Reflection type electronic control adjustable terahertz liquid crystal wave plate and preparing method thereof

A terahertz wave plate and reflective technology, which is applied in the field of terahertz optoelectronics, can solve the problems that the metal layer cannot meet the requirements, is difficult to achieve practicality, and has a small adjustable amount, and achieves good electric field distribution and control of liquid crystals. The effect of absorption loss and large modulation amount

Inactive Publication Date: 2017-08-25
NANJING UNIV OF POSTS & TELECOMM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, when applied to the terahertz frequency band, on the one hand, the commonly used transparent conductive film indium tin oxide will no longer be applicable, and a simple metal layer cannot meet the requirements, so it is necessary to seek a new electrode design
On the other hand, the birefringence of most liquid crystal materials will be relatively small in the terahertz frequency band, so the adjustable amount is also small, and it is difficult to meet practical requirements in general design
And some special means to increase the amount of modulation, such as stacked structures, etc., will seriously increase the loss under the condition of lack of transparent electrodes.

Method used

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  • Reflection type electronic control adjustable terahertz liquid crystal wave plate and preparing method thereof
  • Reflection type electronic control adjustable terahertz liquid crystal wave plate and preparing method thereof
  • Reflection type electronic control adjustable terahertz liquid crystal wave plate and preparing method thereof

Examples

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Effect test

Embodiment 1

[0053] This embodiment is an example of a box of broadband tunable terahertz waveplates.

[0054] The specific structural design is attached figure 1 As shown, two quartz substrates 1 are provided with sub-wavelength metal wire grid 2 and metal mirror 3, optically controlled alignment layer 4 and liquid crystal material 5 of the liquid crystal cell respectively. The orientation direction of the controlled alignment layer is 90° to the direction of the metal wire grid. The liquid crystal material selected in this example is room temperature large birefringence liquid crystal NJU-LDn-4 (patent number: 2012103780326), the birefringence of this liquid crystal is about 0.30 at 0.5-2.5 THz, the calculation shows that to make the liquid crystal The cell achieves the effect of a tunable quarter-wave plate at 1THz, and the required minimum cell thickness is 25 μm.

[0055] In order to realize such a structure, the present invention (including the azo liquid crystal cell) can be prepa...

Embodiment 2

[0058] This embodiment shows the relationship between liquid crystal layers with different thicknesses and phase difference when the refractive index of the liquid crystal is 1.8. The specific structural design is attached figure 1 Shown, preparation mode is identical with embodiment 1. By changing the thickness of the liquid crystal layer, different phase modulations can be achieved for different wavelengths of terahertz waves. Such as Figure 6 As shown, the smaller the wavelength, the larger the phase difference. Corresponding to the terahertz wave of 400 μm, the thickness of the liquid crystal layer only needs to be 50 μm to achieve the effect of a half-wave plate.

Embodiment 3

[0060] When the thickness of the liquid crystal layer is 125 μm, the relationship between the refractive index and phase difference of different liquid crystals. The specific structural design is attached figure 1 Shown, preparation mode is identical with embodiment 1. By electronically changing the refractive index of liquid crystals, different phase modulations can be achieved for different wavelengths of terahertz waves. Such as Figure 7 As shown, the greater the change in the refractive index of the liquid crystal, the smaller the wavelength and the greater the phase difference. For the terahertz wave of 200 μm, when the refractive index of the liquid crystal is changed from 1.5 to 2.0, the dynamic adjustable range of its phase difference is from 0 to π, which can be realized from the linear polarization state to the circular polarization state, and then to the direction perpendicular to the original linear polarization. The polarization change of the linear polarizati...

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Abstract

The invention discloses a reflection type electronic control adjustable terahertz liquid crystal wave plate based on a subwavelength metal wire grating. The wave plate comprises two pieces of melting quartz baseplates, wherein the subwavelength metal wire grating is arranged on the inner side of one piece of melting quartz baseplates, a metal reflection mirror is arranged on the inner side of the other piece of melting quartz baseplates, and a liquid crystal box is formed by the two pieces of melting quartz baseplates which are combined through frame glue; two-layer light control aligning layers are arranged on the subwavelength metal wire grating and the metal reflection mirror in the liquid crystal box respectively, liquid materials are arranged in the middle of the two-layer light control aligning layers, and the liquid materials are terahertz electronic control large double refractive index liquid crystal materials; parallel orientation of liquid crystals is achieved by the liquid crystal box through a light control orientation mode, and a 90-degree angle is formed between the orientation direction and the metal wire grating direction. The invention further discloses a preparing method of the reflection type electronic control adjustable terahertz liquid crystal wave plate based on the subwavelength metal wire grating; the reflection type electronic control adjustable terahertz liquid crystal wave plate has the advantages of super-wide frequency band, large modulated quantity and quick response, and can be applied to THz wave polarization transition, THz wavefront regulation and THz vector light beams.

Description

technical field [0001] The invention relates to the technical field of terahertz optoelectronics, in particular to a reflective electrically controlled and adjustable terahertz liquid crystal wave plate and a preparation method thereof. Background technique [0002] Liquid crystal materials have both the fluidity of liquids and the orderliness of crystals. Due to their excellent tuning characteristics of external fields (electric field, magnetic field, light field, sound field, temperature field, etc.), they play an important role in information display and adjustable photonic devices. Applications. Nematic liquid crystal is the most commonly used phase state, and in all nematic liquid crystal applications, orientation is the first step. The traditional orientation method, rubbing orientation, is the most widely used method, which has defects such as mechanical damage to the surface, electrostatic charge residue and particle contamination, and difficulty in realizing multi-...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02F1/139
CPCG02F1/1393
Inventor 王磊陈梦仪王鹏
Owner NANJING UNIV OF POSTS & TELECOMM
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