CN106125176B - A kind of one-dimensional three-dimensional phase grating of Terahertz - Google Patents
A kind of one-dimensional three-dimensional phase grating of Terahertz Download PDFInfo
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- CN106125176B CN106125176B CN201610538871.8A CN201610538871A CN106125176B CN 106125176 B CN106125176 B CN 106125176B CN 201610538871 A CN201610538871 A CN 201610538871A CN 106125176 B CN106125176 B CN 106125176B
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/18—Diffraction gratings
- G02B5/1861—Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0102—Constructional details, not otherwise provided for in this subclass
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Abstract
The invention discloses a kind of one-dimensional three-dimensional phase grating of Terahertz, the phase grating is that a kind of pitch is variable, groove depth sequentially changes, suitable for one-dimensional three-dimensional, the reflective phase grating of terahertz wave band.Diffraction theory of the invention based on electromagnetic wave, by controlling the height of upper and lower plane, additional optical distance is introduced, hereby wave carries out phase-modulation to reflected terahertz, make reflected terahertz hereby wavefront different zones have different phase informations, suitable for tera-hertz spectra imaging, analysis etc. related fields.
Description
The one-dimensional phase grating of Terahertz according to the present invention is that a kind of pitch is variable, groove depth sequentially changes, suitable for too
Three-dimensional, the reflective phase grating of hertz wave band.Diffraction theory of the invention based on electromagnetic wave is become by the depth for controlling groove
Change, introduce additional optical distance, to reflected terahertz hereby wave realize phase-modulation, make reflected terahertz hereby wavefront different zones have difference
Phase information, suitable for related fields such as light spectrum image-forming, analyses.
Background technology
At present, mainly there are two classes suitable for the spectral instrument of terahertz wave band：When infrared Fourier spectrometer and Terahertz
Domain spectrometer.Infrared Fourier spectrometer has the characteristics that multichannel, high throughput using Fourier Transform Technique light splitting, but in Fu
Leaf transformation technology relies on the sequential scanning of index glass, it is impossible to which, in real time into spectrum, limit it makes in quick variation, complex environment
With；Secondly, basic configuration of the infrared Fourier spectrometer based on Michelson's interferometer, wherein essential beam splitting chip make into
Luminous energy loss 50% is penetrated, limits use of the instrument in signal detection；In addition infrared Fourier spectrometer introduces shifting
Dynamic component and step motion control motor while increasing volume and power consumption, affect the service life of instrument.Terahertz time-domain spectroscopy
Instrument is based on photoconductive sampling or electro-optic sampling to the detection of terahertz signal, to object into time spectrum, needs to be sequentially completed wavelength dimension,
The scanning of space dimension needs to take a substantial amount of time.Therefore, the existing means of above two, it is impossible to meet under environment complicated and changeable,
Terahertz composes the needs of quick detection.
Light-splitting device is the critical component of imaging spectral instrument, directly affects the performance of instrument, the complexity of structure, again
Amount and volume etc..Have currently as visible, infrared spectrum instrument light-splitting device：Prism, amplitude grating, AOTF etc..However this
The spectrum detection of terahertz wave band substance and imaging pair can not be met by being suitable for visible, infrared band light-splitting device or technology a bit
The demand of light-splitting device.First, prism has that Free Spectral Range is wide, simple in structure, thang-kng amount as classical light-splitting device
Greatly, the advantages of capacity usage ratio is high, and stray light is easy to inhibit, however in terahertz wave band, with the increase of wavelength, electromagnetic wave
Penetration performance enhances, that the dispersion phenomenon of material becomes and its faint, it means that the side of fine spectrum is obtained by material dispersion
Formula is in Terahertz spectrum detection not feasible.Secondly, amplitude grating is divided by diffraction effect, however by neighboring diffraction secondary light
The limitation of overlapping is composed, the spectral region of monolithic grating is limited；The balzed grating, used to improve the efficiency of light energy utilization, glittering
The finite bandwidth of wavelength has further reduced the Free Spectral Range of grating.The wave-length coverage of THz wave is the 3000 of visible wave
Times, it is 100 times of infrared waves.Which dictates that the light-splitting device of the spectral instrument of terahertz wave band must have wide Free Spectral Range
Characteristic, therefore balzed grating, amplitude modulation grating are not suitable for use in the light-splitting device of terahertz wave band.Finally, AOTF relies on sound
Luminous effect realizes diffraction light splitting, has the advantages of small, crystal diffraction rate height, big visual field, but not yet reported at present open
Document in find acousto-optic crsytal suitable for terahertz wave band.Therefore existing light-splitting device cannot meet Terahertz at present
Demand of the spectrum imaging to wide-spectrum light splitter part.
The shortcomings that above-mentioned four kinds of prior arts, is mainly reflected in following two aspects：First, Fourier spectrometer and Terahertz
Time-domain spectroscopy instrument, the imaging process needs for completing object take a long time, and are not suitable for wild environment complicated and changeable；2nd,
For being suitable for visible, infrared band existing light-splitting device or being limited by the dispersive power of terahertz wave band or be limited by device
Part free wide spectral range in itself or the development level for being limited by device cannot meet Terahertz and compose quick detection to width
The demand of free spectrum light-splitting device.
