TWM464672U - Porous birefringence photonic crystal optical fiber - Google Patents

Description

Hole-type birefringent photonic crystal fiber

A photonic crystal fiber, in particular a hole type birefringent photonic crystal fiber.

Photonic Crystal Fiber (PCF) consists of an undoped single material, such as cerium oxide (SiO2) and air holes, which are regularly or irregularly arranged in the axial direction of the Cladding layer. Air hole. When a circular air hole is periodically broken at a position of a core to form a defect, light can propagate along the defect. This type of photonic crystal fiber can be basically divided into two categories: one-line average-index effect and the other photon band gap effect. Wherein the average refractive index effect photonic crystal fiber has a Guide Mode mechanism of total reflection, and generally does not require periodic arrangement of air holes in the fiber layer; and the photonic crystal bandgap guided mode photonic crystal fiber The guiding mechanism is the photonic band gap effect, which generally requires the air holes in the fiber coating layer to be periodically arranged.

Since the conventional single-mode fiber has two orthogonal polarization modes, and the two polarization modes are almost degeneracy, the field in the fiber is easily removed from the field as long as it generates a small amount of perturbation. The polarization mode is switched to another polarization mode. If the polarization state is removed due to degeneracy, the field transition between the polarization modes will be greatly reduced and the fiber will become a birefringent fiber.

Different from traditional optical fibers, photonic crystal fibers are often used because of their high refractive index difference between the core and the fiber coating layer, and can be flexibly designed into symmetric and asymmetric structures. Designed as a high birefringence fiber. The use of asymmetric structures in photonic crystal fibers generally creates high birefringence differences due to the difference in equivalent refractive index between the two orthogonal directions of the fiber optic fibers, creating such high birefringence photons. The purpose of the crystal fiber is to reduce the coupling of the fundamental mode of the fundamental mode, thereby allowing light to propagate through the fiber, and the field pattern can be easily maintained.

The prior art, as shown in FIG. 1 , is a structural diagram of a circular photonic crystal fiber, which is composed of a plurality of first air holes, which are layered around the core, and the core does not have the plurality of first air holes. Light propagates through the core with total reflection. Figure 1 is the structure diagram of the circular photonic crystal fiber proposed by us. The central part is pulled out of a circular air hole to form a core. The refractive index of the circular air hole is n=1. The background is silica, and the refractive index n = 1.45. The structure of the structure adopts a tetragonal lattice, which is different from the conventional method of using a triangular lattice arrangement. First, Λ x and Λ y are defined, which are components respectively disassembled from the lattice constant (Λ), respectively. x, Λ y. Λ x is the distance from the center point of the two ellipse, that is, the direction of the horizontal axis; Λ y is the distance from the center point of the two circles, that is, the direction of the vertical axis. Then, the elliptical air hole length (Y) axis and the short (X) axis are set. Here, the size is 2a, and the size is 2a=0.8 μm. The other simulation parameters select the excitation source wavelength as the current communication wavelength λ=1.55 μm.

The present invention provides a hole-type birefringent photonic crystal fiber comprising: a fiber core located at a center of the hole-type birefringent photonic crystal fiber; and a fiber body composed of a plurality of elliptical air holes The plurality of elliptical air holes near the center of the hole-type birefringent photonic crystal fiber surround the core; wherein the plurality of air holes surround the number of layers of the core, and the layer has 5 layers, and the core does not have the plurality of In the air hole, the light propagates through the core with total reflection. The center of the air hole is connected to the center of the next air hole, and the x-axis spacing (Λ _x ) in the x-axis direction is 1,9um, and the y-axis direction is extended. The y-axis spacing (Λ _y ) is 2.2 um.

The present invention provides an embodiment of a hole-type birefringent photonic crystal fiber comprising: a third structure comprising: a first layer, a second layer, a third layer, a fourth layer, and a Layer 5. The first layer is surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis, wherein the plurality of elliptical air holes extending up and down along the x-axis are four second air holes, and Two third air holes are disposed between the upper and lower sides extending along the x-axis, wherein the plurality of elliptical air holes along the y-axis are three second air holes; the second layer is formed along the x-axis and along the a plurality of elliptical air holes of the y-axis rectangular structure are surrounded by the first layer, wherein the plurality of elliptical air holes of the second layer are arranged alternately between the centers of the two second air holes. Wherein, the fourth apex of the second layer of the rectangular structure does not place the second air hole; the third layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis to form the second layer, wherein The plurality of elliptical air holes extending along the x-axis are nine second air holes, wherein the plurality of elliptical air holes along the y-axis are seven second air holes; the fourth layer is formed by the x-axis And a plurality of elliptical air holes along the y-axis rectangular structure surrounding the outer layer of the third layer, wherein the fourth layer An elliptical air hole is continuously arranged between the centers of the two second air holes, wherein the fourth apex of the fourth layer of the rectangular structure does not place the second air hole; and the fifth layer, The plurality of elliptical air holes along the x-axis and along the y-axis are successively surrounding the second layer, wherein the plurality of elliptical air holes extending along the x-axis are 13 second air holes, wherein the y-axis The plurality of elliptical air holes are 11 second air holes.

