JP2986031B2 - Spectral switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frequency division multiplexing optical transmission system, which has a function of demultiplexing an optical signal transmitted by frequency division multiplexing and having a function of optically exchanging the optical signal as it is. It relates to an optical switch.

[0002]

2. Description of the Related Art Heretofore, as an optical component in which a vertical diffraction grating and an optical waveguide are integrally formed, there has been an optical component which disperses light of 1.48 to 1.56 μm (Appl. Phys. Lett. 58 (19)
91) pp. 1949-1951). FIG. 9 is a plan view showing a conventional compact spectroscope, wherein 1 is a slab waveguide portion, 2 is a ridge waveguide, 3 is a vertical diffraction grating, and 4 is input light (λ ₁ , λ ₂ ,...).
λ _n ), 5 is output light. Frequency multiplexed input light 4
Enters the ridge waveguide 2, spreads in the slab waveguide section 1, is split by the vertical diffraction grating 3, and condenses on different ridge waveguides 2. Since the vertical diffraction grating 3 is on the Rowland circle and the input portion of the ridge waveguide 1 is on the 1/2 Rowland circle, light of each wavelength is transferred to a different ridge waveguide 2 without defocus. Collect light.

[0003]

However, this conventional example has a disadvantage that it has no optical switching function. Also, since the refractive index of the slab waveguide is fixed,
There is a disadvantage that the demultiplexing angle cannot be adjusted, that is, an optical wavelength that is suitable for each ridge waveguide cannot be adjusted.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks of the prior art, disperse a plurality of lights, adjust a light splitting angle by controlling a refractive index by an electro-optic effect, and provide a ridge waveguide. By devising an optical circuit network, a spectral optical switch having a function of mutually exchanging a plurality of split lights is provided.

[0005]

In order to achieve this object, a spectroscopic optical switch according to the present invention comprises a slab waveguide formed on a surface of a substrate, and a back surface of the substrate and an upper surface of the slab waveguide. A pair of electrodes is provided on one end of the slab waveguide, and the vertical diffraction grating has an arc shape on one end surface of the slab waveguide, and the direction of the groove of the vertical diffraction grating is perpendicular to the surface of the substrate, and the arc shape is A vertical diffraction effect is provided on the Rowland circle, and one input waveguide and a plurality of condensing waveguides are provided at the other end face of the slab waveguide at an incidence portion of 1/100.
A plurality of output waveguides are formed on the surface of the substrate, and each output light from the plurality of light-collecting waveguides is applied to the plurality of output waveguides. Forming an optical waveguide network for selectively supplying;
The optical waveguide network is configured such that a plurality of input lights having different wavelengths input to the one input waveguide selectively exchange light with a plurality of output waveguides according to a value of a reverse bias voltage applied between the paired electrodes. It is formed to be.

[0006] Further, the shape of the diffraction grating is saw-toothed,
The incident light and the diffracted light are formed so as to have a substantially regular reflection relationship with respect to the groove surface of the diffraction grating, and a high reflection film made of an insulating film and a metal film is formed on an end surface of the diffraction grating. can do.

[0007] By splitting the light transmitted by frequency multiplexing, adjusting the splitting angle of the light by controlling the refractive index by the electro-optic effect, and devising the optical network of the ridge waveguide. This is different from the conventional technology in that a function of mutually exchanging a plurality of split light beams is realized.

[0008]

FIG. 1 is a perspective view for explaining a first embodiment of the present invention, wherein 11 is an n-InP substrate, 12 is a vertical diffraction grating, 13 is a slab waveguide, 14 is an input waveguide, 15 is a condensing waveguide I, 16 is a condensing waveguide II, 17 is a condensing waveguide
III, 18 are output waveguides I, 19 are output waveguides II, 20
Is a total reflection mirror, 21 is a waveguide multiplexing part, 22 is a waveguide intersection, 23 is a p-electrode, 24 is an n-electrode, 25 is input light,
26 is an output light I, 27 is an output light II, and 28 is a lead wire. The layer structure of the waveguide is omitted for simplification of the drawing.

FIG. 2 is a diagram for explaining the function of the first embodiment. The function of the first embodiment will be described with reference to FIG. First, when the reverse bias voltage V = V ₁ , the input light 25 of the input lights λ ₁ and λ ₂ incident on the input waveguide 14 spreads in the slab waveguide section 13, and the diffracted light of λ ₁ is converted into the condensing waveguide (I ) Condensed to 15 and diffracted light of λ ₂ is condensed waveguide (II)
Focus on 16 The light of λ ₁ goes straight and the output waveguide (I) 1
8, and becomes output light (I) 26, and the light of λ _{2 also} travels straight, exits from output waveguide (II) 19, and becomes output light (II) 27. When the reverse bias voltage V = V ₂ , the diffraction angle of the light of λ ₁ changes, and the light of the condensing waveguide (II) 16
And the light of λ ₂ is also focused on the focusing waveguide (III) 17. The light of λ ₁ goes straight and passes through the waveguide intersection 22,
The light exits from the output waveguide (II) 19 and becomes the output light (II) 27. On the other hand, the light of λ ₂ has its optical path bent by the total reflection mirror 20 from the condensing waveguide (III) 17, passes through the waveguide intersection 22, bends the optical path again by the total reflection mirror 20, and The light merges with the output waveguide (I) 18, exits from the output waveguide (I) 18, and becomes an output light (I) 26. That is, the lights of λ ₁ and λ ₂ are split, and the light is exchanged according to the magnitude of the reverse bias voltage.

