CN202110378U - Device for producing rotational composite vortex light beam by using reflection type spatial light modulator - Google Patents

Abstract

The utility model relates to a device for producing a rotational composite vortex light beam by using a reflection type spatial light modulator. The device is characterized in that: light emitted by a laser source sequentially passes through a beam expander and a beam splitter; one of two split light beams passes through a second reflecting mirror and is modulated through a first spatial light modulator and filtered through a first Fourier spatial filter, and the other light beam is reflected through a first reflecting mirror, modulated through a second spatial light modulator and filtered through a second Fourier spatial filter; a frequency shift is used for producing frequency shift; and the two light beams are coaxially overlapped through a beam combined mirror to obtain the rotational composite vortex light beam. The device provided by the utility model can conveniently control the rotational speed and a spot pattern of the composite vortex light beam; and the light beam produced by the device can be used as an optical spanner, and particles are controlled and rotated by means of the particular orbital angular momentum characteristic of the device.

Description

Adopt reflective spatial light modulator to produce the device of the combined vortex light beam of rotation

Technical field

The present invention relates to a kind of device that adopts reflective spatial light modulator to produce the combined vortex light beam of rotation, is a kind of device that produces the combined vortex light beam of rotation based on two different vortex light beams of topological charge.

Background technology

The vortex light beam in nearly decades because its unique phase structure has all received concern widely with topological property in fields such as fundamental research and applied researcies.Similar with the vortex phenomenon in the fluid; At optical field, there is the phase place singular point in the center of the light wave fields of vortex light beam, and phase place changes around this singular point in the shape of a spiral continuously; The light wave wavefront can rotate around a line on the direction of propagation in a spiral manner, forms spiral wavefront.

Two parallel out-of-alignment vortexs stacks have just been analyzed as far back as people such as I.D.Maleev in 2003 and G.A.Swartzlander; Describe the optical phase singular point with the relative phase of two vortexs or the situation of change of amplitude, and obtained the critical condition that vortex produces and buries in oblivion.Coaxial stack research to optical eddy in recent years increased gradually, and wherein A.Ya.Bekshaev etc. has studied two Laguerres-Gauss's vortex beam mode in 2005 and has been respectively LG _{0 ,+1}LG _{0 ,-1}) transport property after the coaxial stack, and prophesy is if two Laguerres-Gauss's vortex beam frequencies is different, interference pattern will rotate in same plane; E.J.Galvez leader's research group is devoted to the research of composite optical eddy in the period of 2006-2009, drawn the regularity of distribution of the combined vortex of two vortexs stack back generation.But these work only are confined to the identical coaxial stack of two vortex light beams of frequency, and the coaxial stack of two vortex light beams of different frequency is not reported as yet.

Summary of the invention

The technical matters that solves

For fear of the weak point of prior art, the present invention proposes a kind of device that produces the combined vortex of rotation through coaxial stack frequency difference and two different vortex light beams of topological charge.

Thought of the present invention is: to the gauss laser beam modulation introducing topological charge factor, obtain having the vortex Laguerre-Gaussian beam LG light beam of specifying topological charge through spatial filtering through reflective spatial light modulator then.Produce difference on the frequency through the frequency displacement device.Any existing frequency displacement device can be used in this technology, and like acoustooptic modulation, electrooptical modulation, rotating grating perhaps can continuously change the method for phase place light path.At last, can simply realize the coaxial stack of light beam through the light path that designs in the present technique.

Technical scheme

A kind of device that adopts reflective spatial light modulator to produce the combined vortex light beam of rotation is characterized in that comprising laser instrument 1, beam expander device 2, beam splitter 3, first semi-transparent semi-reflecting lens 4, the first spatial light modulator 5-1, the second spatial light modulator 5-2, the first Fourier space wave filter 6-1, the second Fourier space wave filter 6-2, frequency displacement device 7, second semi-transparent semi-reflecting lens 8 and light combination mirror 9; The light beam of LASER Light Source 1 outgoing passes through beam expander 2 and beam splitter 3 successively; Be reflected to spatial light modulator modulation 5-1 surface by second semi-transparent semi-reflecting lens 8 through two light beams of beam splitting are wherein a branch of; The former road of light beam after modulated is returned and second semi-transparent semi-reflecting lens 8 is crossed in the part transmission, and transmitted light is through the first Fourier space wave filter 6-1; Another bundle is reflected to spatial light modulator modulation 5-2 surface by first semi-transparent semi-reflecting lens 4, and the former road of light beam after modulated returns and first semi-transparent semi-reflecting lens 4 is crossed in the part transmission, and transmitted light is through the second Fourier space wave filter 6-2 and frequency displacement device 7; This two-beam realizes that through light combination mirror 9 coaxial stack obtains producing the combined vortex light beam of rotation; The described first spatial light modulator 5-1 and the second spatial light modulator 5-2 adopt reflective spatial light modulator.

