All-dielectric microlens and method of using the same

Abstract

The invention discloses an all-dielectric microlens and a method for using the same, belonging to the technical field of optical device microstructures. The inner side of the all-dielectric microlens is provided with a plurality of annular step structures with consistent heights and equal widths, the incident surface at the bottom of the all-dielectric microlens is a circular ring surface, and the exit surface at the top of the all-dielectric microlens is an inverted cone concave surface with an annular step structure; the outer wall of the all-dielectric microlens is a vertical wall, and the inner wall of the annular step is a vertical wall; the invention has a simple structure and is easy to prepare, and can obtain a light chain by focusing an incident column vector light beam, which is convenient and quick; and can also realize flexible regulation of the number of focal spots in the light chain by regulating the radial energy distribution of the incident Gaussian column vector light beam or the number of annular step layers.

Description

Technical Field

[0001] The invention relates to an all-medium microlens and a use method thereof, belonging to the technical field of optical device microstructures. Background Art

[0002] Optical chains are often used as optical tweezers and are widely used in optical micromanipulation, particle capture, guidance and binding of microparticles and biological cells, and have very broad application prospects.

[0003] There are many methods to generate light chains, such as using an annular Walsh function filter to modulate a generalized cylindrical vector beam through a lens to achieve a multi-light pin-focus field. However, this method is relatively complex and not flexible enough. Another example is using an axicon to focus a non-diffracting Bessel beam to generate a three-dimensional optical bottle beam. This method requires two conical lenses and is complex to control the light field. The above technical methods for generating light chains are relatively complex. Summary of the invention

[0004] The purpose of the present invention is to provide an all-dielectric microlens and a method for using the same, so as to solve the problem that the technical means for generating light chains in the prior art are too complicated.

[0005] To achieve the above objectives, the present invention is implemented by adopting the following technical solutions:

[0006] In a first aspect, the present invention provides an all-dielectric microlens, wherein the inner side of the all-dielectric microlens has a plurality of annular step structures with consistent heights and equal widths, the incident surface at the bottom of the all-dielectric microlens is a circular ring surface, and the exit surface at the top of the all-dielectric microlens is an inverted conical concave surface with an annular step structure; the outer wall of the all-dielectric microlens is a vertical wall, and the inner wall of the annular step is a vertical wall.

[0007] In combination with the first aspect, further, the all-dielectric microlens is made of a uniform medium.

[0008] In combination with the first aspect, further, the height of the annular step satisfies the following relationship:

[0009] d ⊥ =λ0 / (nn eff )

[0010] Among them, d ⊥ is the height of the annular step, λ0 is the wavelength of the incident beam, λ0∈[0.4,1.6]μm, n is the refractive index of the dielectric material, n∈[1.0,3.0], n eff is the equivalent negative refractive index, n eff ∈[-0.8,-1.2].

[0011] In combination with the first aspect, further, the inner diameters of adjacent annular steps increase at equal intervals from bottom to top, and the intervals satisfy the following relationship:

[0012] d ⊥ <d ∥

[0013]

[0014] Among them, d ⊥ is the height of the annular step, d ∥ is the interval, n0 is the refractive index of air, n0=1;

[0015] The calculation formula for the inner diameter of the kth annular step from the bottom is:

[0016] r k =(a+k-1)d ∥ ,a∈[5,15]

[0017] Among them, r k is the inner diameter of the kth annular step from the bottom, and a is an integer.

[0018] In combination with the first aspect, further, the all-dielectric microlens is an axisymmetric lens.

[0019] In a second aspect, the present invention further provides a method for using the all-dielectric microlens according to any one of the first aspects, characterized in that it comprises:

[0020] The cylindrical vector light beam is incident on the incident surface at the bottom of the all-dielectric microlens, and the all-dielectric microlens focuses to generate a light chain;

[0021] By changing the number of layers of the ring steps, the number of focal points in the light chain can be regulated;

[0022] By adjusting the radial energy distribution of the cylindrical vector beam, the number of focal points in the optical chain can be controlled.