Next, a description will be given of a mechanism in which a branch angle is changed by applying a reverse bias voltage to the slab waveguide 13. The change in the refractive index due to the electro-optic effect is given by the following equation.

Δn = (1/2) n ³ r ₄₁ E where Δn is a change in refractive index, n is a refractive index, E is an applied electric field, and r ₄₁ is an electro-optic coefficient. 1.6 × 10 ^-12 (m
/ V). Set the total thickness of the undoped layer to 0.
Assuming that 5 μm = 5 × 10 ⁻⁷ (m), when 100 V is applied, E = 2 × 10 ⁸ (V / m). If n ≒ 3.3, then Δn ≒ 5.8 × 10 ^-8 , and in the 1.55 μm band, the shift of the optical wavelength is about Δλ ≒ 27Å.

The core layer of the slab waveguide has InGaAs / I
If an nAlAs or InGaAs / InP multiple quantum well layer is used, the electro-optic coefficient can be increased, and the wavelength shift can be increased at low voltage.

The resolution of the diffraction grating is

Δλ = λ / (mNn _eff ) where Δλ is the resolution, λ is the wavelength, m is the order of diffraction, N is the number of diffraction gratings, and n _eff is the effective refractive index of the slab waveguide. It is. If the slab waveguide portion is made sufficiently long, the number N of the diffraction gratings becomes large, and the slab waveguide portion can be used sufficiently for the frequency division multiplexing system. Further, if the shape of the diffraction grating is made saw-tooth, the diffracted light of the characteristic order can be strengthened, and the diffraction efficiency can be made about 85 to 95% by adding a high reflection film.

FIG. 3 is a plan view for explaining a second embodiment, in which 31 is a slab waveguide portion, 32 is a vertical diffraction grating,
33 is an input waveguide, 34 is a condensing waveguide (I), 35 is a condensing waveguide (II), 36 is a condensing waveguide (III), 37 is a condensing waveguide (IV), and 38 is an output waveguide (I). , 39 is an output waveguide (II), 40 is a total reflection mirror, 41 is a waveguide multiplexing section,
2 is a waveguide intersection, 43 is input light, 44 is output light (I), and 45 is output light (II).

FIG. 4 is a diagram for explaining the function of the second embodiment. When the reverse bias voltage V = V ₁ , the input light λ ₁ , λ
₂ enters the input waveguide 33, spreads in the slab waveguide section 31, is diffracted by the vertical diffraction grating 32, and condenses the light of λ ₁ to the condensing waveguide (I) 34 and the light of λ ₂ to the condensing waveguide (II) 3
Focus on 5 That is, the light of λ ₁ is output from the output waveguide (I) 3
8, the output light (I) 44, the light of λ ₂ is output from the output waveguide (II) 39 via the waveguide multiplexing part 41 and the waveguide intersection part 42, and is output from the output light (II) 45. Become. When the reverse bias voltage V = V ₂ , the diffraction angle changes, and the light of λ ₁ enters the condensing waveguide (III) 36, passes through the waveguide multiplexing part 41 and the waveguide intersection part 42, and outputs the output waveguide (II). ) Emitted from 39,
Output light (II) 45 is obtained. The light of λ ₂ is a focusing waveguide (IV)
37, a total reflection mirror 40, a waveguide intersection 42, a total reflection mirror 40, and a waveguide multiplexing unit 41, and an output waveguide (I) 38.
Out, and becomes output light (I) 44. That is, λ ₁ , λ ₂
Is split and the light is exchanged according to the magnitude of the reverse bias voltage.

FIG. 5 is a plan view for explaining the third embodiment, in which 51 is a slab waveguide portion, 52 is a vertical diffraction grating,
53 is an input waveguide, 54 is a condensing waveguide (I), 55 is a condensing waveguide (II), 56 is a condensing waveguide (III), 57 is a condensing waveguide (IV), and 58 is a condensing waveguide (V). , 59 is an output waveguide (I), 60 is an output waveguide (II), 61 is an output waveguide (III), 62 is input light, 63 is output light (I), 64 is output light (II), 65 Is an output light (III), 66 is a total reflection mirror,
67 is a waveguide multiplexing part, and 68 is a waveguide crossing part.

