KR20200071590A - Diffractive optical element, manufacturing method thereof and optical device having the same - Google Patents

Abstract

The present invention relates to a diffractive optical element, to a manufacturing method thereof, and to an optical device including the same. According to one aspect of the present invention, the diffractive optical element comprises a substrate and a group of structures forming a geometric metasurface on the substrate. The substrate includes a plurality of continuous unit cells, and the group of structures includes a plurality of nanostructures arranged at predetermined intervals and angles. One nanostructure is disposed in one unit cell, and a beam incident through a light source is reflected and transmitted to the nanostructure to control the intensity and phase of the beam, so that the diffractive optical element can spray the beam in the full space of 360 degrees.

Description

Diffractive optical element, manufacturing method thereof, and optical device including same {DIFFRACTIVE OPTICAL ELEMENT, MANUFACTURING METHOD THEREOF AND OPTICAL DEVICE HAVING THE SAME}

The present invention relates to a diffractive optical element, a method for manufacturing the same, and an optical device including the same.

Augmented reality and virtual reality technology is a research field that is attracting attention in the era of the fourth industrial revolution, and research is being conducted to utilize it in various fields. A device capable of recognizing an object in 3D space is required in a device for implementing such augmented reality and virtual reality technologies. For example, in recent smartphones, a dot project that projects more than 30,000 lights onto the face for face recognition and a point on the face are read by an infrared camera to read the face 3D map. There are techniques to generate.

Conventionally, in order to recognize an object in 3D space, a distance to an object is obtained by using diffractive optical elements (DOEs) that produce a diffraction effect by adjusting the depth of the element or receiving light reflected from the object and returning. By measuring, light detection and ranging (LIDAR) technology was used.

However, in the case of the conventional diffraction optical element, it is difficult to manufacture because it produces a diffraction effect through the depth control of the element, and in the case of the rider (LIDAR) technology, there is a problem in miniaturization of the device due to the complicated and bulky scanning system. have.

Non-Patent Documents: Khoshelham, K. & Elberink, S. O. Accuracy and resolution of kinect depth data for indoor mapping applications. Sensors 12, 1437-1454 (2012).

Embodiments of the present invention have been proposed to solve the above problems, and provide a diffraction optical element capable of recognizing an object in a 360-degree full-space including a direction in which a beam is incident, and a method for manufacturing the same I want to.

In addition, it is intended to provide a diffractive optical element capable of miniaturization and ultra-lightweight and a manufacturing method thereof.

In addition, it is intended to provide a diffractive optical element that can be produced by a simple manufacturing process and a method for manufacturing the same.

In addition, it is intended to provide a diffractive optical element having a low production cost through mass production and a method for manufacturing the same.

According to an embodiment of the present invention, the substrate; The structure includes a group of structures forming a geometric metasurface on the substrate, the substrate includes a plurality of consecutive unit cells, and the group of structures comprises a plurality of nanostructures arranged at predetermined intervals and angles. Included, one of the nano-structure is disposed in one of the unit cells, the beam incident through the light source is reflected and transmitted to the nano-structure to control the intensity and phase of the beam, 360 degrees full space (full space) It can be provided with a diffractive optical element capable of spraying the beam.

According to an embodiment of the present invention, the thickness (H) of the nanostructure may be provided with a diffraction optical element that is less than half the wavelength of the beam incident through the light source.

According to an embodiment of the present invention, the group of structures includes a plurality of nanostructures arranged in an m X n matrix, and beams incident through a light source are reflected and transmitted to the nanostructures and divided into four beams, The adjacent nanostructures arranged in m rows or n columns may be provided with diffraction optical elements arranged at predetermined angle differences (where m and n are natural numbers).

According to an embodiment of the present invention, the plurality of nanostructures disposed in the m row or the n column may be provided with diffraction optical elements having different angles.

According to an embodiment of the present invention, the plurality of nanostructures arranged in the m row or n column is 13, and the difference in angle between adjacent nanostructures arranged in the m row or n column is 6π/13, provided by a diffraction optical element Can be.

According to an embodiment of the present invention, the nanostructure is a rectangular parallelepiped, the length (C) of one side of the unit cell is 300nm, the plurality of nanostructures disposed in the m row and n column is 5, respectively, the The size of the structure group can be provided with a diffractive optical element having a size of 1.5 x 1.5 μm ² .

According to an embodiment of the present invention, a wavelength of a beam incident on the nanostructure is 630 nm, and the height (H) of the nanostructure may be provided with a diffraction optical element having a height of 315 nm or less.

According to an embodiment of the present invention, the four beams are two beams traveling in the same direction as the traveling direction of the beam incident through the light source and the opposite side of the traveling direction of the beam incident through the light source. A diffractive optical element diffracted by two beams traveling in the direction may be provided.

According to an embodiment of the present invention, the nanostructure is a rectangular parallelepiped, the length (C) of one side of the unit cell is 300nm, the plurality of nanostructures disposed in the m row and n column is 100 each, The size of the structure group is 30 x 30 μm ² , and the structure group is plural, and a diffractive optical element arranged in a continuous p X q matrix may be provided (where p and q are natural numbers).

According to an embodiment of the present invention, each of p and q may be provided with a diffraction optical element of 10.

