Optical apparatus which uses a virtually imaged phased array to produce chromatic dispersion

• US 6,332,689 B1
• Filed: 05/23/2000
• Issued: 12/25/2001
• Est. Priority Date: 12/14/1999
• Status: Expired due to Term

• Current Assignee: II-VI Delaware, Inc. (Coherent Corp.), Fujitsu Limited
• Original Assignee: Fujitsu Limited, Avanex Corporation (Oclaro (North America), Inc.)
• Inventors: Shirasaki, Masataka, Cao, Simon
• Primary Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US09/576,541
• Time in Patent Office: 581 Days
• Field of Search: 359/868, 359/869, 359/577, 359/578, 359/579, 359/615, 359/618, 359/629, 359/634, 359/839, 359/856, 359/857, 359/366, 362/297, 362/560
• US Class Current: 359/868
• CPC Class Codes: G02B 27/0087 Phased arrays
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 27/106 for splitting or combining a plurality of identical beams or images, e.g. image replication
• CPC Class Codes: G02B 27/1073 characterized by manufacturing or alignment methods
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/126 The splitting element being a prism or prismatic array, including systems based on total internal reflection
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces
• CPC Class Codes: G02B 27/148 including stacked surfaces having at least one double-pass partially reflecting surface
• CPC Class Codes: G02B 5/10 with curved faces
• CPC Class Codes: G02B 6/2931 Diffractive element operating in reflection
• CPC Class Codes: G02B 6/29311 Diffractive element operating in transmission
• CPC Class Codes: G02B 6/29358 Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator G02B6/29347, G02B6/29349, G02B6/2935, G02B6/29361 take precedence; resonator evanescently coupled to light guide G02B6/29335
• CPC Class Codes: G02B 6/29361 Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
• CPC Class Codes: G02B 6/29392 Controlling dispersion G02B6/02214 takes precedence; modal dispersion control G02B6/268
• CPC Class Codes: G02B 6/29394 Compensating wavelength dispersion G02B6/29376 takes precedence; dispersion compensated optical transmission systems H04B10/2507
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35
• CPC Class Codes: H04B 10/25133 including a lumped electrical or optical dispersion compensator H04B10/2519, H04B10/2525 takes precedence

Abstract

An optical apparatus for producing chromatic dispersion. The apparatus includes a virtually imaged phased array (VIPA) generator, a mirror and a lens. The VIPA generator receives an input light at a respective wavelength and produces a corresponding collimated output light traveling from the VIPA generator in a direction determined by the wavelength of the input light, the output light thereby being spatially distinguishable from an output light produced for an input light at a different wavelength. The mirror has a cone shape, or a modified cone shape. The lens focuses the output light traveling from the VIPA generator onto the mirror so that the mirror reflects the output light. The reflected light is directed by the lens back to the VIPA generator. In this manner, the apparatus provides chromatic dispersion to the input light. The modified cone shape of the mirror can be designed so that the apparatus provides a uniform chromatic dispersion to light in the same channel of a wavelength division multiplexed light.

Claims

1. An apparatus comprising:

a virtually imaged phased array (VIPA) generator receiving an input light at a respective wavelength and producing a corresponding collimated output light traveling from the VIPA generator in a direction determined by the wavelength of the input light; and

a reflecting surface reflecting the output light back to the VIPA generator, the reflecting surface having different curvatures at different positions along a direction perpendicular to a plane which includes the traveling directions of collimated output light from the VIPA generator for input light at different wavelengths, curvature c(y) of the reflecting surface being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

 

where

Θ

y=is a light focusing position on the reflecting surface,

Φ

=is an input angle of the input light to the VIPA generator in air,

f=is a focal length of a lens or mirror focusing the output light traveling from the VIPA generator onto the reflecting surface,

a=is a depth of a center beam waist of the VIPA generator, and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of light, λ

being wavelength, an n being a refractive index of material forming the VIPA generator.

2. An apparatus as in claim 1, further comprising:

said lens or mirror focusing the output light traveling from the VIPA generator onto the reflecting surface so that the reflecting surface reflects the output light, the reflected light being directed by said lens or mirror back to the VIPA generator.

3. An apparatus as in claim 1, wherein

the input light is a wavelength division multiplexed (WDM) light having a plurality of channels, each channel having an amount of chromatic dispersion corresponding to wavelength and due to traveling through a transmission line, and

parameters of the reflecting surface cause the apparatus to provide chromatic dispersion to each channel in the same amount but opposite sign to that due to traveling through the transmission line.

4. An apparatus as in claim 1, wherein the VIPA generator comprises:

first and second surfaces, the first surface allowing substantially no light to be transmitted therethrough; and

a radiation window in the same plane as the first surface, the input light passing through the radiation window to enter the VIPA generator, the first and second surfaces positioned so that the input light entering the VIPA generator through the radiation window is reflected a plurality of times between the first and second surfaces to produce said output light.

5. An apparatus as in claim 4, wherein:

the first surface has substantially 100% reflectivity, and

the radiation window has substantially 100% transmissivity.