FIG. 6 is a diagram for explaining the function of the third embodiment. First, when the reverse bias voltage V = V ₁ , the input light λ
₁ , λ ₂ and λ ₃ enter the input waveguide 53, spread in the slab waveguide section 51, are diffracted by the vertical diffraction grating 52, and the light of λ ₁ is condensed on the condensing waveguide (I) 54, Multiplexing section 67
, And emerges from the output waveguide (I) 59 through the output light (I).
63. The light of λ ₂ is condensed on the condensing waveguide (II) 55, exits from the output waveguide (II) 60 via the waveguide intersection 68 and the waveguide multiplexing part 67, and becomes the output light (II) 64. .
The light of λ ₃ is condensed on the converging waveguide (III) 56, exits from the output waveguide (III) 61 via the waveguide intersection 68, and becomes the output light (III) 65. When the reverse bias voltage V = V ₂ , the diffraction angle changes and the light of λ ₁ is condensed on the condensing waveguide (II) 55, and is output through the waveguide intersection 68 and the waveguide multiplexing part 67. The light exits from the wave path (II) 60 and becomes the output light (II) 64. The light of λ ₂ is condensed on the converging waveguide (III) 56, exits from the output waveguide (III) 64 via the waveguide intersection 68, and becomes the output light (III) 65. light lambda ₃ is Atsumarikoshirube waveguide (IV)
The light is condensed at 57, passes through a total reflection mirror 66, a waveguide intersection 68, a total reflection mirror 66, and a waveguide multiplexing unit 67, and is output from the output waveguide (I).
The light exits from 59 and becomes output light (I) 63.

When the reverse bias voltage is V = V ₃ , the light of λ ₁ is condensed on the converging waveguide (III) 56, exits from the output waveguide (III) 61 via the waveguide intersection 68, and is output. (III) 6
It becomes 5. The light of λ ₂ is focused on the focusing waveguide (IV) 57,
The light exits the output waveguide (I) 59 via the total reflection mirror 66, the waveguide intersection 68, the total reflection mirror 66, and the waveguide multiplexing unit 67, and becomes output light (I) 63. The light of λ ₃ is condensed on the converging waveguide (V) 58, and the total reflection mirror 66 and the waveguide multiplexing unit 6
After passing through 7, the light exits from the output waveguide (II) 60 and becomes the output light (II) 64. That is, three wavelengths λ ₁ , λ ₂ , and λ ₃ can be optically exchanged by the change of the reverse bias voltage.

FIG. 7 is a partial schematic view of an optical network of a spectral type optical switch according to a fourth embodiment. For simplicity of the drawing, only the optical network is illustrated. 71 is an input waveguide, 72 is an output waveguide (I), 73 is an output waveguide (II), 74 is an output waveguide (III), 75 is a total reflection mirror, 76 is a waveguide intersection,
77 is a waveguide multiplexing part. As can be seen from FIG.
Light of three wavelengths of ₁ , λ ₂ and λ ₃ can be spectrally separated and exchanged.

FIG. 8 is a partial schematic view of an optical network of a spectroscopic optical switch according to a fifth embodiment. For simplicity of the drawing, only the optical network is illustrated. 81 is an input waveguide, 82 is an output waveguide (I), 83 is an output waveguide (II), 84 is an output waveguide (III), 85 is an output waveguide (IV), and 86 is a total reflection mirror. As can be seen from FIG. 9, λ ₁ , λ ₂ , λ ₃ ,
Light of four wavelengths of λ ₄ can be separated and light exchanged.

Although the embodiment uses an InGaAsP / InP-based crystal, it may be made of a GaAs / AlGaAs-based crystal.

As is apparent from these results, the control of the refractive index by the electro-optic effect is more effective than in the prior art.
By adjusting the demultiplexing angle of light and devising an optical circuit network, there is an improvement in that a plurality of split lights can be exchanged with each other.

[0022]

As described above, according to the present invention, a plurality of lights transmitted at high frequency by frequency multiplexing are separated, and the demultiplexing angle of each light is adjusted by controlling the refractive index by the electro-optic effect. In addition, by devising the optical circuit network of the ridge waveguide, there is an advantage that a function of mutually exchanging a plurality of separated lights can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view of a spectral optical switch according to a first embodiment.

FIG. 2 is a diagram illustrating functions of the first embodiment.

FIG. 3 is a plan view of a spectral optical switch according to a second embodiment.

FIG. 4 is a diagram illustrating functions of a second embodiment.

FIG. 5 is a plan view of a spectral optical switch according to a third embodiment.

FIG. 6 is a diagram illustrating functions of a third embodiment.

FIG. 7 is a schematic diagram of an optical network of a spectroscopic optical switch according to a fourth embodiment.