According to an embodiment of the present invention, the nanostructure may be provided with a diffractive optical element which is amorphous silicon.

According to an embodiment of the present invention, the substrate may be formed of a resilient material, and the nanostructure may be provided on the substrate to provide a diffractive optical element that can be bent or folded.

According to an embodiment of the present invention, a diffractive optical element in which the one unit cell represents one pixel may be provided.

According to an embodiment of the present invention, the wavelength of the beam incident on the nanostructure is 810nm to 830nm, the nanostructure is a cuboid shape, the height (H) 310nm, length (L) 200nm, width (W) of the nanostructure ) Is 120 nm, and the length (C) of one side of the unit cell may be provided with a diffractive optical element of 400 nm.

According to an embodiment of the present invention, a light source including a diffractive optical element and incident a beam on the diffractive optical element; An iris through which the beam emitted from the light source passes; A far field in which an image of a beam reflected and transmitted to the diffractive optical element is formed; And a camera for capturing the reflected and transmitted beams.

According to an embodiment of the present invention, the far field may be provided with an optical device including a front far field in which a transmitting beam appears and a rear far field in which a reflected beam appears.

According to an embodiment of the present invention, forming a substrate; Depositing a dielectric layer comprising a geometric metasurface on the substrate; And forming a group of structures including a plurality of nanostructures by forming a pattern on the dielectric layer, and the incident beam is reflected and transmitted to the nanostructures to control the intensity and phase of the beam, thereby controlling the entire space of 360 degrees ( A method of manufacturing a diffractive optical element including the step of forming the nanostructures may be provided to enable injection of a beam to a full space).

According to an embodiment of the present invention, after the chromium is deposited on the plurality of nanostructures, a method of manufacturing a diffractive optical element implemented through a lift off process may be provided.

According to an embodiment of the present invention, forming a structure group including a plurality of nanostructures by forming a pattern on the dielectric layer comprises coating an upper portion of the dielectric layer with a resist and applying an electron beam to the resist. A method of manufacturing a diffractive optical element comprising steps can be provided.

According to an embodiment of the present invention, a method of manufacturing a diffractive optical element may be provided, including spin-coating a conductive polymer at 2000 rpm for 60 seconds prior to the step of irradiating the electron beam.

According to embodiments of the present invention, it is possible to provide a diffractive optical element capable of recognizing an object in a 360-degree total space including a direction in which a beam is incident, and a method for manufacturing the same.

In addition, it is possible to provide a diffractive optical element capable of downsizing and ultra-lightweight and a method for manufacturing the same.

In addition, it is possible to provide a diffractive optical element that can be produced by a simple manufacturing process and a manufacturing method thereof.

In addition, it is possible to provide a diffractive optical element having a low production cost by mass production and a method for manufacturing the same.

1 is a perspective view schematically showing a portion of a diffractive optical element according to an embodiment of the present invention.
2 is a perspective view schematically illustrating a beam that is reflected and transmitted when a linearly polarized (LP) beam is incident on a diffraction optical element including a plurality of nanostructures according to an embodiment of the present invention.
3 is a graph showing the phase delay of a beam that is transmitted and reflected according to the angle of the nanostructure of FIG. 2.
FIG. 4 is a view showing reflected and transmitted beams according to a wavelength of a beam incident on the diffraction optical element of FIG. 2.
5 is an optical device for injecting a beam into the diffraction optical element of FIG. 4 and showing a path of reflection and transmission of a beam incident on the diffraction optical element.
FIG. 6 is a diagram illustrating that a beam reflected and transmitted to a diffraction optical element according to an embodiment of the present invention forms an image in a far filed.
7 shows a phase difference according to a wavelength when a beam is incident on a unit cell having the nanostructure of FIG. 1.
FIG. 8 shows reflection and transmission coefficients when a beam incident perpendicularly to the meta surface of FIG. 1 is polarized along the long and short axes of the nanostructure.
9 shows reflection and transmission efficiency according to the wavelength of a circularly polarized light (CP) beam incident on the diffraction element of FIG. 1.
10 shows a diffraction optical element for simultaneously emitting a beam in a 360-degree full space according to an embodiment of the present invention and an optical device including the same.
FIG. 11 shows spot arrays of beams ejected in a 360-degree space by the diffractive optical element of FIG. 10.
FIG. 12 shows spot arrays enlarged from part A of FIG. 11.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

In addition, in the description of the present invention, when it is determined that detailed descriptions of related known configurations or functions may obscure the subject matter of the present invention, detailed descriptions thereof will be omitted.

1 is a perspective view schematically showing a part of a diffraction optical element 10 according to an embodiment of the present invention, and FIG. 2 is a diffraction optical element 10 including a plurality of nanostructures according to an embodiment of the present invention When a linear polarization (LP) beam is incident on ), it is a perspective view schematically showing a reflected and transmitted beam, and FIG. 3 is a graph showing a phase delay of a transmitted and reflected beam according to the angle of the nanostructure of FIG. 2, and 4 is a view showing a reflected and transmitted beam according to the wavelength of the beam incident on the diffraction optical element 10 according to an embodiment of the present invention, Figure 5 is a beam incident on the diffraction optical element 10 of Figure 4 And an optical device 1 for indicating the path of reflection and transmission of light incident on the diffractive optical element 10, and FIG. 6 shows reflection and transmission on the diffractive optical element 10 according to an embodiment of the present invention. It is a diagram showing that the beam to be imaged on the far field.

