CN1749810A - Chiral liquid crystal depolarizer and its preparing method - Google Patents

Abstract

The invention provides a chiral liquid crystal depolarizer and a preparation method thereof. The chiral liquid crystal depolarizer comprises optical transparent materials (1, 2), wherein a wedge-shaped or trapezoid groove array is processed on the optical transparent material (2), and is coated to form orientation films (3, 5), and the chiral liquid crystal is induced to self-organize into a structure with crystal characteristics; the optical transparent materials (1 and 2) are jointed to form a liquid crystal box with a wedge-shaped or trapezoidal cavity, and a mixture (6) consisting of chiral molecules with optical rotation property and liquid crystal with birefringence property is filled in the liquid crystal box. When the chiral liquid crystal depolarizer is in a single wedge structure, the chiral liquid crystal depolarizer also comprises a gasket (4) for controlling the wedge angle. The chiral liquid crystal depolarizer has the characteristics of both a wedge-shaped crystal depolarizer and an optical crystal depolarizer, can realize monochromatic light depolarization in a wide spectral range, and has a good depolarization effect on incident polarized light in any direction. The invention has simple manufacturing process and greatly reduced cost, and has more obvious advantage of depolarization of large-caliber light beams.

Description

Chiral liquid crystal depolarizer and preparation method thereof

Technical field

The invention belongs to the device or the device field of control light polarization, be specifically related to a kind of chiral liquid crystal depolarizer and preparation method thereof.

Background technology

The light of propagating in media such as optical fiber, atmosphere or sea, its polarization characteristic can great changes will take place.How controlling or eliminate because of polarization state changes the influence that brings, is the problem that numerous technical fields such as light laser, high precision spectroradiometric measurement, space optical remote, optical communication are paid close attention to.The scholar of country such as the U.S. is more in the applied research of aspects such as remote sensor, light laser to the depolarization device, and is applied in remote sensors such as CZCS, EAWIFS, MODIS2N, MERIS.

Depolarizer commonly used at present mainly is to utilize crystal dichroism, after being incident light process dichroism crystal, because each wavelength has different bit phase delays, produced the elliptically polarized light of different ellipse inclined to one side rates, outgoing beam is combined by the polarized radiation of multiple polarization state, and the result makes emergent light near unpolarized.Change, control the transmission direction of light by the optical property that changes the medium in the optical device.Wherein, cumeat depolarizer and quartzy optically-active depolarizer are comparatively commonly used.

The cumeat depolarizer is a bevel wedge shape, optical axis direction is parallel with logical light face, plane of incidence polarized light direction of vibration should with optical axis of crystal direction angle at 45, because of the thickness of device in continuous variation, transmitted beam has comprised by the space superposition from circular polarization, elliptic polarization to the microbeam of the multiple polarization situation of linear polarization, thereby plays the effect of depolarization.The cumeat depolarizer has strict requirement to the polarization of incident light direction, and its application is subject to many limitations, and the light beam deflection phenomenon is arranged, and crystal wedge processing difficulties, and bigbore crystal wedge is very expensive.

Quartzy optically-active depolarizer is formed two prism equal and opposite in directions, structure angle unanimity according to the compound depolarizer of the optical activity development of quartz crystal by left-handed and dextrorotation two parts quartz prism.Polarized light transmits along optical axis direction, and the different parts in the logical light face different thickness with correspondence, and the angle of revolving is also different, and outgoing beam will be the depolarization light beam of a branch of mixing superposition.Quartzy optically-active depolarizer is very responsive to the incident light polarization direction, in case the incident light polarization direction changes, the depolarization effect just is subjected to very big influence.

United States Patent (USP) U.S.Appl.NO.097471, U.S.Appl.NO.256785 adopt the method for beam split phase delay to realize depolarization, comprise that beam splitting waits accurate device with synthetic, but complex structure are with high costs.

Summary of the invention

A kind of chiral liquid crystal depolarizer and preparation method thereof is provided on the technical problem to be solved in the present invention.

Chiral liquid crystal depolarizer of the present invention be a kind of can control or eliminate because of polarization state changes do not rely on polarization of incident light attitude and polarization direction when bringing adverse effect, depolarization, be easy to make, cost is lower, the optics depolarizer of excellent performance.

