CN103123421B - One-dimensional magnetic photonic crystal for achieving broadband optical isolation - Google Patents

Abstract

Provided is a one-dimensional magnetic photonic crystal for achieving broadband optical isolation. The structural formula of the basic component S0 of the one-dimensional magnetic photonic crystal is [H/L] 2/M/ [L/H] 5/M/ [H/L] 2/M/ [L/H] /2/M/ [H/L] 5/M/ [L/H] 2, wherein H is silicon, L is silicon oxide, and M is cerium mixed yttrium iron garnet. A first composite structure S1 of the one-dimensional magnetic photonic crystal meets the following equation: S1=S0/M/S0, and a second composite structure S2 of the one-dimensional magnetic photonic crystal meets the following equation: S2=S0/M/S0/M/S0. According to the one-dimensional magnetic photonic crystal, the composite structures reduce the total layer number of film layers, reduce preparation difficulty and improve work stability of an optical isolator.

Description

A One-dimensional Magnetophotonic Crystal Realizing Broadband Optical Isolation

technical field

The invention relates to a broadband optical isolator, in particular to a one-dimensional magneto-photonic crystal for realizing a broadband optical isolator.

Background technique

An optical isolator is a non-reciprocal passive device that only allows forward-transmitted light to pass through. Its main function is to prevent reverse-transmitted light from adversely affecting the light source and improve the stability of optical system transmission.

The existing optical isolator is composed of a pair of polarizers whose optical axes are at an angle of 45 ^° , and a Faraday rotator placed between the two polarizers. The Faraday rotator includes a central magneto-optic crystal and a ring-shaped permanent magnet surrounding the magneto-optic crystal.

The rapid development of modern optical communication technology requires the miniaturization of devices used in optical circuits for easy integration. Due to the limitation of the volume of the magneto-optic crystal, the existing bulk optical isolator has a minimum size of the order of millimeters, which obviously cannot meet the requirements of optical circuit integration.

H． Kato et al. (Theoretical analysis of optical and magneto-optical properties of one-dimensional magnetophotonic crystals, Journal of Applied Physics.2003, Vol:93, 3906-3911) prepared single-defect crystals experimentally by magnetron sputtering coating method. One-dimensional magneto-optic crystal structure, and compared the experimental value with the theoretical simulation value, the results are completely consistent, confirming that the introduction of magneto-optic crystal defects in the photonic crystal can significantly enhance the Faraday effect of the magneto-optic crystal. A new direction is proposed for the integration of optical isolators.

H． Kato et al. (Properties of one-dimensional magnetophotonic crystals for use in optical isolator devices, Transactions On Magnetics.2002, Vol:38, 3246-3248) reported that when one-dimensional photonic crystals contain two or three layers of magneto-optic crystal defects, It can achieve a transmittance as high as 99% and a Faraday rotation angle near 45 ^o , and the Faraday rotator of this structure is only a dozen microns. However, the frequency spectrum of optical isolators with these structures is extremely narrow and can only be used at the central working wavelength. When the light source is unstable or in broadband communication, the optical isolator of this structure cannot be applied.

M. Zamani et al. (Adjustable magneto-optical isolators with flat-top responses, Optics Express.2012, Vol:20, 24524-24535) proposed several one-dimensional magneto-photonic crystal structures that can achieve broadband optical isolation, and pointed out a A method of making the Faraday rotation angle exactly equal to ^45o by horizontally rotating an applied magnetic field. However, the above-mentioned structures have a large number of layers, which are not easy to manufacture in terms of technology, and the isolation effect in the broadband range produced is not optimal.

Contents of the invention

The specific technical problem to be solved by the present invention is that the existing optical isolation structure has a large number of layers, and the resulting isolation effect in the broadband range is not good. The purpose is to provide a one-dimensional magnetophotonic crystal that realizes broadband optical isolation.

The above-mentioned one-dimensional magneto-photonic crystal that realizes broadband optical isolation provided by the present invention includes a one-dimensional magneto-photonic crystal, and is characterized in that: the structural formula of the basic component _S of the one-dimensional magneto-photonic crystal is as follows:

[H/L] ² /M/[L/H] ⁵ /M/[H/L] ² /M/[L/H] ² /M/[H/L] ⁵ /M/[L/H] ² ;

Wherein: H is silicon, L is silicon dioxide, M is cerium-doped yttrium iron garnet;

Its first composite structure S ₁ =S ₀ /M/S ₀ ; the second composite structure S ₂ =S ₀ /M/S ₀ /M/S ₀ .

In the above technical solution, further additional technical features are:

The central operating wavelengths of the first composite structure S ₁ and the second composite structure S ₂ are 1550 nm.

