CN103105686A - Reflection type terahertz tunable polarization controller - Google Patents
Reflection type terahertz tunable polarization controller Download PDFInfo
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- CN103105686A CN103105686A CN2011103507071A CN201110350707A CN103105686A CN 103105686 A CN103105686 A CN 103105686A CN 2011103507071 A CN2011103507071 A CN 2011103507071A CN 201110350707 A CN201110350707 A CN 201110350707A CN 103105686 A CN103105686 A CN 103105686A
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Abstract
The invention discloses a reflection type terahertz tunable polarization controller and a control method thereof. The reflection type terahertz tunable polarization controller is mainly composed of a metal gate polarizer, an anti-reflection film, liquid crystal and a metal reflector. The phase difference of two beams of orthogonal polarized light is changed through continuously changing the refractive index of the liquid crystal between the metal gate polarizer and the metal reflector by an extra electric field, and thus adjustable phase delay in a range of 0 - 2 pi in a frequency range of 1 terahertz (THz) can be achieved. According to the reflection type terahertz tunable polarization controller, a reflection type structure is used, the application range of a terahertz system is extended, and the reflection type terahertz tunable polarization controller has the advantages of being high in extinction ratio, small in consumption, simple in structure, and favorable for miniaturization and integration.
Description
Technical field
The invention belongs to the Terahertz applied technical field, be specifically related to the tunable polarized controller of a kind of THz wave and control method thereof.
Background technology
Terahertz (THz, 1THz=10
12THz) ripple refers to frequency at the electromagnetic wave of 0.1-10THz (corresponding wavelength is 3mm-30 μ m) scope, and this wave band between microwave and light wave, is the crossing domain of electronics and photonics.Due to its residing specific position in electromagnetic wave spectrum, THz wave has many advantageous characteristic such as perspectivity, security, high s/n ratio, has very important science and using value in spectrum, imaging and the field such as communicate by letter.Terahertz function element such as wave filter, switch, beam splitter, the polarizer, phase delay device etc. are important component parts in the Terahertz application system, and wherein the terahertz polarization controller is the important devices of tera-hertz spectra and imaging system.It not only can obtain the THz wave of different polarization state, and can obtain different phase delay, thereby obtains the complex permittivity of object.
At present, common terahertz polarization controller mainly contains: the tunable phase shift device is controlled in (1) transmission-type magnetic field.The method has utilized magnetic field to control the birefringent characteristic of lower liquid crystal, realize 0～2 π phase shift near 1THz, but the method needs mechanically rotary magnetic field direction, and is not easy to operate.(2) transmission-type electric field controls tunable phase shift device.The method is utilized the birefringent characteristic under electric field controls, and is simple in structure, but voltage is higher.In addition, above-mentioned device is the transmission-type device, can't satisfy the requirement of reflective tera-hertz spectra and imaging system, and therefore developing reflective accurate phase control device has very important using value.
Summary of the invention
For the deficiency of above terahertz polarization controller, the object of the present invention is to provide a kind of reflective Terahertz continuously adjustable polarized controller and control method thereof.
The device of the tunable Polarization Controller of Terahertz is as follows: the metal gate polarizer, anti-reflection film, electrode, metallic mirror, liquid crystal, THz source.Liquid crystal is packaged in the seal cavity of anti-reflection film, electrode and metallic mirror composition.The metal gate polarizer forms through ultraviolet photolithographic, metal evaporation and metal-stripping in the HIGH-PURITY SILICON substrate, metal gate cycles 10 μ m, and dutycycle is less than 0.4, and thickness is less than 5 μ m.Anti-reflection film is at the equal very little duplicature of terahertz wave band reflectivity and absorption coefficient, and it is made of silicon layer and germanium layer, silicon layer thickness 22 μ m, and germanium layer thickness 18.75 μ m, the terahertz wave band reflectivity is less than 1%.Between electrode apart from 3mm.Liquid crystal selects 5CB, E7 etc. to have high birefringence low-loss nematic liquid crystal at terahertz wave band, and double refractive inde is greater than 0.15.The broadband THz source that the THz source that uses produces as Terahertz photoelectricity lead antenna, spectrum composition 0.1-3THz.
