls the P-polarized component by comparing a target value for the P-polarized component with the recorded contents of the light source output recording unit 17 (the output of linearly polarized light emitted from the light source 10) minus the measurement result of the S-polarized component measuring unit 16.

[0031] 2 is a functional block diagram showing the configuration of an optical attenuator 1 according to a second embodiment of the present invention. The optical attenuator 1 according to the second embodiment of the present invention includes a light source 10, a wave plate 12, a polarizing beam splitter (polarized component acquisition unit) 14, an S-polarized component measurement unit (polarized component measurement unit) 16, a light source output recording unit 17, and a temperature control unit 18. Hereinafter, parts similar to those in the first embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0032] The light source 10, the wave plate 12, and the polarizing beam splitter (polarized component acquisition unit) 14 are similar to those in the first embodiment, and the description thereof will be omitted.

[0033] The S polarization component measuring unit (polarized component measuring unit) 16 measures one of the P polarization component and the S polarization component acquired by the polarizing beam splitter (polarized component acquiring unit) 14. In the second embodiment, the polarization component measuring unit 16 measures the output (light energy) of the S polarization component.

[0034] The light source output recording section 17 records the optical output of the light source 10 (the output (light energy) of linearly polarized light emitted from the light source 10).

[0035] Temperature control unit 18 receives a target value for the other of the P and S polarized components. In the second embodiment, it receives the target value of the P polarized component. Furthermore, temperature control unit 18 receives the light output of light source 10 from light source output recording unit 17 and the measurement result (output of the S polarized component) from S polarized component measurement unit 16. Furthermore, temperature control unit 18 compares the target value of the P polarized component with the light output of light source 10 minus the measurement result of S polarized component measurement unit 16 (i.e., the actual measured value of the P polarized component) to control the output of the P polarized component. Other points regarding temperature control unit 18 are similar to those in the first embodiment.

[0036] Next, the operation of the second embodiment will be described.

[0037] Linearly polarized light emitted from light source 10 passes through wave plate 12, and a P-polarized component and an S-polarized component are extracted by polarizing beam splitter 14. Here, in order to set the intensity of the P-polarized component to a desired value, a temperature control unit 18 controls the temperature of wave plate 12. For this purpose, an output of the S-polarized component is measured by S-polarized component measuring unit 16.

[0038] Temperature control unit 18 obtains an actual value of the P polarized component by subtracting the measurement result (output of the S polarized component) received from S polarized component measurement unit 16 from the optical output of light source 10 received from light source output recording unit 17. This actual value of the P polarized component is compared with a target value of the P polarized component, the temperature of wave plate 12 is controlled, and the output of the P polarized component is controlled.

[0039] According to the second embodiment, the same effects as those of the first embodiment can be automatically achieved by the S-polarized component measuring unit 16, the light source output recording unit 17, and the temperature control unit .

[0040] Third embodiment The third embodiment differs from the second embodiment in that a P / S ratio recording unit 19 is provided instead of the light source output recording unit 17.

[0041] 3 is a functional block diagram showing the configuration of an optical attenuator 1 according to a third embodiment of the present invention. The optical attenuator 1 according to the third embodiment of the present invention includes a light source 10, a wave plate 12, a polarizing beam splitter (polarized component acquisition unit) 14, an S-polarized component measurement unit (polarized component measurement unit) 16, a temperature control unit 18, and a P / S ratio recording unit 19. Hereinafter, parts similar to those in the second embodiment are given the same reference numerals and descriptions thereof will be omitted.

[0042] The light source 10, wave plate 12, polarizing beam splitter (polarized component acquisition section) 14 and S polarized component measurement section (polarized component measurement section) 16 are similar to those in the second embodiment, and description thereof will be omitted.

[0043] The P / S ratio recorder 19 records the output ratio of the P polarized component and the S polarized component.

[0044] Temperature control unit 18 receives the output ratio of one of the P and S polarized components (S polarized component) to the other (P polarized component) from P / S ratio recording unit 19. Furthermore, temperature control unit 18 controls the P polarized component by comparing a target value for the P polarized component with the output ratio of one of the P and S polarized components (S polarized component) to the other (P polarized component) multiplied by the measurement result of S polarized component measuring unit 16. Other points regarding temperature control unit 18 are the same as those in the second embodiment.

[0045] Next, the operation of the third embodiment will be described.

