JP2999743B2 - Fabry-Perot microcavity optical switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a Fabry-Perot microcavity type optical switch utilizing a nonlinear optical effect.

[0002]

2. Description of the Related Art In recent years, the development of optical switches utilizing the nonlinear optical effect has attracted attention, and various optical switches utilizing the third-order nonlinear optical characteristics of polysilane compounds have been proposed.

The third-order nonlinear optical effect is a phenomenon in which the refractive index changes depending on the light intensity. In the case of a polysilane compound, excellent transparency to visible light and a high-speed nonlinear response in which the refractive index changes on the order of picoseconds are used. Therefore, application to an optical switch that surpasses a nonlinear optical element using a semiconductor is expected. For example, Japanese Unexamined Patent Publication No. Hei 6 (1994) -64, using a polysilane compound as a nonlinear medium of a Fabry-Perot type optical bistable element.
Japanese Patent Application Laid-Open No. Hei 7-313113 discloses a waveguide type nonlinear optical switch using polysilane.

However, as disclosed in Japanese Patent Application Laid-Open No. Hei 6-313113, the third-order nonlinear susceptibility of a polysilane compound is about 10 to ¹² esu at the maximum, and its size is sufficient for an optical switch. There is a problem that is not. To cope with this problem, Japanese Patent Laid-Open No. 313113 proposes a method of dispersing semiconductor fine particles having a large third-order nonlinear susceptibility in a polysilane compound thin film.

However, since the third-order nonlinear optical response of the semiconductor fine particles usually includes a thermal response, the response speed is as slow as several hundred picoseconds. Second) cannot be used.

On the other hand, JP-A-6-175168 discloses that
A Fabry-Perot resonator type optical switch using a polysilane compound as a nonlinear medium has been proposed. The change in the refractive index of the material due to the third-order nonlinear optical effect is proportional to the third-order nonlinear susceptibility of the material and is proportional to the square of the light intensity. The proposal to trigger and perform optical switching is noteworthy.

However, as described in Fukuo Inaba et al., “Laser Handbook” (Asakura Shoten, Tokyo, 1973), pp. 43-60, a Fabry-Perot resonator usually has a large number of optical resonance modes, so There is a problem that the energy of the emitted light is dispersed in each mode, and the intensity of the incident light cannot be concentrated on a specific wavelength.

However, as shown in Hasegawa et al., Physical Review Letters, Vol. 45, pp. 6317-6320, the nonlinear susceptibility of a polysilane compound is such that the incident light wavelength is smaller than the light absorption peak wavelength of the compound. Since the value becomes remarkable only in the case of resonance (resonance effect), it is difficult to use the nonlinear polarizability of the polysilane compound due to the resonance effect in the method of the publication, and the light intensity required for the switch operation increases. There is a drawback that it will.

[0009]

As described above, it is difficult to provide an optical switch utilizing the high-speed nonlinear optical response of a polysilane compound in the prior art.

An object of the present invention is to provide an optical switch that makes use of the high-speed nonlinear response of a polysilane compound.

[0011]

To achieve the above object, the gist of the present invention is to provide a Fabry-Perot microresonator type optical switch in which both surfaces of a nonlinear optical medium film are coated with a dielectric thin film or a metal thin film. film is a polysilane compound, 1 der half of its thickness input light wavelength
The input wavelength and the light absorption peak of the polysilane compound.
A Fabry-Perot microresonator type optical switch characterized in that it is configured to resonate with a peak wavelength .

FIG. 1 is an explanatory view of a Fabry-Perot microresonator of the present invention. 1 is a non-linear medium (polysilane compound) and 2 is a half mirror (dielectric thin film or metal thin film).

A Fabry-Perot microresonator is described in H.
Eberly et al. “Coherence and Quantum Optics” (Coherence and Quantum Optic)
s) (Plenum Press NY, 1989) 1249-
Since it has a single resonance mode as described on page 1257, the incident light intensity can be concentrated on this mode.

For example, the resonance conditions of an optical resonator having a size of 2a × 2a × d are given by the following equation [1] as described in “Laser Handbook”, p. 56, edited by Fumio Inaba et al. Given by

[0015]

(2 / λ) ² = (q / d) ² + (m / 2a) ² + (n / 2a) ² (1) where λ is the resonance wavelength, and q, m, and n are resonance. An index that represents the mode of the wave. In a normal Fabry-Perot resonator, there are many combinations of q, m, and n that satisfy Expression [1], and thus have many resonance modes.