The method of work of the tunable Polarization Controller of Terahertz is: the orientation angle that changes liquid crystal molecule between the metal gate polarizer and metallic mirror by extra electric field, thereby change the phase differential of two bundle crossed polarized lights, the 1THz frequency range realizes adjustable phase delay in 0～2 π scope; When voltage was zero, liquid crystal was parallel to metal gate; When voltage increases gradually, the liquid crystal orientation angle turns to gradually perpendicular to metal gate, in this process, liquid crystal becomes greatly gradually in the refractive index of terahertz wave band, and the phase differential of two bundle crossed polarized lights changes with liquid-crystal refractive-index, realizes tunable Polarization Control function.
The invention has the beneficial effects as follows: (1) has adopted reflective structure to come control phase poor.Be subject to the impact of thickness of liquid crystal due to the phase differential of two bundle crossed polarized lights, reflective structure is larger than transmission-type structure range of adjustment under identical thickness of liquid crystal.(2) adopt the metal gate polarizer make TM ripple and TE wavelength-division from, avoided due to liquid crystal the different errors that produce of two kinds of polarized light absorption coefficients, and adopted the anti-reflection film structure, make two kinds of polarized light amplitudes close, realize the continuous regulation and control to the terahertz polarization attitude.
Advantage of the present invention is: adopt reflective structure, expanded the application category of Terahertz system, and it is high to have extinction ratio, loss is little, and is simple in structure, is convenient to miniaturization and integrated characteristics, satisfies the requirement of Terahertz communication, spectrum and imaging system.
Description of drawings
Fig. 1 is the two-dimensional representation of the tunable Polarization Control apparatus of reflective Terahertz;
Fig. 2 is the change curve of electrode liquid crystal birefringence when applying different voltage;
Fig. 3 (a) is the relation curve that metal gate plays inclined to one side characteristic and metal gate thickness;
Fig. 3 (b) is the relation curve that metal gate plays inclined to one side characteristic and metal gate dutycycle;
Fig. 4 is that TM wave reflection rate is with the change curve of liquid-crystal refractive-index;
Fig. 5 (a) TE and TM wave phase are poor with the variations in refractive index curve;
Fig. 5 (b) TE and TM wave phase are poor with the change in voltage curve;
In figure: the metal gate polarizer 1, anti-reflection film 2, positive and negative electrode 3, metallic mirror 4, liquid crystal 5, broadband Terahertz wave source 6.
Embodiment
The course of work of the present invention is by near the tunable Polarization Controller example explanation of reflective Terahertz that is operated in 1THz:
Metal gate polarizer spacing 10 μ m, dutycycle 0.3, thickness 4 μ m, device overall dimensions 3mm * 2mm, high 1mm.The terahertz signal that is sent by photoconductive antenna incides on the metal gate polarizer, as Fig. 1, and TE wave reflection, the transmission of TM ripple, transmission-polarizing extinction ratio 22.86dB.During lower than threshold voltage 3.75V, in device, liquid crystal points to and is parallel to the metal gate polarizer when electrode voltage.At this moment, liquid crystal the refractive index of terahertz wave band be 1.62, TM ripple and TE wave phase poor be-242.6865 °.When electrode application voltage, the liquid crystal in device points to rotating perpendicular to metal gate polarizer direction.The refractive index of liquid crystal can be drawn by following formula:
N wherein
e=1.79, n
0=1.62, n
zBe actual refractive index.Therefore, along with voltage increases, liquid-crystal refractive-index increases, and the phase differential of TM and TE ripple changes along with the variation of TM ripple light path in device.When voltage reached 80V, liquid crystal pointed to metal gate polarizer angle and reaches 90 degree, and the refractive index of while liquid crystal is that the phase differential of 1.79, TM ripple and TE ripple reaches 116.1389 °.Simultaneously, in the liquid-crystal refractive-index variation range, TM wave reflection rate means front surface TE ripple and TM wave amplitude approximately equal at device, as shown in Figure 4 near 100%.Like this, the phase differential of TE ripple and TM ripple changes to 116.1389 ° from-242.6865 °, as shown in Fig. 5 (a) and 5 (b), and 358.8254 ° of variation ranges, and amplitude is identical, has shown the Polarization Control function that device is good.Therefore, the tunable Polarization Controller of this Terahertz can realize that phase differential is from the continuous tuning of 0 ° to 360 °, its tuning range 0～2 π.And owing to having adopted reflective structure, made up the deficiency that such device can not be applied to reflective tera-hertz spectra and imaging system.