[0046] Linearly polarized light emitted from light source 10 passes through wave plate 12, and a P-polarized component and an S-polarized component are extracted by polarizing beam splitter 14. Here, in order to set the intensity of the P-polarized component to a desired value, a temperature control unit 18 controls the temperature of wave plate 12. For this purpose, an output of the S-polarized component is measured by S-polarized component measuring unit 16.

[0047] Temperature control unit 18 obtains an actual value of the P polarized component by multiplying the output ratio of one (S polarized component) and the other (P polarized component) of the P polarized component and the S polarized component received from P / S ratio recording unit 19 by the measurement result (output of the S polarized component) received from S polarized component measuring unit 16. This actual value of the P polarized component is compared with a target value for the P polarized component, the temperature of wave plate 12 is controlled, and the output of the P polarized component is controlled.

[0048] According to the third embodiment, it is possible to obtain the same effects as those of the second embodiment.

[0049] Fourth embodiment The fourth embodiment differs from the third embodiment in that, instead of recording the output ratio of one (S polarized component) of the P polarized component and the other (P polarized component) of the S polarized component in the P / S ratio recording unit 19, the ratio of the P polarized component and the S polarized component of the light after passing through the wave plate 12 is measured and determined.

[0050] 4 is a functional block diagram showing a configuration of an optical attenuator 1 according to a fourth embodiment of the present invention. The optical attenuator 1 according to the fourth embodiment of the present invention includes a light source 10, a tap mirror 11, a wave plate 12, a polarizing beam splitter (polarized component acquisition section) 14, an S polarized component measurement section (polarized component measurement section) 16, a temperature control section 18, a pre-entry polarizing beam splitter 24, a pre-entry S polarized component measurement section 26S, a pre-entry P polarized component measurement section 26P, and a P / S ratio measurement section 29. Hereinafter, parts similar to those in the third embodiment are given the same reference numerals and description thereof will be omitted.

[0051] The light source 10, wave plate 12, polarizing beam splitter (polarized component acquisition section) 14 and S polarized component measurement section (polarized component measurement section) 16 are similar to those in the third embodiment, and description thereof will be omitted.

[0052] Tap mirror 11 transmits almost all of the linearly polarized light emitted from light source 10 and transmitted through wave plate 12, but reflects a portion of weak light. The light transmitted through tap mirror 11 travels toward polarizing beam splitter 14. The light reflected by tap mirror 11 travels toward pre-entry polarizing beam splitter 24.

[0053] The pre-entry polarized beam splitter 24 acquires a P polarized component and an S polarized component from the incident light. The pre-entry S polarized component measurement unit 26S measures the output (light energy) of the S polarized component acquired by the pre-entry polarized beam splitter 24. The pre-entry P polarized component measurement unit 26P measures the output (light energy) of the P polarized component acquired by the pre-entry polarized beam splitter 24. The P / S ratio measurement unit 29 receives the measurement result of the pre-entry P polarized component measurement unit 26P and the measurement result of the pre-entry S polarized component measurement unit 26S, and measures the ratio between the two. The measurement result of the P / S ratio measurement unit 29 is the output ratio between the P polarized component and the S polarized component when linearly polarized light is transmitted through the wave plate 12.

[0054] Temperature control unit 18 receives the output ratio of one (S polarized component) of the P polarized component and the other (P polarized component) of the S polarized component from P / S ratio measurement unit 29. Other points regarding temperature control unit 18 are similar to those in the third embodiment.

[0055] Next, the operation of the fourth embodiment will be described.

[0056] Of the linearly polarized light emitted from light source 10 and transmitted through wave plate 12, only a small portion is reflected by tap mirror 11 and enters pre-input polarizing beam splitter 24. Pre-input polarizing beam splitter 24 extracts the P polarized component and the S polarized component, and the output of the P polarized component is measured by pre-input P polarized component measurement unit 26P, and the output of the S polarized component is measured by pre-input S polarized component measurement unit 26S. These measurement results are provided to P / S ratio measurement unit 29, which measures the output ratio of one of the P polarized component and the S polarized component (S polarized component) to the other (P polarized component).

[0057] Of the linearly polarized light emitted from light source 10 that passes through wave plate 12, almost all of it passes through tap mirror 11, and the P-polarized component and the S-polarized component are extracted by polarizing beam splitter 14. Here, in order to set the intensity of the P-polarized component to a desired value, temperature control unit 18 controls the temperature of wave plate 12. For this purpose, the output of the S-polarized component is measured by S-polarized component measurement unit 16.

