KR102070349B1 - Lithium niobate-silicon nitride phase modulator and optical phased array antenna using the same - Google Patents

Abstract

An optical phase alignment antenna according to one aspect of the present invention comprises: an optical power distributor which distributes a light wave inputted from a light source; a phase modulator based on LN-SiN, which controls the phase of the distributed light wave; and a lattice antenna based on SIN, which releases the light wave to a space corresponding to the controlled phase. Here, in the phase modulator based on LN-SiN, optical phase modulators are aligned in a plurality of rows. In addition, the optical phase modulators are characterized by comprising: a silicon substrate layer having a second electrode formed at an upper portion; a second insulation silica layer formed at the upper portion of the silicon substrate layer; a lithium niobite thin film layer formed at an upper portion of the insulation silica layer; a silicon nitride layer formed at an upper portion of the lithium niobite thin film layer; a first insulation silica layer formed at an upper portion of the silicon nitride layer; and a first electrode formed at an upper portion of the first insulation silica layer.

Description

Lithium niobate-silicon nitride based optical phase modulator and optical phased array antenna using the same

The present invention relates to an optical phase modulator based on lithium niobate-silicon nitride and an optical phase array antenna using the same.

With the advent of the Fourth Industrial Revolution, the use of photonic integrated circuits (PICs), which use optical waveguides instead of conventional metal wiring, is being used to communicate between various components within electronic system systems. Silicon photonics-based optical communication technology is called silicon photonics. Since optical integrated circuits transmit information by optical signals rather than electrical signals, silicon photonics-based optical phase modulators are required to implement optical integrated circuits using silicon photonics technology.

The importance of ultra-fast beamforming technology, which plays the role of eyes in the fourth industrial revolution, which is characterized by hyper-connectivity, ultra-intelligence, and super-fusion, is increasing.

Beamforming technology is becoming a key element technology in various fields such as autonomous vehicles, free space optical communication, smart factory, and 3D scanning.

Until now, beamforming technology has been mainly implemented through light detection and ranging (LiDAR) using MEMS mirrors and motors. These methods are capable of scanning a wide range and are in the commercialization stage, but are bulky and expensive to manufacture, which is uneconomical, and wear due to mechanical movement may cause problems in reliability.

In response to this, the LiDAR research, which uses an optical phase array instead of a mechanical motor rotation method, is being actively conducted.

The silicon-based optical phased array (OPA) currently being studied has a very small size and considerably faster beam scanning rate compared to mechanical lidar, but the scanning speed remains at several kHz based on the thermo-optic effect. to be.

The silicon-based photophase array under study is applied to silicon photonics technology, which is mainly used in existing semiconductor integrated circuits, and silicon photonics technology is used for silicon (Si) and silicon nitride (Si3N4): SiN materials. Are used.

Silicon photonics, despite its usefulness, remains at a modulation rate of several kHz due to the low electro-optic effect of silicon, using thermooptic effects for phase modulation.

Background art of an optical phase modulator using an optical waveguide based on silicon photonics has been published in Korean Patent Publication No. 10-1768676.

In optical phased arrays (US Publication US 2014/0192394 A1) for nanophotonics based optical phased array antennas, an optical phased array antenna in which a phase-controlled optical device is matrix-integrated based on a semiconductor silicon material has been proposed.

Conventional phased array antenna uses the principle that the refractive index is changed by the thermo-optic effect for phase control of light waves. In the conventional invention, an optical delay line is provided in front of the antenna, and an electric current is injected and heated in the optical delay line portion. When the delay line portion is heated and the temperature rises, the refractive index increases by the thermo-optic effect. Thus, the phase of the light wave passing through the delay line is changed. As in the prior art, when the thermo-optic effect is used, power consumption is large and the phase modulation speed is limited by the thermo-optic.

Therefore, this photonic optical phased arrays (OPA) structure is mainly used as the optical antenna of the 1D array using the high refractive index (n = 3.5) and temperature sensitivity of the Si waveguide.

In addition, a technique related to a phase control modulated optical phased array antenna having a lattice structure based on a silicon material has been published in Korean Patent Publication No. 10-1720434.