9‧‧‧Silicon

10‧‧‧Finishing

11‧‧‧1st air hole

12‧‧‧2nd air hole

13‧‧‧3rd air hole

1 is a schematic view of a hole-type birefringent photonic crystal fiber of the prior art.

Fig. 2 is a schematic view showing the aperture type birefringent photonic crystal fiber of the first embodiment of the present invention.

Fig. 3 is a schematic view showing a hole type birefringent photonic crystal fiber according to a second embodiment of the present invention.

Fig. 4 is a schematic view showing a hole type birefringent photonic crystal fiber according to a third embodiment of the present invention.

5A to 5D are comparison diagrams showing main structural differences between the prior art, the first embodiment, the second embodiment, and the third embodiment.

Figure 6. Schematic diagram of the corresponding effective refractive index at different wavelengths.

Fig. 7A is a schematic diagram of a conventional birefringence difference and a mode field.

Fig. 7B is a schematic diagram showing the difference in birefringence and the mode field in the first embodiment.

Fig. 7C is a schematic view showing the birefringence difference and the mode field of the second embodiment.

Fig. 7D is a schematic diagram showing the difference in birefringence and the mode field in the third embodiment.

Figure 8 is a schematic illustration of the difference in wavelength versus corresponding birefringence for different embodiments.

Figure 9 is a schematic diagram of wavelength versus corresponding fiber loss for different embodiments.

The present invention provides a hole-type birefringent photonic crystal fiber, comprising: a core 9 which is located at the center of the hole-type birefringent photonic crystal fiber; and a fiber 10 which is composed of a plurality of ellipses The air hole is composed of the plurality of elliptical air holes near the center of the hole-type birefringent photonic crystal fiber, surrounding the core 9; wherein the plurality of air holes surround the layer of the core 9 and is 5 layers, the fiber The core 9 does not have the plurality of air holes, and the light propagates through the core 9 with total reflection. The center of the air hole is connected to the center of the next air hole, and the x-axis distance (Λ _x ) in the x-axis direction is 1 , 9um, the y-axis spacing (Λ _y ) in the y-axis direction is 2.2um.

The hole-type birefringent photonic crystal fiber of the present invention comprises: a first structure, As shown in FIG. 2, it includes: a first layer, a second layer, a third layer, a fourth layer, and a fifth layer. The first layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis, and the plurality of elliptical air holes extending along the x-axis are five second air holes 12, Wherein the plurality of elliptical air holes along the y-axis are three second air holes 12; the second layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis. a layer, wherein the plurality of elliptical air holes of the second layer are arranged alternately between the centers of the two second air holes 12, wherein the four vertices of the second layer structure are not placed a second air hole 12; the third layer is continuous around the second layer by a plurality of elliptical air holes along the x-axis and along the y-axis, wherein the plurality of elliptical air holes extending along the x-axis are 9 a second air hole 12, wherein the plurality of elliptical air holes along the y-axis are seven second air holes 12; the fourth layer is composed of a plurality of elliptical air holes along the x-axis and along the y-axis Surrounded by the third layer, wherein the plurality of elliptical air holes of the fourth layer are separated by two of the second spaces The center distance of the hole 12 is continuously arranged between the structures, wherein the 4th apex of the 4th layer structure does not place the second air hole 12; and the 5th layer is formed by the x-axis and the y-axis A plurality of elliptical air holes are successively surrounding the second layer, wherein the plurality of elliptical air holes extending along the x-axis are 13 second air holes 12, wherein the plurality of elliptical air holes along the y-axis are 11 second air Hole 12.