The central working wavelength is at 1550nm: the refractive index of silicon Si is 3.48; the refractive index of silicon dioxide SiO ₂ is 1.495; cerium-doped yttrium iron garnet Ce:YIG is ε ₁ =4.884, ε ₂ =0.009 in the dielectric tensor.

The thickness of silicon in the basic component S ₀ is 111.35 nm; the thickness of silicon dioxide is 259.2 nm; the thickness of cerium-doped yttrium iron garnet is 158.68 nm.

The Faraday rotation angle of the first composite structure S ₁ is 45 ^° when the applied magnetic field and the optical axis form an angle of 14.14 ^° on the horizontal plane.

The Faraday rotation angle of the second composite structure S ₂ is 45 ^° when the applied magnetic field and the optical axis form an angle of 49.61 ^° on the horizontal plane.

To realize the technical solution of a broadband optical isolation one-dimensional magneto-optic crystal provided by the present invention is to add magneto-optic crystal defects in the one-dimensional photonic crystal more reasonably, which solves the problem that the existing optical isolation structure has a large number of layers. The isolation effect in the broadband range is not good. Compared with the existing technology, the formed one-dimensional magneto-photonic crystal combines the advantages of photonic crystal and magneto-optic crystal, and realizes the corresponding magneto-optic effect on the scale of photonic crystal. .

The first composite structure S ₁ , compared with the existing one-dimensional magneto-photonic crystal that achieves 3.5nm broadband isolation, the total number of film layers is reduced from 173 to 83, which reduces the difficulty of preparation. The one-dimensional magneto-photonic crystal of this structure The application of crystals in optical isolators can further reduce the scale of optical isolators and facilitate integration;

The second composite structure is S ₂ . Compared with the existing one-dimensional magneto-photonic crystal structure that achieves 2.5nm broadband isolation, the fluctuation range of the Faraday rotation angle is reduced from 45 ^o -54.56 ^o to 45 ^o -48.55 ^o . The application of the one-dimensional magneto-photonic crystal in the optical isolator can improve the stability of the optical isolator.

Description of drawings

Fig. 1 is a schematic structural diagram of the basic component _S0 of the present invention.

Fig. 2 is a schematic structural view of the first composite structure _S1 of the present invention.

Fig. 3 is a schematic structural diagram of the second composite structure _S2 of the present invention.

Fig. 4 is a graph showing the fluctuation curves of the transmittance and Faraday rotation angle of the first composite structure _S1 of the present invention around the central wavelength when the applied magnetic field is parallel to the direction of the optical path.

Fig. 5 is a value diagram of the transmittance and Faraday rotation angle of the first composite structure S ₁ of the present invention under different rotation angles of the applied magnetic field when the applied magnetic field rotates in the horizontal direction.

Fig. 6 is a graph showing the fluctuation curves of the transmittance and Faraday rotation angle of the first composite structure S ₁ of the present invention around the central wavelength when the applied magnetic field rotates at an angle of 14.14 ^o in the horizontal direction.

Fig. 7 is a graph showing the fluctuation curves of the transmittance and Faraday rotation angle of the second composite structure _S2 of the present invention around the central wavelength when the applied magnetic field is parallel to the direction of the optical path.

Fig. 8 is a value diagram of the transmittance and Faraday rotation of the second composite structure S ₂ of the present invention at different rotation angles of the applied magnetic field when the applied magnetic field rotates in the horizontal direction.

Fig. 9 is a graph showing the fluctuation curves of the transmittance and Faraday rotation angle of the second composite structure S ₂ of the present invention around the central wavelength when the applied magnetic field rotates at an angle of 49.61 ^o in the horizontal direction.

Detailed ways

A one-dimensional magneto-photonic crystal with broadband optical isolation for implementing the present invention has a central working wavelength of 1550nm.

Implement a kind of one-dimensional magneto-photonic crystal of broadband optical isolation of the present invention, comprise one-dimensional magneto-photonic crystal, as shown in Figure 1, its constitution is that the structural formula of the basic component _S of the one-dimensional magneto-photonic crystal described above is:

[H/L] ² /M/[L/H] ⁵ /M/[H/L] ² /M/[L/H] ² /M/[H/L] ⁵ /M/[L/H] ² , where H is silicon Si with a thickness of 111.35nm and a refractive index of 3.48; L is silicon dioxide SiO ₂ with a thickness of 259.2nm and a refractive index of 1.495; M is a thickness of 158.68nm and ε ₁ =4.884 in the dielectric tensor, ε ₂ =0.009 cerium-doped yttrium iron garnet Ce:YIG.