Claims (6)
1. tunable polarized controller of reflective Terahertz, it is characterized in that comprising the metal gate polarizer (1), anti-reflection film (2), electrode (3), metallic mirror (4), liquid crystal (5), THz source (6), wherein liquid crystal (5) is packaged in the seal cavity of anti-reflection film (2), electrode (3) and metallic mirror (4) composition.
2. the tunable polarized controller of reflective Terahertz according to claim 1, it is characterized in that the metal gate polarizer forms through ultraviolet photolithographic, metal evaporation and metal-stripping in the HIGH-PURITY SILICON substrate, metal gate cycles 10 μ m, dutycycle is less than 0.4, and thickness is less than 5 μ m.
3. the tunable polarized controller of reflective Terahertz according to claim 1, it is characterized in that anti-reflection film is at the equal very little duplicature of terahertz wave band reflectivity and absorption coefficient, it is made of silicon layer and germanium layer, silicon layer thickness 22 μ m, germanium layer thickness 18.75 μ m, the terahertz wave band reflectivity is less than 1%.
4. the tunable polarized controller of reflective Terahertz according to claim 1, it is characterized in that regulating material is to have high birefringence, low-loss nematic liquid crystal (5) at terahertz wave band, double refractive inde is greater than 0.15.
5. the tunable polarized controller of reflective Terahertz according to claim 1, the broadband THz source that the THz source (4) that it is characterized in that using produces as Terahertz photoelectricity lead antenna, spectrum composition 0.1-3THz.
6. the tuning methods of the tunable polarized controller of use reflective Terahertz as described in right 1, it is characterized in that changing by extra electric field the orientation angle of liquid crystal molecule between the metal gate polarizer and metallic mirror, thereby change the phase differential of two bundle crossed polarized lights, the 1THz frequency range realizes adjustable phase delay in 0～2 π scope; When voltage was zero, liquid crystal was parallel to metal gate; When voltage increases gradually, the liquid crystal orientation angle turns to gradually perpendicular to metal gate, in this process, liquid crystal becomes greatly gradually in the refractive index of terahertz wave band, and the phase differential of two bundle crossed polarized lights changes with liquid-crystal refractive-index, realizes tunable Polarization Control function.
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536075A (en) * | 2015-01-19 | 2015-04-22 | 中国科学院重庆绿色智能技术研究院 | Terahertz polaroid |
| CN105974503A (en) * | 2016-06-15 | 2016-09-28 | 南开大学 | Terahertz artificial birefringence device based on periodic chirped grating |
| CN107092147A (en) * | 2017-05-27 | 2017-08-25 | 南京邮电大学 | A kind of reflective automatically controlled adjustable Terahertz liquid crystal wave plate and preparation method thereof |
| CN107942538A (en) * | 2017-11-13 | 2018-04-20 | 中国计量大学 | Automatically controlled THz wave amplitude controller |
| CN108227243A (en) * | 2018-01-19 | 2018-06-29 | 电子科技大学 | Automatically controlled THz wave regulation and control device of silicon substrate all dielectric type and preparation method thereof |
| CN109164304A (en) * | 2018-09-19 | 2019-01-08 | 天津大学 | A kind of Test extraction biological macromolecule material Terahertz complex dielectric permittivity method |
| CN109581698A (en) * | 2018-12-07 | 2019-04-05 | 清华大学 | Tunable terahertz polarization light-splitting device |
| CN109728428A (en) * | 2018-12-29 | 2019-05-07 | 中国科学院半导体研究所 | Photoconductive antenna and preparation method based on sub-wavelength structure modulation terahertz emission |