The present invention discloses a hole-type birefringent photonic crystal fiber comprising: a second structure, as shown in FIG. 3, comprising: a first layer, a second layer, a third layer, a fourth layer, and a first 5th floor. The first layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis, and the plurality of elliptical air holes extending along the x-axis are five second air holes 12, Wherein, the plurality of elliptical air holes along the y-axis are three second air holes 12, and the center positions of the two second intermediate air holes 12 extending along the y-axis are respectively shifted outward. X-axis spacing ( The position of Λ _x ) is placed; the second layer is surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis, and is surrounded by the plurality of elliptical air of the second layer. The holes are arranged at intervals between the centers of the two second air holes 12, wherein the second air holes 12 are not placed at the four vertices of the second layer structure; the third layer is The second layer is continuously surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis, wherein the plurality of elliptical air holes extending along the x-axis are nine second air holes 12, wherein the y-axis a plurality of elliptical air holes are 7 second air holes 12; the fourth layer is surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis to be outsourced to the third layer, wherein the fourth layer The plurality of elliptical air holes are arranged alternately between the centers of the two second air holes 12, wherein the second air holes 12 are not placed at the four vertices of the fourth layer structure; The fifth layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis Wherein the plurality of air holes is elliptical 13 second air hole 12 extending along the x axis, where the y-axis of the ellipse of the plurality of the air holes is 11 second air hole 12.

The present invention discloses a hole-type birefringent photonic crystal fiber comprising: a third structure, as shown in FIG. 4, including: a first layer, a second layer, a third layer, a fourth layer, and a first 5th floor. The first layer is composed of a knot along the x-axis and along the y-axis The plurality of elliptical air holes are arranged to surround the core 9 in series, wherein the plurality of elliptical air holes extending up and down along the x-axis are four second air holes 12, and two third airs placed in the middle of the upper and lower sides extending along the x-axis a hole 13, wherein the plurality of elliptical air holes along the y-axis are three second air holes 12; the second layer is surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis In the first layer, the plurality of elliptical air holes of the second layer are arranged alternately between the centers of the two second air holes 12, wherein the second layer structure is four The second air hole 12 is not placed at the apex; the third layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis to continuously surround the second layer, wherein the plurality of elliptical air extending along the x-axis The hole is nine second air holes 12, wherein the plurality of elliptical air holes along the y-axis are seven second air holes 12; the fourth layer is composed of a plurality of structures along the x-axis and along the y-axis An elliptical air hole is surrounded by the third layer, wherein the plurality of elliptical air holes of the fourth layer are interphased The center distances of the two second air holes 12 are successively arranged, wherein the fourth apex of the fourth layer structure is not placed in the second air hole 12; and the fifth layer is along the x axis and A plurality of elliptical air holes along the y-axis rectangular structure continuously surround the second layer, wherein the plurality of elliptical air holes extending along the x-axis are 13 second air holes 12, wherein the plurality of elliptical air holes along the y-axis There are 11 second air holes 12.

The material of the core 9 and the fiber 10 is a cerium oxide (SiO2) having a refractive index of 1.45. The refractive index of the plurality of elliptical air holes is 1. The short half shaft of the second air hole 12 is 0.45 um, and the long half shaft is 0.542 um. The short half shaft of the third air hole 13 is 0.225 um, and the long half shaft is 0.272 um.

The present invention has a hole-type birefringent photonic crystal fiber which is simulated by a Finite Element Method (FEM). 7A to 7D, as can be seen from the numerical model, since the second air hole 12 and the third air hole 13 surrounding the ellipse are surrounded by the core 9, the refractive index of the air is 1, thereby causing the fiber 10 The average refractive index decreases, and the mode domain of the light is concentrated in the portion 9 of the core of the higher refractive index distribution than the refractive index of 1.45. An average refractive index difference between two orthogonal directions in the x-direction and y-direction, the lines in the x-direction of the equivalent refractive index n _x eff, and the equivalent refractive index in the y direction of n _y eff, both of the absolute differences The value | n _x eff- n _y eff |, is the birefringence difference Δn, and the formula is as follows: Δn=| n _x eff- n _y eff |, as for other simulation parameters, the excitation source wavelength is selected as The current communication wavelength λ = 1.55 μm. According to the simulation results, as shown in FIG. 7A, the conventional technique birefringence difference and n _x eff=1.401289, n _y eff=1.397126 in the mode field diagram are substituted into the above formula, and Δn=| n _x eff is obtained. - n _y eff |=3.36×10 ^-3 . As shown in Fig. 7B, the birefringence difference of the first embodiment and the n _x eff = 1.421323, n _y eff = 1.418567 in the mode field diagram are substituted into the above formula to obtain Δn = | n _x eff - n _y eff |=2.75×10 ^-3 . As shown in Fig. 7C, in the second embodiment, the birefringence difference and n _x eff = 1.420714, n _y eff = 1.414082 in the mode field diagram are substituted into the above formula to obtain Δn = | n _x eff - n _y eff |=6.63×10 ^-3 . As shown in Fig. 7D, the birefringence difference of the third embodiment and the n _x eff=1.426852, n _y eff=1.406015 in the mode field diagram are substituted into the above formula to obtain Δn=| n _x eff- n _y eff |=20.85×10 ^-3 =2.085×10 ^-2 . It can be seen from the third embodiment that the birefringence difference after the simulation analysis of the present invention can reach the order of 10 ^-2 , which is an order of magnitude higher than the birefringence difference of 10 ^{-3 of the} general photonic crystal fiber, and the double of the conventional optical fiber. The refractive index difference of 10 ^{-4 is} two orders of magnitude higher.

