CN1866064A - Electric field controlled negative refractor based on liquid crystal - Google Patents

Abstract

The disclosed electric field control light frequency negative refraction device, which comprises a polarizer, a LC, an electrode, and optical glass, is prepared as: coating polyimide on conductive surface of glass plate to solidify and form film, using fiber for orientated friction to obtain the conductive glass with LC molecule orientated along surface; parallel sticking two glass plated with fiction surface opposite to form parallel electrode structure with mum-level distance; fixing a polarizer above the upper electrode, and injecting LC into middle of electrodes. This invention shows negative refraction angle from -4.1deg to 0deg at 1.0-2.8V external voltage.

Description

Electric field controlled negative refractor based on liquid crystal

Technical field

The present invention relates to a kind of negative refraction device, particularly a kind of electric field regulation and control optical frequency negative refraction device based on liquid crystal.

Background technology

Negative refraction is a kind of peculiar physical phenomenon that receives much attention in recent years, it has unusual physics and optical characteristics theoretical prophesy, as unusual Doppler effect, unusual Cherenkov radiation, breakthrough diffraction limit imaging and perfect lens effect etc., be with a wide range of applications at optics and information science technology field.At present, utilize left-handed materials (left-handed metamaterials) and photonic crystal artificial periodic structure materials such as (photonic crystals) to realize negative refraction, its negative refraction frequency range mainly concentrates on microwave region and the response frequency range is narrower.Infrared and the realization visible light wave range negative refraction has more importantly meaning, but is subjected to present stage micro-processing technology and the restriction of metal construction unit material characteristic, realizes also difficulty comparatively of artificial periodic structure material such as this frequency band left-hand material and photonic crystal.In addition, the negative refraction behavior in the existing artificial periodic structure material is unadjustable, has limited its practical application.

Liquid crystal is a kind of peculiar and by people's systematic study and the material fully realized, has been widely applied to many new technical fields.Its key property is a molecules align and firm unlike crystal structure, be subjected to the influence of outside stimuluss such as electric field, magnetic field, temperature and stress easily, thereby optical property changes.The molecules align that this acting force of liquid crystal is faint, the basis of its numerous optical application just.The present invention utilizes liquid crystal good optical respondent behavior under electric field action just, realizes regulatable optical frequency negative refraction.

Summary of the invention

The purpose of this invention is to provide a kind of electric field controlled negative refractor based on liquid crystal.This device is made up of the polarizer, liquid crystal, electrode and optical glass, and the light that incides on this device is reflected, and refracted ray and incident ray be positioned at the homonymy of normal, and negative refraction promptly takes place.Utilize external electric field that liquid crystal molecular orientation is regulated, realize the Modulatory character of negative refraction.

The structure and the making of described electric field controlled negative refractor based on liquid crystal, it specifically is conducting surface coating polyimide (PI) at oxidation steel tin (ITO) electro-conductive glass, and make it film-forming 80 ℃ ~ 240 ℃ bakings, reprocess fibre carries out the orientation friction, obtains making the electro-conductive glass of liquid crystal molecule along surface orientation.Two electro-conductive glass that above-mentioned friction is orientated, attrition surface relatively and be orientated the parallel parallel electrode structure that is bonded into spacing L μ m, at the known polarizer in top electrode upper fixed polarization direction, and make it play folk prescription to consistent with the direction of electro-conductive glass friction orientation; Single shaft nematic (E7) liquid crystal is injected between two electrodes, and liquid crystal molecule issues to give birth at outer field action and rotates.

The invention has the beneficial effects as follows and utilize external electric field to regulate the Modulatory character that liquid crystal molecular orientation is realized negative refraction, the light that incides on this device is reflected, and refracted ray and incident ray be positioned at the homonymy of normal, negative refraction promptly takes place.The test shows of designed device, when impressed voltage was 1.0V～2.8V, the negative refraction angle can change to 0 ° by-4.1 °.This device is with a wide range of applications in the flat panel imaging field.

Description of drawings

Fig. 1 is based on the electric field controlled negative refractor of liquid crystal.

The synoptic diagram of negative refraction takes place in the linearly polarized light that Fig. 2 electric field direction of vibration is positioned at the principal section when inciding transparency electrode with positive single shaft liquid crystal interface.OB and OC represent the direction of group velocity and phase velocity respectively.

Fig. 3 original axial row type liquid-crystal refractive-index ellipsoid and group's refraction and the synoptic diagram that reflects mutually with the external electric field variation.S and k represent the direction of group velocity and phase velocity respectively.