[0023] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0024] The present invention provides an all-dielectric microlens and a method for using the same. The all-dielectric microlens has a simple structure and is easy to prepare. It can focus an incident cylindrical vector light beam to obtain a light chain, which is convenient and quick. It can also flexibly control the number of focal spots in the light chain by adjusting the radial energy distribution or the number of circular ring layers of the incident Gaussian cylindrical vector light beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of the three-dimensional structure of an all-dielectric microlens provided in an embodiment of the present invention;

[0026] Figure 2It is a partial cross-sectional view of the all-dielectric microlens provided by an embodiment of the present invention, including (a) a cross-sectional view along the rz plane; (b) a bottom view; (c) a top view;

[0027] Figure 3 is a schematic diagram of coordinate relations of a radial cross-sectional structure of an all-dielectric microlens provided by an embodiment of the present invention;

[0028] Figure 4 is an intensity distribution curve of Gaussian radially polarized light along the positive direction of the r-axis used by the all-dielectric microlens composed of 28 layers of annular steps provided in an embodiment of the present invention;

[0029] Figure 5 The all-dielectric microlens composed of 28 layers of annular steps provided by the embodiment of the present invention is Figure 4 The focal field under the illumination of Gaussian radially polarized light with intensity distribution shown by the solid line, including (a) focal field light chain distribution diagram; (b) light chain electric field intensity distribution curve along the z-axis;

[0030] Figure 6 The all-dielectric microlens composed of 28 layers of annular steps provided by the embodiment of the present invention is Figure 4 The focal field under the illumination of Gaussian radially polarized light with intensity distribution shown by the dotted line, including (a) focal field light chain distribution diagram; (b) light chain electric field intensity distribution curve along the z-axis;

[0031] Figure 7 The focal field of the all-dielectric microlens composed of 34 layers of annular steps provided in an embodiment of the present invention includes (a) a focal field light chain distribution diagram; and (b) a light chain electric field intensity distribution curve along the z-axis. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the protection scope of the present invention.

[0033] Example 1

[0034] like Figure 1 As shown, an embodiment of the present invention provides an all-dielectric microlens, which is made of a uniform material, and the refractive index of the material is n=2.36; the bottom surface of the all-dielectric microlens is the incident surface, and the incident surface is a torus surface; the top surface of the all-dielectric microlens is the exit surface, and the exit surface is an inverted conical concave surface with an annular step microstructure; the outer diameter of the all-dielectric microlens in this embodiment is R k =65d ⊥ ; The width of all annular steps d ∥ =306nm; the outer wall of the microlens is a vertical wall; the inner wall of the annular step on the incident surface is a vertical wall, and the height of the vertical wall of the annular step is d ⊥ =163.190nm;;Equivalent negative refractive index neff =-0.9; the microlens of this embodiment is composed of 28 annular steps, and the total height of the microlens is H = 28d ⊥ .

[0035] In order to better demonstrate the structure of the all-medium microlens provided in this embodiment, Figure 2 The partial cross-sectional views shown include (a) rz plane cross-sectional view, (b) bottom view, (c) top view, and Figure 3 Schematic diagram of the coordinate relationship of the radial cross-section structure shown.

[0036] In order to verify the effect of this embodiment, the following experimental data are provided: Figure 4 The intensity distribution curve of Gaussian radially polarized light along the positive direction of the r-axis used by the all-dielectric microlens composed of 28 layers of annular steps provided by the embodiment of the present invention is shown; and Figure 5 As shown in Figure 4 The focal field under Gaussian radial polarized light with intensity distribution shown by the solid line, including (a) the focal field light chain distribution diagram and (b) the light chain electric field intensity distribution curve along the z-axis; and Figure 6 As shown in Figure 4 The focal field under Gaussian radially polarized light with intensity distribution shown by the dotted line, including (a) the focal field light chain distribution diagram and (b) the light chain electric field intensity distribution curve along the z-axis.