In Patent No. 10-1720434, the optical power divider, the phase controller, and the phase supply lines are disposed outside the 1xM emitter array in order to secure sufficient space in the longitudinal direction of the light emitter. In Patent 10-1720434, N 1xM diverter arrays are arranged independently up and down, and each 1xM diverter array is provided with a beam scanning function of a two-dimensional (2D) space by having a longitudinal radiation angle at different angles. It is characterized by the structure.

In addition to the low-speed electro-optic effects of silicon photonics, research on optical phase arrays (OPAs), which can actively control the optical nonlinearity problem and active control of the emission angle, has been continuously conducted.

It is considered to be an ideal electro-optic material that has a large electro-optic effect, which is a property of changing the refractive index by an applied electric field, has a low temperature characteristic compared to Si, and has a high speed modulation characteristic of several GHz. There is a need for a method that can effectively apply lithium niobate (Lithium Niobate [LN]) to the phase modulator.

Background Art Background of the photonics of a waveguide material using silicon nitride has been published in the Republic of Korea Patent Publication 2007-0117378 (Integrated photonics containing a waveguide material).

Korean Unexamined Patent Publication 2007-0117378 (Integrated Photonics Including Waveguide Material) Republic of Korea Patent Publication No. 10-1720434 (Optical Phased Array Antenna) United States Patent Application Publication US 2014/0192394 A1 (Optical phased arrays)

The present invention is to provide an optical phase modulator based on lithium niobate-silicon nitride and an optical phase array antenna using the same.

It is still another object of the present invention to provide a lithium nanobate-silicon nitride based optical phase modulator capable of providing high modulation characteristics up to several GHz and an optical phase array antenna using the same.

The object of the present invention is not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood from the following description.

According to an aspect of the present invention, an optical phased array antenna includes: an optical power distributor for distributing light waves input from a light source; LN-SiN-based optical phase modulator for controlling the phase of the distributed light wave; And a SIN-based grating antenna that emits light waves according to the controlled phase into a space. The LN-SiN-based phase modulator is characterized in that the individual optical phase modulator is arranged in a plurality of columns, wherein the individual optical phase modulator comprises a silicon substrate layer having a second electrode formed thereon; A second insulating silica layer formed on the silicon substrate layer; A lithium niobate thin film layer formed on the insulating silica layer; A silicon nitride layer formed on the lithium niobate thin film layer; A first insulating silica layer formed on the silicon nitride layer; And a first electrode formed on the first insulating silica layer. Characterized in that it comprises a.

In addition, the lithium niobate thin film layer is characterized by relatively low refractive index of both sides of the optical waveguide by irradiating both side surfaces of the portion to be formed as the optical waveguide of the portion through which the light passes with a femtosecond laser.

In addition, the lithium niobate thin film layer is formed by irradiating a femtosecond laser having an 800 nm wavelength, a 120 fs pulse width, and a pulse energy of 400 nJ to 600 nJ on both side walls of a portion to be formed as an optical waveguide. It is characterized by.

In addition, the optical waveguide is characterized in that formed in a width of 1㎛.

In addition, the input optical signal passing through the optical waveguide has an output optical signal L _O whose refractive index is changed by the following expression according to the electric field applied to the optical waveguide by the first electrode and the second electrode. It is obtained, It is characterized by the above-mentioned.

Where n _e is the extraordinary refractive index, r ₃₃ is the electro-optic coefficient, and E is the strength of the electric field.

In addition, a plurality of electrode terminals extending from the upper electrode of each of the plurality of optical phase modulator of the plurality of columns connected to the control terminal, respectively, wherein the applied voltage of the plurality of electrode terminals is set so that the optical phase increases linearly for each adjacent column It is characterized by.

In addition, the silicon nitride layer may be replaced with an amorphous silicon (a-Si) layer or a TiO 2 layer.

The optical power distributor may divide the input optical wave into 1: A n by connecting a splitter for splitting the optical wave into 1: A in multiple stages of ⁿ .

In addition, the optical power divider, LN-SiN-based optical phase modulator and SiN-based grating antenna has the same number of channels, characterized in that they are combined into one device through chip-to-chip alignment.