1 to 6, the diffractive optical element 10 according to an embodiment of the present invention includes a substrate 100, a group of structures 200 forming a geometric metasurface on the substrate 100 The structure group 200 may include a plurality of nano structures 211. Here, the geometric meta-surface can be understood that the nano-structure included in the structure group 200 has a geometric shape and functions as a metamaterial. In addition, metamaterial is a new artificial material that includes both electrical and magnetic elements that do not exist in the natural world, and can be understood as implementing negative refraction by having a negative refractive index. That is, in this embodiment, the substrate 100 and the structure group 120 may function as metamaterials as a whole.

In addition, the diffractive optical element 10 of the present invention may be represented by a scrambling metasuface as a plurality of nanostructures rotated at a predetermined angle on a substrate.

Diffraction optical element 10 according to an embodiment of the present invention, when the incident beam reaches the diffraction optical element 10 may be diffracted into a transmitting and reflecting beam. For example, when the incident beam reaches the diffraction optical element 10, it may be divided into a plurality of beams and then sprayed in a 360 degree full space. For example, the beam reaching the diffractive optical element 10 may be diffracted at an angle of 90 degrees, and more than 4044 spots or light may be scattered all over 360 degrees.

The diffractive optical element 10 based on the meta-surface of the present invention can diffract a beam reaching the diffractive optical element 10 in both transmission and reflection directions. Specifically, the device using the conventional meta surface was able to advance the beam in only one direction of transmission or reflection of the beam, but the diffractive optical element 10 based on the meta surface of the present invention has the direction of both light transmission and reflection. It is possible to advance the incident beam.

The substrate 100 may be formed of a plurality of continuous unit cells 111 and may have a flat plate shape. Here, the unit cell 111 may be defined as a part of the substrate 100 in a predetermined range supporting one nanostructure 211, and the unit cell 111 may be continuous in a plane direction. Also, one unit cell 111 may be represented by one pixel. In addition, for example, the substrate may be made of silicon, polydimethylsiloxane, or a flexible material. That is, the substrate may be a flexible flexible substrate (flexible). The thickness of the substrate can be provided from a few micrometers to several millimeters.

The structure group 200 is formed on the substrate 100 and may include a plurality of nano structures 211. Here, one nanostructure 211 may be disposed on one unit cell 11.

In addition, the plurality of nano-structures 211 included in the structure group 200 may be arranged in an m X n matrix with a predetermined angle so that the incident beam spreads through the entire 360-degree space (here, m and n) Is a natural number).

The structure group 200 may be provided with amorphous silicon, and the structure group 200 may be composed of a plurality of nano structures 211. At this time, each nano-structure 211 may be spaced apart from the adjacent nano-structure 211 at a predetermined interval, and at this time, the spacing between the nano-structures 211 may be the same. Here, the spacing between the nanostructures 211 may be understood as the distance between the centers on the plane of each nanostructure 211. In addition, nanostructures of amorphous silicon formed in the structure group 200 may be understood as a dielectric layer.

In addition, the structure group 200 of the present invention may constitute geometric metasurfaces (GEMS). At this time, the geometric metasurface (GEMS) means a metasurface capable of arbitrarily adjusting the intensity and phase of reflected and transmitted light according to the geometric structure, and may be based on the Pancharatnam-Berry (PB) phase.

In addition, the beam incident from a separate light source is reflected and transmitted to the nanostructure 211 to be divided into a plurality of beams, and the intensity and phase of the reflected beam and the transmitted beam can be controlled. Thereby, a beam can be sprayed to the whole 360-degree space.

Each nano-structure 211 may have a cuboid shape having a height (H), a width (W), and a length (L). Here, the height (H) is the length on the same axis (Z axis) as the incident beam, the width (W) means the length of the short side on the XY plane, and the length (L) can be understood as the length of the long side.

The height H of the nanostructure 211 may be provided at half (1/2) or less of a wavelength of an incident beam. For example, when the wavelength of the beam incident on the diffractive optical element 10 is 630 nm, the height of the nanostructure 211 may be 315 nm or less.

By having the height (H) range of the nanostructure 211, it is possible to simultaneously implement transmission and reflection of incident light by causing electromagnetic resonances. In addition, diffraction responsiveness may be increased by having a structure group including a nanostructure 211 and a plurality of nanostructures 211 having the same height (H) of less than half the wavelength of an incident beam.

In addition, by controlling the geometrical parameters (width (W), length (L), height (H), and unit cell spacing (C)) of the nanostructure 211, the power ratio between the reflected beam and the transmitted beam (power ratio) ) Can be controlled.

(orientation angle)를 갖고, 단위 셀(111)의 상부에 제공될 수 있다. 여기서, 나노 구조체(211)의 각도

(orientation angle)는 x축과 나노 구조체(211) 사이의 각도로 이해될 수 있다. Each nanostructure 211 is an angle

(orientation angle) and may be provided on the top of the unit cell 111. Here, the angle of the nanostructure 211

(orientation angle) may be understood as an angle between the x-axis and the nanostructure 211.

