JP2010230955A - Optical component and wavelength dispersion compensator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical component capable of dissolving wavelength characteristics of optical loss and expanding a transmission band. <P>SOLUTION: The optical component is constituted, by including: a glass plate 1a having parallel planes facing each other; a reflecting surface layer 1b which is a reflection film with reflectance of 100%; and an emitting surface layer 1c which is a reflecting film with reflectance lower than 100% formed on the parallel planes of the glass plate, respectively, wherein intensity of emitted light to be emitted, by transmitting the emitting surface layer 1c becomes approximately uniform from the first emitting position to the last emitting position by the formation of the emitting surface layer 1c so that transmittance becomes higher as reflection frequency of the light increases from a part, where the light made incident in the glass plate first reflects in the multiple reflection directions. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The technology disclosed herein relates to an optical component having a function of demultiplexing input light according to a wavelength, and a chromatic dispersion compensator that compensates chromatic dispersion using the optical component.

  Recently, VIPA (Virtually Imaged Phased Array) is one of the optical components that demultiplex input light into multiple light fluxes that can be spatially differentiated according to wavelength. Is used. VIPA performs demultiplexing by multiply-reflecting input light in a VIPA in which a reflective film is formed on a glass plate. More specifically, the VIPA includes a glass plate having opposing parallel planes, and a reflective film formed on each of the parallel planes of the glass plate. One reflective film of the glass plate is a reflective surface layer having a reflectivity of almost 100% with respect to light incident on the glass plate, and the other reflective film is for light incident on the glass plate. , An output surface layer having a reflectance lower than 100%, for example, a reflectance of 95% to 98%. Input light to the VIPA enters the glass plate through an irradiation window formed on the reflective surface layer side.

  The light incident on the glass plate gradually passes through the exit surface layer while being multiple-reflected between the two reflecting films, and is emitted as a plurality of light beams. At the time of the emission, as described in FIG. 14 of Patent Document 1 and FIG. 4 “Constant” of Non-Patent Document 1, the emitted light has an intensity distribution (profile) corresponding to the number of reflections in the VIPA. It has been known. That is, the intensity of the emitted light becomes weaker as the number of reflections increases in the multiple reflection direction.

  When such a VIPA is used for a chromatic dispersion compensator, outgoing light emitted from the VIPA while being subjected to multiple reflections is collected through a lens, then reflected by a mirror, and again enters the VIPA through the lens. At this time, the reflected light that is reflected by the mirror and re-enters the VIPA has an intensity distribution obtained by substantially inverting the intensity distribution of the emitted light (see FIG. 4 of Non-Patent Document 1).

  In an optical device such as a chromatic dispersion compensator where the exit light of VIPA is reflected by a mirror and re-enters VIPA, the inversion of the intensity distribution of the reflected light with respect to the intensity distribution of the exit light as described above, Affects optical loss in VIPA. Therefore, Patent Document 1 and Non-Patent Document 1 propose changing the reflectance of the exit surface layer that transmits the exit light in the multiple reflection direction.

  In the case of Patent Document 1, the emission surface layer is formed so that the reflectance decreases from the first emission position to the last emission position, and the emission light intensity distribution has a substantially bell-shaped curve symmetrical shape. (FIG. 15 of Patent Document 1). Further, in the case of Non-Patent Document 1, the output surface layer is further formed so that the transmittance changes in two steps (2-level) so that two intensity peaks appear. The distribution has a substantially symmetrical shape.

JP 2000-028849 A

"Analysis of coating design in a virtually imaged phased array (VIPA) chromatic dispersion compensator", Christopher Lin and Masataka Shirasaki, WDM and Photonic Switching Device for Network Applications II, Proceeding of SPIE Vol. 4289 (2001)

  In an optical device in which the exit light of VIPA is reflected by a mirror and re-enters VIPA, it is known that if there is a peak in the exit light intensity distribution in VIPA, wavelength characteristics will occur in the optical loss in VIPA . This will be described with reference to FIG. In the intensity distribution diagram in FIG. 8, the solid line represents the emitted light intensity distribution, and the dotted line represents the reflected light intensity distribution.

