Optical fiber structure with high numerical aperture

Abstract

The utility model relates to the technical field of optical fibers, in particular to an optical fiber structure with a high numerical aperture, which comprises an optical fiber core layer with a first refractive index; the optical fiber cladding has a second refractive index, and the second refractive index is smaller than the first refractive index; a plurality of trenches extending from the fiber cladding to the fiber core; wherein the depth of each groove is larger than the thickness of an optical fiber cladding, and each groove is arranged along the axis direction of the optical fiber. According to the optical fiber structure provided by the utility model, the grooves are arranged on the surfaces of the optical fiber core layer and the optical fiber cladding layer, the light guide areas with different refractive indexes are formed on the periphery of the optical fiber core layer, the original cladding layer is damaged by the grooves, a new cladding layer is formed by the medium on the periphery of the optical fiber core layer, and the refractive index of the areas is far lower than that of the original cladding layer. And the numerical aperture of the optical fiber structure is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of optical fiber, specifically to high numerical aperture's optical fiber structure. BACKGROUND

[0002] Optical fiber light beam is made of a large number of optical fiber materials, and is a light intensity transmission element that can be arbitrarily bent, corrosion-resistant and high-temperature-resistant. Its principle is based on the total reflection principle inside the optical fiber material, that is, the light propagates forward by multiple total reflections inside the optical fiber. When the light is incident from the optical dense medium (high refractive index medium) into the optical sparse medium (low refractive index medium), if the incident angle is greater than the critical angle, the light will be totally reflected on the interface, and will not enter the optical sparse medium. In the optical fiber, the refractive index of the core layer is higher than that of the cladding layer, so the light is totally reflected on the interface between the core layer and the cladding layer, thereby being transmitted along the optical fiber.

[0003] The light incident to the end face of the optical fiber cannot be totally transmitted by the optical fiber, only the incident light within a certain angle range can be transmitted. The sine value of this angle a is called the numerical aperture (NA=sina) of the optical fiber. The numerical aperture of the optical fiber is related to the core refractive index and the relative refractive index difference between the core and the cladding. Physically, the numerical aperture of the optical fiber represents the ability of the optical fiber to receive incident light. The larger the NA, the stronger the ability of the optical fiber to receive light. From the point of view of increasing the light power entering the optical fiber, the larger the NA, the better, because a larger numerical aperture of the optical fiber is beneficial to the butt joint of the optical fiber.

[0004] The conventional technical means to realize high NA of the optical fiber usually includes fluorine doping and low refractive index coating of the optical fiber. The maximum NA that can be realized by the former in practice is 0.25, and the maximum NA that can be realized by the latter is 0.48. Moreover, the low refractive index coating must be used to realize the low refractive index coating of the optical fiber, which is expensive, and the temperature resistance of such coating is usually below 85 degrees. This actually limits the design freedom and application range of the optical fiber. UTILITY MODEL CONTENT

[0005] In view of the technical problems existing in the optical fiber structure in the prior art, the first aspect of the utility model provides a high numerical aperture optical fiber structure, comprising:

[0006] An optical fiber core layer, the optical fiber core layer has a first refractive index;

[0007] An optical fiber cladding layer, the optical fiber cladding layer has a second refractive index, the second refractive index is smaller than the first refractive index;

[0008] A plurality of grooves extending from the optical fiber cladding layer to the optical fiber core layer;

[0009] The depth of the groove is greater than the thickness of the optical fiber cladding layer, and each groove is arranged along the axis direction of the optical fiber.

[0010] Preferably, along the radial section of the optical fiber, the cross-sectional shape of the groove is semicircular, triangular, trapezoidal or rectangular.

[0011] Preferably, the thickness ratio of the optical fiber cladding and the optical fiber core layer is 1:9.

[0012] Preferably, the width of the groove is 5-50 microns, and the number of the grooves is 1-18.

[0013] Preferably, the depth of the groove on the surface of the optical fiber core layer is 1 / 5 of the diameter of the optical fiber core layer.

[0014] Preferably, the total arc length b of the groove on the circumference of the optical fiber core layer is 0.1π-π.

[0015] Preferably, in the cross-section of the optical fiber structure, a first light guide region is formed towards the groove, and a second light guide region is formed towards the optical fiber cladding, the numerical aperture at the first light guide region is NA1, the numerical aperture at the second light guide region is NA2, and the numerical aperture of the optical fiber structure NA=NA1×b / 2π+NA2·(2π-b / 2π).

