CN102608701A - Medium slit optical waveguide - Google Patents

Abstract

The invention discloses a medium slit optical waveguide. The cross section of the waveguide structure comprises a substrate layer (1), a high-refractive index buffer layer (2), a high-refractive index medium layer (3), a low-refractive index medium layer (4), a high-refractive index medium area (5), a low-refractive index medium area (6), a high-refractive index medium area (7) and a wrapping layer (8), wherein the high-refractive index buffer layer (2), the high-refractive index medium layer (3) and the low-refractive index medium layer (4) are sequentially arranged from bottom to top on the substrate layer; and the high-refractive index medium area (5), the low-refractive index medium area (6) and the high-refractive index medium area (7) are sequentially arranged from left to right on the low-refractive index medium layer. The waveguide can realize relatively strong mode field restriction on two polarized lights at the same time, and can realize multiple characteristics such as positive and negative birefringence, zero birefringence and the like through regulation and control on the structure size. The medium slit waveguide is matched with the existing silicon substrate processing technology and can be used for realizing multiple photon devices.

Description

A dielectric slit optical waveguide

technical field

The invention relates to the field of optical waveguide technology, in particular to a dielectric slit optical waveguide. the

Background technique

Traditional dielectric optical waveguides usually use high-refractive-index materials as waveguide cores, and low-refractive-index materials as cladding layers. The light field is mainly transmitted in the waveguide core made of high-refractive index materials. Due to the diffraction limit, its size tends to be relatively large. The dielectric slit optical waveguide first proposed in 2004 can realize the transmission of optical signals in nanometer-sized low-refractive index media, breaking through the size limitation of traditional optical waveguides. This type of waveguide is composed of adjacent high-refractive-index medium regions, and the middle of the high-refractive-index medium region is a low-refractive-index medium region. Its working principle is to use the discontinuity of the electric field component on the interface of materials with different permittivity, and its magnitude is inversely proportional to the square of the permittivity of the material. Using the discontinuity of the electric field distribution, the light field distribution density in the low refractive index material will be much higher than the electric field distribution density in the adjacent high refractive index region, so as to realize the transmission and confinement of the light field in the low refractive index material. the

At present, the dielectric slit waveguide has become a hot spot in the field of optical waveguide research, and has attracted extensive attention from domestic and foreign scholars. There are two main types of traditional dielectric slot waveguides, horizontal slot waveguides and vertical slot waveguides, both of which can only constrain the strong mode field of one polarized light (TE polarization or TM polarization). However, the confinement ability to another polarized light (TM polarization or TE polarization) is often weaker. The present invention proposes a dielectric slit optical waveguide structure capable of achieving strong mode field confinement for two kinds of polarized light at the same time. By adjusting the geometrical size of the structure, it can also realize various characteristics such as positive, negative birefringence or zero birefringence. . The dielectric slit waveguide matches the existing silicon-based processing technology and can be used to construct various photonic devices. the

Contents of the invention

The invention provides a dielectric slit optical waveguide structure, the cross-section of which comprises a base layer, a high-refractive-index buffer layer, a high-refractive-index medium layer, a low-refractive-index medium layer, The high-refractive-index medium region, the low-refractive-index medium region, the high-refractive-index medium region, and the cladding layer arranged from left to right on the low-refractive-index medium layer; the width of the upper surface of the high-refractive-index medium layer in the structure is related to the The width of the lower surface of the refractive index medium layer is equal; The width of the upper surface is equal; the height of the high-refractive index buffer layer is 0.006-0.06 times the wavelength of the transmitted optical signal; the width of the upper and lower surfaces of the high-refractive index medium layer is 0.1-0.3 times the wavelength of the transmitted optical signal , the height of the high-refractive index medium layer is 0.03-0.1 times the wavelength of the transmitted optical signal; the height of the low-refractive index medium layer is 0.006-0.06 times the wavelength of the transmitted optical signal, The width of the surface is 0.1-0.3 times the wavelength of the transmitted optical signal; the heights of the two high-refractive-index medium regions and the low-refractive-index medium region on the low-refractive-index medium layer are equal, and their height is the height of the transmitted optical signal 0.07-0.22 times the wavelength, and the width of the upper and lower surfaces of the area formed by the low-refractive index medium region and the high-refractive index medium region is 0.1-0.3 times the wavelength of the transmitted optical signal; the upper and lower surfaces of the low-refractive index medium region The width of the lower surface is 0.006-0.06 times the wavelength of the transmitted optical signal, and is smaller than the width of the low-refractive index medium layer; the high-refractive-index buffer layer, high-refractive-index medium layer and two high-refractive-index mediums on the base layer The materials of the regions are the same or different materials, and the refractive index of the four materials is higher than that of the base layer, the low refractive index medium layer and the cladding layer, and the materials of the base layer, the low refractive index medium layer and the cladding layer are the same Material or different materials, the maximum value of the material refractive index of the base layer, the low refractive index medium layer and the cladding layer and the minimum value of the material refractive index of the high refractive index buffer layer, the high refractive index medium layer and the two high refractive index medium regions The ratio is less than 0.75. the