  In a VIPA module including an optical system such as a lens and a mirror for reflecting outgoing light, the positional relationship between the VIPA and the optical system is set according to the wavelength of the input light. For this setting, the relationship in which the coupling between the intensity distribution of the outgoing light emitted from the VIPA and the intensity distribution of the reflected light re-entering the VIPA is maximized. The relationship between the outgoing light intensity distribution and the reflected light intensity distribution at the optimum setting is a distribution diagram of the center wavelength shown in the center in FIG. That is, as shown in the drawing, the positions of the VIPA and the optical system are optimized so that the area of the overlapping portion between the outgoing light intensity distribution and the reflected light intensity distribution is maximized.

  Specifically, the signal light input to the VIPA has a spectrum shape corresponding to a transmission speed, a modulation method, etc., and a component on the long wavelength side and a component on the short wavelength side with respect to the center wavelength of the spectrum shape. Is included. Since the angle of the outgoing light emitted from the VIPA changes according to the wavelength component of the light incident on the VIPA, a deviation occurs in the intensity distribution corresponding to each wavelength component. That is, in FIG. 8, when the wavelength component of the incident light to VIPA shifts to the longer wavelength side with respect to the center wavelength, the emitted light intensity distribution is on the lower side (irradiation window side) with respect to the multiple reflection direction in VIPA. When shifted to the short wavelength side, the emitted light intensity distribution shifts to the upper side (the opposite side of the irradiation window) with respect to the same multiple reflection direction. In accordance with this shift, the reflected light intensity distribution shifts upward when the outgoing light shifts downward, and shifts downward when the outgoing light shifts upward. Therefore, as the wavelength component of the signal light deviates from the center wavelength, the coupling efficiency between the two becomes smaller and the optical loss increases.

  The techniques of Patent Document 1 and Non-Patent Document 1 both make the emitted light intensity distribution exhibit a substantially symmetrical shape, but do not suppress the peak of the emitted light intensity distribution. Therefore, it is difficult to prevent the above-described decrease in the coupling efficiency due to the deviation of the emitted light intensity distribution according to the wavelength component included in the input light.

  In view of such a background, there is a need for a VIPA that can eliminate the wavelength characteristic of optical loss and can widen the transmission band.

The optical component proposed here is
A glass plate having opposing parallel planes, and a reflective film formed on each of the parallel planes of the glass plate,
One of the reflective films is a reflective surface layer having a reflectance of approximately 100% with respect to light incident on the glass plate, and the other reflective film is for light incident on the glass plate. And an output surface layer having a reflectance lower than 100%,
The light that has entered the glass plate is transmitted through the emission surface layer while being multiple-reflected between the two reflection films, and then emitted.
An optical component having the following mode.

The optical component related to the proposal is
The emission surface layer is formed so that the transmittance increases as the number of reflections of light increases from the portion where the light incident on the glass plate is first reflected to the multiple reflection direction. The intensity of the outgoing light that is transmitted through the surface layer is substantially uniform from the first outgoing position to the last outgoing position.

  The so-called VIPA, which is an optical component according to this proposal, is one in which the transmittance of the exit surface layer is changed in the multiple reflection direction. With regard to the change in transmittance, the emitted light from the first exit position to the last exit position. The strength is changed so as to be almost uniform. In other words, the transmittance is changed so as to increase as the number of times of reflection of the light reflected in the glass plate increases, so that the intensity of the emitted light becomes substantially uniform. The light that is multiple-reflected in the glass plate is gradually emitted from the emission surface layer, and thus gradually becomes weaker each time reflection is repeated. Correspondingly, if the transmittance of the emission surface layer gradually increases, the intensity of the emitted light can be made substantially constant.

  If the intensity of the emitted light is uniform in the multiple reflection direction, the intensity distribution has a flat and symmetric shape with suppressed peaks. If the intensity distribution shows a flat and symmetric shape, the coupling ratio of the outgoing light intensity distribution and the reflected light intensity distribution increases, and the coupling efficiency at the center wavelength of the light input to the optical component is improved. Further, even if the intensity distribution is shifted in the multiple reflection direction according to the wavelength component of the input light, the coupling efficiency between the outgoing light intensity distribution and the reflected light intensity distribution is not reduced as in the prior art. Therefore, a decrease in coupling efficiency is suppressed, and it is possible to improve the wavelength characteristic of optical loss and expand the transmission band.

