CN202110376U - Device for producing propeller type rotational light beam by using reflection type spatial light modulator - Google Patents

Abstract

The utility model relates to a device for producing a propeller type rotational light beam by using a reflection type spatial light modulator. The device is characterized in that: light emitted by a laser is expanded and collimated through a beam expander and modulated through the spatial light modulator; the modulated light is transformed to a frequency domain through a Fourier transform lens and filtered on a frequency spectrum surface through a dual-hole filter, and +/-1 level frequency spectrum component is maintained; two vortex light beams which are separated in space and have opposite topological charge +/-m are obtained through the Fourier transform lens, wherein one of the light beams enters a frequency shift through a third reflecting mirror; the frequency shift is used for performing frequency conversion on the light beam; and the other light beam sequentially passes through a first reflecting mirror and a second reflecting mirror and is coaxially overlapped with the light beam subjected to frequency conversion to obtain the propeller type rotational light beam. The device can conveniently control the rotational speed and a spot pattern of the rotational 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 propeller type rotary beam

Technical field

The present invention relates to a kind of device that adopts reflective spatial light modulator to produce the propeller type rotary beam, is the device of the two vortex light generation propeller type rotary beam that a kind of coaxial stack topological charge is opposite and frequency is different.

Background technology

Recent decades, the propeller type rotary beam causes extensive concern owing to its unique optical characteristics and potential using value.Present such light beam has been applied to the little aspect such as control of color of wave-einstein condensation experiment, optical tweezer technology, optical communication, optics.For this has carried out deep theoretical research to the propeller type rotary beam; As the hot spot pattern distribute, characteristics such as the lateral transport of energy and angular momentum; Also proposed simultaneously to produce the several different methods of the rotary beam of propeller type; C.Anastassiou etc. propose to utilize the catoptron of rotation to realize the method that hot spot rotates; C.Rotschild etc. propose to realize the propeller type rotary beam through the method for rotation aperture diaphragm; P.

etc. lets light beam produce the propeller type rotary beam through the binary phase diffraction element, and Peng Zhang Zhang Peng etc. has also reported the method for utilizing Moire technique to produce the propeller type rotary beam recently.But most of in the said method have very high requirement to device, and the beam shape of generation is comparatively single, and will come the rotational speed of control bundle through the structure of complicacy.

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.This just provides a kind of new method for producing the propeller type rotary beam.

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 adopts reflective spatial light modulator to produce the propeller type rotary beam.

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 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 realize the coaxial stack of light beam easily 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 propeller type rotary beam is characterized in that comprising laser instrument 1, beam expander 2, semi-transparent semi-reflecting lens 3, spatial light modulator 4, Fourier transform lens 5, two mesh filter 6, inverse Fourier transform lens 8, first catoptron 9, the 3rd catoptron 10, frequency shifter 11, beam splitter 12 and second catoptron 13; The light beam of the light of laser instrument 1 outgoing behind beam expander 2 beam-expanding collimations; Reflex to reflective spatial light modulator 4 modulation through semi-transparent semi-reflecting lens 3 rear sections earlier; The former road of light beam after modulated is returned and semi-transparent semi-reflecting mirror 3 is crossed in the part transmission; Transmitted light transforms to frequency domain through Fourier transform lens 5, after two mesh filter 6 filtering, is keeping ± 1 grade of spectrum component on the frequency plane, again through obtain behind the inverse Fourier transform lens 7 on the space separately and topological charge opposite ± the two vortex light beams of m; Wherein a branch of warp the 3rd catoptron 10 gets into frequency shifter 11, and frequency shifter produces frequency conversion to this light beam; Another light beam is successively through first catoptron 9 and second catoptron 13, and the light beam after frequency conversion obtains the propeller type rotary beam through beam splitter 12 coaxial stacks; Said m is the topological charge number; The light modulated of said spatial light modulator 4 is that topological charge is the vortex hologram of m; Said spatial light modulator 4 is a reflective spatial light modulator.

