CN101592783B - Coherent array laser inverse Dammann grating beam-combining aperture filling device - Google Patents

Abstract

The invention relates to a coherent array laser inverse Dammann grating beam-combining aperture filling device, which consists of coherent laser arrays with the same optical axis, a spectral distribution phase plate, a Fourier transformation lens and an inverse Dammann grating in turn, wherein the spectral distribution phase plate and the inverse Dammann grating are placed on an object plane and a spectrum plane of the Fourier transformation lens respectively. The filling device can combine array coherent laser light and fill the laser light into a single light beam to achieve the aim of greatly improving the output power of a laser and the light beam quality, has the characteristics of simple structure and principle, and stable and reliable performance, can control the size of output light beams and the width of far-field light beams, can be widely applied in correlative fields requiring high-power laser emission sources, is particularly applied in the fields of laser radars, laser weapons and the like, and has practical significance for developing compact, light-weight and high-beam-quality high-power laser systems.

Description

The coherent array laser inverse Dammann grating beam-combining aperture filling device

Technical field

The present invention relates to high powered laser system, particularly a kind of coherent array laser inverse Darman raster close the beam orifice filling device.

Background technology

Along with the development of laser application technique, need high power, high-quality and high-brightness laser bundle in fields such as laser radars, and develop towards miniaturization, all solid stateization, high-power direction.In general, the output power that obtains from single laser instrument is very limited, and a kind of otherwise effective technique scheme of setting up high power laser system is to use laser array, and all light beams that require to export from array element can be concerned with and synthesize single light beam.Adopt wherein that diffraction optical element has the diffraction efficiency height, volume is little, easy to adjust and can massive duplication etc. characteristics, be subjected to domestic and international researcher's extensive concern.

Relevant close bundle in general be that multichannel coherent array laser is combined into a single pass technology, and the aperture filling is that each laser of coherent laser array is exported the whole technology that are full of whole laser array bore in corrugated.Marginal technology is called closes beam orifice filling technology, promptly produces a single beam wave surface, and its output beam aperture can change control, can be between unit bore and array aperture.

Formerly technology [1] is (referring to G.J.Swanson, J.R.Leger and M.Holz, Aperture filling ofphase-locked laser arrays, Opt.Lett., 12,245-247,1987) utilize optical Fourier transformation phase filtering and two value method for correcting phase in, realize the aperture filling of laser array.Fourier phase filtering can be converted into the periodically position light field that distributes mutually of two values to the array laser bundle, make original amplitude cycle train of impulses become the continuous corrugated that an amplitude periodic phase such as unremitting changes, become the continuous corrugated of amplitude same-phase such as unremitting again by phase correction plate and obtained far field this technology of single main lobe and be applicable to the array beams that amplitude two values distribute, but be not suitable for the laser beam such as the Gaussian beam of amplitude continuous distribution.

Formerly technology [2] is (referring to L.Liu and L.Zhao, Aperture filling of a phase-locked laserarray by phase correction with self-imaging, Chinese Physics, 9,810-814,1989) utilize the mark Taibo to have the aperture packing method that image effect certain distance behind phase-locked array is placed phase compensator of one's own in, obtained the single main lobe in far field.Laser array is regarded a kind of amplitude grating with amplitude type periodic structure of particular duty cycle as.From the imaging theory, the mark talbot distance place certain waits the phase cycle amplitude structure can be converted into constant amplitude cycle phase structure by Fresnel diffraction according to Taibo.By the frequency multiplication effect of Taibo from the imaging diffraction, the train of impulses of multiplication will just fill up the neutral gear of former interval light source, make original periodic pulse train become an amplitude continuous wave face such as unremitting, promptly obtain to have uniform amplitude homophase corrugated, thereby can eliminate the inferior generation of high order diffraction level, obtain the single main lobe of far field intensity, the array beams that this technology is applicable to that amplitude two values distribute and can consecutive periods arranges, but be not suitable for the laser beam such as the Gaussian beam of amplitude continuous distribution, and long diffraction distance arranged for the array request of bigger single aperture yardstick.