The figure explaining the structure of the chromatic dispersion compensator which uses VIPA. The figure explaining the relationship between the transmittance | permeability of the output surface layer in VIPA, and emitted light intensity distribution. The figure explaining the wavelength characteristic of the emitted light intensity distribution of VIPA which concerns on embodiment. The figure explaining the output surface layer structure of VIPA which concerns on embodiment. The graph which showed the transmittance | permeability change of the output surface layer in a multiple reflection direction (Y direction). The graph which showed the emitted light intensity distribution in the multiple reflection direction (Y direction). The graph which showed the wavelength characteristic of optical loss. The figure explaining the wavelength characteristic of the emitted light intensity distribution of the conventional VIPA.

FIG. 1 shows a chromatic dispersion compensator as an example of an optical device including a VIPA.
The illustrated chromatic dispersion compensator irradiates the VIPA 1 with uncompensated input light and outputs the compensated output light from the VIPA 1 as an optical circulator 2, an optical fiber 3, a collimator lens 4, and a line focus lens. 5 is provided. Input light to the chromatic dispersion compensator is output from the optical fiber 3 through the optical circulator 2, and then condensed on one line segment through the collimator lens 4 and the line focus lens 5.

  The VIPA 1 has a structure in which a reflective film is formed on the opposing parallel planes of the glass plate 1a. One of the reflective films is a reflective surface layer 1b having a reflectance of approximately 100% with respect to the light incident on the glass plate 1a, and the other reflective film is on the light incident on the glass plate 1a. As described later, the emission surface layer 1c has a reflectance lower than 100%. An irradiation window 1d for irradiating light from the line focus lens 5 into the glass plate 1a is formed at the lower end portion of the reflective surface layer 1b.

  The light irradiated from the line focus lens 5 is condensed linearly on the emission surface layer 1c through the irradiation window 1d. The portion where this light is collected becomes the first reflection portion in the emission surface layer 1c. Thus, the light incident on the glass plate 1a gradually passes through the emission surface layer 1c while being multiple-reflected between the emission surface layer 1c and the reflection surface layer 1b, and is emitted as a plurality of light beams.

  The outgoing light transmitted through the outgoing surface layer 1c is reflected by the second optical system including the converging lens 6 and the mirror 7, and enters the glass plate 1a again from the outgoing surface layer 1c. That is, the emitted light is condensed and reflected on the mirror 7 through the converging lens 6 that condenses at different positions according to the wavelength, and this reflected light passes through the emitting surface layer 1c through the converging lens 6 again. The light enters the glass plate 1a. The reflected light re-entered into the glass plate 1a sequentially passes through the irradiation window 1d, the line focus lens 5, the collimating lens 4, and the optical fiber 3, and is output to a port different from the input light through the optical circulator 2.

  In the VIPA 1 used for this chromatic dispersion compensator, the output surface layer 1c has the lowest transmittance at the part where the light incident from the line focus lens 5 into the glass plate 1a is first reflected. The transmittance gradually increases in the multiple reflection direction indicated by the Y axis. That is, the transmittance increases as the number of reflections of incident light increases. As a result, the intensity of the emitted light that is transmitted through the emission surface layer 1c is substantially uniform from the first emission position to the last emission position. The transmittance of the emission surface layer 1c will be described with reference to FIG.

  As a comparative example, FIG. 2A shows a general VIPA in which the transmittance of the exit surface layer is constant, and FIG. 2B shows the VIPA1. In the case of the comparative example shown in FIG. 2A, since the transmittance of the exit surface layer is constant, as described above, the exit light intensity distribution is the strongest at the first exit position and becomes weaker as the number of reflections increases. Show. When the emitted light having this intensity distribution returns as reflected light, as shown in FIG. 8, the intensity distribution is inverted, so that the wavelength characteristic of optical loss appears strongly.

  On the other hand, the exit surface layer 1c in the VIPA 1 of the present embodiment shown in FIG. 2B is formed so that the transmittance increases as the number of reflections of light increases. As a result, the intensity of the emitted light that is transmitted through the emission surface layer 1c is substantially uniform from the first emission position to the last emission position, and thus the intensity distribution is a flat (rectangular) distribution. That is, the light that is multiple-reflected in the glass plate 1a is gradually emitted from the emission surface layer 1c, and therefore gradually becomes weaker each time the reflection is repeated. Correspondingly, the intensity of the outgoing light can be made substantially constant by gradually increasing the transmittance of the outgoing face layer 1c.