A kind of chiral liquid crystal depolarizer of the present invention contains two kinds of optically transparent materials, and one of optically transparent material is provided with wedge shape or dovetail groove array therein; Two kinds of optically transparent materials are fitted and are formed the liquid crystal cell with wedge shape or ladder cavity, be provided with the alignment films that forms by polyimide solution in the liquid crystal cell, and being perfused with the potpourri that chiral molecules with polarimetry nature and the liquid crystal with birefringent characteristic are formed, it is the structure of crystal characteristic that alignment films is induced the chiral liquid crystal self-organization.

Chiral liquid crystal depolarizer of the present invention can also optically transparent material be provided with the cavity liquid crystal cell of single wedge structure, is provided with the pad of control angle of wedge size at the big end of the cavity liquid crystal cell of single wedge structure.

Consisting of of the potpourri of chiral molecules that chiral liquid crystal depolarizer adopts and liquid crystal composition with birefringent characteristic with polarimetry nature:

Liquid crystal (Δ n value is 0.07～0.35) mass percent is 65%～95%

The chiral molecules mass percent is 35%～5%.

The alignment film rubbing direction of chiral liquid crystal depolarizer of the present invention is parallel to each other.

The preparation method of a kind of chiral liquid crystal depolarizer of the present invention comprises following content:

A) optically transparent material is cut into the required size shape, and carry out edging;

B) utilize supersonic wave cleaning machine that transparent material is cleaned;

C) (1000 grades) dried 30～40 minutes under 110 ℃ of cleaning conditions;

D) applying concentration on optically transparent material is 4% polyimide solution, in the alignment films that forms on the optically transparent material after the cleaning about 100nm;

E) carrying out precuring earlier in the baking box of 70 ℃～80 ℃ of temperature, is formally to solidify under 180 ℃～200 ℃ in temperature again;

F) alignment films is carried out friction treatment;

G) the optically transparent material contraposition that will handle is fitted, perfusion chiral liquid crystal, edge sealing.

The preparation method of a kind of chiral liquid crystal depolarizer of the present invention, can also adopt the following content preparation:

A) optically transparent material is cut into the required size shape, and carry out edging;

B) utilize supersonic wave cleaning machine that optically transparent material is cleaned;

C) (1000 grades) dried 30-40 minute under 110 ℃ of cleaning conditions;

D) applying concentration on optically transparent material is 4% polyimide solution, in the alignment films that forms on the optically transparent material after the cleaning about 100nm;

E) carrying out precuring earlier in the baking box of 70 ℃～80 ℃ of temperature, is formally to solidify under 180 ℃～200 ℃ in temperature again;

F) alignment films is carried out friction treatment;

G) the optically transparent material contraposition that will handle is fitted, and uses pad to control the angle of wedge, perfusion chiral liquid crystal, edge sealing.

Chiral liquid crystal depolarizer of the present invention comprises the liquid crystal cell with space geometry structure, liquid crystal cell is perfused with the potpourri (abbreviation chiral liquid crystal) of chiral molecules and liquid crystal composition, the interface of liquid crystal and liquid crystal cell is an alignment films, and it is the institutional framework that crystal characteristic is arranged that alignment films can be induced the interior chiral liquid crystal self-organization of liquid crystal cell.Chiral liquid crystal is only thick less than the box of 100 μ m, under the inducing of alignment films, just has crystal characteristic preferably, increase with bore, the wedge shape height also increases, just need be designed to array structure after surpassing 100 μ m, this bigbore chiral liquid crystal depolarizer is applied to the beam diameter greater than 5mm usually.When the small-bore chiral liquid crystal depolarizer that is applied to less than the 5mm beam diameter does not need complicated spatial structure, can form the wedge shape box by optically transparent material up and down, control the angle of wedge of depolarizer with pad, perfusion chiral liquid crystal in the wedge shape box, the interface of liquid crystal and liquid crystal cell is an alignment films.

The space geometry structure, as leg-of-mutton wedge shape, trapezoidal tiltedly split or wedge shape is tiltedly split array etc., can make the chiral liquid crystal thicknesses of layers in continuous variation, the light beam that sees through has just comprised by the space superposition from circular polarization, elliptic polarization to the microbeam of the multiple polarization situation of linear polarization, thereby plays the effect of depolarization; Chiral molecules has helical structure, during with the liquid crystal composition mixture, under the inducing of alignment films, but self-organization is the chiral liquid crystal with crystal structure and polarimetry nature, correspondence the chiral liquid crystal rete of different thickness at different parts, the angle of revolving is also different, and outgoing beam will be the depolarization light beam of a branch of mixing superposition.Alignment films is induced the chiral liquid crystal orientation after the specific direction friction treatment, just have the ability that polarized light is modulated.