[0037] Example 2

[0038] The embodiment of the present invention also provides an all-dielectric microlens, the lens is made of a uniform material, the refractive index of the material is n=2.36; the bottom surface of the lens is the incident surface, the incident surface is a torus surface; the top surface of the lens is the exit surface, the exit surface is an inverted conical concave surface with an annular step microstructure; the outer diameter of the lens in this embodiment is R k =65d ⊥ ; The width of all annular steps d ∥ =306nm; the outer wall of the microlens is a vertical wall; the inner wall of the annular step on the incident surface is a vertical wall, and the height of the vertical wall of the annular step is d ⊥ =163.190nm;;Equivalent negative refractive index n eff =-0.9; the microlens of this embodiment is composed of 34 annular steps, and the total height of the microlens is H = 34d ⊥ .

[0039] In order to verify the effect of this embodiment, the following experimental data are provided: Figure 7 The focal field of the all-dielectric microlens composed of 34 layers of annular steps shown in FIG. 1 , including (a) the focal field light chain distribution diagram and (b) the light chain electric field intensity distribution curve along the z-axis.

[0040] Example 3

[0041] The present invention provides a method for using the all-dielectric microlens of embodiment 1, comprising:

[0042] The cylindrical vector light beam is incident on the incident surface at the bottom of the all-dielectric microlens, and the all-dielectric microlens focuses to generate a light chain;

[0043] By changing the number of layers of the ring steps, the number of focal points in the light chain is adjusted to produce Figure 7 The quadrufocal light chain shown;

[0044] By adjusting the radial energy distribution of the cylindrical vector beam, the number of focal points in the optical chain can be controlled.

[0045] The following process is also included: controlling the incident Gaussian radial polarized light ( Figure 4 The intensity distribution curve of the radially polarized light (① incident) along the positive direction of the r axis is shown in Figure 4 As shown by the solid line, the lens in the first embodiment is generated as follows Figure 5 The three-focus optical chain shown in Figure 2 regulates the incident Gaussian radial polarized light ( Figure 4 The intensity distribution curve of the radially polarized light (incident) along the positive direction of the r axis is shown in Figure 4 As shown by the dotted line, the lens in the first embodiment will generate Figure 6 Bifocal light chain shown.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An all-dielectric microlens, characterized in that: The inner side of the all-dielectric microlens has a plurality of annular step structures with the same height and equal width. The incident surface at the bottom of the all-dielectric microlens is a circular ring surface, and the exit surface at the top of the all-dielectric microlens is an inverted conical concave surface with an annular step structure. The outer wall of the all-dielectric microlens is a vertical wall, and the inner wall of the annular step is a vertical wall. The inner diameters of adjacent annular steps increase at equal intervals from bottom to top, and the intervals satisfy the following relationship: d ⊥ <d ∥ Among them, d ⊥ is the height of the annular step, d ∥ is the interval, n0 is the refractive index of air, n0=1, n is the refractive index of the medium material, λ0 is the wavelength of the incident light beam used; The calculation formula for the inner diameter of the kth annular step from the bottom is: r k =(a+k-1)d ∥ ,a∈[5,15] Among them, r k is the inner diameter of the kth annular step from the bottom, and a is an integer.

2. The all-dielectric microlens according to claim 1, characterized in that: The all-medium microlens is made of uniform medium.

3. The all-dielectric microlens according to claim 1, characterized in that: The height of the annular step satisfies the following relationship: d ⊥ =λ0 / (nn eff ) Among them, d ⊥ is the height of the annular step, λ0 is the wavelength of the incident beam, λ0∈[0.4,1.6]μm, n is the refractive index of the dielectric material, n∈[1.0,3.0], n eff is the equivalent negative refractive index, n eff ∈[-0.8,-1.2].

4. The all-dielectric microlens according to claim 1, characterized in that: The all-dielectric microlens is an axisymmetric lens.

5. A method for using the all-dielectric microlens according to any one of claims 1 to 4, characterized in that: include: The cylindrical vector light beam is incident on the incident surface at the bottom of the all-dielectric microlens, and the all-dielectric microlens focuses to generate a light chain; By changing the number of layers of the ring steps, the number of focal points in the light chain can be regulated; By adjusting the radial energy distribution of the cylindrical vector beam, the number of focal points in the optical chain can be controlled.

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