In the optical waveguide structure, the outer contour of the cross-section of the area formed by the high-refractive-index medium region, the low-refractive-index medium region and the high-refractive-index medium region arranged in sequence from left to right on the low-refractive-index medium layer is rectangular, or any of the trapezoids. the

In the optical waveguide structure, the outer contours of the cross-sections of the high-refractive-index medium layer and the low-refractive-index medium layer are any one of rectangle and trapezoid. the

The dielectric slit optical waveguide of the present invention has the following advantages:

1. The proposed dielectric slit optical waveguide is based on the coupling of the traditional silicon waveguide and the vertical dielectric slit waveguide, which can achieve strong polarization of light in the inverted "T"-shaped low refractive index slit area. Mode field constraints. the

2. Through the adjustment of the structure size, the two mode characteristics supported by the waveguide can be effectively regulated, and various characteristics such as positive, negative birefringence or zero birefringence can be realized.

3. The proposed dielectric slit waveguide can be realized by the existing mature silicon-based processing technology, and various integrated photonic devices can be constructed on this basis. In addition, it can also be applied in the fields of nonlinearity, optical modulation, and optical tweezers. the

Description of drawings

Fig. 1 is a schematic diagram of the structure of a dielectric slit optical waveguide. Area 1 is the base layer; Area 2 is the high-refractive-index buffer layer with a height of h ₂ ; Area 3 is a high-refractive-index medium layer with a lower surface width w ₃ , an upper surface width w ₄ , and a height h ₃ ; Region 4 is a low-refractive-index dielectric layer with a width of w ₄ on its lower surface, a width of w _b on its upper surface, and a height of h ₄ ; region 5 is the high-refractive-index dielectric layer on the left, with a width of w _5b on its lower surface and The surface width is w _5t ; area 7 is the high refractive index medium area on the right side, its lower surface width is w _6b , and its upper surface width is w _6t ; area 6 is a low refractive index medium area, its lower surface width is w _6b , The width of the upper surface is w _6t ; the height of the regions 5, 6 and 7 is h _t ; the region 8 is the cladding.

Fig. 2 is a structural diagram of the dielectric slit optical waveguide described in the example. 201 is the base layer, n _s is its refractive index; 202 is a high refractive index buffer layer, its height is h _b ; 203 is a high refractive index medium layer, its cross section is square, and its height is h ₁ ; 204 is a low refractive index Dielectric layer, its cross section is square, its height is h _l , n ₁ is its refractive index; 205 and 207 are high refractive index medium areas, its cross section is square, w _h is its width; 206 is a low refractive index medium area , its cross section is square, n ₁ is its refractive index, w _s its width; the heights of 205, 206, and 207 are equal and both are h ₂ ; The widths of 203 and 203 are equal, and both are w; the refractive indices of 202, 203, 205, and 207 are all n _h ; 208 is the cladding layer, and n _c is its refractive index.

Fig. 3 is a distribution diagram of the electric field intensity of the mode light field of the dielectric slit optical waveguide described in the example when the wavelength of the transmitted optical signal is 1.55 μm. Figure 3(a) corresponds to the TE mode, and Figure 3(b) corresponds to the TM mode. the

Fig. 4 is the variation curve of the mode birefringence of the dielectric slit optical waveguide described in the example with the width w when the wavelength of the transmitted optical signal is 1.55 μm. the

Fig. 5 is a curve of the confinement factor of the two modes propagating in the dielectric slit optical waveguide described in the example as a function of the width w when the wavelength of the transmitted optical signal is 1.55 μm. Figure 5(a) is the TE mode, and Figure 5(b) is the TM mode. the

Detailed ways

Two important properties of slot waveguides, mode birefringence and confinement factor, are investigated here. the

Mode birefringence is defined as B = n _eff (TE) - n _eff (TM), where n _eff (TE) and n _eff (TM) denote the effective indices of refraction for the TE and TM polarization modes, respectively.

The confinement factor is defined as the ratio of the optical power in the slit area of the low-refractive index medium to the total optical power of the waveguide, and this value can be used to measure the confinement ability of the slit area to the optical field. In the present invention, the corresponding slit area is an inverted "T"-shaped slit. the

Example:

Fig. 2 is a structural diagram of the dielectric slit optical waveguide described in the example. 201 is the base layer, n _s is its refractive index; 202 is a high refractive index buffer layer, its height is h _b ; 203 is a high refractive index medium layer, its cross section is square, and its height is h ₁ ; 204 is a low refractive index Dielectric layer, its cross-section is square, its height is h _l ; 205 and 207 are high-refractive index medium areas, its cross-section is square, w _h is its width; 206 is a low-emissivity medium area, its cross-section is square, n ₁ is its refractive index, w _s is its width; the heights of 205, 206, and 207 are equal and both are h ₂ ; the width of the section of the area jointly formed by 205, 206, and 207, the width of 204, and the width of 203 are equal, and are all w; the refractive indices of 202, 203, 205, and 207 are all n _h ; 208 is the cladding layer, and n _c is its refractive index.