The chiral liquid crystal depolarizer depolarizer is applicable to random polarization direction and polarization state (linear polarization, circular polarization, elliptic polarization), and applicable wavelengths is at 0.4um～20um, and bore can be adjusted in hundreds of mm scopes at 1mm.

The present invention utilizes the optical activity and the birefringence of chiral liquid crystal, and liquid crystal cell with space geometry structure, the outgoing beam of incident polarized light is combined, i.e. the polarization state preferred orientation of tool direction no longer by the equally distributed elliptically polarized light of long axis direction in 2 π.Chiral liquid crystal depolarizer comprises liquid crystal cell, chiral liquid crystal with space geometry structure, induce that the chiral liquid crystal self-organization is the alignment films that the crystal characteristic structure is arranged in the liquid crystal cell.Be mainly used in all fields to the polarization state of light sensitivity such as light laser, optical communication, remote optical sensing, spectral analysis.

Chiral liquid crystal depolarizer has the advantage of cumeat depolarizer and gyrotropi crystal depolarizer concurrently, and more outstanding is to realize the monochromatic light depolarization in wide spectral range, and any incident polarization light direction is all had good depolarization effect.The chiral liquid crystal depolarizer manufacture craft is simple, and cost declines to a great extent, and is for heavy caliber light beam depolarization, with the obvious advantage especially.

Description of drawings

Fig. 1 is chiral liquid crystal depolarizer structure of the present invention (wedge shape array) synoptic diagram, (a) is the chiral liquid crystal depolarizer front view, (b) is the chiral liquid crystal depolarizer top plan view.

Fig. 2 (a) is the chiral liquid crystal depolarizer front view for the present invention is applied to the small-bore chiral liquid crystal depolarizer structural representation of beam diameter less than 5mm, (b) is the chiral liquid crystal depolarizer top plan view.

Fig. 3 is that chiral liquid crystal depolarizer of the present invention is used sample situation figure (a) and (b), (c).

Fig. 4 is that chiral liquid crystal depolarizer of the present invention detects index path.

Fig. 5 is that light polarization detects figure after the chiral liquid crystal depolarizer depolarization of the present invention.

When Fig. 6 is 0.6328 μ m laser by the polarizer, chiral liquid crystal depolarizer and analyzer, the RST figure (a) and (b) that the rotation analyzer is obtained.

Among the figure: optically transparent material (1,2), alignment films (3,5), 4 pads,

6 have the chiral molecules of polarimetry nature and the potpourri (chiral liquid crystal) of the liquid crystal composition with birefringent characteristic, the friction direction of 7 alignment films, 8 edge sealing adhesives

Embodiment

Below in conjunction with accompanying drawing chiral liquid crystal depolarizer of the present invention is described in detail.

Fig. 1 is heavy caliber chiral liquid crystal depolarizer space geometry structure (wedge shape array) synoptic diagram, (a) is the chiral liquid crystal depolarizer front view, (b) is the chiral liquid crystal depolarizer top plan view.

Chiral liquid crystal depolarizer of the present invention, wherein optically transparent material (1,2) adopts glass, and chiral liquid crystal depolarizer is made up of upper substrate glass and lower baseplate glass with wedge-shaped slot array; The glass surface coating concentration that constitutes wedge shape is 4% polyimide solution formation alignment films (3,5); Alignment films (3,5) is through friction treatment, forms raceway groove, and liquid crystal molecule is arranged along raceway groove, forms structurally ordered crystal, and the frictional direction of alignment films (3,5) is parallel and along direction shown in 7 among Fig. 1 (a).Perfusion chiral molecules andliquid crystal compound 6 are used edge sealing adhesive 8 edge sealing then in the wedge shape array cavity.Chiral liquid crystal just has crystal characteristic preferably only thick less than the box of 100 μ m under the inducing of alignment films.With the increase of bore, the wedge shape height also increases, and just need be designed to array structure above behind the 100 μ m.

Fig. 2 is small-bore chiral liquid crystal depolarizer structural representation, (a) is the chiral liquid crystal depolarizer front view, (b) is the chiral liquid crystal depolarizer top plan view.More small-bore depolarizer can be made into single wedge structure, comprises upper and lower optical glass, alignment films (3,5), and the frictional direction of alignment films (3,5) must be parallel and along 7 directions,pad 4, chiral molecules and theliquid crystal compound 6 of the control angle of wedge.