Example 1

As shown in Figure 2, the first composite structure S ₁ =S ₀ /M/S ₀ of the present invention can deposit these three films on the optical substrate in the order of structure S ₁ by the method of magnetron sputtering coating, totally 83 layers . When the applied magnetic field is parallel to the direction of the optical path, the fluctuation curves of the transmittance and Faraday rotation angle of the first composite structure S ₁ of the present invention around the central wavelength are shown in FIG. 4 . In order to obtain the Faraday rotation angle of 45 ^° for the first composite structure _S1 of the present invention, we need to rotate the applied magnetic field in the horizontal direction, and the values of the transmittance and the Faraday rotation angle of the first composite structure _S1 vary with the rotation angle of the applied magnetic field. The changes are shown in Figure 5. When the applied magnetic field is horizontally rotated to an angle of 14.14 ^o with the direction of the optical path, the fluctuation curves of transmittance and Faraday rotation angle around the central wavelength can be obtained as shown in Figure 6. It can be seen from Figure 6 that this optical isolator has a relatively flat broadband in the range of 1548.25nm-155.75nm. In this range, the Faraday rotation angle fluctuates within 45 ^° -53.5 ^° , and the transmittance fluctuates within 99.73%-99.75%.

Example 2

As shown in Figure 3, the second composite structure S ₂ =S ₀ /M/S ₀ /M/S ₀ of the present invention can be deposited on the optical substrate in the order of structure S ₂ by magnetron sputtering coating method. Film, a total of 125 layers. When the applied magnetic field is parallel to the direction of the optical path, the fluctuation curves of the transmittance and Faraday rotation angle of the first composite structure S ₂ of the present invention around the central wavelength are shown in FIG. 7 . In order to obtain the Faraday rotation angle of 45 ^° for the first composite structure _S2 of the present invention, we need to rotate the applied magnetic field in the horizontal direction, and the values of the transmittance and the Faraday rotation angle of the first composite structure _S2 vary with the rotation angle of the applied magnetic field. The changes are shown in Figure 8. When the applied magnetic field is horizontally rotated to an angle of 49.61 ^o to the direction of the optical path, the fluctuation curves of transmittance and Faraday rotation angle around the central wavelength can be obtained as shown in Figure 9. It can be seen from Figure 9 that the optical isolator with this structure can achieve a relatively stable isolation effect in the range of 1548.75nm ^{- 155.25nm} . % fluctuations.

Claims (6)

1. a one-dimensional magneto-photonic crystal realizing broadband optical isolation, is characterized in that: the basic component S of described one-dimensional magneto-photonic crystal The structural formula of _S is as follows: [H/L] ² /M/[L/H] ⁵ /M/[H/L] ² /M/[L/H] ² /M/[H/L] ⁵ /M/[L/H] ² ; Wherein: H is silicon, L is silicon dioxide, M is cerium-doped yttrium iron garnet; Its first composite structure S1=S0/M/S0, or the second composite structure S2=S0/M/S0/M/S0. 2. A kind of one-dimensional magneto-photonic crystal realizing broadband optical isolation as claimed in claim 1, is _{characterized} in that: the first composite structure S ₁ =S ₀ /M/S ₀ and S ₀ of the S 0 The central working wavelength of the two composite structure S ₂ =S ₀ /M/S ₀ /M/S ₀ is 1550nm. 3. A kind of one-dimensional magnetophotonic crystal _that realizes broadband optical isolation as claimed in claim 2, is characterized in that: described central working wavelength is under 1550nm: the refractive index of silicon Si is 3.48; The ratio is 1.495; the dielectric tensor ε ₁ =4.884, ε ₂ =0.009 of the cerium-doped yttrium iron garnet Ce:YIG. 4. a kind of one-dimensional magnetophotonic crystal that realizes broadband optical isolation as claimed in claim 1 is characterized in that: the thickness of the silicon in described basic component _S0 is 111.35nm; The thickness of silicon dioxide is 259.2nm ; The thickness of cerium-doped yttrium iron garnet is 158.68nm. 5. A kind of one-dimensional magneto-photonic crystal that realizes broadband optical isolation as claimed in claim 1, is characterized in that: described first compound structure S ₁ is horizontally rotated to be 14.14 ^o angle with optical path direction on horizontal plane under external magnetic field , the Faraday rotation angle is 45 ^o . 6. A one-dimensional magneto-photonic crystal realizing broadband optical isolation as claimed in claim 1, characterized in that: the second composite structure _S2 is horizontally rotated to form an angle of 49.61 ^° with the direction of the optical path in the horizontal plane when an external magnetic field is applied , the Faraday rotation angle is 45 ^o .