On the other hand, the resonance condition of the Fabry-Perot microresonator is given by equation [2] where d = λ / 2 in equation [1].

[0017]

## EQU2 ## (2 / λ) ² = (2 / λ) ² q ² + (m / 2a) ² + (n / 2a) ² [2] q, m, which satisfy the resonance condition of equation [2] The combination of n is only when q = 1, m = 0, n = 0, and it can be seen that the Fabry-Perot microresonator has a single resonance mode.

Accordingly, in the present invention, as shown in FIG. 1, both surfaces of a polysilane compound thin film are coated with a dielectric thin film or a metal thin film to form a Fabry-Perot microresonator. At the same time when the optical susceptibility Ru are concentrated in the wavelength increasing Porishira
A large optical field is generated inside the
A large change in the refractive index is induced inside the polysilane . Therefore, according to the present invention, the nonlinear susceptibility is not sufficient.
Even with polysilane compounds that are not too large, strong incident light
Optical switch operation can be performed without using
is there. In addition, Yang et al.
(Applied Physics Letters) Vol. 53, No. 12
Report on pages 45-1247 (October 3, 1988)
As shown, the nonlinear optical response of polysilane compounds
Response time is picosecond due to the electronic state of the Si-Si bond
Degree and fast. On the other hand, Fabry-Perot optical resonator type
The response speed of the optical switch depends on the
Medium that has the same response speed as linear optical response speed
The more they are used, the faster the response speed of the optical switch. This
This is because the Fabry-Perot optical resonator type optical switch is
Is changed by the third-order nonlinear optical effect.
This is due to the optical switch used. According to the present invention,
An optical switch utilizing a high-speed nonlinear response of a polysilane compound can be provided .

In the polysilane compound-(SiR ₂ ) n-represented by the above formula, n is preferably in the range of 10 to 10,000. Further, CH ₃ , C ₂ H ₅ , CH ₂
(CH ₂ ) ₂ CH ₃ , CH ₂ (CH ₂ ) ₄ CH ₃ or CH ₂ (C
H ₂ ) ₁₂ CH ₃ can be used.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 2 is an explanatory view of an embodiment of the present invention using an Al thin film for a half mirror. In FIG. 2, reference numeral 3 denotes a half mirror (an Al thin film having a reflectance of 90% or more), 4 denotes a polysilane compound thin film, and 5 denotes a glass substrate. In this embodiment, the polysilane compound thin film 4 has the n
Is about 5000 polydihexyl polysilane (PDHS)
A Fabry-Perot microresonator type optical switch of the present invention using the above will be described.

[0021]

Embedded image

Tachinaba et al., Physical Review B, Vol. 47, 4363-4.
As described on page 370, the light absorption spectrum of PDHS reaches a peak when the incident light energy is 3.38 eV. Therefore, in this embodiment, in order to increase the nonlinear susceptibility of PDHS by three-photon absorption resonance, light having an energy of 1.13 eV (wavelength 1.09 μm) is used as incident light, and the thickness of the polysilane compound (PDHS) thin film 4 is reduced. The wavelength was set to 0.55 μm, which is の of the wavelength of the incident light, to constitute a Fabry-Perot microcavity.

The above-mentioned three-photon absorption resonance means that when the energy of three incident light photons coincides with the light absorption peak energy of the compound, the nonlinear susceptibility of the compound is significantly increased. The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity only on light having a wavelength of 1.09 μm, which increases the nonlinear susceptibility of PDHS by three-photon absorption resonance. An optical switch operation using about 10 to ¹² esu) can be performed.

Embodiment 2 In this embodiment, the polysilane compound thin film 4 shown in FIG.
A Fabry-Perot microcavity type optical switch of the present invention using polydibutylpolysilane (PDBS) of 0 will be described.

[0025]

Embedded image

As described in the above-mentioned article by Tachinaba et al., The light absorption spectrum of PDBS reaches a peak when the incident light energy is 4.00 eV. Therefore, in this embodiment, the energy is 1.33 eV in order to increase the nonlinear susceptibility of PDBS by three-photon absorption resonance.
(Wavelength 0.92 μm) is used as the incident light, and the thickness of the polysilane compound (PDBS) thin film 4 is set to 1 / the wavelength of the incident light.
2, 0.46 μm, thereby forming a Fabry-Perot microresonator.

