CN107315246A - A kind of photoswitch based on medium electrowetting effect - Google Patents

Abstract

The invention discloses an optical switch based on the electrowetting effect of a medium. The optical switch adopts a three-layer structure. The first layer is an upper plate, which is composed of a square transparent glass 1, a transparent electrode 2 and a hydrophobic film 3; the second layer It is a square transparent glass layer 10, and a micro-flow channel 5 is opened along its diagonal, and there are controlled discrete electrolyte droplets 4 in the flow channel, and four strip-shaped dielectric optical waveguides 6, 7, 8 are opened on the same horizontal plane of the glass layer , 9; the third layer is the bottom plate, made of square transparent glass as substrate 15, polysilicon as substrate 14, phosphor-expanding and photolithography patterned microelectrode array 13 on the substrate, dielectric layer 12 is arranged on the electrode array, dielectric layer A layer of hydrophobic film 11 is coated on it. The optical switch does not need to use complex devices such as motors, which greatly reduces the production cost and production process, and has important technical and economic values.

Description

An Optical Switch Based on Dielectric Electrowetting Effect

technical field

The invention relates to an optical switch based on the electric wetting effect of a medium, and belongs to the technical field of optical cross-connection and optical add-drop multiplexing devices in the optical Internet.

Background technique

The optical switch is the core device of optical switching, and it is also one of the main factors affecting the performance of the optical network. As a key device of the new-generation all-optical networking network, the optical switch is mainly used to realize functions such as routing selection, wavelength selection, optical cross-connection and self-healing protection on the optical level. In an all-optical network, optical add-drop multiplexing devices (OADM) and optical cross-connects (OXC) are indispensable network node devices, and optical switches and optical switch arrays are the core devices in these devices. The optical switches that have been put into practical use at present, except for a few types of optical switches such as MEMS, the switching capacity of existing optical switches is always limited, it is difficult to make a large array, and the MEMS optical switch itself is resistant to mechanical friction, wear or vibration, etc. There are also deficiencies. Therefore, the development of a microfluidic optical switch has important technical value and application prospects.

Contents of the invention

The purpose of the present invention is to address the shortcomings of the above-mentioned prior art, and propose an optical switch based on the dielectric electrowetting effect. The optical switch applies the dielectric electrowetting effect to modern optical communication technology, and drives discrete electrolyte droplets to Control the total reflection and total transmission of the light beam, and then realize the "on" and "off" actions of the optical switch. The optical switch combines the electrowetting effect with modern optical communication technology. The optical switch does not need to use complex devices such as motors, which greatly reduces the production cost and production process, and has important technical and economic values.

The technical solution adopted by the present invention to solve the technical problem is: an optical switch based on the dielectric electrowetting effect, the optical switch adopts a three-layer structure, the first layer is an upper plate, and the upper plate includes square transparent glass 1 , transparent electrode 2 and hydrophobic film 3; the second layer is a square transparent glass layer 10, along its diagonal there is a micro-flow channel 5, and there are controlled discrete electrolyte droplets 4 in the flow channel, and its refractive index matches the transparent glass , there are four strip-shaped dielectric optical waveguides 6, 7, 8, 9 on the same horizontal plane of the glass layer; the third layer is the lower plate, which includes a square transparent glass substrate 15, a polysilicon substrate 14, and Phosphorus diffusion and photolithography patterned micro-electrode array 13, a layer of _SiO2 is thermally oxidized on the electrode array as a dielectric layer 12, and a layer of hydrophobic film 11 is coated on the dielectric layer. In the present invention, after the middle and lower layers of transparent glass plates are bonded, a drop of electrolyte liquid drop 4 is injected into the micro-flow channel 5, and then the upper plate and the middle glass plate are bonded. At this time, the liquid drop is clamped between the upper and lower plates. The surrounding filling substance is air. The micro-electrode array 13 on the lower plate and the transparent electrode 2 on the upper plate are led to the positive and negative poles of the AC power supply 17 by lead wires 19 and 16 respectively. Since the droplet is driven by applying a voltage on a single microelectrode array, the present invention sets a four-control switch k18 to ensure that the droplet moves back and forth in the entire microfluidic channel.

Beneficial effect:

1. The present invention applies the dielectric electrowetting technology to the optical switch, realizes the opening and closing of the optical switch by electronically controlling the discrete liquid droplets, and has good controllability and adaptability.

2. The present invention is simple in structure, easy to manufacture, low in cost, low in voltage, low in energy consumption, fast in response, and can be integrated and packaged, and has practical application value.

3. The invention belongs to the microfluidic optical device, which does not need complex devices such as motors, has very important technical value and economic value, and will be widely used in the field of optical communication.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Logo description: square transparent glass-1; transparent electrode-2; upper plate hydrophobic film-3; square transparent glass layer-10; microchannel-5; controlled discrete electrolyte droplets-4; 7, 8, 9; lower plate hydrophobic film-11; SiO ₂ dielectric layer-12; microelectrode array-13; polysilicon substrate-14; square transparent glass substrate-15; upper plate electrode leads-16; Plate electrode lead-19; AC power supply-17; four-control switch k-19.

