CN100390584C - Temperature-controlled negative refractor based on liquid crystal - Google Patents

Abstract

The present invention discloses a temperature regulating optical frequency negative refraction device based on liquid crystal, which is composed of a polarizer, liquid crystal and optical glass. Firstly, the surface of the optical glass is treated with a light control orientation method by linear polarization ultraviolet radiation in a liquid crystal tilt angle treatment mode, and a double flat plate structure with 5 mu m to 200 mu m of spacing is formed by placing the treated optical glass to be opposite to an orientation surface. The liquid crystal is added in the double flat plate structure and is simultaneously placed at certain tilt angle. The polarizer is fixed to an upper surface of the optical glass in order to lead polarization direction of the polarizer to be parallel to an interface and be in the same plane with the tilt angle of liquid crystal molecules. The present invention is characterized in that incidence light on the device can be refracted, and refractive rays and incident rays are positioned at the same side of a normal line, name that a negative refraction phenomenon occurs. Performance of capability of regulating of negative refraction is realized by utilizing a characteristic that birefringence ratio of the liquid crystal molecules can be regulated according to temperature. The device has wide application prospects in the technical field of flat plate imaging.

Description

Temperature-controlled negative refractor based on liquid crystal

Technical field

The present invention relates to a kind of negative refraction device, particularly a kind of temperature adjusting optical frequency negative refraction device based on liquid crystal.

Background technology

In recent years, along with artificial cycle material, as the intensification of left-handed materials (left-handed metamaterials) and photonic crystal (photonic crystals) research, negative refraction also has been subjected to people's extensive concern.Negative refraction is a kind of people of running counter to physical phenomenons of optics general knowledge in the past.Theoretical prophesy negative refraction has great application prospect at optics and information science technology field, as breaking through diffraction limit imaging etc., is expected to and can brings new technological revolution for the information science technology field.

At present, negative refraction mainly is to realize by above-mentioned artificial cycle material.Yet, be subjected to the restriction of artificial cycle material physical properties and manufacturing process, adopt this mode to realize that negative refraction has following shortcoming: at first, service band concentrates on microwave region basically and response bandwidth is narrower; Secondly, material just can not be regulated and control once making its negative refraction behavior.In addition, infrared and negative refraction visible light wave range has brighter application prospect in fields such as radio communication, infotecies.Therefore, utilize artificial cycle material to realize that negative refraction has restricted its application and development to a great extent.

Liquid crystal be a kind of peculiar and gone into systematic study and the material fully realized, be 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, 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 the optic response behavior of liquid crystal sensitivity under different temperatures just, realizes regulatable optical frequency negative refraction.

Summary of the invention

The purpose of this invention is to provide a kind of temperature-controlled negative refractor based on liquid crystal.This device is made up of the polarizer, liquid crystal, temperature regulating device and optical glass, can make the light generation refraction incided on this device and refracted ray and incident ray be positioned at the homonymy of normal, and negative refraction promptly takes place.Utilize temperature the control characteristic of liquid crystal birefringence rate to be realized the Modulatory character of negative refraction.

At first optical glass surface being carried out liquid crystal pretilt angle handles, with containing cinnamic acid, cumarin with and material such as the macromolecule of derivatives group and photosensitive poly-phthalein amino acid, method by linear polarized uv radiation-induced liquid crystal aligning (being called for short " photo orientated ") is carried out surface treatment to optical glass, obtain the optical glass sheet that surface pretilt angle is handled, the alignment surfaces of the optical glass handled is relative, be bonded into two slab constructions of spacing L μ m spacing, in two slab constructions, add liquid crystal, and fix a polarizer above the optical glass up, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane.

It is described that optical glass surface is carried out the tilt angle that liquid crystal pretilt angle handles is 0～90 °.

Describedly optical glass is carried out the photo orientated method of surface-treated can realize the tilt angle size of control surface, and be a kind of untouchable method for alignment, so can avoid generation of static electricity and contamination by dust by regulating incident angle of light.Except that adopting above method, also can adopt the oblique evaporation method, Polyimide Langmuir-Blodgett Film alignment method etc. of SiOx film that optical glass is carried out the liquid crystal molecule tilt angle and handle.

The invention has the beneficial effects as follows and utilize the adjustable characteristic of liquid crystal molecular orientation parameter with temperature, promptly birefraction realizes the Modulatory character of negative refraction with the adjustable characteristic of temperature.In 80 ℃～160 ℃ temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-5.8 °, can realize adjustable negative refraction less than 8.4 ° light wave to incident angle.This device is with a wide range of applications in the flat panel imaging field.