The effective refractive index of the present invention is in the range of 1.55 um to 2.0 um in the wavelength, and is the main structural difference of the prior art, the first embodiment, the second embodiment, and the third embodiment, as shown in FIGS. 5A to 5D. The structure comparison shows that the third embodiment has a better effective refractive index, as shown in FIG.

The mode field diagram of the present invention, as shown in FIG. 7A to FIG. 7D, is in the environment of a wavelength of 1.55 um under the difference of the main structures of the prior art, the first embodiment, the second embodiment, and the third embodiment. The mode field diagram, the structure of the third embodiment, has a preferred mode field map, and the concentrated energy is transmitted in the fiber core 9 of the third embodiment. According to the conventional technique, the first air hole 11 cannot be concentrated in the fiber 9 of the prior art as shown in FIG. 7A and FIG.

The corresponding birefringence difference of the present creation, as shown in FIG. 8, is in the environment of the wavelength of 1.4 um to 2.0 um under the main structural differences of the prior art, the first embodiment, the second embodiment, and the third embodiment. The corresponding birefringence difference diagram can be seen from the third embodiment. The birefringence difference of the present simulation can reach 10 ^-2 order, which is higher than the birefringence difference of 10 ^{-3 of the} general photonic crystal fiber. birefringence difference of magnitude, the conventional optical fiber ^10-4 and two orders of magnitude higher.

As shown in FIG. 9, is a schematic diagram of wavelength and corresponding fiber loss in different embodiments. In the third embodiment, the fiber loss in the environment of a wavelength of 1.55 um is 1.63 x 10 ^-5 (dB/km), which is 1.44 x 10 ^-2 (dB/km) compared to the prior art, and 26.74 of the first embodiment. x 10 ^-5 (dB/km) and 20.25 x 10 ^-5 (dB/km) of the second embodiment, it is understood that the structure of the third embodiment has a low fiber loss.

The above descriptions are merely illustrative of the preferred embodiments or examples of the technical means employed to solve the problems, and are not intended to limit the scope of the invention. Any change or modification that is consistent with the scope of the patent application scope of this creation or the scope of the patent creation is covered by the scope of the creation patent.

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10‧‧‧Silicon

12‧‧‧2nd air hole

13‧‧‧3rd air hole

Claims (8)