In addition, the waveguides distributed between and in each of the optical power dividers and connected in the divider are connected to SiN waveguides, and the connection between the distributed waveguides and each individual optical phase modulator of the LN-SiN based optical phase modulator and the The connection from the individual optical phase modulator to the SiN based grating antenna is characterized in that it is connected to the SiN waveguide.

In addition, the SiN-based lattice antenna is formed of a structure in which a plurality of structures in which a lattice of a predetermined pitch is formed in the SiN waveguide formed on the silica layer are arranged in a plurality of rows, and are radiated from each column of the SiN-based lattice antenna. The square θ is characterized by being obtained from the following equation.

는 입력 광파의 자유공간에서 중심 파장,

는 격자의 주기,

는 격자를 포함하는 광 도파로의 유효 귤절률(effective index), θ는 주기적인 격자로부터 산란된 광파의 회절로 형성된 회절패턴 중에서 빛의 세기가 가장 큰 중심에 해당되는 방사 각도를 나타낸다.In Equation 2,

Is the center wavelength in the free space of the input light wave,

Cycle of the grid,

Is an effective index of the optical waveguide including the grating, and θ represents an emission angle at which the light intensity is the center of the diffraction pattern formed by diffraction of the light waves scattered from the periodic grating.

According to an embodiment of the present invention, an LN-SiN optical phased array antenna capable of ultra-fast beam scanning (steering) may be implemented by combining an LN-SiN optical phase modulator array and a SiN grating antenna.

According to an embodiment of the present invention, an optical phased array antenna may be implemented in a structure capable of 2D scanning with a SiN optical antenna through chip-to-chip coupling between an LN-SiN-based optical phase modulator and a SiN optical waveguide. Can be.

In addition, the LN-SiN-based phase modulator using the electro-optic effect can enable the ultra-fast phase control of the optical phased array antenna up to several GHz.

FIG. 1 illustrates a process of forming a lithium niobate (LN) thin film on insulator layer in an optical waveguide device according to an embodiment of the present invention.
FIG. 2 illustrates a process of forming a high refractive index layer on a lithium niobate (LN) thin film on insulator in an optical waveguide device according to an embodiment of the present invention.
FIG. 3 illustrates a mode file in which a finite-difference time-domain (FDTD) -based simulation of the silicon-lithium niobate photonics-based optical waveguide of FIG. 2 is performed.
FIG. 4 illustrates a process of forming a waveguide by stamping both sidewalls of a portion to be formed as a waveguide with a femtosecond laser on the lithium niobate substrate formed in FIG. 1.
FIG. 5 illustrates a cross-sectional image of a silicon-lithium niobate photonics-based optical waveguide performing a femtosecond laser processing process and a mode file in which a finite-difference time-domain (FDTD) -based simulation is performed.
6 and 7 show the structure of the individual optical phase modulator based on the LN-SiN according to an embodiment of the present invention.
8 illustrates an example of an LN-SiN-based optical phase modulator to be applied to an optical phased array antenna according to an embodiment of the present invention.
9 shows an example of an LN-SiN-based optical phase modulator and an optical phase array antenna using the same according to an embodiment of the present invention.
10 illustrates a mode converter applied to an input terminal of an optical power distributor according to an embodiment of the present invention.
11 illustrates a structure of an emitter of a SiN-based grating antenna according to an embodiment of the present invention.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

In the present application, when a part is said to "include" a certain component, it means that it can further include other components, without excluding the other components unless otherwise stated.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

According to an embodiment of the present invention, in order to overcome the limitations of existing silicon photonics, an optical waveguide layer based on Si-LN photonics in which an LN thin film, which is an electro-optic material, is grafted.

Lithium Niohate (LiNbO ₃ ) may be used as an optical waveguide device such as an optical switch and an optical modulator by using an electro-optic effect, which is a property of changing refractive index by an applied electric field. .

Such a lithium niobate is not easy to etch process, it takes a lot of cost and time in the deformation process for use as a waveguide.

An embodiment of the present invention provides an efficient and economical silicon-lithium niobate photonics-based optical waveguide through a semiconductor deposition process in which a lithium niobate (LN) thin film is generally applicable.

1 and 2 illustrate a process of manufacturing an optical waveguide based on silicon-lithium niobate photonics according to an embodiment of the present invention.