[0016] Preferably, the diameter of the optical fiber core layer is 50-1500 microns.

[0017] Compared with the prior art, the optical fiber structure has the advantages that:

[0018] The optical fiber structure disclosed by the present application has the advantages that: BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are not intended to be drawn to scale. In the drawings, each same or like component shown in each of the figures can be designated with the same reference numerals. In the interest of clarity, not each component of each figure is labeled. Embodiments of various aspects of the present application will now be described, by way of example only, with reference to the drawings in which:

[0020] Figure 1 is a schematic view of the high numerical aperture optical fiber structure with semicircular grooves on the surface shown in the present application;

[0021] Figure 2 is a schematic view of the high numerical aperture optical fiber structure with triangular grooves on the surface shown in the present application;

[0022] Figure 3 is the schematic view of the high numerical aperture fiber structure surface opening trapezoidal groove shown in the utility model;

[0023] Figure 4 is the schematic view of the high numerical aperture fiber structure surface opening rectangular groove shown in the utility model. DETAILED DESCRIPTION

[0024] In order to understand the technical content of the utility model more, specific embodiments are raised and the following is described with the attached drawings.

[0025] Combining Figure 1 And Figure 2 The first aspect of the utility model proposes a kind of high numerical aperture fiber structure, including fiber core layer 1, fiber cladding 2 and multiple grooves 3, fiber core layer 1 has first refractive index, fiber cladding 2 has second refractive index, second refractive index is less than first refractive index.

[0026] In this way, light is shot into fiber core layer 1 at angle less than critical angle, since the refractive index of fiber cladding 2 is less than the refractive index of fiber core layer 1, therefore, light is totally reflected in fiber core layer 1.

[0027] When first refractive index and second refractive index are more close, critical angle is smaller, therefore, the ability of fiber structure to receive and couple light is not strong, i.e. numerical aperture is low, by setting multiple grooves 3, each groove 3 extends from fiber cladding 2 to fiber core layer 1, can change the refractive index of fiber cladding 2.

[0028] In alternative embodiment, groove 3 can be formed on the surface of the fiber by laser etching.

[0029] Specifically, the laser energy density used in laser etching is 10 6 -10 8 w / cm 2 .

[0030] Wherein, the depth of groove 3 is greater than the thickness of fiber cladding 2, i.e. reaches the surface of fiber core layer 1 and extends inward, each groove 3 is arranged along the axis direction of fiber, the opening length of groove 3 is 0.5-5 microns.

[0031] It should be understood that, at this time, when light is shot into fiber core layer 1 from the end surface of fiber structure, part of light can penetrate fiber cladding 2 to reach fiber core layer 1 from groove 3, and when the proportion of groove 3 on the surface of fiber cladding 2 is greater, then more light can enter into fiber core layer 1.

[0032] Optionally, the total arc length b of groove 3 on the circumference of fiber core layer 1 is 0.1π-π.

[0033] CombiningFigure 1 As shown in the cross section of the fiber structure, a first light guide region A is formed towards the groove 3, and a second light guide region B is formed towards the fiber cladding 2. In the first light guide region A, the numerical aperture is NA1, and in the second light guide region B, the numerical aperture is NA2. NA = NA1 x b / 2π + NA2 x (2π - b / 2π).

[0034] It should be understood that the fiber core layer 1 is surrounded by two cladding materials. One is the original fiber cladding 2 outside the fiber core layer 1, and the other is a new cladding formed by the medium surrounding the fiber core layer 1 after the original fiber cladding 2 is etched in the first light guide region A. The medium surrounding the fiber core layer 1 can be air.

[0035] If the refractive index of the fiber core layer 1 is defined as 1.46, the refractive index of the fiber cladding 2 is defined as 1.42, and the total arc of the etched groove 3 is defined as b (the total arc of the unetched groove 3 is 2π - b), the refractive index of air is approximately 1.0.