  If the intensity of the emitted light is constant in the multiple reflection direction indicated by the Y axis in FIG. 1, the intensity distribution of the emitted light exhibits a flat and symmetric shape. If the intensity distribution shows a flat and symmetric shape with suppressed peaks, even if the intensity distribution shifts in the multiple reflection direction according to the wavelength component contained in the input light, the outgoing light intensity distribution and the reflected light intensity The coupling efficiency of the distribution is not reduced as in the prior art. This is illustrated in FIG.

  As described above, the positional relationship between the VIPA 1 and the second optical system (the converging lens 6 and the mirror 7) is such that the coupling between the intensity distribution of the emitted light exiting from the VIPA 1 and the intensity distribution of the reflected light re-entering the VIPA 1 is maximum. Is set to a relationship. The relationship between the emitted light intensity distribution and the reflected light intensity distribution at this time is a distribution diagram of the center wavelength shown at the center in FIG. If the outgoing light has an intensity distribution flattened by adjusting the transmittance of the outgoing surface layer 1c, the intensity distribution of the reflected light that is inverted and reflected is also flat. Therefore, if the positions of VIPA 1 and the second optical system are optimized so that the area of the overlapping portion of the emitted light intensity distribution and the reflected light intensity distribution is maximized, the two are almost the same. As a result, the coupling efficiency is improved as compared with a distribution having peaks.

  Further, as shown in FIG. 3, the wavelength component deviated from the center wavelength of the input light changes the intensity distribution because the emission angle of the emitted light changes. That is, in FIG. 3, the wavelength component shifted to the long wavelength side with respect to the center wavelength of the input light has the emission light intensity distribution shifted downward (irradiation window side) with respect to the multiple reflection direction in the VIPA 1, and the short wavelength side. For the wavelength component shifted to, the outgoing light intensity distribution shifts upward (opposite to the irradiation window) with respect to the multiple reflection direction in VIPA1. In accordance with this shift, the reflected light intensity distribution shifts upward when the outgoing light shifts downward, and shifts downward when the outgoing light shifts upward. However, if the intensity distribution of both is flattened, the ratio of coupling is higher than that of the distribution with the peak, so even if the intensity distribution of the outgoing light and the reflected light is shifted from each other, However, the coupling efficiency does not decrease. Therefore, a decrease in coupling efficiency is suppressed, and it is possible to improve the wavelength characteristic of optical loss and expand the transmission band.

The change in transmittance of the exit surface layer 1c that obtains such an exit light intensity distribution can be obtained as follows. Here, the intensity of light emitted from the exit surface layer 1c is expressed as P (y) as a function of the distance y in the Y-axis (multiple reflection direction), and the transmittance per unit length of the exit surface layer 1c is also expressed as a distance. Let α (y) be a function of y. At this time, assuming that the initial emission position on the emission surface layer 1c is y = y1, the emission light intensity P (y1) follows the following formula 1 with the input light intensity to VIPA1 being Pi.
[Formula 1]
P (y1) = Pi · α (y1)

If the second emission position is y = y2, the intensity of the light that reaches the emission position y2 after multiple reflection in VIPA1 is Pi · {1-α (y1)}. P (y2) follows the following equation 2.
[Formula 2]
P (y2) = Pi · {1-α (y1)} · α (y2)

Using the relationship that the light intensities P (y1) and P (y2) at the respective emission positions are constant in the above formulas 1 and 2, the following formula 3 is obtained.
[Formula 3]
Pi · α (y1) = Pi · {1−α (y1)} · α (y2)
[Formula 4]
α (y2) = α (y1) / {1-α (y1)}

Further, if the third emission position is y = y3, the intensity of the light reaching the emission position y3 after multiple reflection in VIPA1 is Pi · {1-α (y1)} · {1-α (y2) }, The output light intensity P (y3) follows the following formula 5.
[Formula 5]
P (y3) = Pi · {1-α (y1)} · {1-α (y2)} · α (y3)

When the relationship that P (y2) and P (y3) are constant is used for the above formulas 2 and 5, the following formula 6 is obtained. When this formula is arranged using formula 4, formula 7 is obtained.
[Formula 6]
Pi · {1-α (y1)} · α (y2)
= Pi · {1-α (y1)} · {1-α (y2)} · α (y3)
[Formula 7]
α (y3) = α (y2) / {1-α (y2)}
= Α (y1) / {1-2 · α (y1)}

When the function α (yn) at the n-th output position is obtained in the same manner as Expression 4 and Expression 7, the relationship of Expression 8 below is obtained.
[Formula 8]
α (yn) = α (y1) / {1- (n−1) · α (y1)}

  By the relationship of the above equation 8, the intensity of the outgoing light is made constant and flat by increasing the transmittance of the outgoing surface layer 1c as the number of multiple reflections increases (the distance in the Y-axis direction becomes longer). An intensity distribution can be obtained.