)의 두 배의 위상 지연을 갖도록 제어 될 수 있다. Each nano-structure 211, the angle of the nano-structure 211, both in the transmission and reflection of the incident beam (

) Can be controlled to have a phase delay of twice.

The plurality of nano structures 211 included in the structure group 200 may be arranged in an m X n matrix such that the incident beam is reflected and transmitted and spreads through the entire 360-degree space. Here, m and n are natural numbers and are preset values.

In addition, the continuous nanostructures 211 in any m row of one structure group 200 may be continuously arranged with a difference in predetermined angles.

/13 =83.077의 각도의 차이로 배치될 수 있다. 또한, 13개의 나노 구조체(211)는 1주기(one period)로 이해 될 수 있다. 여기서, 1주기(one period)란, 임의의 각도(

)를 갖는 나노 구조체(211)로부터 일 축 방향을 따라 이동 후 동일한 각도(

)를 갖는 갖는 나노 구조체(211)가 나타날 때까지의 나노 구조체의 개수(또는 구조체 그룹의 크기)로 이해될 수 있다. For example, any m row of the structure group 200 may include 13 consecutive nanostructures 121, and 13 adjacent nanostructures 211 may be 6

/13 =83.077. In addition, the 13 nano-structures 211 may be understood as one period. Here, one period means an arbitrary angle (

) After moving along the one-axis direction from the nano-structure 211 having the same angle (

It can be understood as the number of nanostructures (or the size of a group of structures) until nanostructures 211 with) appear.

Specifically, 13 m nanostructures (first nanostructure 211a, second nanostructure 211b), third nanostructure 211c, and fourth nanostructure in any m row in the structure group 200 of FIG. 2 Structure 211d, fifth nanostructure 211e, sixth nanostructure 211f, seventh nanostructure 211g, eighth nanostructure 211h, ninth nanostructure 211i, tenth nanostructure ( 211j), the eleventh nanostructure 211k, the twelfth nanostructure 211l, and the thirteenth nanostructure 211m) are arranged at an angle of 6π/13 from the adjacent nanostructures.

As such, when 13 nanostructures form one period, one nanostructure included in the structure group 200 includes unit cells of the seventh nanostructure 211g and the eighth nanostructure 211h ( 111) may include another nanostructure having the same angle, based on a line intersecting on the xy plane. That is, 13 nanostructures 211 of the structure group 200 form one cycle, and may be arranged to be symmetrical left and right based on a line intersecting on the xy plane. As such, the nanostructures are arranged symmetrically, so that the linearly polarized beam can be divided into two circularly polarized beams, and can serve as a blazed grating that diffracts with the same angle.

For example, the seventh nanostructure 211g and the eighth nanostructure 211h are based on a line intersecting the unit cell 111 in which the seventh nanostructure 211g and the eighth nanostructure 211 are located. It can have the same angle. Similarly, the sixth nanostructure 211f and the ninth nanostructure 211i, the fifth nanostructure 211e and the tenth nanostructure 211j, the fourth nanostructure 211d and the eleventh nanostructure 211k, The third nanostructure 211c, the twelfth nanostructure 211l, the second nanostructure 211b, and the thirteenth nanostructure 211m are located in the seventh nanostructure 211g and the eighth nanostructure 211. The unit cells 111 may have the same angle based on the line intersecting. On the other hand, the first nano-structure 211a has the same angle as any first nano-structure of a period to restart.

In addition, the plurality of nano structures 211 existing in one structure group 200 may be disposed at different angles.

As described above, when the angle of the nanostructure 211 is changed in units of cells, the beam can be advanced in a desired direction on the entire space of 360 degrees.

In addition, according to an embodiment of the present invention, the plurality of nanostructures 211 are designed such that points appearing in 3D space diffracted by the diffractive optical element 10 become rotational symmetry. For example, each spot having arbitrary coordinates x and y may be the same as a conjugate spot of a spot having coordinates -x and -y. With this arrangement, the diffraction pattern of the LCP beam coincides with the diffraction pattern of the RCP beam in the far field, and points appearing in 3D space diffracted by the diffractive optical element 10 are independent of the polarization state of the incident beam ( insensitive).

In addition, the nanostructures 211 in any n-column of the structure group 200 are also rotated at a predetermined angle and arranged in a periodic manner, like the nanostructures in the m-row described above.

In order to understand the principle of operation of the diffractive optical element 10 having a metasurface as described above, a Jones calculus represented by Equation (1) below can be used.

Equation (1):

Here, r _s, t _s , r _l , t _l, are reflection and transmission coefficients when a polarized wave passes along short axes and long axes of the nanostructure. In addition, δ _r and δ _t are the phase differences between two or diagonal directions of the reflected beam and the transmitted beam, respectively.

When the circularly polarized light (CP) incident light is illuminated, for example, when the left circularly polarized light (LCP) is projected on the meta surface, the output light may be divided into four. Specifically, two sub-beams having the same handedness as incident light that does not generate a phase delay for both reflection and transmission called co-polarized beams, and cross-polarization Polarized beaams can be divided into two sub-beams with opposite circular handedness, ie right circular polarization (RCP), with a phase delay of 2φ for both reflection and transmission. Here, φ is the angle (orientation angle) of the nanostructure.