Description of drawings

Fig. 1 is the temperature-controlled negative refractor based on liquid crystal.

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

Fig. 3 is the regulation and control curve of the negative refraction of original axial row type liquid crystal (4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate) with temperature.

Fig. 4 is that the maximum negative refraction angle of original axial row type liquid crystal (4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate) and the maximum incident angle that negative refraction takes place are with the variation of temperature relation curve.

Embodiment

The invention provides a kind of temperature-controlled negative refractor based on liquid crystal.In the structural representation of temperature-controlled negative refractor based on liquid crystal shown in Figure 1, this device by the polarizer 1, liquid crystal 3 and upper and lower two optical flats 2 and 4, ring encloses optical glass 5, temperature regulating device 6 is formed.The method by linear polarized uv radiation-induced liquid crystal aligning (be called for short " photo orientated ") is at first carried out liquid crystal pretilt angle to the conductive surface of optical glass 2 and 4 and is handled.Particularly, light-sensitive polyimide is dissolved in is made into 1% solution in the N-Methyl pyrrolidone solvent, rotation is coated on the optical glass conductive surface; With the above-mentioned optical glass of light-sensitive polyimide that scribbles at 150 ℃, toasted 5 hours, vertical irradiation 25 minutes under polarized ultraviolet then, obtain surface orientation and handle optical flat 2 and 4, the optical flat that two surface orientations were handled is bonded into two slab constructions that spacing L is the last optical flat 2 and the following optical flat 4 of 5 μ m ~ 200 μ m spacings according to surface orientation face opposing parallel, place ring therebetween and enclose optical glass 5, in two slab constructions, inject liquid crystal 3, and on last optical glass 2, fix a polarizer 1, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane.Can make the light generation refraction incided on this device and refracted ray and incident ray be positioned at the homonymy of normal, negative refraction promptly takes place; The core of this device is that the birefraction of liquid crystal varies with temperature and changes simultaneously, thereby its negative refraction behavior is subjected to temperature adjusting.Particularly, above-mentioned liquid-crystal apparatus is placed in the temperature regulating device 6,, thereby regulates the Modulatory character that the liquid crystal birefraction realizes negative refraction by the temperature of adjusting temperature regulating device 6.

The present invention realizes according to following technical scheme:

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 is incident on uniaxial crystal (optical axis and interface the are at an angle) interface at a certain angle, refract light S ₃With incident light S ₁The refract light that may be positioned at the homonymy of interface normal is refract light S ₂, negative refraction promptly takes place.Liquid crystal 3 is a kind of special crystalline materials that rely 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 temperature adjustable characteristic of negative refraction by changing temperature.

Consider situation as shown in Figure 2, incident light S ₁Become the linearly polarized light that the polarization direction is positioned at the principal section behind the polarizer 1, 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 OA (being optical axis) becomes ∠ TOA=γ with interface T, so e light phase velocity and group velocity direction and interface 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 ₁?sinθ ₁＝n _e(α)sinθ _p ……(1)

Wherein, the phase refractive index is

$n_e\left(\mathrm{\&alpha;}\right)=\frac{n_o{n}_e}{{(n_o^2{\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">sin</figure-callout>}}^2\mathrm{\&alpha;}+{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">n</figure-callout>}}_e^{}{\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">cos</figure-callout>}}^2\mathrm{\&alpha;})}^{1/2}}\&CenterDot;\&CenterDot;\&CenterDot;\left(2\right)$

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:

$\mathrm{\&Omega;}=\mathrm{ac}\tan \left((1-\frac{n_o^2}{n_e^2})\frac{\tan \mathrm{\&alpha;}}{(1+\frac{n_o^2}{{\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">n</figure-callout>}}_e^{}}{\mathrm{<figure-callout\; id="2"\; label="tan"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">tan</figure-callout>}}^2\mathrm{\&alpha;})}\right)\&CenterDot;\&CenterDot;\&CenterDot;\left(3\right)$

According to above-mentioned relation formula (1) ~ (3) as can be known, when liquid crystal optic axis OA and the angled γ of interface T, incident light S ₁Refract light S ₃May with incident light S ₁The homonymy that is positioned at interface normal is refract light S ₂, negative refraction promptly takes place.