Fig. 2 is a schematic cross-sectional view of an optical switch.

Logo description: square transparent glass-1; transparent electrode-2; upper plate hydrophobic film-3; controlled discrete electrolyte droplets 4; microchannel-5; square transparent glass layer-10; ; SiO ₂ dielectric layer-12; microelectrode array-13; polysilicon substrate-14; square transparent glass substrate-15.

Figure 3 and Figure 4 are schematic diagrams of optical switches that drive discrete droplets based on the principle of dielectric electrowetting.

Among them, Fig. 3 shows the total reflection of the light beam, that is, the "on" state of the optical switch; Fig. 4 shows the total transmission of the light beam, that is, the "off" state of the optical switch.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figure 1, the present invention provides an optical switch based on the dielectric electrowetting effect. The optical switch adopts a three-layer structure, the first layer is an upper plate, and the upper plate is made of a square transparent glass 1, a transparent electrode 2 and a hydrophobic film 3; the second layer is a square transparent glass layer 10, and a micro-channel 5 is opened along its diagonal, and there are controlled discrete electrolyte droplets 4 in the channel, whose refractive index matches that of the transparent glass. Four strip dielectric optical waveguides 6, 7, 8, 9 are opened on the same horizontal plane of the glass layer. The third layer is the lower plate, which is made of square transparent glass as the substrate 15, polysilicon as the substrate 14, phosphor-spreading and photolithography patterned micro-electrode array 13 on the substrate, and a layer of _SiO2 thermally oxidized on the electrode array. A layer of hydrophobic film 11 is applied as the medium layer 12 and on the medium layer. In the present invention, after the middle and lower transparent glass plates are bonded, a drop of electrolyte liquid drop 4 is injected into the micro-channel 5, and then the upper plate and the middle glass plate are bonded. The filling substance is air. The micro-electrode array 13 on the lower plate and the transparent electrode 2 on the upper plate are led to the positive and negative poles of the AC power supply 17 by lead wires 19 and 16 respectively. Since the droplet is driven by applying a voltage on a single microelectrode array, a four-control switch k18 is provided in the present invention to ensure that the droplet moves back and forth in the entire microfluidic channel.

The cross-sectional view of the three-layer structure dielectric electrowetting-driven optical switch shown in FIG. 2 . The realization of the optical switch "on" and "off" is based on the dielectric electrowetting actuation effect of discrete electrolyte droplets. Specifically, the present invention changes the wetting characteristics of the dielectric film and the surface liquid by applying a potential on the microelectrode array below the dielectric film, that is, by locally changing the three-phase contact angle between the liquid droplet and the solid surface (that is, in the gas, liquid , the angle between the tangent line of the gas-liquid interface and the solid-liquid boundary line at the intersection point of the solid three-phase), resulting in asymmetric deformation at both ends of the droplet, causing a pressure difference inside the droplet, and realizing the transmission of the droplet operation and control. The electrowetting effect designed in the present invention only occurs between the upper and lower plates and the discrete electrolyte droplets. Although there are contact angles between the side walls of the microchannel and the droplets, there are no electrodes on the two side walls, so it can be considered as a liquid The contact angle with the sidewall does not change during actuation. When the switch k is turned on, the shape of the droplet is distributed symmetrically, as shown in the dotted line in the figure, the contact angles between the droplet and the upper and lower plates are θ _t and θ ₀ respectively, ignoring the influence of gravity, the values are all hydrophobic surfaces The initial contact angle of ; when the switch k is closed, due to the electrowetting effect on the medium, the contact angle between the droplet and the right plate changes, as shown in the solid line in the figure. Since the hydrophobic layer of the upper plate is very thin, the capacitance of the upper hydrophobic layer is very large, and the partial voltage of the applied voltage is very small, so the contact angle θ _t on the upper plate hardly changes; while most of the applied voltage drops on the lower plate plate, so the contact angle between the droplet and the lower plate becomes significantly smaller, and its value θ _v can be approximately described by the Young-Lippmann equation.

θ ₀ is the initial contact angle when v=0, ε ₀ and ε _r are the dielectric constant of vacuum and the effective dielectric constant of the dielectric layer, respectively, and d is the effective thickness of the hydrophobic dielectric layer. γ _lg is the surface tension between the electrolyte droplet and the air. When a potential v is applied between the electrode and the discrete electrolyte droplet, it can be seen from the Young-Lippmann equation that the three-phase contact angle of the droplet varies with the absolute value of the applied potential v The value increases and becomes smaller, and it is related to the thickness and dielectric constant of the dielectric layer. It should be pointed out that when the applied voltage increases to a certain value, the contact angle becomes the minimum. If the applied potential is increased again, the contact angle will not change. This phenomenon is called contact angle saturation. Therefore, in order to avoid this phenomenon in the chip design process, the present invention proposes to drive with AC power.