The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity only on light having a wavelength of 0.92 μm, which increases the nonlinear susceptibility of the PDBS by three-photon absorption resonance. The optical switch operation using the susceptibility (about 10 to ¹² esu) becomes possible.

[Embodiment 3] In this embodiment, the polysilane compound thin film 4 shown in FIG.
A Fabry-Perot microresonator type optical switch of the present invention using polyditetradecipolysilane (PDTDS) of 0 will be described.

[0029]

Embedded image

As described in the above-mentioned article by Tachinaba et al., The light absorption spectrum of PDTDS is:
It reaches a peak when the incident light energy is 3.63 eV.
Therefore, in this embodiment, PDTDS is performed by three-photon absorption resonance.
Energy is increased to 1.21 to increase the nonlinear susceptibility of
Using a light of eV (wavelength 1.024 μm) as the incident light, the thickness of the polysilane compound (PDTDS) thin film 4 was set to 0.51 μm which is １ ／ of the wavelength of the incident light, thereby forming a Fabry-Perot microcavity.

The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity only on light having a wavelength of 1.024 μm, which increases the nonlinear susceptibility of the PDTDS by three-photon absorption resonance. The optical switch operation using the susceptibility (about 10 to ¹² esu) is enabled.

Embodiment 4 In this embodiment, the polysilane compound thin film 4 shown in FIG.
The Fabry-Perot microcavity type optical switch of the present invention using polydimethylpolysilane (PDMS) of 0 will be described.

[0033]

Embedded image

Crespo et al., Journal of Chemical Physics (J. Chem. Phys.) No. 10
0, pages 6953-6960,
The light absorption spectrum of DMS has an incident light energy of 3.3.
It reaches a peak at 2 eV.

Therefore, in this embodiment, in order to increase the nonlinear susceptibility of PDMS by three-photon absorption resonance, light having an energy of 1.11 eV (wavelength: 1.12 μm) is used as incident light, and the polysilane compound (PDMS) thin film 4 is used. The film thickness was set to 0.56 μm, which is の of the wavelength of the incident light, to constitute a Fabry-Perot microresonator.

The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity only on light having a wavelength of 1.12 μm, which increases the nonlinear susceptibility of PDMS by three-photon absorption resonance. The optical switch operation using the susceptibility (about 10 to ¹¹ esu) is enabled.

Embodiment 5 In the present embodiment, in the polysilane compound thin film 4 of FIG.
The Fabry-Perot microcavity type optical switch of the present invention using polyethylpolysilane (PDES) of 0 will be described.

[0038]

Embedded image

As described in the above-mentioned article by Crespo et al., The light absorption spectrum of PDMS reaches a peak when the incident light energy is 3.45 eV. Therefore, in this embodiment, the energy is 1.15 eV (wavelength: 1.15 eV) to increase the nonlinear susceptibility of PDES by three-photon absorption resonance.
08 μm) as incident light, and a polysilane compound (P
DES) The thickness of the thin film 4 is set to 0.2, which is half the wavelength of the incident light.
A Fabry-Perot microresonator was formed at 54 μm.

The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity only on light having a wavelength of 1.08 μm, which increases the nonlinear susceptibility of the PDES by three-photon absorption resonance. The optical switch operation using the susceptibility (about 10 to ¹¹ esu) is enabled.

[Embodiment 6] FIG. 3 shows an optical switch according to an embodiment of the present invention. Here, 6 is a TiO ₂ thin film, 7 is Si
An O ₂ thin film, 8 is a polysilane compound thin film, 9 is a glass substrate, and alternate multilayer films of 6 and 7 constitute a dielectric mirror.

In this embodiment, a Fabry-Perot microcavity type optical switch using PDHS [Chemical Formula 2] shown in Embodiment 1 as the polysilane compound thin film 8 will be described.

As described in the first embodiment, the nonlinear susceptibility of PDHS is such that the incident light energy is 1.13 eV (wavelength: 1.13 eV).
09 μm), 10 to ¹² es due to three-photon absorption resonance.
u.

Therefore, in this embodiment, a dielectric multilayer mirror in which the thickness of the TiO ₂ thin film 6 and the SiO ₂ thin film 7 is 0.545 μm is provided to reflect only the light having a wavelength of 1.09 μm. (PDHS) A Fabry-Perot microresonator having a thickness of the thin film 8 of 0.55 μm was formed.