For nematic crystal, its o light (ordinary light) and e light (non-ordinary light) refractive index and molecular polarization anisotropy and orientation vow that the pass of parameter S is:

$\frac{n_e^2-n_o^2}{{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">n</figure-callout>}}^2+2}=\frac{\mathrm{\&rho;}\&CenterDot;N_A\&CenterDot;({\mathrm{\&alpha;}}_l-{\mathrm{\&alpha;}}_t)\&CenterDot;\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">S</figure-callout>}}{{3\mathrm{M\&epsiv;}}_0}\&CenterDot;\&CenterDot;\&CenterDot;\left(4\right)$

In the following formula $n^{}$ ${}^2=({\mathrm{<figure-callout\; id="2"\; label="n\; e"\; filenames="C20061008940400101.png"\; state="\{\{state\}\}">n</figure-callout>}}_e^{}+{2n}_o^2)/3,$ ρ is a liquid crystal density, N _ABe the Avogadro constant, S vows parameter, M molecular mass, ε for orientation ₀Be permittivity of vacuum, α _lAnd α _tBe respectively the polarizability of branch vertical and horizontal.

By (4) formula as can be known, the size of liquid crystal birefringence rate is vowed reducing of parameter S and liquid crystal density p with orientation and is reduced.In addition, because orientation vows that parameter S and density p all reduce with the rising of temperature, keeps constant and the o optical index is basic under different temperatures, so the e optical index will reduce with the rising of temperature, thereby negative refraction reduces with temperature rising dullness, has realized the regulation and control of temperature to negative refraction.

Therefore, at first optical glass surface being carried out liquid crystal pretilt angle handles.With contain cinnamic acid, cumarin with and material such as the macromolecule of derivatives group and photosensitive poly-phthalein amino acid, method by linear polarized uv radiation-induced liquid crystal aligning (being called for short " photo orientated ") is handled optical glass surface, thereby realizes certain tilt angle when adding liquid crystal.This method can realize the tilt angle size of control surface by regulating incident angle of light, and is a kind of untouchable method for alignment, so can avoid generation of static electricity and contamination by dust.Except that adopting above method, also can adopt the oblique evaporation method, Polyimide Langmuir-Blodgett Film alignment method etc. of SiOx film that optical glass is carried out the liquid crystal molecule tilt angle and handle.

The alignment surfaces of the optical glass of above-mentioned processing is relative, form two slab constructions with 5 μ m ~ 200 μ m spacings.Fix a polarizer in optical glass top surface, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane.

Next nematic crystal is injected two slab constructions that above-mentioned optical glass constitutes.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 pretilt alignment effect of optical glass surface, the liquid crystal molecule is arranged along the tilt angle direction between this moment pole plate, so angulation equals the size of tilt angle between liquid crystal optic axis and the optical glass.

The two slab constructions that said fixing had the polarizer and inject nematic crystal are placed among the temperature regulating device.This temperature regulating device must meet the following conditions: at first, its temperature-controlled precision should reach ± and 0.1 ℃; Secondly, this temperature regulating device should leave incident light and emergent light passage.

Make light wave be incident to the interface of optical glass and liquid crystal, thereby realize that by regulating temperature regulating device temperature variation changes the birefraction of liquid crystal, realizes regulatable optical frequency negative refraction through the polarizer.

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

Embodiment one:

By linear polarized uv radiation-induced liquid crystal aligning method the conductive surface of optical flat 2 and 4 being carried out liquid crystal pretilt angle handles.Particularly, light-sensitive polyimide is dissolved in is made into 1% solution in the N-Methyl pyrrolidone solvent, rotation is coated on the optical glass conductive surface; The above-mentioned optical glass that scribbles light-sensitive polyimide at 150 ℃, was toasted 5 hours, and vertical irradiation 25 minutes under polarized ultraviolet then obtains the optical flat 2 and 4 of 30 ° tilt angle.Above-mentioned optical glass alignment surfaces is relative, be bonded into two slab constructions of spacing 50 μ m, ring encloses optical glass and is placed between two slab constructions.Fix a polarizer in optical glass top surface, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane.

Inject single shaft nematic crystal (4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate) between two optical glass, the refractive index of its o light (ordinary light) and e light (non-ordinary light) is closed with variation of temperature and is:

Through the polarizer and with the light wave of 5 ° of angle incidents, light refraction angle with the variation of temperature relation curve as shown in Figure 3.As can be seen, in 80 ℃～160 ℃ temperature range, can obtain continuously adjustable negative refraction, and its negative refraction angle absolute value reduces with the temperature rising.Maximum incident angle when Fig. 4 has provided maximum negative refraction angle and negative refraction takes place is with the variation of temperature relation curve.In 80 ℃～160 ℃ temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-5.8 ° as can be seen; Simultaneously, this liquid crystal negative refraction device can be realized adjustable negative refraction less than 8.4 ° light wave to incident angle.