Adopt image acquisition device 10 to obtain the propeller type rotary beam and gather, and observe the pattern of rotation through beam splitter 9 coaxial stacks.

On the first spatial light modulator 5-1 and the second spatial light modulator 5-2, adopt the vortex hologram of graphics controller 11 control light modulated.

On frequency displacement device 7, adopt the frequency shift amount of frequency difference controller 12 control frequency shifters.

Said frequency displacement device 7 is any existing acousto-optic frequency shift device or rotation slide frequency displacement device.

Principle of work: the light beam of LASER Light Source 1 outgoing passes through beam expander 2 and beam splitter 3 successively.Through wherein a branch of second semi-transparent semi-reflecting lens 8 that passes through of two light beams of beam splitting, successively by the first spatial light modulator 5-1, the first Fourier space wave filter 6-1 modulates respectively and filtering.Successively by the second spatial light modulator 5-2, the second Fourier space wave filter 6-2 modulates respectively and filtering another bundle, and produces frequency displacement by frequency displacement device 7 after 4 reflections of first semi-transparent semi-reflecting lens.Afterwards, this two-beam is realized coaxial stack by light combination mirror 9, and is received by image acquisition device 10.

Beneficial effect

The employing reflective spatial light modulator that the present invention proposes produces the device of rotation combined vortex light beam, can control the rotating speed and the hot spot pattern of combined vortex light beam easily; Light beam with its generation can be used as " optics spanner ", relies on its distinctive orbital angular momentum characteristic to be handled and rotates particulate.

Description of drawings

Fig. 1: second kind of form that coaxial stack produces the combined vortex beam device of rotation based on two different vortex light of topological charge difference and frequency of the present invention used two reflective spatial light modulator structural drawing;

The 1-LASER Light Source, 2-beam expander device, 3-beam splitter, 4-first semi-permeable and semi-reflecting mirror; 5-1-first reflective spatial light modulator, 5-2-second reflective spatial light modulator, the 6-1-first Fourier space wave filter, the 6-2-second Fourier space wave filter; 7-frequency displacement device, 8-second semi-permeable and semi-reflecting mirror, 9-light combination mirror, 10-image acquisition device; The 11-graphics controller, 12-frequency difference controller, 13-computing machine;

Embodiment

Combine embodiment, accompanying drawing that the present invention is further described at present:

Embodiment:

See also Fig. 1.

The light beam of LASER Light Source 1 outgoing passes through beam expander 2 and beam splitter 3 successively.Be reflected to reflective spatial light modulator modulation 5-1 surface by semi-permeable and semi-reflecting mirror 8 through two light beams of beam splitting are wherein a branch of, the former road of light beam after modulated returns and semi-transparent semi-reflecting mirror 8 is crossed in the part transmission, and transmitted light is through the first Fourier space wave filter 6-1.Another bundle is reflected to reflective spatial light modulator modulation 5-2 surface by semi-permeable and semi-reflecting mirror 4, and the former road of light beam after modulated returns and semi-transparent semi-reflecting mirror 4 is crossed in the part transmission, and transmitted light is through the second Fourier space wave filter 6-2 and frequency displacement device 7.Afterwards, this two-beam is realized coaxial stack through light combination mirror 9, and is received by image acquisition device 10.System also comprises the graphics controller 11 of controlling two spatial light modulators, the frequency difference controller 12 and computing machine 13 of control frequency displacement device frequency shift amount.The notional result of surveying gained is as shown in Figure 4.In this programme, the image through the computer control spatial light modulator is " blade " number of may command rotation hot spot, and the frequency displacement size that the control frequency shifter produces is the rotating speed of may command hot spot.