An optical waveguide according to an embodiment of the present invention may be formed on a silicon on insulator (SOI) wafer or a bulk silicon wafer.

1 illustrates a process of forming a lithium niobate (LN) thin film on insulator layer according to an embodiment of the present invention.

For example, when forming an optical waveguide on an SOI silicon wafer, a lithium niobate thin film (LiNbO ₃ ) used as an optical waveguide on the insulating silica layer 10 formed on the silicon substrate layer 20 as shown in FIG. 1. Including a thin film (100) layer to form a layer of a lithium niobate (LN) thin film on insulator (LN) as a whole.

FIG. 1 illustrates a process of forming a LiNbO ₃ thin film 100 used as an optical waveguide on an insulating silica layer 10 formed on a silicon substrate layer 20.

FIG. 2 illustrates a process of forming a high refractive index layer on a lithium niobate (LN) thin film on insulator according to an embodiment of the present invention.

Following the process of FIG. 1, next, as shown in FIG. 2, a relatively high refractive index amorphous silicon (a-Si) layer and silicon nitride (SiN) are formed on a LN thin film on insulator. A layer or a TiO ₂ layer is deposited to form the high refractive index layer 60.

According to an embodiment of the present invention, a relatively high refractive index of amorphous silicon (a-Si), silicon nitride (SiN), or TiO ₂ on a lithium niobate (LN) thin film on insulator It is possible to locally increase the effective refractive index by depositing, thereby forming an optical waveguide layer based on silicon-lithium niobate photonics.

Referring to FIG. 2, a layer of LiNbO ₃ thin film 100, which is an area in which the effective refractive index is increased, operates as a strip waveguide. The area activated to the actual optical signal is the lithium niobate thin film layer 100.

In one embodiment of the present invention by depositing a silicon nitride (SiN) layer, amorphous silicon (a-Si) layer thickness of about 100nm at 1um width on a lithium nano-bait (LN) thin film layer of 700nm thickness to form a strip waveguide, An optical waveguide based on silicon-lithium niobate photonics was formed.

FIG. 3 illustrates a mode file in which a finite-difference time-domain (FDTD) -based simulation of the silicon-lithium niobate photonics-based optical waveguide layer of FIG. 2 is performed.

Referring to the mode profile verified through the finite-difference time-domain (FDTD) -based simulation of FIG. 3, a high refractive index formed of a silicon nitride (SiN) layer or amorphous silicon combined with the lithium niobate thin film layer 100. Layer 200 may form a lithium niobate waveguide, thereby effectively forming a silicon-composite strip waveguide.

According to an optical waveguide device according to an embodiment of the present invention, a relatively high refractive index of amorphous silicon (a-Si) or silicon nitride (SiN) on a lithium niobate (LN) thin film on insulator Waveguide can be formed by partially increasing the effective refractive index of lithium niobate (LN) by depositing a layer or titanium dioxide (TiO ₂ ), thereby introducing a general semiconductor deposition process without an etching process. It is possible to form an optical waveguide based on a niobate photonics.

In the case of an optical waveguide based on silicon-lithium niobate photonics according to the embodiment of FIG. 2, a waveguide can be generated by a general semiconductor deposition process, thereby economically and effectively forming an optical waveguide based on silicon-lithium niobate photonics. . However, propagation loss may occur due to relatively weak mode confinement.

In another embodiment of the present invention as a method for reducing the disadvantage of such a propagation loss occurs by irradiating both side surfaces of the portion to be formed as a waveguide with a femtosecond laser to relatively lower the refractive index of both sides of the waveguide mode restraint The method of making it strong is adopted.

FIG. 4 illustrates a process of forming a waveguide by stamping both sidewalls of a portion to be formed as a waveguide with a femtosecond laser on the lithium niobate thin film formed in FIG. 1.

Referring to FIG. 4, by using a femtosecond laser, damage is applied to both side walls of the waveguide inside the thin film of lithium niobate (LN) to change the refractive index, so that the high energy density at the point where the laser is focused. As the lithium niobate (LN) characteristics change, the refractive index is lowered.