Invention content
For the above-mentioned deficiency of the prior art, the present invention provides a kind of one-dimensional three-dimensional phase gratings of Terahertz, are suitable for
The demand of spectrum analysis, detection, imaging to wide spectrum phase grating.
As shown in Figure 1, broadband solid phase grating is a series of by being carved on cuboid metallic plate (1) for specific invention
The rectangular recess of flat smooth is formed, wherein, groove plane is parallel with the upper surface of cuboid metallic plate (1), further groove
Depth is respectively h1、h2、…、hN-1、hN, h1、h2、h3、…、hN-2、hN-1、hNSequentially increase；The width of groove is a, grating
Period is d.The identical slot of depth is considered as a cellular, then above-mentioned three-dimensional phase grating is made of the N number of cellular of cellular.
For unit born of the same parents, modulation to incident light as shown in Fig. 2, the parallel THz wave of wide range (2) with angle [alpha] oblique incidence
Diffraction occurs for unit born of the same parents (3), and the concentrated lens of diffraction light (4) focus at lens focal plane (5), occurs 0 grade ,+1 grade, -1 grade
The fringe distribution met each other Deng " light and shade ".The distribution of optical grating diffraction level meets grating diffration equation, as shown in (1) formula, wherein α
Represent incidence angle, β represents the angle of diffraction, and d represents pitch, and m represents diffraction time, and λ represents Terahertz wavelength.
In Fig. 2, on the focal plane (5) of convergent lens (4), the Terahertz intensity distribution of any point as shown in (2) formula, wherein
α represents incidence angle, and β represents the angle of diffraction, and a represents groove width, and k represents wave vector,Represent phase modulation factor, h represents groove depth, n tables
Show the number of slot, A represents the amplitude of incident light, and λ represents wavelength, and f represents the focal length of focus lamp, and b represents the length of slot.
It is more in the light distribution expression formula of phase-modulation grating compared with the light distribution of traditional amplitude modulation grating
Phase modulation factorI.e. the light distribution of phase-modulation grating is modulated by groove depth h.
For zero-order diffraction light, meet β=- α, then the intensity of zero order light is as shown in (4) formula.
There is (4) formula it is found that for same cellular, different wave length component is different by the modulation voltage of groove depth h, the zero level of diffraction
Component intensity is different；For different cellulars, phase co-wavelength is due to groove depth h differences, and modulation factor is different, the zero level component of diffraction
Intensity is also different.
The present invention realizes the schematic diagram of phase-modulation as shown in figure 3, the parallel THz wave of wide range (6) is oblique THz wave
It penetrates three-dimensional phase grating (7) and diffraction occurs, diffraction light is focused on by convergent lens (8) at lens focal plane (9) ,+1 order diffraction
The diffracted wave of wave (10), -1 order diffraction wave (11) and other higher levels is by the aperture diaphragm (12) positioned at lens focal plane (9)
It filters out, 0 order diffraction light of three-dimensional phase grating continues Free propagation, due to cellular one (13), cellular two (14), cellular three
(15), cellular four (16), cellular five (17), cellular six (18) have different groove depths, to the difference of incident THz wave (6)
Region generates different phase-modulations, makes the different zones of 0 order diffraction wave wavefront (19) have different phase informations, and 0 grade is spread out
The different location of ejected wave wavefront (19) has different intensity distributions.
The spectral resolution of the one-dimensional three-dimensional phase grating of Terahertz described above depends on maximum groove depth, when light is parallel to
During the incidence of paper direction, the spectral resolution of grating is as shown in (5) formula.
Bandwidth of the number N of cellular according to terahertz wave band used, there is nyquist sampling theorem in three-dimensional phase grating
It determines, as shown in (6) formula, wherein N represents the number of cellular, hmaxRepresent maximum groove depth, σmaxTerahertz wave band used in expression
Maximum wave number, α represent incidence angle.
Wave numbers of the number n of three-dimensional phase raster unit born of the same parents' bracket groove according to terahertz wave band used, systematic signal-to-noise ratio
It determines, as shown in (7) formula, wherein n represents the number of unit born of the same parents' further groove, σmax、σminTerahertz wave band used in representing respectively
Maximum wave number, smallest wavenumber.
In three-dimensional phase grating, the groove width a of groove meets the λ of a >=10max, the duty ratio of grating meets d:a>1, the length of slot
B is at least maximum wavelength λmax100 times；The groove depth of adjacent cellular sequentially changes in three-dimensional phase grating, but can not wait ladders
Degree；Number, screen periods, the groove width of slot can not wait between different cellulars in three-dimensional phase grating, such as；Groove depth phase in cellular
Together, groove width can not wait, as shown in schematic diagram 4.
The core of the present invention is by introducing different groove depths, applies different phase tune to the different zones of incident light
System makes the different zones before optical grating diffraction light wave have different phase informations.