The process that produces the combined vortex light beam that rotates with control through this embodiment is: with topological charge is m ₁And m ₂Calculating vortex hologram through graphics controller respectively among input space photomodulator 5-1 and the 5-2, and on the frequency plane of spatial filter 6-1 and 6-2, only keep 1 grade or-1 grade of frequency spectrum light.When these two wave filters all keep+during 1 grade of frequency spectrum, at the rear of wave filter correspondence being obtained topological charge is m ₁And m ₂LG vortex light, when keeping-1 grade, be-m with obtaining corresponding topological charge ₁Or-m ₂LG vortex light, and this two bundles vortex light is designated as u ₁And u ₂, its light field expression formula does

$u(r,\mathrm{\&theta;},z)=E_0\exp \left[\frac{{-\mathrm{<figure-callout\; id="2"\; label="ikr"\; filenames="DEST\_PATH\_HSB00000630964700011.png"\; state="\{\{state\}\}">ikr</figure-callout>}}^2}{2R\left(z\right)}\right]\exp \left[i\left(\right|m|+1){\tan }^{-1}\frac{z}{z_0}\right]\exp \left(\mathrm{i\&omega;t}\right)\exp (-\mathrm{im\&theta;})---\left(1\right)$

$E_0=\frac{C_R}{\sqrt{1+{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DEST\_PATH\_HSB00000630964700011.png"\; state="\{\{state\}\}">z</figure-callout>}}^2/z_0^2}}{\left[\frac{r\sqrt{2}}{w\left(z\right)}\right]}^{\left|m\right|}\exp \left[\frac{{-r}^2}{w^2\left(z\right)}\right],w\left(z\right)=w_0\sqrt{1+z/z_0}---\left(2\right)$

Wherein, E ₀Be the amplitude of background light field, ω is the circular frequency of light beam, and w (z) expression light beam is at the radius at z place, w ₀Be the waist radius of light beam, z ₀=π w ₀ ²/ λ is the Rayleigh distance.R (z)=z (1+z ²/ z ₀ ²) be the radius-of-curvature on corrugated, m is the topological charge number, k is a wave number.Simultaneously, frequency displacement device 7 makes a branch of light produce certain frequency difference Δ ω with respect to another bundle light, and the frequency difference amount can be controlled through the frequency difference controller.At this moment, can get the coaxial stack light beam complex amplitude of exporting light combination mirror 9 backs according to formula 1 and 2 does

$u^2={[u_1(r,\mathrm{\&theta;},z)+u_2(r,\mathrm{\&theta;},z)]}^2=u_1{u}_1^{*}+u_2{u}_2^{*}+u_1{u}_2^{*}+u_1^{*}{u}_2$

$\&ap;E_{01}^2+E_{02}^2+2E_{01}{E}_{02}\cos [\frac{{\mathrm{\&Delta;<figure-callout\; id="2"\; label="kr"\; filenames="DEST\_PATH\_HSB00000630964700011.png"\; state="\{\{state\}\}">kr</figure-callout>}}^2}{2R\left(z\right)}-(m_1-m_2)\mathrm{\&theta;}+\left(\right|m_1|-|{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="DEST\_PATH\_HSB00000630964700011.png"\; state="\{\{state\}\}">m</figure-callout>}}_2\left|\right){\tan }^{-1}\frac{z}{z_0}+({\mathrm{\&omega;}}_1-{\mathrm{\&omega;}}_2)t]---\left(3\right)$

Wherein

E ₀₁＝E ₀₂＝E，? Δω＝ω ₁-ω ₂ (4)

Footmark 1 and 2 is wherein represented first bundle and the second bundle vortex light respectively, and Δ k is the wave-number difference of two-beam.During as ; Perhaps when

, light intensity is a maximum value.Wherein N is an integer, and is the coordinate of time t and observation place z.Satisfy the θ of this formula _MaxThe angular coordinate at each light intensity " blade " center in the hot spot that the system that is produces, promptly

On certain particular moment and certain special plane,

is definite value.According to the periodicity of cosine function, in the single cycle

0≤N＜m ₁-m ₂ (6)

N has m in one-period ₁-m ₂Individual value, promptly adopt present technique to the rotation hot spot have m ₁-m ₂Individual intensity " blade ".