Adopt image acquisition device to obtain the propeller type rotary beam and gather, and observe the pattern of rotation through beam splitter 12 coaxial stacks.

On spatial light modulator 4, adopt the vortex hologram of the topological charge m of graphics controller control light modulated.

On frequency shifter 11, adopt the frequency shift amount of frequency difference controller control frequency shifter.

Said frequency shifter 11 is any existing acousto-optic frequency shift device or rotation slide frequency displacement device.

The light of laser instrument 1 outgoing is through beam expander 2 beam-expanding collimations; Modulate by the spatial light modulator of input vortex hologram (topological charge is m) again; Light beam after the modulation transforms to frequency domain through Fourier transform lens 4, after two mesh filter 5 filtering, only keeping ± 1 grade of spectrum component on the frequency plane, behind inverse Fourier transform lens 6; Become on the space separately and topological charge opposite ± the two vortex light beams of m; Wherein a branch of 7-1 gets into frequency shifters 10 through the 3rd catoptron 9, and frequency shifter produces a frequency displacement to light beam 7-1, and another light beam 7-2 is successively through first catoptron 8, second catoptron 12; Light beam 7-1 after frequency conversion is through light combination mirror 11 coaxial stacks, and the spin intensity pattern after the stack is surveyed by image acquisition device 13 and obtained.

Beneficial effect

The employing reflective spatial light modulator that the present invention proposes produces the device of propeller type rotary beam, can control the rotating speed and the hot spot pattern of rotary 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: the employing reflective spatial light modulator that the present invention proposes produces the structural drawing of the device of propeller type rotary beam.

The 1-LASER Light Source, 2-beam expander, 3-semi-transparent semi-reflecting lens, 4-reflective spatial light modulator; The 5-Fourier transform lens, 6-two mesh filter, 7-inverse Fourier transform lens, the 8-1-first vortex light beam; The 8-2-second vortex light beam, 9-first catoptron, 10-the 3rd catoptron, 11-frequency shifter; The 12-beam splitter, 13-second catoptron, 14-image acquisition device;

Embodiment

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

Embodiment 1:

See also Fig. 1.

The light of laser instrument 1 outgoing is through beam expander 2 beam-expanding collimations; Be reflected to reflective spatial light modulator by semi-transparent semi-reflecting lens 3 then and modulate 4 surfaces; The former road of light beam after modulated is returned and semi-transparent semi-reflecting mirror 3 is crossed in the part transmission, and transmitted light transforms to frequency domain through Fourier transform lens 5, after two mesh filter 6 filtering, is passing through inverse Fourier transform lens 7 again on the frequency plane; Become on the space separately and topological charge opposite ± the two vortex light beams of m; Wherein a branch of 8-1 gets into frequency shifters 11 through the 3rd catoptron 10, and frequency shifter produces a frequency displacement to light beam 8-1, and another light beam 8-2 is successively through first catoptron 9, second catoptron 13; Light beam 8-1 after frequency conversion is through beam splitter 12 coaxial stacks, and the spin intensity pattern after the stack is surveyed by image acquisition device 14 and obtained.The Overlay figure that surveys gained is as shown in Figure 3.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 and control the rotary beam of propeller type through the present invention is: the calculating vortex hologram that with topological charge is m is distinguished in the input space photomodulator 3 through graphics controller, and makes two mesh filter 5 only keep ± 1 grade of spectrum component.Two bundles that behind inverse Fourier transform lens 6, obtain like this separating have the same frequency LG vortex light of opposite topological charge ± m.The expression formula of the Laguerre-Gaussian beam LG that simplifies can be written as

$u(r,\mathrm{\&theta;},z)=E_0\exp \left[\frac{{-\mathrm{<figure-callout\; id="2"\; label="ikr"\; filenames="DEST\_PATH\_HSB00000630965500011.png"\; state="\{\{state\}\}">ikr</figure-callout>}}^2}{2R\left(z\right)}\right]\exp \left[i\left(\right|m|+1){\tan }^{-1}\frac{z}{z_0}\right]\exp \left(\mathrm{i\&omega;t}\right)\exp (-\mathrm{im\&theta;})---\left(1\right)$