The Fabry-Perot microresonator of this embodiment can concentrate the incident light intensity on the light having a wavelength of 1.09 μm, which increases the nonlinear susceptibility of PDHS by three-photon absorption resonance. 10 ~ ¹² es
u) is enabled.

Embodiment 7 FIG. 4 shows a method of driving a Fabry-Perot microresonator type optical switch of the present invention, FIG. 5 shows its operation principle, and Table 1 shows an operation logic table.

In FIG. 4, reference numeral 10 denotes input light, 11 denotes gate light, 12 denotes a half mirror, 13 denotes a Fabry-Perot microresonator type optical switch of the present invention, and 14 denotes output light.
Here, the input light 10 and the gate light 11 are light having a wavelength slightly longer than the resonance wavelength of the resonator of the Fabry-Perot microresonator type optical switch 13.

The refractive index and light wavelength inside the microresonator change depending on the intensity of incident light due to the nonlinear optical characteristics of the polysilane compound (see FIG. 5). When the gate light 11 is not present, the incident light intensity is equal to the intensity I _in of the input light 10;
When the gate light 11 is present, the incident light intensity is equal to the input light 1
0 is the sum of the intensity I _g of the intensity I _in and the gate light 11.

Therefore, in this embodiment, when the gate light 11 is off, the resonator is in a non-resonant state (point A in FIG. 5), and when the gate light 11 is on, the resonator is in a resonant state (see FIG. 5). B out of 5
(Point), so that the output light intensity I _out can be modulated by turning on / off the gate light 11 as shown in Table 1.

[0050]

[Table 1]

Since the rate of change in the refractive index of the polysilane compound is on the order of picoseconds, light modulation can be performed at a picosecond rate according to this embodiment.

[0052]

According to the present invention, it is possible to provide a Fabry-Perot microresonator type optical switch that performs high-speed optical modulation by utilizing the high-speed nonlinear optical response of polysilane.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a Fabry-Perot microresonator.

FIG. 2 is an explanatory view of an embodiment of the present invention using an Al thin film for a half mirror.

FIG. 3 is an explanatory view of an embodiment of the present invention using a dielectric multilayer film for a half mirror.

FIG. 4 is an explanatory diagram of a method for driving an optical switch according to an embodiment of the present invention.

FIG. 5 is an explanatory diagram of the operation principle of the optical switch according to the embodiment of the present invention.

[Explanation of symbols]

1 ... nonlinear medium, 2 ... half mirror, 3 ... half mirror (Al film), 4 ... polysilane compound thin film, 5 ... glass substrate, 6 ... TiO ₂ thin film, 7 ... SiO ₂ thin film, 8 ... polysilane compound thin film, 9 ... Glass Substrate, 10 ... input light, 11
... Gate light, 12 half mirror, 13 optical switch of the present invention, 14 output light.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-175168 (JP, A) JP-A-6-313113 (JP, A) JP-A-9-22033 (JP, A) JP-A-2- 77028 (JP, A) Synth. Met. , Vol. 50 No. 1/3 pp. 415-421 (1992), Iwasa et. a l. , "Resonance enhancement effect in non-linear optical susceptibility of Polysilanes" (58) Fields investigated (Int.Cl. ⁷ , DB name) G02F 1/35-3/02 JICST file (JOIS)

Claims (4)

(57) [Claims] In a Fabry-Perot microresonator type optical switch in which both surfaces of a nonlinear optical medium film are coated with a dielectric thin film or a metal thin film, the nonlinear optical medium film is a polysilane compound, and the film thickness of the nonlinear optical medium film is equal to the input light wavelength. in 1 of 2 minutes
And the input wavelength is the light absorption of the polysilane compound.
A Fabry-Perot microresonator type optical switch characterized by being configured to resonate at a peak wavelength . 2. The polysilane compound represented by the formula: [Where R is CH ₃ , C ₂ H ₅ , CH ₂ (CH ₂ ) ₂ CH ₃ , C
H ₂ (CH ₂ ) ₄ CH ₃ or CH ₂ (CH ₂ ) ₁₂ CH ₃ ,
n is an integer of 10 to 10000]. The Fabry-Perot microresonator type optical switch according to claim 1, wherein 3. The Fabry-Perot microresonator type optical switch according to claim 1, wherein the metal thin film is made of Al or Au. 4. The Fabry-Perot microresonator type optical switch according to claim 1, wherein said dielectric thin film comprises an alternately laminated film of a SiO ₂ layer and a TiO ₂ layer.