For example, a femtosecond laser is imprinted with a dual-line, and processed to change the refractive index by damaging both side walls of the portion to be formed as the optical waveguide in the lithium niobate thin film. As a result, mode confinement occurs in the center space of the lithium niobate thin film, thereby increasing mode confinement.

In an embodiment of the present invention, a femtosecond laser having a 800 nm wavelength, a pulse width of 120 fs, and a pulse energy of 400 nJ to 600 nJ was irradiated with a dual-line, and the light output from the laser was 100 times. In addition, an objective lens having NA = 0.85 was irradiated to focus on the inside of the lithium niobate (LN) thin film layer, and the focal area of the focal area was reduced by about 0.003.

Femtosecond laser according to an embodiment of the present invention is controlled to operate at a speed of 30um / s.

After the femtosecond laser machining process of FIG. 4, a high refractive index layer formed of a silicon nitride layer is formed on the LN thin film on insulator of FIG. 2 to form a silicon having a waveguide having a width of 1 μm. It is possible to form an optical waveguide based on lithium niobate photonics.

According to an embodiment of the present invention, a silicon nitride layer, a-Si SiN layer, or TiO ₂ layer having a relatively high refractive index is deposited on a lithium niobate (LN) thin film on insulator. An optical waveguide based on silicon-lithium niobate photonics subjected to a laser processing process may be formed.

FIG. 5 illustrates a cross-sectional image of a silicon-lithium niobate photonics-based optical waveguide performing a femtosecond laser processing process and a mode file in which a finite-difference time-domain (FDTD) -based simulation is performed.

Referring to FIG. 5, it can be seen that the mode confinement characteristic is increased due to the change of the refractive index by the femtosecond laser in the portion of the waveguide that is in contact with both boundary surfaces.

The optical waveguide based on silicon-lithium niobate photonics formed by performing a laser processing process as described above may form an ultra-fine optical waveguide that may reduce the generation of propagation loss by increasing mode confinement characteristics.

6 and 7 show the structure of the individual optical phase modulator based on the LN-SiN according to an embodiment of the present invention.

6 and 7 illustrate structures of individual optical phase modulators using a silicon-lithium niobate photonics-based optical waveguide formed by performing a femtosecond laser processing process according to the embodiments of FIGS. 3 and 4.

FIG. 6 illustrates a front surface (XY) of an ultrafine individual optical phase modulator in which electrodes are formed on the top and bottom of a silicon-lithium niobate photonics-based optical waveguide on which a femtosecond laser processing process is performed, and FIG. The side surface XZ is shown.

Referring to FIG. 6, an ultra-fine individual optical phase modulator based on silicon-lithium niobate according to an embodiment of the present invention may include a first formed on the silicon substrate layer 20 having the second electrode 42 formed thereon. LiNbO3 thin film 100 that is formed on the insulating silica layer 10 and the insulating silica layer 10 and is processed by femtosecond laser on both side walls of the portion to be formed as the optical waveguide. ) Is formed, a high refractive index layer 60 of silicon nitride (SiN) material is formed on the LiNbO3 thin film (LiNbO3 thin film, 100) layer, the first on the high refractive index layer 60 The first electrode 41 is formed.

According to an embodiment of the present invention, a second silica layer 11 is further provided between the first electrodes 41 on the high refractive index layer 60 to facilitate insulation and bonding of the first electrodes 41. May be included.

Accordingly, an individual optical phase modulator according to an embodiment of the present invention may be manufactured as an LN-SiN based optical phase modulator.

6 and 7, the input optical signal L _I passing through the optical waveguide 100 has a refractive index according to an electric field applied perpendicularly to the optical waveguide 105 by the first and second electrodes 41 and 42. This change results in an output optical signal L _O whose phase is shifted.

When the lithium niobate thin film (LiNbO ₃ thin film) 105 is subjected to an electric field, a change in refractive index by the size of Equation 1 is induced by the electro-optic effect.

Where n _e is the extraordinary refractive index, r ₃₃ is the electro-optic coefficient, and E is the intensity of the electric field.

The LN-SiN-based optical phase modulator according to an embodiment of the present invention may increase optical energy density in a narrow region (waveguide), thereby obtaining optical signal phase control by obtaining high electro-optic modulation efficiency.