A hole-type birefringent photonic crystal fiber comprising: a fiber core located at a center of the hole-type birefringent photonic crystal fiber; and a fiber body composed of a plurality of elliptical air holes, adjacent to the fiber The plurality of elliptical air holes in the center of the hole-type birefringent photonic crystal fiber surround the core; wherein the plurality of air holes surround the number of layers of the core, and the layer has 5 layers, and the core does not have the plurality of air holes. Light propagates through the core through total reflection. The center of the air hole is connected to the center of the next air hole. The x-axis spacing (Λ _x ) in the x-axis direction is 1,9um, and the y-axis in the y-axis direction. The spacing (Λ _y ) is 2.2 um. The aperture type birefringent photonic crystal fiber according to claim 1, comprising: a first structure, comprising: a first layer, which is composed of a plurality of elliptical air structures along the x-axis and along the y-axis The holes are continuous around the core, wherein the plurality of elliptical air holes extending along the x-axis are five second air holes, wherein the plurality of elliptical air holes along the y-axis are three second air holes; a second layer And surrounding the first layer by a plurality of elliptical air holes along the x-axis and along the y-axis, wherein the plurality of elliptical air holes of the second layer are spaced apart by the second air The center of the hole is continuously arranged between the structures, wherein the second apex of the second layer of the rectangular structure does not place the second air hole; and the third layer is composed of a plurality of ellipses along the x-axis and along the y-axis An air hole continuously surrounds the second layer, wherein the plurality of ellipses extending along the x-axis The circular air holes are nine second air holes, wherein the plurality of elliptical air holes along the y-axis are seven second air holes; a fourth layer is a plurality of structures along the x-axis and along the y-axis An elliptical air hole is surrounded by the third layer, wherein the plurality of elliptical air holes of the fourth layer are arranged alternately between the centers of the two second air holes, wherein the fourth layer The second apex of the rectangular structure does not place the second air hole; and a fifth layer is continuously surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis, wherein the second layer extends along the x-axis The plurality of elliptical air holes are 13 second air holes, and the plurality of elliptical air holes along the y-axis are 11 second air holes. The aperture type birefringent photonic crystal fiber according to claim 2, comprising: a second structure, comprising: a first layer, which is composed of a plurality of ellipses along the x-axis and along the y-axis The air holes are continuous around the core, wherein the plurality of elliptical air holes extending along the x-axis are five second air holes, wherein the plurality of elliptical air holes along the y-axis are three second air holes, two The center position of the second air hole in the middle layer of the first layer extending along the y axis is shifted outward X-axis spacing ( a position of Λ _x ); a second layer surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis to form the first layer, wherein the plurality of elliptical air of the second layer The hole is arranged between the two center holes of the second air hole at intervals, wherein the second apex of the second layer structure does not place the second air hole; a third layer is formed by the edge An x-axis and a plurality of elliptical air holes along the y-axis moment structure surround the second layer, wherein the plurality of elliptical air holes extending along the x-axis are nine second air holes, wherein the plurality of ellipse along the y-axis The air hole is 7 second air holes; a fourth layer is surrounded by a plurality of elliptical air holes along the x-axis and along the y-axis to be outsourced to the third layer, wherein the plurality of the fourth layer An elliptical air hole is continuously arranged between the centers of the two second air holes, wherein the fourth apex of the fourth layer structure does not place the second air hole; and a fifth layer A plurality of elliptical air holes along the x-axis and along the y-axis are successively surrounding the second layer, wherein along the x The plurality of air holes is elliptical second air hole 13, wherein the y-axis of the ellipse of the plurality of air holes is the second air hole 11 extends. The aperture type birefringent photonic crystal fiber according to claim 3, comprising: a third structure, comprising: a first layer, which is composed of a plurality of ellipses along the x-axis and along the y-axis The air holes are continuous around the core, wherein the plurality of elliptical air holes extending up and down along the x-axis are four second air holes, and two third air holes are disposed between the upper and lower sides extending along the x-axis, wherein, along the y-axis The plurality of elliptical air holes are three second air holes; a second layer consisting of a plurality of elliptical structures along the x-axis and along the y-axis The air hole surrounds the first layer, wherein the plurality of elliptical air holes of the second layer are arranged alternately between the centers of the two second air holes, wherein the second layer structure The second apex does not place the second air hole; a third layer is surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis to continuously surround the second layer, wherein the plurality of holes extend along the x-axis The elliptical air hole is 9 second air holes, wherein the plurality of elliptical air holes along the y axis are 7 second air holes; a fourth layer is composed of a plurality of structures along the x-axis and along the y-axis An elliptical air hole is surrounded by the third layer, wherein the plurality of elliptical air holes of the fourth layer are arranged alternately between the centers of the two second air holes, wherein the fourth layer The second apex of the rectangular structure does not place the second air hole; and a fifth layer is continuously surrounded by the plurality of elliptical air holes along the x-axis and along the y-axis, wherein the second layer extends along the x-axis The plurality of elliptical air holes are 13 second air holes, wherein the plurality of ellipses along the y axis The circular air holes are 11 second air holes. The hole-type birefringent photonic crystal fiber according to claim 4, wherein the core and the material of the fiber are cerium oxide (SiO2) having a refractive index of 1.45. The aperture type birefringent photonic crystal fiber according to claim 5, wherein the plurality of elliptical air holes have a refractive index of 1. The aperture type birefringent photonic crystal fiber according to claim 6, wherein the second air hole has a short half-axis of 0.45 um and a long half-axis of 0.542 um. The aperture type birefringent photonic crystal fiber according to claim 7, wherein the third air hole has a short half-axis of 0.225 um and a long half-axis of 0.272 um.