Therefore, the reflected and transmitted beams can be represented by matrix matrices such as Equations 2(a) and 2(b) below for circularly polarized light (CP).

2(a):

2(b):

Here, (R _cross , T _cross ) and (R _co , T _co ) are output light (reflection) having a cross-polarization component having a phase delay and a co-polarization component having no phase delay, respectively. And both transmission wavelengths).

In addition, the polarization conversion efficiency can be expressed by the following equation (3).

(3):

By designing the nanostructures to have a predetermined size and angle as described above, the co-polarized portion can be suppressed, and the ratio of the cross-polarized portion between transmission and reflection can be controlled. have. In particular, if T _cross = R _cross and T _co = R _co = 0, or equivalently, δ _r = δ _t = π and r _l = r _s = t _l = t _s , the reflectance and transmittance may be the same. have. This means that in the matrices of Equations 2(a) and 2(b), the transmission and reflection are the same, and all incident circularly polarized light (CP) beams move in the same direction as the two opposite directions perpendicular to the meta surface. -polarized beam).

Also, while δ _r = δ _t = π and r _l = r _s = t _l = t _s is not observed, optimal polarization conversion efficiency with designed phase control can be achieved.

7 shows a phase difference according to a wavelength when a beam is incident on a unit cell having the nanostructure of FIG. 1. Here, the x-axis represents the wavelength, and the y-axis represents the phase difference.

Referring to FIG. 7, phase differences between long axes and short axes of the nanostructure approach π in both reflection and transmission.

FIG. 8 shows reflection and transmission coefficients when a beam incident perpendicularly to the meta surface of FIG. 1 is polarized along the long and short axes of the nanostructure. Here, r _s, t _s , r _l , t _l, represent reflection and transmission coefficients when a polarized wave passes along the short axes and long axes of the nanostructure.

9 shows reflection and transmission efficiency according to the wavelength of a circularly polarized light (CP) beam incident on the diffraction element of FIG. 1. Here, R _cross represents the reflection polarization conversion efficiency of a cross-polarization component having a phase delay, and T _cross represents the transmission polarization conversion efficiency of a cross-polarization component having a phase delay.

In addition, R _co represents the reflection polarization conversion efficiency of the co-polarization component without phase delay, and T _co represents the transmission polarization conversion efficiency of the co-polarization component without phase delay.

Referring to FIG. 9, the polarization conversion efficiency of both reflection and transmission at a wavelength of 630 nm reaches 27%, while the co-polarized beam contributing to the 0th order diffraction can be suppressed to a negligible level of 3% or less. Yes (0.4% reflection and 2.6% transmission).

Thus, each nanostructure can convert a circularly polarized light (CP) incident beam into opposite handedness with a phase delay of twice the nanostructure angle in both transmission and reflection, and the residual components with the same handedness It can be controlled to a negligible level.

That is, when the angle of the nanostructure is changed in units of cells, the beam can be controlled in a desired direction in a space of 360 degrees.

In addition, the reflection and transmission metrics can have a Hermitian conjugate with zero in the diagonal element. Therefore, the diffraction patterns formed by the LCP and RCP beams can be matched to each other if the nanostructures are designed with rotational symmetry.

Using this principle, the diffraction optical element 10 can be implemented such that the beam incident through the light source is reflected and transmitted to the nano-structure and diffracted into four beams. That is, the diffractive optical element 10 can simultaneously perform a beam splitter and a phase modulator function.

Linearly polarized (LP) beams can be treated as a combination of left circularly polarized (LCP) and right circularly polarized (RCP) beams with the same intensity, and meta surfaces with such nanostructures propagate incident beams symmetrically It can be diffracted into 4 sub-beams with propagation directions. Such diffraction has the same intensity due to the same polarization conversion efficiency, and may be represented by the spin dependent nature of the PB phase.

In addition, when the operating wavelength of the beam incident from the light source changes from 470 nm to 650 nm, the diffraction angle of the beam with the designed order (m = 6) increases, and when the operating wavelength is 650 nm, the diffraction angle is 90° When the operating wavelength is 650nm, the diffraction angle exceeds 90 °. These results indicate that the diffracted beam in the diffractive optical element 10 having a meta surface can be radiated in full 360 degrees.

In addition, by rotating the nanostructure, that is, by controlling the angle of the nanostructure, it can be controlled by a 2 x 2 spot array having uniform intensity in both the transmission and reflection spaces from the incident beam.

In the diffraction optical element 10 according to an embodiment of the present invention, the length C of one side of the unit cell 111 in which the nanostructure 211 is disposed is set to 300 nm, and m in one structure group 200 It includes a plurality of nanostructures 211 arranged in an X n matrix, and a plurality of nanostructures arranged in m rows and n columns can be set to 5 each to set the size of the structure group 200 to 1.5 x 1.5 μm ² have. Here, the structure group 200 may be represented by a grating period. A beam having a wavelength of 630 nm is transmitted through the diffractive optical element 10 having such conditions, and thus can be diffracted into four beams reflected and transmitted.