Chiral liquid crystal depolarizer of the present invention, optical glass also can adopt optical materials such as plastics, crystal to substitute.Space structure can adopt wedge shape, trapezoidal, trapezoidal array, trapezoidal structure such as tiltedly split.

The chiral liquid crystal depolarizer preparation method:

The optically transparent material glass-cutting is become required size shape, transparent material is carried out edging.Utilize supersonic wave cleaning machine that transparent material is cleaned, all contaminations on glass and the dust that sticks etc. are thoroughly cleaned up.(1000 grades) dried 35 minutes under 110 ℃ of cleaning conditions then.Next be 4% polyimide solution in coating concentration on glass,, control the homogeneity of film well in the alignment films (3,5) that forms on the clear glass after the cleaning about 100nm.Precuring in 80 ℃ baking box, formal solidification temperature is 190 ℃.

The friction treatment of alignment films (3,5) is to make important link in the depolarizer, compares with the common liquid crystals box, and chiral liquid crystal depolarizer has space geometry structures such as wedge shape, and friction process is more assorted, needs to arrange frictional direction according to the space geometry structure.For making the chiral liquid crystal orientation more orderly, the frictional direction of alignment films (3,5) is parallel to each other, along 7 direction shown in the wedge surface among Fig. 2 (a).

For small-bore chiral liquid crystal depolarizer, usepad 4 to control the angle of wedge; For bigbore chiral liquid crystal depolarizer, the last lower-glass with space geometry structure to good position, to be fitted, perfusion chiralliquid crystal 6 is with edge sealing adhesive 8 edge sealing.

The process for preparation of chiral liquid crystal, chiral molecules has helical structure, is added in the liquid crystal as adjuvant, forms the chiral liquid crystal with polarimetry nature.As using the chiral liquid crystal that chiral molecules CB15 and Δ n value are 0.272 liquid crystal BL-038 (Merck company) composition among the present invention, when the mass percent of liquid crystal is 90%, the chiral molecules mass percent is 10% o'clock, and the green laser of linear polarization is realized good depolarization.According to concrete request for utilization, can select Δ n value is 0.07～0.35 (Δ n=n_o-n_o) monomer liquid crystal or mixed liquid crystal, mass percent is 65～95% and (to the infrared light depolarization that waits longer wavelength, selects better quality number percent; To the light depolarization of shorter wavelength, select than inferior quality number percent) add suitable left-handed or dextrorotation chiral molecules, mass percent is 35%～5% (to the infrared light depolarization that waits longer wavelength, to select than inferior quality number percent; To the light depolarization of shorter wavelength, select better quality number percent), to obtain to have the chiral liquid crystal potpourri of helical structure, the pitch of chiral liquid crystal should be heated to the above fully mixing of liquid crystal clearing point temperature greater than the depolarized lambda1-wavelength of needs.

The chiral liquid crystal depolarizer applicable cases as shown in Figure 3.

Shown in Fig. 3 (a), when fiber laser is not interfered, behind analyzer, the output laser power stability.

Shown in Fig. 3 (b), because the fiber birefringence characteristic, the output light of fiber laser or can change with various factorss such as temperature, pressure and bendings through the Optical Fiber Transmission polarization state of light, after the polarizer rose partially, its output power can occur than macrorelief.

Usually adopt the initiatively fiber ring laser system of depolarization, the laser seed sources of two bundle polarization state quadratures are superposed to circular polarization state, and with the influence that the variation that reduces in the transmission course because of polarization state brings, its shortcoming is a complex structure, and is with high costs, and technical difficulty is big.Therefore passive depolarization has urgent demand.

Shown in Fig. 3 (c), add that before the polarizer chiral liquid crystal depolarizer just can improve the influence that is caused by various factorss such as said temperature, pressure and bendings, laser output power is stable.

The test of depolarizer depolarization detects: experiment detects index path as shown in Figure 4, the elliptic polarization laser beam of single wavelength laser emission becomes linearly polarized light after by the polarizer, depolarization effect through chiral liquid crystal depolarizer becomes nonpolarized light then, received by photodetector through analyzer at last, signal is read processing through oscillograph.When concrete the detection, fixedly the polarization direction of the polarizer is motionless earlier, rotates the depolarization degree that analyzer detects liquid crystal depolarizer then; Next change the polarization direction of the polarizer, rotate analyzer again and detect the sensitivity of liquid crystal depolarizer incident polarized light.