FIG. 8 is a schematic view of an optical network of a spectroscopic optical switch according to a fifth embodiment.

FIG. 9 is a plan view showing an example of a conventional compact spectroscope.

[Explanation of symbols]

Reference Signs List 1 slab waveguide section 2 ridge waveguide 3 vertical diffraction grating 4 input light (λ ₁ , λ ₂ ... Λ _n ) 5 output light 11 n-InP substrate 12 vertical diffraction grating 13 slab waveguide section 14 input waveguide section 15 Optical waveguide (I) 16 Focusing waveguide (II) 17 Focusing waveguide (III) 18 Output waveguide (I) 19 Output waveguide (II) 20 Total reflection mirror 21 Waveguide combining part 22 Waveguide intersection 23 p -Electrode 24 n-electrode 25 input light 26 output light (I) 27 output light (II) 28 lead wire 31 slab waveguide 32 vertical diffraction grating 33 input waveguide 34 focusing waveguide (I) 35 focusing waveguide (II) 36 Condensing waveguide (III) 37 Condensing waveguide (IV) 38 Output waveguide (I) 39 Output waveguide (II) 40 Total reflection mirror 41 Waveguide multiplexing part 42 Waveguide intersection part 43 Input light 44 Output light ( I) 45 Output light (II) 5 Slab waveguide part 52 Vertical diffraction grating 53 Input waveguide 54 Focusing waveguide (I) 55 Focusing waveguide (II) 56 Focusing waveguide (III) 57 Focusing waveguide (IV) 58 Focusing waveguide (V) 59 Output conduction Waveguide (I) 60 Output waveguide (II) 61 Output waveguide (III) 62 Input light 63 Output light (I) 64 Output light (II) 65 Output light (III) 66 Total reflection mirror 67 Waveguide combining section 68 Waveguide intersection 71 Input waveguide 72 Output waveguide (I) 73 Output waveguide (II) 74 Output waveguide (III) 75 Total reflection mirror 76 Waveguide intersection 77 Waveguide multiplexing part 78 Condensing waveguide 81 Input Waveguide 82 Output waveguide (I) 83 Output waveguide (II) 84 Output waveguide (III) 85 Output waveguide (IV) 86 Total reflection mirror 87 Condensing waveguide

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-171115 (JP, A) JP-A-4-367819 (JP, A) JP-A-3-501065 (JP, A) Appl. Phys. Lett. , Vol. 58 No. 18 pp. 1949-1951 (6 May 1991) Electronics Letters, Vol. 27 No. 2 pp. 132-134 (17th January 1991) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/00-1/055 505 G02F 1/29-1/313 G02B 6/12-6 /14

Claims (5)

(57) [Claims] 1. A slab waveguide is formed on a front surface of a substrate, and a pair of electrodes is provided on a back surface of the substrate and an upper surface of the slab waveguide. The other end surface of the slab waveguide, wherein the grating has an arc shape and the direction of the groove of the vertical diffraction grating is perpendicular to the surface of the substrate, and the arc-shaped vertical diffraction effect is on a Rowland circle; Is provided with one input waveguide and a plurality of light-collecting waveguides such that their incident portions are on a 1/2 Rowland circle, and a plurality of output waveguides are formed on the surface of the substrate. And an optical waveguide network for selectively supplying each output light from the plurality of condensing waveguides to the plurality of output waveguides is formed, and the optical waveguide network is input to the one input waveguide. A plurality of input light beams having different wavelengths Spectroscopic optical switch formed to be selectively optical switching to a plurality of output waveguides by the value of the applied reverse bias voltage between. 2. A saw-tooth shape of the vertical diffraction grating,
The spectral optical switch according to claim 1, wherein the incident light and the diffracted light are formed so as to have a substantially regular reflection relationship with respect to the surface of the groove of the diffraction grating. 3. The spectral optical switch according to claim 1, wherein a high reflection film made of an insulating film and a metal film is formed on an end face of the vertical diffraction grating. 4. The slab waveguide according to claim 1, wherein the slab waveguide is an n-type InP substrate,
n-type InP cladding layer, undoped InGaAsP core layer, undoped InP layer, p-type InP cladding layer, p
4. The optical switch according to claim 1, wherein the optical switch comprises a contact type InGaAsP layer, and is configured to apply a reverse bias voltage. 5. The slab waveguide according to claim 5, wherein the slab waveguide is an n-type InP substrate,
n-type InP cladding layer, undoped InGaAs / I
9. A semiconductor device comprising an nAlAs or InGaAs / InP multiple quantum well core layer, an undoped InP layer, a p-type InP cladding layer, and a p-type InGaAsP contact layer, wherein a reverse bias voltage can be applied. 4. The spectral optical switch according to any one of 1, 2, and 3.