The diffractive optical element 10, that is, a device required to implement the performance of the semi-transmissive beam splitter is illustrated in FIG. 5, and the beam reflected and transmitted to the diffractive optical element 10 of FIG. 5 is a wave field 50, Figure 6 shows an image formed on the far filed).

5 and 6, the optical device 1 according to an embodiment of the present invention includes a light source 20 for projecting a beam onto the diffractive optical element 10, an iris 30 through which the beam passes, Diffractive optical element 10, may include a far field (far field 50) of the reflected and transmitted sub-beam (sub-beam) and a camera 60 for capturing the reflected and transmitted sub-beam have.

The light source 20 is controllable such that the wavelength of the incident beam continuously changes. For example, the wavelength of 470nm to 650nm from the light source 20 may be incident on the diffractive optical element 10 to continuously change, or may be incident with a spacing of 20nm. Further, the light source 20 may be a YSL SC-pro in which light continuously changes (supercontinuum).

The beam emitted from the light source 20 may be incident on the diffraction optical element 10 after passing through the iris 30. The beam reflected and transmitted to the diffractive optical element 10 (with different diffraction orders) can be captured by the camera 60 and observed in the far field 50. The far field 50 may include a front far field 52 on which a transmitting beam is projected, and a rear far field 54 on which a reflected beam is projected.

The distance from the diffractive optical element 10 to the front farfield 52 and the rear farfield 54 may be the same. For example, the distance from the diffractive optical element 10 to the front farfield 52 may be 150 nm, and likewise the distance from the diffractive optical element 10 to the rear farfield 54 may also be 150 nm.

In addition, according to an embodiment of the present invention, the nanostructures 211 shown in FIG. 1 are continuously arranged at a predetermined angle, and beams can be simultaneously injected to a full space of 360 degrees.

10 shows a diffraction optical element 10 and an optical device 1 including the same, which simultaneously sprays a beam to a 360-degree full space according to an embodiment of the present invention, and FIG. 11 shows the diffraction of FIG. 10 The spot arrays of the beams ejected to the entire 360-degree space by the optical element 10 are shown, and FIG. 12 shows spot arrays enlarged from part A of FIG. 11.

10 to 12, the diffractive optical element 10 according to an embodiment of the present invention may simultaneously spray a beam in a 360 degree full space. The diffraction element 10 sets a length C of one side of the unit cell 111 in which the nanostructure 211 is disposed to 300 nm, and is arranged in a m X n matrix in one structure group 200 A plurality of nanostructures including two nanostructures 211 and disposed in m rows and n columns may be set to 100, respectively, to set the size of the structure group 200 to 30 x 30 μm ² . Here, the structure group 200 may be represented by a grating period.

In addition, by setting a plurality of such structure groups 200 and arranging them in a continuous p X q matrix, beams incident on the diffractive optical element 10 can be simultaneously sprayed to the entire 360-degree space. Here, p and q are natural numbers, and may be set to 10, respectively. That is, in such a diffractive optical element 10, the nano-structure 211 having a constant angle is periodically repeated so that a beam can be simultaneously injected into a full space of 360 degrees. In addition, the wavelength incident on the diffractive optical element 10 may be a wavelength in the range of 600nm to 650nm. For example, the operating wavelength of the beam incident on the diffractive optical element 10 may be 633 nm.

In addition, since the structure group 200 includes nanostructures 211 arranged in a 100 X 100 matrix, it may have 100 X 100 diffraction orders, but an operating wavelength of an incident beam is 633 nm, and a unit cell Since the size of one side of is 300 nm, 6924 sub-beams can reach the far field.

In addition, in order to remove the polarization dependence existing in the PB phase component (PB phase based elements), the nanostructures of the structure group 200 are designed with rotational symmetry around the optical axis. Can be.

In addition, by matching one point generated by diffraction by the LCP and one point generated by the RCP by diffusing by LCP, the diffracted point cloud form can be rotationally symmetrical so that the polarization dependence of the diffraction optical element 10 can be ignored. .

In addition, the structure group 200 of the diffractive optical element 10 according to an embodiment of the present invention includes M _x Х M _y unit cells, and it can be assumed that the spacing between adjacent cell centers is C. When the incident beam is vertically incident on the diffractive optical element 10, diffraction orders generated in the transmission and reflection spaces are equal to the number of pixels, that is, M _x Х M _y . In particular, the transverse spatial frequency of the (m _x , m _y )-th diffraction order can be expressed by Equation (4) as follows.

Equation (4):

M_x/2, |m_y|

M_y/2 이다. 또한, 횡단 공간 주파수(transverse spatial frequency) k'

일 때, 대응하는 회절 차수는 소멸 파(evanescent wave)가 되고 파 필드(far field)로 전파 될 수 없다.Where |m _x |

M _x /2, |m _y |

M _y /2. Also, transverse spatial frequency k'

In this case, the corresponding diffraction order becomes an evanescent wave and cannot be propagated to a far field.