Experimental result such as Fig. 5, shown in Figure 6.

Among Fig. 5, the light polarization after the chiral liquid crystal depolarizer depolarization is isotropic distribution almost in the space, and polarization side's attitude is the preferred orientation of tool direction no longer, has promptly realized depolarization.

Among Fig. 6, horizontal ordinate has been described the variation of the analyzer anglec of rotation, and ordinate has represented to penetrate the variation of laser intensity, and Fig. 6 (a) expression does not have the situation of depolarization, the variation of laser intensity generating period behind analyzer; Fig. 6 (b) expression is after chirality liquid crystal depolarizer depolarization, and laser intensity is almost constant behind analyzer, show polarization state in the space preferred orientation of tool direction no longer, realized depolarization.

Claims (6)

1. chiral liquid crystal depolarizer, it is characterized in that: described chiral liquid crystal depolarizer comprises optically transparent material (1) and optically transparent material (2), and optically transparent material (2) is provided with wedge shape or dovetail groove array; Optically transparent material (1) and optically transparent material (2) are fitted and are formed the liquid crystal cell with wedge shape or ladder cavity, be provided with the alignment films (3,5) that forms by polyimide solution in the liquid crystal cell, and being perfused with the potpourri (6) that chiral molecules with polarimetry nature and the liquid crystal with birefringent characteristic are formed, it is the structure of crystal characteristic that alignment films (3,5) is induced the chiral liquid crystal self-organization.

2. chiral liquid crystal depolarizer according to claim 1, it is characterized in that: described optically transparent material (2) is provided with the cavity liquid crystal cell of single wedge structure, also is provided with the pad (4) of control angle of wedge size at the big end of the cavity liquid crystal cell of single wedge structure.

3. chiral liquid crystal depolarizer according to claim 1 and 2 is characterized in that: described chiral molecules with polarimetry nature and have consisting of of potpourri (6) that the liquid crystal of birefringent characteristic forms:

Liquid crystal (Δ n value is 0.07～0.35) mass percent is 65%～95%

The chiral molecules mass percent is 35%～5%.

4. according to claim 1 or 2 arbitrary described chiral liquid crystal depolarizers, it is characterized in that: described alignment film rubbing direction is that the frictional direction of alignment films (3) and alignment films (5) is parallel to each other.

5. preparation method who is used for the described chiral liquid crystal depolarizer of claim 1 is characterized in that comprising following content:

A) optically transparent material (1,2) is cut into the required size shape, and carry out edging;

B) utilize supersonic wave cleaning machine that transparent material (1,2) is cleaned;

C) (1000 grades) dried 30～40 minutes under 110 ℃ of cleaning conditions;

D) go up applying concentration at optically transparent material (1,2) is 4% polyimide solution, goes up the alignment films (3,5) that forms about 100nm at the optically transparent material after the cleaning (1,2);

E) carrying out precuring earlier in the baking box of 70 ℃～80 ℃ of temperature, is formally to solidify under 180 ℃～200 ℃ in temperature again;

F) alignment films (3,5) is carried out friction treatment;

G) the optically transparent material contraposition that will handle is fitted, and perfusion has the chiral molecules of polarimetry nature and has the potpourri (6) of the liquid crystal composition of birefringent characteristic, edge sealing.

6. preparation method who is used for the described chiral liquid crystal depolarizer of claim 2 is characterized in that comprising following content:

A) optically transparent material (1,2) is cut into the required size shape, and carry out edging;

B) utilize supersonic wave cleaning machine that optically transparent material (1,2) is cleaned;

C) (1000 grades) dried 30～40 minutes under 110 ℃ of cleaning conditions;

D) go up applying concentration at optically transparent material (1,2) is 4% polyimide solution, goes up the alignment films (3,5) that forms about 100nm at the optically transparent material after the cleaning (1,2);

E) carrying out precuring earlier in the baking box of 70 ℃～80 ℃ of temperature, is formally to solidify under 180 ℃～200 ℃ in temperature again;

F) alignment films (3,5) is carried out friction treatment;

G) the optically transparent material contraposition that will handle is fitted, and uses pad (4) to control the angle of wedge, and perfusion has the chiral molecules of polarimetry nature and has the potpourri (6) of the liquid crystal composition of birefringent characteristic, edge sealing.

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