In this example, the wavelength of the transmitted optical signal is selected as 1.55 μm, and the material of 201, 204, 206, and 208 is set as silicon dioxide, and its refractive index is 1.5; the material of 202, 203, 205, and 207 is set as silicon , whose refractive index is 3.5. the

In this example, _the height h _b of 202 = 50 nm; the height h ₁ of 203 = 100 nm; the height h _l of 204 = 50 nm; the width w _s of 206 = 50 nm; The value range of w is 200-400nm, correspondingly, the value range of the width w _h of 205 and 207 is 75-175nm.

The above-mentioned waveguide structure in this embodiment is simulated using the full vector finite element method, and the mode field distribution and mode characteristics of the TE and TM modes supported by the dielectric slit waveguide at a wavelength of 1.55 μm are calculated. the

Fig. 3 is a distribution diagram of the electric field intensity of the mode light field of the dielectric slit optical waveguide described in the example when the wavelength of the transmitted optical signal is 1.55 μm. Figure 3(a) corresponds to the TE mode, and Figure 3(b) corresponds to the TM mode. It can be seen from the figure that both modes have obvious field enhancement effect in the slit area. The field enhancement of TE mode is mainly concentrated in the upper vertical slit region, while the field enhancement of TM mode is mainly concentrated in the lower horizontal slit region. the

Fig. 4 is a curve of mode birefringence versus width w of the dielectric slit optical waveguide described in the example when the wavelength of the transmitted optical signal is 1.55 μm. It can be seen from the figure that by adjusting the size of the waveguide, various birefringence characteristics such as negative birefringence, zero birefringence, and positive birefringence can be obtained. the

Fig. 5 is a curve of the confinement factor of the two modes propagating in the dielectric slit optical waveguide described in the example as a function of the width w when the wavelength of the transmitted optical signal is 1.55 μm. Figure 5(a) is the TE mode, and Figure 5(b) is the TM mode. It can be seen that the confinement factors of the two modes increase with the increase of the width w, and their values are relatively large, indicating that a considerable part of the slit can be restricted. The energy of the light field. the

Finally, it should be noted that the embodiments in the above figures are only used to illustrate the dielectric slit optical waveguide structure of the present invention, but are not limiting. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present invention do not depart from the spirit and scope of the technical solutions of the present invention, and all of them should be included in the scope of the present invention. within the scope of the claims. the

Claims (3)

1. medium slit optical waveguide structure, its xsect comprise basalis, be positioned at the high index of refraction cushion that is arranged in order from top to bottom, high refractive index medium layer, low refractive index dielectric layer on the basalis, be positioned at the high refractive index medium district, low refractive index dielectric district and high refractive index medium district and the covering that from left to right are arranged in order on the low refractive index dielectric layer; The width of high refractive index medium layer upper surface equates with the width of low refractive index dielectric layer lower surface in the said structure; The width that is positioned at the lower surface in the common zone that constitutes in high refractive index medium district, low refractive index dielectric district and high refractive index medium district on the low refractive index dielectric layer equates with the width of low refractive index dielectric layer upper surface; The height of high index of refraction cushion be institute's transmitting optical signal wavelength 0.006-0.06 doubly; The width on the upper and lower surface of high refractive index medium layer be institute's transmitting optical signal wavelength 0.1-0.3 doubly, the height of high refractive index medium layer be institute's transmitting optical signal wavelength 0.03-0.1 doubly; The height of low refractive index dielectric layer be institute's transmitting optical signal wavelength 0.006-0.06 doubly, the width on the upper and lower surface of low refractive index dielectric layer be institute's transmitting optical signal wavelength 0.1-0.3 doubly; Two the high refractive index medium districts and the height in low refractive index dielectric district that are positioned on the low refractive index dielectric layer equate; And its highly be institute's transmitting optical signal wavelength 0.07-0.22 doubly, the width on the upper and lower surface in the common zone that constitutes in low refractive index dielectric district and high refractive index medium district is 0.1-0.3 times of wavelength of institute's transmitting optical signal; The width on the upper and lower surface in low refractive index dielectric district be institute's transmitting optical signal wavelength 0.006-0.06 doubly, and less than the width of low refractive index dielectric layer; The material that is positioned at high index of refraction cushion, high refractive index medium layer and two high refractive index medium districts on the basalis is identical or different material; And four material refractive index all is higher than the material refractive index of basalis, low refractive index dielectric layer and covering; The material of basalis, low refractive index dielectric layer and covering is same material or different materials, and the ratio of the minimum value of the material refractive index in the maximal value of the material refractive index of basalis, low refractive index dielectric layer and covering and high index of refraction cushion, high refractive index medium layer and two high refractive index medium districts is less than 0.75.

2. optical waveguide structure according to claim 1; It is characterized in that the outer contour shape that is arranged in the cross section in the common zone that constitutes in the high refractive index medium district, low refractive index dielectric district and the high refractive index medium district that from left to right are arranged in order on the low refractive index dielectric layer in the said structure is a rectangle or trapezoidal any.

3. optical waveguide structure according to claim 1 is characterized in that, in the said structure outer contour shape in the cross section of high refractive index medium layer and low refractive index dielectric layer be rectangle or trapezoidal in any.

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