보다 작으면, 회절 차수는 진행파에 상응하고, 파 필드(far field)로 진행 될 수 있다. 회절 차수의 회절 각(diffraction angle of a diffraction order)은 다음과 같이 식(5)에 의해 결정될 수 있다. On the other hand, the transverse spatial frequency k'is 1/

If smaller, the diffraction order corresponds to a traveling wave, and can proceed to a far field. The diffraction angle of a diffraction order can be determined by Equation (5) as follows.

Equation (5):

는 회절 차수와 좌표 평면 yoz 사이의 각도이고,

는 회절 차수와 좌표 평면 xoz 간의 각도이고,

는 회절 차수와 z 축 사이의 각도이다.here,

Is the angle between the diffraction order and the coordinate plane yoz ,

Is the angle between the diffraction order and the coordinate plane xoz ,

Is the angle between the diffraction order and the z axis.

/2 를 만족할 때, 진행파(propagation wave)의 회절 각은 90°에 접근 할 수 있다. 즉, 회절된 서브 빔은 360도 전 공간을 채울 수 있다. From Eqs. (4) and (5), the central spacing between unit cells is C

When /2 is satisfied, the diffraction angle of the propagation wave can approach 90°. That is, the diffracted sub-beam can fill the entire 360-degree space.

In addition, a method of designing the diffractive optical element 10 according to an embodiment of the present invention can be represented as follows.

First, after finding the magnetic resonance of the nanostructure 211 with respect to the wavelength of the incident beam, this is combined with the geometrical phase (setting the angle of the nanostructure). Then, by adjusting the geometric parameters (height (H), length (L), width (W)) of the nanostructures of the unit cell 111, the power ratio between the reflected beam and the transmitted beam (power ratio) Can be controlled. Thereafter, the performance of the diffraction element 10 including the nanostructure may be grasped using software (eg, COMSOL). In addition, in the nanostructure 211 having the m X n matrix of the structure group 200, m rows and n columns may be set as periodic boundary conditions.

In addition, a method of manufacturing the diffractive optical element 10 according to an embodiment of the present invention can be represented as follows.

After depositing the amorphous silicon on the substrate, coated with a resist, and irradiated with an electron beam to form a pattern, deposit chromium (Cr), and remove the chromium layer after the lift off process and etching process. Thus, the diffractive optical element of the present invention can be formed.

Specifically, amorphous silicon is deposited on a substrate through plasma-enhanced chemical vapor deposition. Here, the thickness of the substrate may be 500 μm, and the amorphous silicon may be a dielectric layer.

Thereafter, the resist layer was spin-coated at 2000 rpm for 60 seconds, and baked on the plate at 180° C. for 5 minutes to a final thickness of about 100 nm.

Thereafter, a pattern is formed by electron beam lithography (ELIONIX, ELS-7800, 80 kV, 50 pA).

In addition, to prevent charging effects from the dielectric substrate, the conductive polymer is spin-coated at 2000 rpm for 60 seconds before the electron beam irradiation step.

The electron beam dose is about 1280 to 1,600 μC/cm ² . Thereafter, the conductive layer was removed from deionized water, and the PMMA resist was exposed in a solution of methyl isobutyl ketone/isopropyl alcohol (IPA) 1: 3 at 0° C. for 12 minutes. , Wash for 30 seconds with IPA. Then, 40 nm of chromium (Cr) is deposited by electron beam deposition, and then a lift-off process is performed at 50°C acetone.

Here, the patterned chromium (Cr) layer is used as an etching mask for silicon, and dry etching can be used to remove the chromium (Cr)-free silicon layer. After the etching process, the chromium (Cr) mask is removed with a chromium (Cr) etching agent. Through this process, a silicon nano structure is formed on the substrate.

In addition, the diffractive optical element 10 according to another embodiment of the present invention may be configured such that an incident beam operates in a range of infrared wavelengths (810-830 nm). In this case, it is possible to exhibit high efficiency compared to the diffraction optical element 10 operating in visible light. That is, the efficiency of the diffractive optical element operating in the visible light range was about 27% in both reflection and transmission, but the efficiency of the diffractive optical element operating in the infrared range may be about 85%.

For example, the height (H) of the nanostructure may be 310 nm, the length (L) of 200 nm, the width (W) of 120 nm, and the length (C) of one side of the unit cell may be 400 nm.

Hereinafter, the operation and effects of the above-described diffraction optical element and its manufacturing method will be described.

The diffractive optical element of the present invention can scatter light on the entire 360-degree space using a meta surface without using a diffractive optical element and radar technology that creates a diffraction effect through the depth control of a conventional element.

In addition, the conventional meta-surface technology has been implemented by adjusting the phase information of reflected light or by controlling the phase of transmitted light, but in the case of the meta-surface of the diffractive optical element of the present invention, both reflected and transmitted light Can be adjusted.

In addition, the nanostructure is 1/2 the thickness of the operating wavelength of incident, and stores the phase information necessary for generating a point cloud, and on the basis of this, the incident beam can be injected into about 4,044 beams (points). .

In addition, since the diffractive optical element of the present invention uses silicon, a device can be manufactured using an existing semiconductor process technology, and is advantageous in terms of commercialization because it uses an existing semiconductor process technology.

In addition, when using an amorphous silicon, it may exhibit low heat loss and can be manufactured as a light and flexible device.