$E_0=\frac{C_R}{\sqrt{1+{\mathrm{<figure-callout\; id="2"\; label="z"\; filenames="DEST\_PATH\_HSB00000630965500011.png"\; state="\{\{state\}\}">z</figure-callout>}}^2/z_0^2}}{\left[\frac{r\sqrt{2}}{w\left(z\right)}\right]}^{\left|m\right|}\exp \left[\frac{{-r}^2}{w^2\left(z\right)}\right],w\left(z\right)=w_0\sqrt{1+z/z_0}---\left(2\right)$

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 10 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, the coaxial stack light beam COMPLEX AMPLITUDE of light combination mirror 11 back outputs is:

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

$\&ap;E_{01}^2+E_{02}^2+2E_{01}{E}_{02}\cos [\frac{{\mathrm{\&Delta;<figure-callout\; id="2"\; label="kr"\; filenames="DEST\_PATH\_HSB00000630965500011.png"\; state="\{\{state\}\}">kr</figure-callout>}}^2}{2R\left(z\right)}-2\mathrm{m\&theta;}+({\mathrm{\&omega;}}_1-{\mathrm{\&omega;}}_2)t]---\left(3\right)$

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 _MaxBe the angular coordinate at each light intensity " blade " center in the hot spot that produces of system, promptly

On certain particular moment and certain specific plane,

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

0≤N＜2m (6)

N has 2m value in one-period, i.e. the hot spot of present technique generation has 2m intensity " blade ".

In addition, can get the angular velocity of rotation of hot spot

$\mathrm{\&Omega;}=\frac{{\mathrm{d\&theta;}}_{\max }}{\mathrm{dt}}=\frac{\mathrm{\&Delta;\&omega;}}{2m}---\left(7\right)$

At this moment, the coaxial stack light beam of light combination mirror 11 back outputs is the rotary beam of propeller type, 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 lobe numbers of pattern is even number and is 2m that m calculates the topological charge number of vortex hologram for input.In present technique, the image through the computer control spatial light modulator is the style 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 propeller type rotary beam is characterized in that comprising laser instrument (1), beam expander (2), semi-transparent semi-reflecting lens (3), reflective spatial light modulator (4), Fourier transform lens (5), two mesh filter (6), inverse Fourier transform lens (8), first catoptron (9), the 3rd catoptron (10), frequency shifter (11), beam splitter (12) and second catoptron (13); The light beam of the light of laser instrument (1) outgoing behind beam expander (2) beam-expanding collimation; Reflex to reflective spatial light modulator (4) modulation through semi-transparent semi-reflecting lens (3) rear section earlier; The former road of light beam after modulated is returned and semi-transparent semi-reflecting mirror (3) is crossed in the part transmission; Transmitted light transforms to frequency domain through Fourier transform lens (5), after two mesh filter (6) filtering, is keeping ± 1 grade of spectrum component on the frequency plane, pass through again obtain behind the inverse Fourier transform lens (7) on the space separately and topological charge opposite ± the two vortex light beams of m; Wherein a branch of warp the 3rd catoptron (10) gets into frequency shifter (11), and frequency shifter produces frequency conversion to this light beam; Another light beam is successively through first catoptron (9) and second catoptron (13), and the light beam after frequency conversion obtains the propeller type rotary beam through the coaxial stack of beam splitter (12); Said m is the topological charge number; The light modulated of said spatial light modulator (4) is that topological charge is the vortex hologram of m.

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 to obtain the propeller type rotary beam and gather, and observe the pattern of rotation through the coaxial stack of beam splitter (12).

3. employing reflective spatial light modulator according to claim 1 produces the device of propeller type rotary beam, it is characterized in that: the vortex hologram of going up the topological charge m that adopts graphics controller control light modulated in spatial light modulator (4).

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 control frequency shifter at frequency shifter (11).

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 shifter (11) is any existing acousto-optic frequency shift device or rotation slide frequency displacement device.

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