[0036] If the light is totally reflected in the fiber cladding 2, then NA2 = (1.46 2 - 1.42 2 ) 1 / 2 = 0.34 (1.1)

[0037] If the light is totally reflected in the groove 3, then NA1 = (1.46 2 - 1.0 2 ) 1 / 2 = 1.06 (1.2)

[0038] The total numerical aperture of the fiber structure is NA = NA1 x b / 2π + NA2 x (2π - b / 2π) (1.3)

[0039] Substituting equations (1.1) and (1.2) into equation (1.3) gives NA = 0.36b + 0.34

[0040] where, when b = 0.1, NA = 0.38, and when b = 1.0, NA = 0.70.

[0041] It can be seen that the numerical aperture of the fiber structure is higher than that of the fiber structure in the conventional technical means.

[0042] In optional embodiments, in combination with Figures 1 to 4 As shown in the radial cross section of the fiber, the cross-sectional shape of the groove 3 is semicircular, triangular, trapezoidal, or rectangular.

[0043] Among them, according to the optical path analysis, in terms of light collection capability, semicircular groove > triangular groove > trapezoidal groove > rectangular groove.

[0044] In the above embodiment, the thickness ratio of the fiber cladding layer 2 and the fiber core layer 1 is 1:9.

[0045] Optionally, the width of the groove 3 is 5-50 microns, and the number of the groove 3 is 1-18.

[0046] Preferably, the depth of the groove 3 on the surface of the fiber core layer 1 is 1 / 5 of the diameter of the fiber core layer 1.

[0047] In the optional embodiment, the diameter of the fiber core layer 1 is 50-1500 microns.

[0048] In this way, the numerical aperture of the fiber structure is increased by the groove 3, the coupling efficiency of the fiber is improved, and the transmission bandwidth of the fiber structure is increased.

[0049] In combination with the above embodiment, the fiber structure provided by the utility model increases the numerical aperture of the fiber structure by setting the groove on the surface of the fiber core layer and the fiber cladding layer, and forms the light guide region with different refractive indexes on the outer periphery of the fiber core layer. Since the groove destroys the original cladding layer, a new cladding layer is formed by the medium around the fiber core layer, the refractive index of the region is much lower than that of the original cladding layer, and the numerical aperture of the fiber structure is improved.

[0050] Although the utility model has been disclosed as above with preferred embodiments, it is not used to limit the utility model. Those skilled in the art without departing from the spirit and scope of the utility model can make various changes and decorations. Therefore, the protection scope of the utility model is defined by the claims.

Claims

1. A high numerical aperture optical fiber structure, characterized by, The application relates to an optical fiber structure, comprising: an optical fiber core layer (1) having a first refractive index; an optical fiber cladding layer (2) having a second refractive index, the second refractive index being smaller than the first refractive index; a plurality of grooves (3) extending from the optical fiber cladding layer (2) to the optical fiber core layer (1); wherein the depth of the grooves (3) is greater than the thickness of the optical fiber cladding layer (2), and each of the grooves (3) is arranged along the axial direction of the optical fiber.

2. The high numerical aperture optical fiber structure of claim 1, wherein, In a radial cross section of the optical fiber, the cross section shape of the grooves (3) is semicircular, triangular, trapezoidal or rectangular.

3. The high numerical aperture optical fiber structure of claim 1, wherein, The thickness ratio of the optical fiber cladding layer (2) to the optical fiber core layer (1) is 1:

9.

4. The high numerical aperture optical fiber structure of any of claims 1-3, wherein, The width of the grooves (3) is 5-50 microns, and the number of the grooves (3) is 1-18.

5. The high numerical aperture optical fiber structure of any of claims 1-3, wherein, The depth of the grooves (3) on the surface of the optical fiber core layer (1) is 1 / 5 of the diameter of the optical fiber core layer (1).

6. The high numerical aperture optical fiber structure of any of claims 1-3, wherein, The total arc length b of the grooves (3) on the circumference of the optical fiber core layer (1) is 0.1pi-pi.

7. The high numerical aperture optical fiber structure of claim 6, wherein, In the cross section of the optical fiber structure, a first light guide area (A) is formed towards the grooves (3), and a second light guide area (B) is formed towards the optical fiber cladding layer (2). In the first light guide area (A), the numerical aperture at the first light guide area (A) is NA1, the numerical aperture at the second light guide area (B) is NA2, and the numerical aperture NA of the optical fiber structure is NA1xb / 2pi+NA2*(2pi-b / 2pi).

8. The high numerical aperture optical fiber structure of claim 1, wherein, The diameter of the optical fiber core layer (1) is 50-1500 microns.

Images