6. An apparatus comprising:

a virtually imaged phased array (VIPA) generator receiving an input light at a respective wavelength and producing a corresponding collimated output light traveling from the VIPA generator in a direction determined by the wavelength of the input light, the output light thereby being spatially distinguishable from an output light produced for an input light at a different wavelength;

a reflecting surface having a cone or modified cone shape; and

a lens or mirror focusing the output light traveling from the VIPA generator onto the reflecting surface so that the reflecting surface reflects the output light, the reflected light being directed by the said lens or mirror back to the VIPA generator, curvature c(y) of the reflecting surface being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

where

y=is a light focusing position on the reflecting surface,

Θ

=is an input angle of the input light to the VIPA generator in air,

f=is a focal length of said lens or mirror,

a=is a depth of a center beam waist of the VIPA generator, and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of lift, λ

being wavelength, an n being a refractive index of material forming the VIPA generator.

7. An apparatus as in claim 6, wherein

the input light is a wavelength division multiplexed (WDM) light having a plurality of channels, each channel having an amount of chromatic dispersion corresponding to wavelength and due to traveling through a transmission line, and

parameters of at least one of said reflecting surface and said lens or mirror cause the apparatus to provide chromatic dispersion to each channel in the same amount but opposite sign to that due to traveling through the transmission line.

8. An apparatus as in claim 6, wherein the VIPA generator comprises:

first and second surfaces, the first surface allowing substantially no light to be transmitted therethrough; and

a radiation window in the same plane as the first surface, the input light passing through the radiation window to enter the VIPA generator, the first and second surfaces positioned so that the input light entering the VIPA generator through the radiation window is reflected a plurality of times between the first and second surfaces to produce said output light.

9. An apparatus as in claim 8, wherein:

the first surface has substantially 100% reflectivity, and

the radiation window has substantially 100% transmissivity.

10. An apparatus comprising:

an angular dispersive component having a passage area to receive light into, and to output light from, the angular dispersive component, the angular dispersive component receiving, through the passage area, an input light having a respective wavelength within a continuous range of wavelengths, and causing multiple reflection of the input light to produce self-interference that forms a collimated output light which travels from the angular dispersive component along a direction determined by the wavelength of the input light and is thereby spatially distinguishable from an output light formed for an input light having any other wavelength within the continuous range of wavelengths; and

a reflecting surface reflecting the output light back to the angular dispersive component to undergo multiple reflection in the angular dispersive component and then be output from the passage area, the reflecting surface having different curvatures at different positions along a direction which is perpendicular to a plane which includes the travel direction of collimated output light from the angular dispersive component for input light at different wavelengths, curvature c(y) of the reflecting surface being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

 

where

y=is a light focusing position on the reflecting surface,

Θ

=is an input angle of the input light to the passage area in air,

f=is a focal length of a lens or mirror focusing the output light traveling from the angular dispersive component onto the reflecting surface,

a=is a depth of a center beam waist of the angular dispersive component and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of light, λ

being wavelength, an n being a refractive index of material forming the angular dispersive component.

11. An apparatus as in claim 10, further comprising:

said lens or mirror focusing the output light traveling from the angular dispersive component onto the reflecting surface so that the reflecting surface reflects the output light, the reflected light being directed by said lens or mirror back to the angular dispersive component.

12. An apparatus as in claim 10, wherein the angular dispersive component comprises:

first and second surfaces, the first surface allowing substantially no light to be transmitted therethrough, the passage area being in the same plane as the first surface, the first and second surfaces positioned so that the input light enters the angular dispersive component through the passage area and is then reflected a plurality of times between the first and second surfaces to produce said output light.

13. An apparatus as in claim 12, wherein:

the first surface has substantially 100% reflectivity, and

the passage area has substantially 100% transmissivity.

14. An apparatus comprising:

an angular dispersive component having a passage area to receive light into, and to output light from, the angular dispersive component, the angular dispersive component receiving, through the passage area, a line focused input light and causing multiple reflection of the input light to produce self-interference that forms a collimated output light which travels from the angular dispersive component along a direction determined by the wavelength of the input light and is thereby spatially distinguishable from an output light formed for an input light having a different wavelength; and

a reflecting surface reflecting the output light back to the angular dispersive component to undergo multiple reflection in the angular dispersive component and then be output from the passage area, the reflecting surface having different curvatures at different positions along a direction which is perpendicular to a plane which includes the travel direction of collimated output fight from the angular dispersive component for input light at different wavelengths, curvature c(y) of the reflecting surface being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

 

where

y=is a light focusing position on the reflecting surface,

Θ

=is an input angle of the input light to the passage area in air,

f=is a focal length of a lens or mirror focusing the output light traveling from the angular dispersive component onto the reflecting surface,

a=is a depth of a center beam waist of the angular dispersive component, and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of light, λ

being wavelength, an n being a refractive index of material forming the angular dispersive component.