| CN109856825A (en) * | 2019-02-14 | 2019-06-07 | 合肥工业大学 | A kind of Terahertz transmission-type modulator based on double-level-metal micro-structure and liquid crystal |
| CN110794596A (en) * | 2019-06-18 | 2020-02-14 | 南开大学 | Reflection type broadband polarization controller based on graphene-medium composite super surface |
| CN111399261A (en) * | 2020-04-27 | 2020-07-10 | 南京南辉智能光学感控研究院有限公司 | Focal length-adjustable terahertz super-structured lens and preparation method and application thereof |
| CN111273467B (en) * | 2020-02-10 | 2021-07-16 | 清华大学 | Terahertz wave front phase control device based on liquid crystal and wire grid-shaped super-structure surface |
| CN113281929A (en) * | 2021-03-04 | 2021-08-20 | 桂林电子科技大学 | Electrotunable liquid crystal gap plasma structure color filter |
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Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104536075A (en) * | 2015-01-19 | 2015-04-22 | 中国科学院重庆绿色智能技术研究院 | Terahertz polaroid |
| CN105974503A (en) * | 2016-06-15 | 2016-09-28 | 南开大学 | Terahertz artificial birefringence device based on periodic chirped grating |
| CN107092147A (en) * | 2017-05-27 | 2017-08-25 | 南京邮电大学 | A kind of reflective automatically controlled adjustable Terahertz liquid crystal wave plate and preparation method thereof |
| CN107942538A (en) * | 2017-11-13 | 2018-04-20 | 中国计量大学 | Automatically controlled THz wave amplitude controller |
| CN108227243B (en) * | 2018-01-19 | 2019-12-27 | 电子科技大学 | Silicon-based all-dielectric electronic control terahertz wave regulation and control device and preparation method thereof |
| CN108227243A (en) * | 2018-01-19 | 2018-06-29 | 电子科技大学 | Automatically controlled THz wave regulation and control device of silicon substrate all dielectric type and preparation method thereof |
| CN109164304B (en) * | 2018-09-19 | 2020-10-23 | 天津大学 | Method for testing and extracting terahertz complex dielectric constant of biological macromolecular material |
| CN109164304A (en) * | 2018-09-19 | 2019-01-08 | 天津大学 | A kind of Test extraction biological macromolecule material Terahertz complex dielectric permittivity method |
| CN109581698A (en) * | 2018-12-07 | 2019-04-05 | 清华大学 | Tunable terahertz polarization light-splitting device |
| CN109728428A (en) * | 2018-12-29 | 2019-05-07 | 中国科学院半导体研究所 | Photoconductive antenna and preparation method based on sub-wavelength structure modulation terahertz emission |
| CN109856825A (en) * | 2019-02-14 | 2019-06-07 | 合肥工业大学 | A kind of Terahertz transmission-type modulator based on double-level-metal micro-structure and liquid crystal |
| CN110794596A (en) * | 2019-06-18 | 2020-02-14 | 南开大学 | Reflection type broadband polarization controller based on graphene-medium composite super surface |
| CN110794596B (en) * | 2019-06-18 | 2021-03-09 | 南开大学 | Reflection type broadband polarization controller based on graphene-medium composite super surface |
| CN111273467B (en) * | 2020-02-10 | 2021-07-16 | 清华大学 | Terahertz wave front phase control device based on liquid crystal and wire grid-shaped super-structure surface |
| CN111399261A (en) * | 2020-04-27 | 2020-07-10 | 南京南辉智能光学感控研究院有限公司 | Focal length-adjustable terahertz super-structured lens and preparation method and application thereof |
| CN111399261B (en) * | 2020-04-27 | 2023-09-19 | 南京南辉智能光学感控研究院有限公司 | Terahertz super-structured lens with adjustable focal length and preparation method and application thereof |
| CN113281929A (en) * | 2021-03-04 | 2021-08-20 | 桂林电子科技大学 | Electrotunable liquid crystal gap plasma structure color filter |
| CN113281929B (en) * | 2021-03-04 | 2022-07-12 | 桂林电子科技大学 | Electrotunable liquid crystal gap plasma structure color filter |
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Application publication date: 20130515 |