A structure for changing the transmittance of the emission surface layer 1c will be described with reference to FIG.
The exit surface layer 1c in the VIPA 1 shown in FIG. 4 uses a dielectric film as an example of a reflective film, and is formed by laminating a plurality of dielectric films 10-15. The number of laminated dielectric films 10 to 15 is reduced in the multiple reflection direction (Y-axis direction) from the portion where the light incident on the glass plate 1a is first reflected, that is, from the irradiation window 1d side. Thereby, the output surface layer 1c is gradually thinned in the multiple reflection direction from the portion where the incident light is first reflected. As the number of laminated dielectric films 10 to 15 decreases, the transmittance increases. Therefore, the illustrated outgoing surface layer 1c increases in the multiple reflection direction as the number of reflections of light increases.

  The lowermost dielectric film 10 is deposited on the entire parallel plane of the glass plate 1a. The dielectric film 11 laminated thereon has a shorter upper end than the dielectric film 10 by reducing the deposition range. Similarly, the dielectric films 12 to 15 are formed by vapor deposition so that the upper end portion is shorter than the lower layer film. The thicknesses of the dielectric films 10 to 15 may all be the same, but the transmittance can be finely adjusted by changing the thickness of the dielectric films 10 to 15. These dielectric films 10 to 15 can be formed on the glass plate 1a using a photolithography process or the like.

  For example, the emission surface layer 1c is formed by laminating a dielectric film so that the transmittance is 1% at the lowest transmittance portion and 100% at the highest transmittance portion, and the transmittance is changed stepwise. Can do.

  As an example, the graph of FIG. 5 shows the result of calculating the transmittance of the exit surface layer 1c so that the intensity of the emitted light is uniform. The horizontal axis represents the distance in the Y-axis direction, and the vertical axis represents the transmittance. The origin of the distance in the Y-axis direction in this example is the position where the light incident on the glass plate 1a is first reflected by the exit surface layer 1c.

  The transmittance in FIG. 5 is 1% at the origin of the distance in the Y-axis direction, and increases with increasing distance from the origin so as to cancel out the emitted light intensity distribution as shown in FIG. 2A. In this example, the transmittance is 100% when the distance in the Y-axis direction exceeds 2 mm. The position where the transmittance is 100% corresponds to the vicinity of the final emission position of the multiple reflected light. On the other hand, when the transmittance of the emission surface layer shown in FIG. 5 is constant, the transmittance is maintained at 1%.

  FIG. 6 shows the intensity distribution of the outgoing light emitted from the outgoing surface layer 1c having the transmittance change shown in FIG. The horizontal axis represents the distance in the Y-axis direction, and the vertical axis represents the output light intensity normalized with the input light intensity to VIPA 1 as 1. Since the transmittance of the exit surface layer 1c is changed so that the intensity of the emitted light is constant, the intensity distribution of the emitted light in the Y-axis direction is flat and exceeds 2 mm where the transmittance is 100% (Last) In the vicinity of the emission position, the emission light is lost. That is, the emitted light intensity distribution is rectangular. On the other hand, when the transmittance of the emission surface layer shown in FIG. 6 is constant, the emission light intensity is strongest at the Y-axis direction distance origin, and the emission light intensity decreases as the Y-axis direction distance increases. I will do it.

  FIG. 7 shows a graph in which the coupling loss is estimated as a result of the emitted light intensity distribution shown in FIG. The horizontal axis represents the wavelength difference from the center wavelength of the input light, and the vertical axis represents the loss (coupling loss) received by the input light traveling back and forth through the VIPA 1 as a negative value. According to the outgoing face layer 1c having a change in transmittance that makes the outgoing light intensity constant, the coupling loss is reduced as a whole, and the coupling loss at the center wavelength is about -0.1 dB. And on the short wavelength side with a wavelength difference of -0.4 nm from the central wavelength, an increase in coupling loss of about 0.1 dB is observed in absolute value, and on the long wavelength side with a + wavelength difference, the increase in coupling loss is almost I can't see it. On the other hand, when the transmittance of the emission surface layer shown in FIG. 7 is constant, the coupling loss at the center wavelength is about −1.3 dB. In addition, an increase in coupling loss of about 0.4 dB in absolute value is observed on the short wavelength side having a wavelength difference of −0.4 nm from the center wavelength, and 0 in absolute value on the long wavelength side having a wavelength difference of +0.4 nm. There is an increase in coupling loss of about 1 dB.