Embodiment two

With embodiment one, carrying out liquid crystal pretilt angle by linear polarized uv radiation-induced liquid crystal aligning method handles, obtain the optical flat 2 and 4 of 10 ° tilt angle, be bonded into two slab constructions of spacing 10 μ m, and between two optical glass, inject single shaft nematic crystal (4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate).Through the polarizer and with the light wave of 5 ° of angle incidents, in 100 ℃～140 ℃ temperature range, can obtain continuously adjustable negative refraction.In this temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-3.2 °; Simultaneously, this liquid crystal negative refraction device can be realized adjustable negative refraction less than 3.7 ° light wave to incident angle.

Embodiment three

With embodiment one, carrying out liquid crystal pretilt angle by linear polarized uv radiation-induced liquid crystal aligning method handles, obtain the optical flat 2 and 4 of 70 ° tilt angle, be bonded into two slab constructions of spacing 180 μ m, and between two optical glass, inject single shaft nematic crystal (4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate).Through the polarizer and with the light wave of 5 ° of angle incidents, in 70 ℃～150 ℃ temperature range, can obtain continuously adjustable negative refraction.In this temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-5.3 °; Simultaneously, this liquid crystal negative refraction device can be realized adjustable negative refraction less than 4.9 ° light wave to incident angle.

Claims (2)

1. temperature-controlled negative refractor based on liquid crystal, this device is by the polarizer, on liquid crystal reaches, following two optical flats, ring encloses optical glass, temperature regulating device is formed, it is characterized in that, method by linear polarized uv radiation-induced liquid crystal aligning, to last, the conductive surface of following two optical flats carries out liquid crystal pretilt angle to be handled, light-sensitive polyimide is dissolved in is made into 1% solution in the N-Methyl pyrrolidone solvent, rotation is coated on the optical flat conductive surface, with the above-mentioned optical flat of light-sensitive polyimide that scribbles at 150 ℃, toasted 5 hours, vertical irradiation 25 minutes under polarized ultraviolet then, obtain the optical flat of 10 ° tilt angle, the optical flat that two surface orientations were handled is bonded into two slab constructions of last optical flat He the following optical flat of spacing 10 μ m according to surface orientation face opposing parallel, place ring therebetween and enclose optical glass, in two slab constructions, inject single shaft nematic crystal 4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate, and on last optical flat, fix a polarizer, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane, through the light wave of the polarizer with 5 ° of angle incidents, in 100 ℃～140 ℃ temperature range, can obtain continuously adjustable negative refraction, in this temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-3.2 °, simultaneously, this liquid crystal negative refraction device can be realized adjustable negative refraction less than 3.7 ° light wave to incident angle.

2. temperature-controlled negative refractor based on liquid crystal, this device is by the polarizer, on liquid crystal reaches, following two optical flats, ring encloses optical glass, temperature regulating device is formed, it is characterized in that, method by linear polarized uv radiation-induced liquid crystal aligning, to last, the conductive surface of following two optical flats carries out liquid crystal pretilt angle to be handled, light-sensitive polyimide is dissolved in is made into 1% solution in the N-Methyl pyrrolidone solvent, rotation is coated on the optical flat conductive surface, with the above-mentioned optical flat of light-sensitive polyimide that scribbles at 150 ℃, toasted 5 hours, vertical irradiation 25 minutes under polarized ultraviolet then, obtain the optical flat of 70 ° tilt angle, the optical flat that two surface orientations were handled is bonded into two slab constructions of last optical flat He the following optical flat of spacing 180 μ m according to surface orientation face opposing parallel, place ring therebetween and enclose optical glass, in two slab constructions, inject single shaft nematic crystal 4-n-butylphenyl-4-(4-n-butylbenzoyloxy) benzoate, and on last optical flat, fix a polarizer, make its polarization direction be parallel to the interface and with the tilt angle of liquid crystal molecule in same plane, through the light wave of the polarizer with 5 ° of angle incidents, in 70 ℃～150 ℃ temperature range, can obtain continuously adjustable negative refraction, in this temperature range, the maximum negative refraction angle that the liquid crystal negative refraction device can be realized is-5.3 °, simultaneously, this liquid crystal negative refraction device can be realized adjustable negative refraction less than 4.9 ° light wave to incident angle.

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