[0058] Temperature control unit 18 obtains an actual value of the P polarized component by multiplying the output ratio of one (S polarized component) and the other (P polarized component) of the P polarized component and the S polarized component received from P / S ratio measurement unit 29 by the measurement result (output of the S polarized component) received from S polarized component measurement unit 16. This actual value of the P polarized component is compared with a target value for the P polarized component, the temperature of wave plate 12 is controlled, and the output of the P polarized component is controlled.

[0059] According to the fourth embodiment, it is possible to obtain the same effects as those of the third embodiment.

[0060] Fifth embodiment The fifth embodiment is an optical attenuator complex including optical attenuators 1A, 1B, . . . , 1N corresponding to the optical attenuator 1 according to the first, second, third and fourth embodiments.

[0061] 5 is a functional block diagram showing a configuration of an optical attenuator 1 according to a fifth embodiment of the present invention. The optical attenuator complex 1 according to the fifth embodiment of the present invention includes a plurality of optical attenuators 1A, 1B, ..., 1N. The outputs of the optical attenuators 1A, 1B, ..., 1N are the same. In other words, the optical energies of the P-polarized components (or S-polarized components) output by the optical attenuators 1A, 1B, ..., 1N are all equal.

[0062] The operation of the fifth embodiment is similar to that described in the first, second, third and fourth embodiments for each of the optical attenuators 1A, 1B, . . . , 1N.

[0063] According to the fifth embodiment, the outputs of a plurality of signals can be made the same.

[0064] Sixth embodiment The sixth embodiment differs from the second embodiment in that it includes another wave plate 32 and another polarization component acquisition unit 34, and has a plurality of outputs (two outputs).

[0065] 6 is a functional block diagram showing the configuration of an optical attenuator 1 according to a sixth embodiment of the present invention. The optical attenuator 1 according to the sixth embodiment of the present invention includes a light source 10, a half mirror 110, a wave plate 12, a polarizing beam splitter (polarized component acquisition unit) 14, an S-polarized component measurement unit (polarized component measurement unit) 16, a light source output recorder 17, a temperature control unit 18, a mirror 31, another wave plate 32, and another polarizing beam splitter (another polarized component acquisition unit) 34. Hereinafter, parts similar to those in the second embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[0066] The light source 10, the wave plate 12, the polarizing beam splitter (polarized component acquisition unit) 14, the S-polarized component measurement unit (polarized component measurement unit) 16, the light source output recording unit 17, and the temperature control unit 18 are the same as those in the second embodiment, and their explanations are omitted. However, the temperature control unit 18 controls the temperature of the wave plate 12 and the temperature of the other wave plate 32 to the same value.

[0067] The half mirror 110 transmits half of the linearly polarized light emitted from the light source 10 and reflects the other half. The light that has transmitted through the half mirror 110 travels toward the wave plate 12. The light reflected by the half mirror 110 travels toward the mirror 31.

[0068] The mirror 31 reflects the light reflected by the half mirror 110 and provides it to another wave plate 32 .

[0069] The other wave plate 32 is a different (separate) wave plate from the wave plate 12. The other wave plate 32 transmits the light (linearly polarized light) reflected by the half mirror 110, and changes the phase difference between the vibration components of the electric field in two directions (for example, the X direction and the Y direction) that are orthogonal to each other in the linearly polarized light. For example, the other wave plate 32 can be a half wave plate. In this case, the phase difference between the vibration component of the electric field in the X direction and the vibration component of the electric field in the Y direction (i.e., the difference between the phase of the vibration component of the electric field in the X direction and the phase of the vibration component of the electric field in the Y direction) can be π+2π×(order of the wave plate 12) (n=0, 1, 2, ...) depending on the thickness of the other wave plate (half wave plate) 32. For example, if the order of the other wave plate 32 is set to 4th order depending on the thickness of the other wave plate (half wave plate), the phase difference between the vibration component of the electric field in the X direction and the vibration component of the electric field in the Y direction can be 9π.

[0070] However, the relationship between the temperature and the transmitted light intensity in the wave plate 12 is the same as the relationship between the temperature and the transmitted light intensity in the other wave plate 32 .

[0071] Another polarizing beam splitter (another polarized light component acquisition section) 34 acquires a P polarized light component and an S polarized light component from the linearly polarized light transmitted through another wave plate 32.

[0072] Next, the operation of the sixth embodiment will be described.

[0073] Half of the linearly polarized light emitted from light source 10 passes through half mirror 110 and wave plate 12, and the P-polarized component and the S-polarized component are extracted by polarizing beam splitter 14. Here, in order to set the intensity of the P-polarized component to a desired value, temperature control unit 18 controls the temperature of wave plate 12. For this purpose, the output of the S-polarized component is measured by S-polarized component measurement unit 16.