LN-SiN-based individual optical phase modulator according to an embodiment of the present invention 1 mode is improved in the mode confinement characteristics that can be effectively produced through the deposition process and femtosecond laser processing process of the lithium niobate thin film difficult to etch It is possible to provide an ultrafine optical phase modulator having a waveguide 105 of.

Lithium niobate can provide high modulation characteristics of high electro-optic coefficient up to several GHz, so the ultra-fine optical phase modulator based on silicon-lithium niobate photonics according to an embodiment of the present invention can provide a modulation bandwidth. Can be used in the GHz range.

In addition, LN-SiN-based individual optical phase modulator according to an embodiment of the present invention can increase the integration degree by the silicon-lithium niobate photonics based on the improved modulation efficiency and laser processing.

LN-SiN-based optical phase modulator according to an embodiment of the present invention can be widely applied as an ideal platform in various applications including a photonic integrated circuit.

8 illustrates an example of an LN-SiN based optical phase modulator to be applied to an optical phased array antenna according to an embodiment of the present invention.

8, an LN-SiN based optical phase modulator in which LN-SiN based individual optical phase modulators 201 to 208 according to an embodiment of the present invention are arranged at regular intervals, and an individual optical phase modulator 201. Eight electrode terminals e1 to e8 extending from the upper electrode of 208 and connected to the control terminal, respectively.

,

,

)하도록 설정된다.The applied voltage of each terminal is linearly increased in optical phase from terminal e1 to terminal e8 due to the same applied voltage difference in the LN-SiN-based individual optical phase modulators of all pairs of adjacent columns (

,

,

It is set to

Accordingly, the LN-SiN-based optical phase modulator according to an embodiment of the present invention may be capable of beam steering in the transverse direction based on the principle of Huygens by adjusting the phase of each channel by forming a plurality of channels to form a phased array. have.

9 illustrates an example of an LN-SiN-based optical phase modulator and an optical phased array antenna using the same according to an embodiment of the present invention.

The optical phased array antenna according to an embodiment of the present invention has an optical power splitter (300) for distributing light waves input from a light source, and an LN-SiN based optical phase for controlling the phase of the light waves of the distributed light waves. A modulator 200 and a grating antenna 500 based on an SiN that emits light waves according to the controlled phase into a space.

The LN-SiN-based optical phase modulator 200 is characterized in that the individual optical phase modulators 201 to 208 are arranged in a plurality of columns.

The optical power splitter 300, the LN-SiN-based optical phase modulator 200, and the SiN-based grating antenna 500 may be manufactured and combined as separate chips, respectively.

Referring to FIG. 9, waveguides distributed between and in the optical power divider 300 and in each of the dividers are connected to SiN waveguides, and each individual optical phase of the distributed waveguide and the LN-SiN based phase modulator. Connections to the modulators 201 to 208 and from the respective optical phase modulators 201 to 208 to the SiN based grating antenna 500 array may be connected to the SiN waveguide.

According to an embodiment of the present invention, each optical power splitter 300, the LN-SiN-based optical phase modulator 200, and the SIN-based grating antenna 500 have the same number of channels and chips It can be combined into a single device through -to-chip alignment.

The optical power splitter 300 may be connected to an input terminal through a spot size converter (SSC) and distributed through a multimode interferometer coupler (MMI).

In addition, the coupling between the LN-SiN-based optical phase modulator chip and the SiN photonic structure may be connected through a spot-size converter (SSC) of the SIN waveguide.

Accordingly, the waveguide structure of the LN phase modulator can be manufactured to be applicable to all forms having modes such as waveguide and film.

10 illustrates an optical mode converter applied to an input terminal of the optical power distributor 300 according to an embodiment of the present invention.

Spot size converter (SSC) changes the mode size in consideration of Taper length, width and height so that light can be transmitted from the fiber to the SiN waveguide without loss.

Referring to FIG. 9, the light transmitted through the spot size converter (SSC) proceeds and distributes through the SiN waveguide to a multi-mode coupler (MMI) which serves as a substantial distributor.