In the present invention, due to the dielectric electrowetting effect, the three-phase contact angle of the droplet on the lower electrode on the right becomes smaller, resulting in asymmetric deformation of the droplet and an internal pressure difference. The relationship between the surface tension and the simplified expression of the pressure difference on both sides of the droplet can be deduced as:

Where D is the distance between the upper and lower plates, ε ₀ and ε _r are the dielectric constant of the vacuum and the effective dielectric constant of the dielectric layer, respectively, and d is the effective thickness of the hydrophobic dielectric layer.

Therefore, the present invention can change the three-phase contact angle on one side of the droplet by applying a potential difference v on the micro-electrode array on one side of the droplet to cause asymmetric deformation of the droplet and generate an internal pressure difference, thereby realizing the control of the droplet. operation and control.

The specific implementation of the optical switch of the present invention includes: the droplet is located between any two microelectrode arrays at the initial moment, when the switch k closes the microelectrode array on one side of the droplet, due to the electrowetting effect on the medium, three The phase contact angle becomes smaller, causing asymmetric deformation of the droplet and creating an internal pressure difference, which drives the droplet to move towards the side of the microelectrode array where the voltage is applied. Properly adjust the voltage, when the droplet moves to the position shown in Figure 3, when the light beam incident from the strip optical waveguide 6 reaches the solid-air interface of the microchannel in the square transparent glass, the light enters the optically thinner medium from the optically denser medium, And the angle of incidence is greater than the critical angle, all the beams are totally reflected and exit from the strip optical waveguide 7, which is the "on" state of the optical switch; when the droplet moves to the position shown in Figure 4, the incident beam from the strip optical waveguide 6 When reaching the solid-liquid interface of the microchannel in the square transparent glass, since the refractive index of the square transparent glass is the same as that of the liquid droplet, all light beams are transmitted into the strip optical waveguide 8 and then exit. This is the "off" state of the optical switch.

Claims (6)

1. An optical switch based on the dielectric electrowetting effect, characterized in that: the optical switch adopts a three-layer structure, the first layer is an upper pole plate, and the upper pole plate includes a square transparent glass (1), a transparent electrode (2) and a hydrophobic film (3), the second layer is a square transparent glass layer (10), along its diagonal there is a microchannel (5), and there are controlled discrete electrolyte droplets (4) in the channel, There are four strip-shaped dielectric optical waveguides (6, 7, 8, 9) on the same horizontal plane of the glass layer; the third layer is the lower pole plate, which includes a square transparent glass substrate (15), a polysilicon substrate ( 14), phosphorous expansion on the substrate and photolithography patterned micro-electrode array (13), a layer of _SiO2 thermally oxidized on the electrode array as a dielectric layer (12), a layer of hydrophobic film (11) is coated on the dielectric layer, and the bottom The plate microelectrode array (13) and the upper plate transparent electrode (2) are respectively led to positive and negative electrodes of an AC power supply (17) by lead wires (19, 16). 2. A kind of optical switch based on the dielectric electrowetting effect according to claim 1, characterized in that: said optical switch injects electrolyte solution into the microchannel (5) after bonding the middle and lower layers of transparent glass plates drop (4), and then bond the upper plate and the middle glass plate, and the droplet is clamped between the upper and lower plates. 3. The optical switch based on dielectric electrowetting effect according to claim 1, characterized in that: said optical switch is provided with a four-control switch k (18) to control the reciprocating movement of droplets in the micro-flow channel. 4. A kind of optical switch based on dielectric electrowetting effect according to claim 1, is characterized in that: expand phosphorus on polysilicon and photolithographic patterning forms microelectrode array (13), thermal oxidation layer on the electrode array _SiO2 is used as the dielectric layer (12), and the hydrophobic thin film layer (3, 11) for driving the switch is prepared by spin-coating Teflon AF1600, and the discrete electrolyte droplet is driven by an AC power source (17). 5. A kind of optical switch based on dielectric electrowetting effect according to claim 1, characterized in that: when the four-control switch k (18) closes the microelectrode array on a certain side of the droplet, the optical switch is properly adjusted The magnitude of the voltage changes the pressure difference on both sides of the droplet, thereby controlling the relative position of the droplet in the microchannel. 6. The optical switch based on dielectric electrowetting effect according to claim 1, characterized in that: the expression of the pressure difference on both sides of the droplet of the optical switch is: <mrow><mi>&amp;Delta;</mi><mi>P</mi><mo>=</mo><mfrac><mn>1</mn><mrow><mn>2</mn><mi>D</mi></mrow></mfrac><mfrac><mrow><msub><mi>&amp;epsiv;</mi><mn>0</mn></msub><msub><mi>&amp;epsiv;</mi><mi>r</mi></msub></mrow><mi>d</mi></mfrac><msup><mi>v</mi><mn>2</mn></msup></mrow> Where D is the distance between the upper and lower plates, ε ₀ and ε _r are the dielectric constant of the vacuum and the effective dielectric constant of the dielectric layer, respectively, d is the effective thickness of the hydrophobic dielectric layer, and v is the applied voltage.