Compared with existing light-splitting device, three-dimensional phase grating has the following advantages：First, phase is realized to incident THz wave
Position modulation breaches the amplitude modulation limitation of traditional raster；2nd, the zero level of phase grating has light splitting ability, this breaches biography
System grating zero level does not have the constraint of light splitting ability, while ensure that grating Free Spectral Range, substantially increases grating
The efficiency of light energy utilization；3rd, compared with Fourier spectrometer, three-dimensional phase grating does not have moving parts, improves the same of the efficiency of light energy utilization
When, it can accomplish real-time detection, disclosure satisfy that the needs of field environment complicated and changeable；4th, it is three-dimensional compared with other light-splitting devices
Phase grating uses reflective structure, easy to process, of low cost.
Description of the drawings
Fig. 1 is one-dimensional Terahertz solid phase grating schematic diagram.
Fig. 2 is the THz wave diffraction schematic diagram of three-dimensional phase raster unit born of the same parents.
Fig. 3 is the phase-modulation principle schematic of three-dimensional phase grating.
Fig. 4 is the other structures schematic diagram of three-dimensional phase grating.
Specific embodiment
3 the present invention is further described below in conjunction with the accompanying drawings.
Embodiment 1：For the one-dimensional three-dimensional phase grating of 400GHz -435GHz wave bands
The present invention is used and is constructed as below：
1. the one-dimensional three-dimensional phase grating of Terahertz is made of six cellulars, the groove depths of six cellulars be respectively 0.1635cm,
0.327cm、0.4905cm、0.654cm、0.8175cm、0.981cm。
2. the groove width of six cellulars, screen periods, slot number are equal, groove width 1cm, screen periods 2cm, the number of slot is 5,
The length of slot is 80cm.
Main operational principle of the present invention such as Fig. 3 is stated：
Diffraction occurs for the parallel 6 oblique incidence solid phase grating 7 of THz wave of wide range, and diffraction light is by convergent lens 8 saturating
It is focused at mirror focal plane 9, the diffracted wave of+1 order diffraction wave 10, -1 order diffraction wave 11 and other higher levels is put down positioned at lens coke
The aperture diaphragm 12 in face 9 filters out, and 0 order diffraction light of three-dimensional phase grating continues Free propagation, due to cellular 1, cellular two
14th, cellular 3 15, cellular 4 16, cellular 5 17, cellular 6 18 have different groove depths, to the difference of incident THz wave 6
Region generates different phase-modulations, makes the different zones of 0 order diffraction wave wavefront 19 have different phase informations, 0 order diffraction
The different location of wave wavefront 19 has different intensity distributions.
Claims (2)
1. a kind of one-dimensional three-dimensional phase grating of Terahertz, it is characterised in that：
A series of rectangular recess that the phase grating is carved flat smooths by cuboid metallic plate (1) upper surface is formed, gold
The material for belonging to plate is aluminium, iron, aluminium alloy or titanium alloy, and the groove floor is parallel with the upper surface of cuboid metallic plate (1),
The depth of groove is respectively h1、h2、…、hN-1、hN, h1、h2、h3、…、hN-2、hN-1、hNSequentially increase, N is the number of cellular, deep
It spends identical groove and is considered as a cellular；The maximum groove depth h of gratingmax, determined jointly by spectral resolution R and angle of incidence of light α
It is fixed, meet：
In formula：α represents the incidence angle of THz wave, and R is the spectral resolution of grating；
The number N of cellular meets：
In formula：σmaxThe maximum wave number of terahertz wave band used in expression；
The number n of cellular further groove meets:
In formula：σminThe smallest wavenumber of THz wave used in expression；
The duty ratio of grating：d:a>1, wherein d are screen periods, and a is groove groove width.
2. a kind of one-dimensional three-dimensional phase grating of Terahertz according to right 1, it is characterised in that：The slot of the rectangular recess
Wide a meets：
a≥10λmax,
Flute length b meets：
b≥100λmax
Wherein λmaxThe maximum wavelength of terahertz wave band used in expression.
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| CN106706130A (en) * | 2017-01-19 | 2017-05-24 | 中国科学院上海技术物理研究所 | THz spectral imager based on stereoscopic phase optical grating and pore diameter segmentation technology |
| JP7455569B2 (en) * | 2019-12-20 | 2024-03-26 | 浜松ホトニクス株式会社 | Terahertz wave lens and method for manufacturing terahertz wave lens |
| CN114545620B (en) * | 2022-02-10 | 2023-09-12 | 中国科学院上海技术物理研究所 | Compensation design method for preparing dielectric super-surface by non-ideal etching process |
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| US6992824B1 (en) * | 2003-12-27 | 2006-01-31 | Motamedi Manouchehr E | Efficient wave propagation for terahertz imaging and sensing |
| CN102540304A (en) * | 2012-03-08 | 2012-07-04 | 电子科技大学 | Two-dimensional periodic hole-type Talbot medium phase grating |
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