The optical power divider 300 is an element for distributing light waves input from a single light source Li to N phase modulators 201 to 208. The optical power divider 300 may connect the splitter for distributing the light waves in 1: A in multiple stages of ⁿ to divide the split in 1: A ⁿ .

As an example, referring to FIG. 9, the first divider divides the optical input at a ratio of 1: 2 in a 50:50 ratio, and is connected through the SiN waveguide. In the second divider 311, the first divider is again divided into two 1: 2 dividers. 1: 4, and the third divider 321 is divided into four 1: 2 distributors, and 1: 8 each.

Referring to FIG. 9, the optical power distributor 300 according to an embodiment of the present invention divides the 1: 2 distributors 311 and 321 in two stages to perform 1: 8 distribution to perform LN-SiN based phase modulators. An example of transmitting to the 200 through the SiN waveguide 90 is shown.

The LN-SiN-based optical phase modulator 200 controls the phase of the optical wave to supply the light waves having phases equally spaced at intervals for each diverter element 501 to 508 to the SiN-based grating antenna 500. It performs the function.

The phase matching beam having a narrow divergence angle in a specific direction in space may be formed by the interference of the emitted light waves by varying the phases of the light waves at equal intervals for each diverger. The phase-matching beam is spaced in space by continuously changing the phase difference ΔΦ at equal intervals between -π ≤ ΔΦ ≤ + π for each optical wave diverter of the phase array.

It can be moved along a certain trajectory and provide a beam scanning function.

The LN-SiN based optical phase modulator 200 of FIG. 8 is applied to the optical phase array antenna according to the exemplary embodiment of the present invention.

The grating antenna 500 emits light waves into space based on the controlled phase of the LN-SiN based optical phase modulator 200.

11 illustrates a structure of an emitter of a SiN-based grating antenna according to an embodiment of the present invention.

Referring to FIG. 11, a SiN-based grating antenna according to an embodiment of the present invention is formed in a structure in which a lattice of a predetermined pitch is formed in a SiN waveguide formed on a silica layer.

The radiation angle of the far field of the output light wave emitted from the lattice structure of each column may be calculated by using Equation 2 based on a diffraction principle.

는 입력 광파의 자유공간에서 중심 파장,

는 격자의 주기,

는 격자를 포함하는 광 도파로의 유효 귤절률(effective index), θ는 주기적인 격자로부터 산란된 광파의 회절로 형성된 회절패턴 중에서 빛의 세기가 가장 큰 중심에 해당되는 방사 각도를 나타낸다.In Equation 2,

Is the center wavelength in the free space of the input light wave,

Cycle of the grid,

Is an effective index of the optical waveguide including the grating, and θ represents an emission angle at which the light intensity is the center of the diffraction pattern formed by diffraction of the light waves scattered from the periodic grating.

Referring to FIG. 10, the radiation angle represents an angle spread based on the normal direction of the grating surface.

는 광 도파로의 소재와 광파의 파장에 따른 굴절률을 기반으로 하여 광 도파로의 구조에 따라 정해진다. Effective refractive index

Is determined according to the structure of the optical waveguide based on the material of the optical waveguide and the refractive index according to the wavelength of the optical waveguide.

The dependence of the radiation angle on the wavelength and the refractive index may be calculated through Equation 2.

을 전기적 제어에 의해 각각 변화시킴으로써 방사각 θ를 효과적으로 제어할 수 있다.Therefore, in an embodiment of the present invention, the effective refractive index in Equation 2

Can be effectively controlled by changing the angle? By electrical control.

According to an embodiment of the present invention, the light passing through the LN-SiN-based phase modulator with the optical phase modulators arranged at a predetermined interval is emitted from the SiN-based lattice antenna, wherein the longitudinal angle of the emitted light is It can be determined by the wavelength and the effective refractive index of the grating antenna.

The number of channels of the SiN grating antenna waveguide and the LN-SiN modulator can be designed by the radial angle range and the number of distribution circuits N of the multimode interferometer coupler (MMI).

Accordingly, the optical phased array antenna according to an embodiment of the present invention may be capable of 2D scanning.

According to an embodiment of the present invention, an LN-SiN optical phased array antenna capable of ultra-fast beam scanning (steering) may be implemented by combining an LN-SiN optical phase modulator array and a SiN grating antenna.