  Additional notes regarding the above embodiments are disclosed below.

(Appendix 1)
A glass plate having parallel planes facing each other, and a first reflective film and a second reflective film respectively formed on the parallel plane of the glass plate,
The first reflective film is a reflective surface layer having a reflectance of approximately 100% with respect to light incident on the glass plate;
The second reflective film is an output surface layer having a reflectance lower than 100% with respect to light incident in the glass plate,
An optical component in which light incident on the glass plate is transmitted through the emission surface layer while being multiple-reflected between the first reflection film and the second reflection film,
The exit surface layer is formed so that the transmittance increases as the number of reflections of light increases from the portion where light incident into the glass plate is first reflected to the multiple reflection direction.
An optical component in which the intensity of outgoing light that is transmitted through the outgoing surface layer is substantially uniform from the first outgoing position to the last outgoing position.

(Appendix 2)
An optical component according to appendix 1,
The optical component in which the said output surface layer becomes thin gradually in the multiple reflection direction from the part which the light which injected into the said glass plate reflects first.

(Appendix 3)
An optical component according to appendix 2,
The light-emitting surface layer is formed by laminating a reflective film, and the number of laminated layers decreases in the multiple reflection direction from the portion where the light incident on the glass plate is first reflected.

(Appendix 4)
The optical component according to any one of appendices 1 to 3,
The emission surface layer has a transmittance of 1% at the lowest transmittance portion. Optical parts.

(Appendix 5)
The optical component according to any one of appendices 1 to 4,
The light emitting surface layer is an optical component having a transmittance of 100% at a portion having the highest transmittance.

(Appendix 6)
The optical component according to any one of appendices 1 to 5,
A lens for condensing outgoing light emitted from the outgoing surface layer of the optical component at different positions according to wavelength;
A mirror that reflects the light collected by the lens and re-enters the reflected light from the exit surface layer into the glass plate of the optical component via the lens;
A chromatic dispersion compensator comprising:

(Appendix 7)
The chromatic dispersion compensator according to appendix 6, wherein
An optical circulator to which input light is applied;
A collimating lens that collimates the input light output from the optical fiber through the optical circulator;
A line focus lens that condenses the light that has passed through the collimator lens onto one line, and enters the glass plate of the optical component; and
A chromatic dispersion compensator further comprising:

1 VIPA
1a Glass plate 1b Reflective surface layer (almost 100% reflective film)
1c Outgoing surface layer (reflective film lower than 100%)
1d Irradiation window 2 Optical circulator 3 Optical fiber 4 Collimating lens 5 Line focus lens 6 Converging lens 7 Mirror

Claims (4)

A glass plate having parallel planes facing each other, and a first reflective film and a second reflective film respectively formed on the parallel plane of the glass plate,
The first reflective film is a reflective surface layer having a reflectance of approximately 100% with respect to light incident on the glass plate;
The second reflective film is an output surface layer having a reflectance lower than 100% with respect to light incident in the glass plate,
An optical component in which light incident on the glass plate is transmitted through the emission surface layer while being multiple-reflected between the first reflection film and the second reflection film,
The exit surface layer is formed so that the transmittance increases as the number of reflections of light increases from the portion where light incident into the glass plate is first reflected to the multiple reflection direction.
An optical component in which the intensity of outgoing light that is transmitted through the outgoing surface layer is substantially uniform from the first outgoing position to the last outgoing position. The optical component according to claim 1,
The optical component in which the said output surface layer becomes thin gradually in the multiple reflection direction from the part which the light which injected into the said glass plate reflects first. The optical component according to claim 2,
The emission surface layer is formed by laminating a reflection film, and the number of the reflection films is reduced in the multiple reflection direction from the part where the light incident on the glass plate is first reflected, Optical parts. The optical component according to any one of claims 1 to 3,
A lens for condensing outgoing light emitted from the outgoing surface layer of the optical component at different positions according to wavelength;
A mirror that reflects the light collected by the lens and re-enters the reflected light from the exit surface layer into the glass plate of the optical component via the lens;
A chromatic dispersion compensator comprising:

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