When | m ₁| ≠ | m ₂| the time, be input space photomodulator image not simultaneously, θ _MaxNot only in same plane, change in time, and change along with the increase of transmission range, the gained light beam is the combined vortex light beam that planar rotates.But in a certain specific plane, do by the angular velocity of rotation of this scheme gained hot spot

$\mathrm{\&Omega;}=\frac{{\mathrm{d\&theta;}}_{\max }}{\mathrm{dt}}=\frac{\mathrm{\&Delta;\&omega;}}{m_1-m_2}---\left(7\right)$

Work as m ₁=-m ₂The time; The image that is input space photomodulator is identical; And 1 grade of spatial filter 6-1 reservation or-1 grade of frequency spectrum light, 6-2 keep-1 grade or 1 grade of frequency spectrum light time, ignore the variation of Beam Wave-Front radius of curvature R (z), and the composite light beam vortex characteristic that obtains in this scheme disappears; Only in same plane, rotate, and angular velocity of rotation

$\mathrm{\&Omega;}=\frac{d{\mathrm{\&theta;}}_{\max }}{\mathrm{dt}}=\frac{\mathrm{\&Delta;\&omega;}}{m_1-{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="DEST\_PATH\_HSB00000630964700011.png"\; state="\{\{state\}\}">m</figure-callout>}}_2}=\frac{\mathrm{\&Delta;\&omega;}}{2m_1}---\left(8\right)$

Annotate: this programme system can not work in m ₁=m ₂Pattern, this pattern is that the image of input space photomodulator is identical, and spatial filter 6-1 and 6-2 keep 1 grade or-1 grade of frequency spectrum light simultaneously.

The coaxial stack light beam of light combination mirror 9 back outputs is the combined vortex light beam of rotation, and can observe the pattern of rotation through image acquisition device.The frequency difference that the frequency displacement device produces is big more, and the velocity of rotation of pattern is fast more.And the difference that the lobe numbers of pattern is calculated the topological charge number of vortex hologram by input determines.In this programme, the image through the computer control spatial light modulator is " blade " number of may command rotation hot spot, and the frequency displacement size that the control frequency shifter produces is the rotating speed of may command hot spot.

Claims (5)

1. a device that adopts reflective spatial light modulator to produce the combined vortex light beam of rotation is characterized in that comprising laser instrument (1), beam expander device (2), beam splitter (3), first semi-transparent semi-reflecting lens (4), first spatial light modulator (5-1), second spatial light modulator (5-2), the first Fourier space wave filter (6-1), the second Fourier space wave filter (6-2), frequency displacement device (7), second semi-transparent semi-reflecting lens (8) and light combination mirror (9); The light beam of LASER Light Source (1) outgoing passes through beam expander (2) and beam splitter (3) successively; Be reflected to spatial light modulator modulation (5-1) surface by second semi-transparent semi-reflecting lens (8) through two light beams of beam splitting are wherein a branch of; The former road of light beam after modulated is returned and second semi-transparent semi-reflecting lens (8) is crossed in the part transmission, and transmitted light is through the first Fourier space wave filter (6-1); Another bundle is reflected to spatial light modulator modulation (5-2) surface by first semi-transparent semi-reflecting lens (4); The former road of light beam after modulated is returned and first semi-transparent semi-reflecting lens (4) is crossed in the part transmission, and transmitted light is through the second Fourier space wave filter (6-2) and frequency displacement device (7); This two-beam realizes that through light combination mirror (9) coaxial stack obtains producing the combined vortex light beam of rotation; Described first spatial light modulator (5-1) and second spatial light modulator (5-2) adopt reflective spatial light modulator.

2. employing reflective spatial light modulator according to claim 1 produces the device of propeller type rotary beam; It is characterized in that: adopt image acquisition device (10) to obtain the propeller type rotary beam and gather, and observe the pattern of rotation through the coaxial stack of beam splitter (9).

3. employing reflective spatial light modulator according to claim 1 produces the device of propeller type rotary beam, it is characterized in that: go up the vortex hologram that adopts graphics controller (11) control light modulated in first spatial light modulator (5-1) and second spatial light modulator (5-2).

4. employing reflective spatial light modulator according to claim 1 produces the device of propeller type rotary beam, it is characterized in that: go up the frequency shift amount that adopts frequency difference controller (12) control frequency shifter at frequency displacement device (7).

5. employing reflective spatial light modulator according to claim 1 produces the device of propeller type rotary beam, it is characterized in that: said frequency displacement device (7) is any existing acousto-optic frequency shift device or rotation slide frequency displacement device.

Images