According to an embodiment of the present invention, an optical phased array antenna may be implemented as a structure capable of 2D scanning with a SiN optical antenna through chip-to-chip coupling between an LN-SiN-based optical phase modulator and a SiN optical waveguide. Can be.

In addition, the LN-SiN-based phase modulator using the electro-optic effect can enable the ultra-fast phase control of the optical phased array antenna up to several GHz.

10: insulating silica layer
20: silicon substrate layer
41, 42: electrode
60: high refractive index layer
100: LiNbO3 thin film layer
200: LN-SiN-based optical phase modulator
201 to 208: individual optical phase modulators
300: optical power distributor
500: SiN-based grating antenna
e1 ~ e8: electrode terminal

Claims (10)

In an optical phase array antenna,
The optical phase array antenna
An optical power distributor for distributing light waves input from a light source;
An LN-SiN based phase modulator for controlling the phase of the light waves distributed by the optical power distributor; And
A SIN-based grating antenna for emitting light waves according to the controlled phase into a space; Including,
The LN-SiN based phase modulator is characterized in that the individual optical phase modulator is arranged in a plurality of columns,
The individual optical phase modulator
A silicon substrate layer having a second electrode formed thereon;
A second insulating silica layer formed on the silicon substrate layer;
A lithium niobate thin film layer formed on the insulating silica layer;
A silicon nitride layer formed on the lithium niobate thin film layer;
A first insulating silica layer formed on the silicon nitride layer; And
A first electrode formed on the first insulating silica layer; An optical phase array antenna comprising a.
The method of claim 1,
The lithium niobate thin film layer is an optical phase array, characterized in that the refractive index of both sides of the optical waveguide is relatively lowered by stamping both side walls of the portion to be formed as the optical waveguide of the portion where the light passes through the femtosecond laser. antenna.
The method of claim 1,
The lithium niobate thin film layer is formed by irradiating a femtosecond laser having an 800 nm wavelength, a 120 fs pulse width, and a pulse energy of 400 nJ to 600 nJ on both side walls of a portion to be formed as an optical waveguide. Characterized by an optical phase array antenna. The method of claim 2,
The input optical signal passing through the optical waveguide is an optical phase obtained by obtaining an output optical signal whose refractive index is changed by the following equation according to an electric field applied perpendicularly to the optical waveguide by the first and second electrodes. Array antenna.

Where n _e is the extraordinary refractive index, r ₃₃ is the electro-optic coefficient, and E is the strength of the electric field. The method of claim 1,
A plurality of electrode terminals extending from upper electrodes of each of the plurality of optical phase modulators and connected to control terminals, respectively;
And the applied voltages of the plurality of electrode terminals are set such that the optical phase increases linearly along an adjacent column. The method of claim 1,
The silicon nitride layer is an optical phase array antenna, characterized in that substituted by an amorphous silicon (a-Si) layer or TiO ₂ layer. The method of claim 1,
The optical power splitter is a wave of the input light waves 1: Optical phased array antenna, comprising a step of distributing the A ^n: a distributor for distributing the A n connections in multiple stages to one. The method of claim 1,
The optical power splitter, the LN-SiN-based optical phase modulator and the SIN-based grating antenna have the same number of channels and are coupled to one device through chip-to-chip alignment.
The method of claim 1,
In the optical power divider, the waveguides distributed between and in each of the dividers are connected by a SiN waveguide, and the distributed waveguides are connected to each of the individual optical phase modulators and the SiN-based at each individual optical phase modulator. An optical phased array antenna, characterized in that the connection to the grid antenna is connected to the SiN waveguide. The method of claim 1,
The SiN-based lattice antenna is formed of a structure in which a lattice of a predetermined pitch is formed in a SiN waveguide formed on a silica layer, arranged in a plurality of columns.
The radiation angle θ radiated from the heat of the SiN-based grating antenna is obtained by the following equation.
[Equation 2]

here,

Is the center wavelength in the free space of the input light wave,

Cycle of the grid,

Is an effective index of the optical waveguide including the grating, and θ represents an emission angle whose center of light intensity is the largest among diffraction patterns formed by diffraction of light waves scattered from the periodic grating.

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