[0074] The operation of the temperature control section 18 in controlling the temperature of the wave plate 12 is similar to that in the second embodiment, and a description thereof will be omitted.

[0075] In addition, the other half of the linearly polarized light emitted from the light source 10 is reflected by the half mirror 110, passed through the mirror 31, and passed to another wave plate 32, where the P-polarized component and the S-polarized component are extracted by the other polarizing beam splitter 34.

[0076] In addition, the output ratio of the P polarized component and the S polarized component extracted by the polarizing beam splitter 14 and the output ratio of the P polarized component and the S polarized component extracted by another polarizing beam splitter 34 are both the same value as the output ratio of the P polarized component and the S polarized component of the linearly polarized light emitted from the light source 10.

[0077] Furthermore, the temperature control unit 18 controls the temperature of the wave plate 12 to be the same as that of the other wave plate 32, and the relationship between the temperature and the transmitted light intensity in the wave plate 12 is the same as that between the temperature and the transmitted light intensity in the other wave plate 32. Therefore, the ratio between the output of light transmitted through the half mirror 110 and the output of reflected light is the same as the ratio between the output of light provided to the polarizing beam splitter 14 and the output of light provided to the other polarizing beam splitter 34.

[0078] Therefore, the ratio between the output of the P polarized component extracted by the polarizing beam splitter 14 and the output of the P polarized component extracted by another polarizing beam splitter 34 is the same as the ratio between the output of the light transmitted through the half mirror 110 and the output of the reflected light (1:1).

[0079] According to the sixth embodiment, two outputs can be obtained from one light source 10.

[0080] Seventh embodiment The seventh embodiment differs from the third embodiment in that it includes another wave plate 32 and another polarization component acquisition unit 34, and has a plurality of outputs (two outputs).

[0081] 7 is a functional block diagram showing the configuration of an optical attenuator 1 according to a seventh embodiment of the present invention. The optical attenuator 1 according to the seventh embodiment of the present invention includes a light source 10, a half mirror 110, a wave plate 12, a polarizing beam splitter (polarized component acquisition unit) 14, an S-polarized component measurement unit (polarized component measurement unit) 16, a temperature control unit 18, a P / S ratio recording unit 19, a mirror 31, another wave plate 32, and another polarizing beam splitter (another polarized component acquisition unit) 34. Hereinafter, parts similar to those in the third embodiment are given the same reference numerals and will not be described.

[0082] The light source 10, wave plate 12, polarizing beam splitter (polarized component acquisition unit) 14, S-polarized component measurement unit (polarized component measurement unit) 16, temperature control unit 18, and P / S ratio recording unit 19 are the same as those in the third embodiment, and their explanations are omitted. However, the temperature control unit 18 controls the temperature of the wave plate 12 and the temperature of the other wave plates 32 to the same value. In addition, the relationship between the temperature and the transmitted light intensity in the wave plate 12 is the same as the relationship between the temperature and the transmitted light intensity in the other wave plates 32.

[0083] The half mirror 110, the mirror 31, the other wave plate 32, and the other polarizing beam splitter (other polarized component acquisition unit) 34 are similar to those in the sixth embodiment, and the description thereof will be omitted.

[0084] Next, the operation of the seventh embodiment will be described.

[0085] Half of the linearly polarized light emitted from light source 10 passes through half mirror 110 and wave plate 12, and the P-polarized component and the S-polarized component are extracted by polarizing beam splitter 14. Here, in order to set the intensity of the P-polarized component to a desired value, temperature control unit 18 controls the temperature of wave plate 12. For this purpose, the output of the S-polarized component is measured by S-polarized component measurement unit 16.

[0086] The operation of the temperature control section 18 in controlling the temperature of the wave plate 12 is similar to that in the third embodiment, and a description thereof will be omitted.

[0087] In addition, the other half of the linearly polarized light emitted from the light source 10 is reflected by the half mirror 110, passed through the mirror 31, and passed to another wave plate 32, where the P-polarized component and the S-polarized component are extracted by the other polarizing beam splitter 34.

[0088] As in the sixth embodiment, the ratio between the output of the P polarized component extracted by the polarizing beam splitter 14 and the output of the P polarized component extracted by the other polarizing beam splitter 34 is the same as the ratio between the output of the light transmitted through the half mirror 110 and the output of the reflected light (1:1).