In addition, since the nanostructure is thin, it is easy to manufacture with an ultra-light and high-efficiency optical device.

In addition, when the diffractive optical element based on the meta surface of the present invention is used, it can be applied to a panoramic camera, a 3D face recognition camera, and an augmented reality/virtual reality display device.

In addition, since the silicon nanostructure constituting the diffractive optical element can be manufactured on a flexible substrate, it is applicable to a flexible display and a rollable display.

The diffraction optical element and its manufacturing method according to the embodiment of the present invention have been described above as specific embodiments, but this is only an example, and the present invention is not limited thereto, and the widest range according to the basic idea disclosed in this specification is described. It should be interpreted as having. Those skilled in the art may combine and replace the disclosed embodiments to implement patterns in a shape that is not timely, but this is also within the scope of the present invention. In addition, those skilled in the art can easily change or modify the disclosed embodiments based on the present specification, and it is obvious that such changes or modifications fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Optical apparatus 10 Diffraction optical element
20: light source 30: iris
50: Farfield 60: Camera
100: substrate 111: unit cell
200: structure group 211: nano structure

Claims (20)

Board;
A group of structures forming a geometric metasurface on the substrate,
The substrate includes a plurality of consecutive unit cells,
The structure group includes a plurality of nanostructures arranged at predetermined intervals and angles,
One nanostructure is disposed in one unit cell,
A diffraction optical element capable of spraying a beam into a full space of 360 degrees by controlling the intensity and phase of the beam by reflecting and transmitting the beam incident through the light source to the nanostructure. According to claim 1,
The thickness (H) of the nano-structure is less than half the wavelength of the beam incident through the light source, a diffractive optical element. According to claim 1,
The structure group includes a plurality of nanostructures arranged in an m X n matrix,
The diffractive optical element is disposed adjacent to the nanostructures arranged in m rows or n columns at a predetermined angle difference so that the beam incident through the light source is reflected and transmitted to the nanostructures and divided into four beams. (Where m and n are natural numbers) According to claim 3,
A plurality of nanostructures arranged in the m row or n column has a diffraction optical element having a different angle. According to claim 3,
The plurality of nanostructures arranged in the m row or n column is 13,
The diffraction optical element having an angle difference between adjacent nanostructures arranged in the m row or n column is 6π/13. According to claim 3,
The nanostructure is a cuboid shape,
The length (C) of one side of the unit cell is 300 nm,
The plurality of nanostructures disposed in the m row and the n column are 5, respectively, and the size of the structure group is 1.5 x 1.5 μm ² . The method of claim 6,
The wavelength of the beam incident on the nanostructure is 630 nm, and the height (H) of the nanostructure is 315 nm or less. According to claim 3,
The four beams are diffracted into two beams traveling in the same direction as the traveling direction of the beam incident through the light source and two beams traveling in the direction opposite to the traveling direction of the beam incident through the light source. Diffractive optical element. According to claim 3,
The nanostructure is a cuboid shape,
The length (C) of one side of the unit cell is 300 nm,
The plurality of nanostructures disposed in the m row and the n column is 100, respectively, and the size of the structure group is 30 x 30 μm ² ,
A plurality of the structure groups, the diffractive optical element is arranged in a continuous p X q matrix. (Where p and q are natural numbers) The method of claim 9,
The p and q are 10 diffractive optical elements, respectively. The method of claim 1
The nanostructure is an amorphous silicon diffractive optical element. According to claim 1,
The substrate is formed of an elastic material,
The nanostructure is provided on the substrate is a diffractive optical element that can be bent or folded. According to claim 1,
A diffractive optical element in which the one unit cell represents one pixel. According to claim 1,
The wavelength of the beam incident on the nanostructure is 810nm to 830nm,
The nanostructure is a cuboid shape,
A diffractive optical element having a height (H) of 310 nm, a length (L) of 200 nm, and a width (W) of 120 nm, and the length (C) of one side of the unit cell is 400 nm. It comprises the diffraction optical element according to claim 1,
A light source incident on the diffractive optical element;
An iris through which the beam emitted from the light source passes;
A far field in which an image of a beam reflected and transmitted to the diffractive optical element is formed; And
And a camera for capturing the reflected and transmitted beams. The method of claim 15,
The far field is an optical device including a front far field where a transmitting beam appears and a rear far field where a reflected beam appears. Forming a substrate;
Depositing a dielectric layer comprising a geometric metasurface on the substrate;
Forming a structure group including a plurality of nanostructures by forming a pattern on the dielectric layer,
The incident beam is reflected and transmitted to the nanostructure, so that the intensity and phase of the beam are controlled so that the beam can be injected in a full space of 360 degrees, so that the nanostructure is formed. Manufacturing method. The method of claim 17,
After the chromium is deposited on the plurality of nanostructures, a method for manufacturing a diffractive optical element implemented through a lift off process. The method of claim 18,
Forming a pattern on the dielectric layer to form a group of structures including a plurality of nanostructures,
A method of manufacturing a diffractive optical element comprising coating an upper portion of the dielectric layer with a resist, and subjecting the resist to an electron beam. The method of claim 19,
And spin-coating a conductive polymer at 2000 rpm for 60 seconds prior to the step of irradiating the electron beam.

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