15. An apparatus as in claim 14, further comprising:

said lens or mirror focusing the output light traveling from the angular dispersive component onto the reflecting surface so that the reflecting surface reflects the output light, the reflected light being directed by said lens or mirror back to the angular dispersive component.

16. An apparatus as in claim 14, wherein the angular dispersive component comprises:

first and second surfaces, the first surface allowing substantially no light to be transmitted therethrough, the passage area being in the same plane as the first surface, the first and second surfaces positioned so that the input light enters the angular dispersive component through the passage area and is then reflected a plurality of times between the first and second surfaces to produce said output light.

17. An apparatus as in claim 16, wherein:

the first surface has substantially 100% reflectivity, and

the passage area has substantially 100% transmissivity.

18. An apparatus comprising:

a radiation window;

first and second reflecting surfaces, the first reflecting surface allowing substantially no light to be transmitted therethrough and being in the same plane as the radiation window, the second reflecting surface having a reflectivity which causes a portion of light incident thereon to be transmitted therethrough, where

an input light at a respective wavelength travels through the radiation window and is focused into a line, and

the first and second reflecting surfaces are positioned so that the input light radiates from the line to be reflected a plurality of times between the first and second reflecting surfaces and thereby cause a plurality of lights to be transmitted through the second reflecting surface, the plurality of transmitted lights interfering with each other to produce a collimated output light which travels from the second reflecting surface along a direction determined by the wavelength of the input light, and is thereby specially distinguishable from an output light formed for an input light having a different wavelength; and

a mirror surface reflecting the output light back to the second reflecting surface to pass through the second reflecting surface and undergo multiple reflection between the first and second reflecting surfaces, the mirror surface having different curvatures at different positions along a direction which is perpendicular to a plane which includes the travel direction of collimated output light from the second reflecting surface for input light at different wavelengths, curvature c(y) of the mirror surface being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

 

where

y=is a light focusing position on the mirror surface,

Θ

=is an input angle of the input light to the radiation window in air,

f=is a focal length of a lens or mirror focusing the output light traveling from the second reflecting surface onto the mirror surface,

a=is a depth of a center beam waist of the apparatus, and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of light, λ

being wavelength, an n being a refractive index of material between the first and second reflecting surfaces.

19. An apparatus as in claim 18, further comprising:

said lens or mirror focusing the output light traveling from the second reflecting surface onto the mirror surface so that the mirror surface reflects the output light, the reflected light being directed by the said lens or mirror back to the second reflecting surface.

20. An apparatus as in claim 18, wherein

the radiation window has substantially 100% transmissivity, and

the first reflecting surface has substantially 100% reflectivity.

21. A communication system comprising:

an optical transmission line;

a transmitter transmitting an optical signal through the transmission line;

a receiver receiving optical signal from the transmission line; and

a compensation device operatively connected in one of the group consisting of the transmitter, the receiver and the transmission line, to provide dispersion slope or higher order dispersion to the optical signal, the compensation device comprising

a radiation window having substantially no reflectivity,

first and second reflecting surfaces, the first reflecting surface allowing substantially no light to be transmitted therethrough and being in the same plane as the radiation window, the second reflecting surface having a reflectivity which causes a portion of light incident thereon to be transmitted therethrough, where

the optical signal travels through the radiation window and is focused into a line as a line focused input light to the compensation device, and

the first and second reflecting surfaces are positioned so that the input light radiates from the line to be reflected a plurality of times between the first and second reflecting surfaces and thereby cause a plurality of lights to be transmitted through the second reflecting surface, the plurality of transmitted lights interfering with each other to produce a collimated output light which travels from the second reflecting surface along a direction determined by a wavelength of the input light, and is thereby specially distinguishable from an output light formed for an input light having a different wavelength, and

a mirror reflecting output the light back to the second reflecting surface to pass through the second reflecting surface and undergo multiple reflection between the first and second reflecting surfaces, the mirror having different curvatures at different positions along a direction which is perpendicular to a plane which includes the travel direction of collimated output light from the second reflecting surface for input light at different wavelengths, curvature c(y) of the mirror being as follows;

$c<br><br>\left(y\right)=\frac{K}{8<br><br>f^4}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^4+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{\Theta <br><br>}}{2<br><br>f^3}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^3+\frac{K<br><br>\text{\hspace{1em}<br><br>}<br><br>{\mathrm{\Theta <br><br>}}^2-\left(f-a\right)}{2<br><br>f^2}<br><br>\text{\hspace{1em}<br><br>}<br><br>y^2$

 

where

y=is a light focusing position on the mirror,

Θ

=is an input angle of the input light to the radiation window in air,

f=is a focal length of a lens or reflecting surface focusing the output light traveling from the second reflecting surface onto the mirror,

a=is a depth of a center beam waist of the compensation device, and

K is a constant so that chromatic dispersion equals −

2n⁴K/cλ

, with c being the speed of light, λ

being wavelength, an n being a refractive index of material between the first and second reflecting surfaces.