[0089] According to the seventh embodiment, two outputs can be obtained from one light source 10. [Explanation of symbols]

[0090] 1 Optical attenuator 1A, 1B, …, 1N Optical Attenuators 10 light source 12 wave plate 14 Polarizing beam splitter (polarized component acquisition part) 16 S-polarized component measurement unit (polarized component measurement unit) 17 Light source output recorder 18 Temperature control unit 19 P / S ratio record section 32 Other Waveplates 34 Other polarizing beam splitter (other polarized component acquisition part)

Claims

1. A light source that emits linearly polarized light; a wave plate that transmits the linearly polarized light and changes a phase difference between vibration components of electric fields in two directions perpendicular to each other in the linearly polarized light; a polarization component acquisition unit that acquires a P polarization component and an S polarization component from the linearly polarized light that has passed through the wave plate; A temperature control unit for controlling a temperature of the wave plate; a polarization component measuring unit that measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit; Equipped with the temperature control unit controls the intensity of the P-polarized component or the S-polarized component acquired by the polarization component acquisition unit; the temperature control unit controls the other of the P-polarized component and the S-polarized component by comparing a target value of the other of the P-polarized component and the S-polarized component with a value obtained by subtracting a measurement result of the polarization component measurement unit from the output of the linearly polarized light. Optical attenuator.

2. A light source that emits linearly polarized light; a wave plate that transmits the linearly polarized light and changes a phase difference between vibration components of electric fields in two directions perpendicular to each other in the linearly polarized light; a polarization component acquisition unit that acquires a P polarization component and an S polarization component from the linearly polarized light that has passed through the wave plate; A temperature control unit for controlling a temperature of the wave plate; a polarization component measuring unit that measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit; Equipped with the temperature control unit controls the intensity of the P-polarized component or the S-polarized component acquired by the polarization component acquisition unit; the temperature control unit controls the other of the P-polarized component and the S-polarized component by comparing a target value of the other of the P-polarized component and the S-polarized component with a ratio of the one of the P-polarized component and the other of the S-polarized component multiplied by a measurement result of the polarization component measurement unit. Optical attenuator.

3. An optical attenuator as claimed in claim 2, The ratio of the one to the other is obtained by measuring the ratio of the P-polarized component to the S-polarized component of the linearly polarized light transmitted through the wave plate. Optical attenuator.

4. A light source that emits linearly polarized light; a wave plate that transmits the linearly polarized light and changes a phase difference between vibration components of electric fields in two directions perpendicular to each other in the linearly polarized light; a polarization component acquisition unit that acquires a P polarization component and an S polarization component from the linearly polarized light that has passed through the wave plate; A temperature control unit for controlling a temperature of the wave plate; The linearly polarized light is transmitted, and a phase difference between vibration components of electric fields in two directions perpendicular to each other is changed in the linearly polarized light. Another wave plate different from the wave plate is provided. another polarization component acquisition unit that acquires the P polarization component and the S polarization component from the linearly polarized light transmitted through the other wave plate; Equipped with the temperature control unit controls the intensity of the P-polarized component or the S-polarized component acquired by the polarization component acquisition unit; the temperature control unit controls the temperature of the wave plate and the temperature of the other wave plate to the same value; The relationship between the temperature and the transmitted light intensity in the wave plate is the same as the relationship between the temperature and the transmitted light intensity in the other wave plate. Optical attenuator.

5. An optical attenuator as claimed in claim 4, a polarization component measuring unit that measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit; the temperature control unit controls the other of the P-polarized component and the S-polarized component by comparing a target value of the other of the P-polarized component and the S-polarized component with a value obtained by subtracting a measurement result of the polarization component measurement unit from the output of the linearly polarized light. Optical attenuator.

6. An optical attenuator as claimed in claim 4, a polarization component measuring unit that measures one of the P polarization component and the S polarization component acquired by the polarization component acquiring unit; the temperature control unit controls the other of the P-polarized component and the S-polarized component by comparing a target value of the other of the P-polarized component and the S-polarized component with a ratio of the one of the P-polarized component and the other of the S-polarized component multiplied by a measurement result of the polarization component measurement unit. Optical attenuator.

7. 7. An optical attenuator according to claim 1, The temperature control unit is a heater. Optical attenuator.

8. 7. An optical attenuator according to claim 1, The temperature control unit is a Peltier element. Optical attenuator.

9. A plurality of optical attenuators according to any one of claims 1 to 3 are provided, The optical energies of the P-polarized components or the S-polarized components output from each of the optical attenuators are equal to each other. Optical attenuator complex.

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