The negative refraction of Fig. 4 original axial row type liquid crystal (E7) negative refraction device is with the regulation and control curve of electric field.

The maximum incident angle of the maximum negative refraction angle of Fig. 5 original axial row type liquid crystal (E7) negative refraction device and generation negative refraction is with the regulation and control curve of electric field.

Embodiment

The invention provides a kind of electric field controlled negative refractor based on liquid crystal.This device is made up of the polarizer, liquid crystal, electrode and optical glass, and the light that incides on this device is reflected, and refracted ray and incident ray be positioned at the homonymy of normal, and negative refraction promptly takes place.Utilize external electric field that liquid crystal molecular orientation is regulated, realize the Modulatory character of negative refraction.

The structure of described electric field controlled negative refractor based on liquid crystal as shown in Figure 1, specifically be to make it film-forming at the conducting surface coating polyimide (PI) of tin indium oxide (ITO) conductive glass plate and 80 ℃ ~ 240 ℃ bakings, reprocess fibre carries out the orientation friction, obtains making the electro-conductive glass of liquid crystal molecule along surface orientation.With two electro-conductive glass that above-mentioned friction is orientated, attrition surface relatively and be orientated the parallel electrode structure of the parallel top electrode 2 that is bonded into spacing L μ m and bottom electrode 5; At the known polarizer 1 in top electrode 2 upper fixed polarization directions, and make it play folk prescription to consistent with the direction of electro-conductive glass friction orientation.Single shaft nematic (E7) liquid crystal 3 is injected between two electrodes, surrounded by optical glass 4 around the liquid crystal 3, liquid crystal molecule will rotate under the V effect of outfield.

The present invention realizes according to following technical scheme:

The present invention is a kind of electric field controlled negative refractor based on liquid crystal, and its core is that liquid crystal molecular orientation rotates with applying electric field, thereby its negative refraction behavior is subjected to the electric field regulation and control.

When light beam incides uniaxial crystal by isotropic medium, usually birefringence can take place.When the light beam that is positioned at the principal section when the polarization direction was incident on uniaxial crystal (optical axis and interface the are at an angle) interface at a certain angle, refracted ray and incident ray may be positioned at the homonymy of interface normal, and negative refraction promptly takes place.Liquid crystal is a kind of special crystalline material that relies on faint acting force to realize the molecular assembly arrangement.The anisotropy optics character and the ordinary optical crystal of liquid crystal are similar, and its molecular axis orientation is optical axis direction.Therefore, when liquid crystal molecule axle and interface were angled, the light with certain polarization characteristic can be realized negative refraction.Be easy to be subjected to the influence of outfield (as: electric field, magnetic field, temperature and stress field etc.) again owing to the optical property of liquid crystal, thereby can regulate its optical property, and then realize the adjustable characteristic of electric field of negative refraction by changing the outfield.

Consider situation as shown in Figure 2, incident light becomes the linearly polarized light that the polarization direction is positioned at the principal section behind the polarizer, and linearly polarized light incides isotropic material and positive single shaft liquid crystal (n then ₀＜n _o＜n _e) on the interface, OC, OB represent e light phase velocity direction and e light group velocity direction respectively.Liquid crystal molecular orientation (being optical axis) becomes ∠ TOA=γ with the interface, so e light phase velocity and group velocity direction and interface normal angle are respectively ∠ NOC=θ _pWith ∠ NOB=θ _g, e light phase velocity and optical axis included angle are ∠ AOC=α.

Then, the Si Nieer theorem is satisfied in refraction mutually:

n ₁sinθ ₁＝n _e(α)sinθ _p ……(1)

Wherein, the phase refractive index is

$n_e\left(\mathrm{\&alpha;}\right)=\frac{n_o{n}_e}{{(n_o^2{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="A20061008940500091.png,A20061008940500101.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&alpha;}+{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="A20061008940500091.png,A20061008940500101.png"\; state="\{\{state\}\}">n</figure-callout>}}_e^{}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="A20061008940500091.png,A20061008940500101.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&alpha;})}^{1/2}}---\left(2\right)$

Because the optical anisotropy of liquid crystal makes that the direction of e light phase velocity and group velocity is inconsistent, fleet angle is called walk-off angle Ω=alpha-beta=∠ AOC-∠ AOB between them, can be expressed as:

$\mathrm{\&Omega;}=\mathrm{ac}\tan \left((1-\frac{n_o^2}{n_e^2})\frac{\tan \mathrm{\&alpha;}}{(1+\frac{n_o^2}{{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="A20061008940500091.png,A20061008940500101.png"\; state="\{\{state\}\}">n</figure-callout>}}_e^{}}{\mathrm{<figure-callout\; id="2"\; label="tan"\; filenames="A20061008940500091.png,A20061008940500101.png"\; state="\{\{state\}\}">tan</figure-callout>}}^2\mathrm{\&alpha;})}\right)---\left(3\right)$

According to above-mentioned relation formula (1) ~ (3) as can be known, when liquid crystal optic axis and the angled γ in interface, the refracted ray of incident ray may be positioned at the homonymy of interface normal with incident ray, and negative refraction promptly takes place.

For nematic crystal, its middle layer molecular orientation and interface angle  are the functions of on-load voltage between pole plate (electric field), shown in figure (3).Specifically can describe by following formula:

$U/U_S=\frac{2}{\mathrm{\&pi;}}{(1+\mathrm{v\&eta;})}^{1/2}{\&Integral;}_0^{\mathrm{\&pi;}/2}{(G_k/G_v{G}_{-1})}^{1/2}\mathrm{dx}---\left(4\right)$

U _S＝π(4πK ₁₁/|Δε|) ^1/2

G _i＝1+iηsin ²x(i＝k，v，-1)

Wherein, k=K ₃₃/ K ₁₁-1, v=(ε _/// ε _⊥)-1, η=sin ², K ₃₃/ K ₁₁Be the elasticity coefficient ratio of liquid crystal molecule, ε _//And ε _⊥Be respectively parallel and the specific inductive capacity perpendicular molecules axle.

And n _e(z) variation relation with middle layer molecular orientation and interface angle  is:

Can clearly be seen that by formula (1)～(5) applying under the condition of external electric field, liquid crystal molecular orientation will turn to the direction parallel with external electric field gradually with the increase of external electric field; Simultaneously, the index ellipsoid of liquid crystal will rotate, thereby realize the regulatable negative refraction of electric field.

Therefore, at first processing can make electro-conductive glass or other transparent electrode material of liquid crystal molecule along surface orientation.Inside surface at conductive glass plate is coated with one deck macromolecular material and makes it film-forming at a certain temperature.By by y direction of principal axis among Fig. 1 film being carried out rubbing with materials such as nylon, fiber or velveteens, fricative fine groove or cut can make liquid crystal molecule be orientated along frictional direction.The method that after adopting the macromolecular material film forming, rubs, also can adopt oblique evaporation method, polarization laser or ultraviolet radiation polymer surfaces molecular orientation method, the Polyimide Langmuir-Blodgett Film alignment method etc. of SiOx film to obtain to make electro-conductive glass or other electrode material of liquid crystal molecule along surface orientation.

The alignment surfaces of the transparent electrode plate of above-mentioned processing is relative, form the electrode structure of 5 μ m ~ 200 μ m polar plate spacings.Fixed folk prescription to the polarizer consistent in upper electrode surface with the electrode orientation direction.

Then, nematic crystal is injected between the above-mentioned battery lead plate.Because the liquid crystal negative refraction is directly proportional with the liquid crystal material birefraction, so locate to select for use birefraction greater than 0.1 liquid crystal material.Because the orientation effect of electrode plate surface, the liquid crystal molecule is arranged along the pole plate direction of orientation between pole plate at this moment, so the optical axis of liquid crystal is parallel with battery lead plate.

So, when light wave when the polarizer is incident to the interface of transparency electrode and liquid crystal, make liquid crystal molecule rotate to different directions by the voltage that changes between pole plate, and then change its effective refractive index, thereby realize regulatable optical frequency negative refraction.

The performance of implementation procedure of the present invention and material is by embodiment and description of drawings:

Embodiment one:

By shown in Figure 1, based on the structural representation of the electric field controlled negative refractor of liquid crystal.With the electro-conductive glass attrition surface of friction orientation relatively and be orientated the parallel electrode structure of the parallel top electrode 2 that is bonded into spacing L=40 μ m and bottom electrode 5; At the known polarizer 1 in top electrode 2 upper fixed polarization directions, and make it play folk prescription to consistent with the direction of electro-conductive glass friction orientation.Single shaft nematic (E7) liquid crystal 3 is injected the space that is surrounded by optical glass 4 between two electrodes, and liquid crystal molecule will rotate under the V effect of outfield, and the alive relation of its angle of orientation ∠ TOA=γ and institute as shown in Figure 3.As incident light S ₁With θ ₁During=5 ° incident, refract light S ₂With the variation relation curve of impressed voltage as shown in Figure 4.As can be seen, the external voltage that applies 1.0V～2.8V can obtain continuously adjustable group velocity negative refraction, and its negative refraction angle ∠ NOB=θ _gAbsolute value increases afterwards earlier with external electric field and reduces, and reaches maximal value during for 1.5V at external voltage.When the voltage that is applied during less than 1.0V or greater than 2.8V, incident light S ₁Modulation obtains positive group's refraction through device.As seen, has only incident light S ₁Incident ray and extra electric field negative refraction could appear when satisfying certain condition.Maximum incident angle when Fig. 5 has provided maximum negative refraction angle and negative refraction takes place is with the variation characteristic of external voltage.As seen, when impressed voltage was 0.8V～3.3V, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized was-1 °～-7 °, and maximum incident angle is 1.5 °～11 °.

Embodiment two

With embodiment one, the result that the bonding spacing L=10 μ m of top electrode and bottom electrode obtains: as incident light S ₁With θ ₁=7 ° of incidents, the external voltage that applies 0.6V～1.1V can obtain continuously adjustable group velocity negative refraction, reaches maximal value when external voltage 0.9V.When impressed voltage was 0.2V～1.5V, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized was-1 °～-7 °, and maximum incident angle is 1.5 °～11 °.

Embodiment three

With embodiment one, the result that the bonding spacing L=100 μ m of top electrode and bottom electrode obtains: as incident light S ₁With θ ₁=4 ° of incidents, the external voltage that applies 2.0V～6.4V can obtain continuously adjustable group velocity negative refraction, reaches maximal value when external voltage 3.6V.When impressed voltage was 1.5V～8.0V, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized was-1 °～-7 °, and maximum incident angle is 1.5 °～11 °.

Embodiment four

With embodiment one, the result that the bonding spacing L=200 μ m of top electrode and bottom electrode obtains: as incident light S ₁With θ ₁=5 ° of incidents, the external voltage that applies 5.4V～14.7V can obtain continuously adjustable group velocity negative refraction, reaches maximal value when external voltage 0.6V.When impressed voltage was 5.0V～15.2V, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized was-1 °～-7 °, and maximum incident angle is 1.5 °～11 °.

Claims (6)

1. electric field controlled negative refractor based on liquid crystal, this device is by the polarizer, liquid crystal, electrode and optical glass are formed, it is characterized in that, described electric field controlled negative refractor based on liquid crystal is at first transparent conductive glass surface to be carried out liquid crystal molecular orientation to handle, obtain to make the transparent conductive glass plate of liquid crystal molecule along surface orientation as electrode, two electro-conductive glass that above-mentioned friction is orientated, attrition surface relatively and be orientated the parallel parallel electrode structure that is bonded into spacing L μ m, liquid crystal is injected the space that optical glass surrounds between two electrodes, at the known polarizer in top electrode upper fixed polarization direction, and make it play folk prescription to consistent with the direction of electro-conductive glass friction orientation, liquid crystal molecule issues to give birth at outer field action and rotates, the light that incides on this device is reflected, and refracted ray and incident ray are positioned at the homonymy of normal, negative refraction promptly taking place, utilize external electric field that liquid crystal molecular orientation is regulated, realizes the Modulatory character of negative refraction.

2. according to claim 1 based on the electric field controlled negative refractor of liquid crystal, it is characterized in that the polarization direction of the polarizer is parallel with electrode.

3. according to claim 1 based on the electric field controlled negative refractor of liquid crystal, it is characterized in that liquid crystal is a birefraction greater than 0.1 single shaft nematic liquid crystal E7.

4. according to claim 1 based on the electric field controlled negative refractor of liquid crystal, it is characterized in that on the conductive glass plate surface as electrode it being the tin indium oxide ITO that handles through surperficial liquid crystal molecular orientation, two electrode separation L are 5 μ m～200 μ m.

5. according to claim 1 based on the electric field controlled negative refractor of liquid crystal, it is characterized in that two electrode surfaces that contact with liquid crystal will be orientated friction, and its orientation frictional direction is parallel with the polarization direction of the polarizer.

6. according to claim 1 based on the electric field controlled negative refractor of liquid crystal, it is characterized in that additional power source is direct current or interchange, voltage is 0.1～50V.

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