Formerly technology [3] is (referring to R.M.Jenkins, R.W.J.Devereux, and J.M.Heaton, Waveguidebeam splitters and recombiners based on multimode propagation phenomena, Opt.Lett., 17,991-993,1992), the multi-mode interference coupler that has image effect based on optical waveguide of one's own can be realized the waveguide beam splitting and close bundle, can carry out the relevant synthetic of multichannel light beam under meeting some requirements.But owing to limited by the space scale of waveguide condition, the laser array unit number can not be a lot of in the short space of waveguide yardstick, and therefore the further raising to output power has considerable restraint.

Summary of the invention

The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of coherent array laser inverse Dammann grating beam-combining aperture filling device is provided.This device should have simple in structure, and is reliable and stable, can increase substantially the laser beam of laser output power and brightness and suitable light beam output bore.

Technical solution of the present invention is as follows:

A kind of coherent array laser inverse Dammann grating beam-combining aperture filling device, its characteristics are that this device is made of coaxial coherent laser array, spectrum distribution phase plate, fourier transform lens and contrary Darman raster successively, and described spectrum distribution phase plate and contrary Darman raster are positioned over respectively on the object plane and frequency plane of described fourier transform lens.

Aplanatic coherent laser array input beam is behind spectrum distribution phase plate and after the fourier transform lens conversion, after the light field on this fourier transform lens back focal plane is carried out phase compensation with contrary Darman raster, the single light beam of the same-phase of exportable go-no-go, realize that the coherent laser array closes bundle, realize the aperture filling simultaneously.This device can realize that not only coherent array laser closes bundle, has improved the far field beam brightness greatly, and beam size can change control, produces the output beam that is different from single beam bore and the total bore of array.

Described coherent laser array is phase-locked coherent laser array beams, can be the laser array light beam that diode laser matrix, laser array, solid state laser array or gas laser array produce.

Described coherent laser array can be one dimension periodic array or two-dimensionally periodic structure array.

Described Darman raster is the pure phase position grating of an optimal design, its function is that the spacing that can produce particular diffraction order time on the fourier spectra face equates and the isocandela array of light spots of limited number, described Darman raster is positioned at the front focal plane of fourier transform lens, and the fourier spectra face is the back focal plane of fourier transform lens;

Described spectrum distribution phase plate is the phase-plate that the phase place by the equal strength distribution light field of particular diffraction order on the fourier spectra face of Darman raster time is made into.

The PHASE DISTRIBUTION of described contrary Darman raster is the complex conjugate of the PHASE DISTRIBUTION of Darman raster.

The present invention compared with prior art has following technique effect:

1. contrary Darman raster method belongs to the far field construction principle, and array surface and grating face are the optical Fourier transformation relation, and operation is reliable, is easy to realize;

2. principle is simple, and the PHASE DISTRIBUTION in the time of only need designing Darman raster as array beam splitting is got complex conjugate to the Darman raster PHASE DISTRIBUTION and can be obtained contrary Darman raster.

3. contrary Darman raster closes the beam size that the beam orifice filling can obtain to change the suitable size of control, and its bore can be different from unit beam size and the total bore of array beams, so can effectively control power density and far field width of light beam in the output face;

4. the amplitude of array beams can distribute or continuous distribution for two values, is specially adapted to the Gaussian laser beam of amplitude continuous distribution.

Description of drawings

Fig. 1 is a coherent array laser inverse Dammann grating beam-combining aperture filling device synoptic diagram of the present invention.

Fig. 2 is the Damman raster splitting beam principle schematic.

Among the figure: 11-coherent laser array, 12-spectrum distribution phase plate, 13-fourier transform lens, the contrary Darman raster of 14-.The 21-Darman raster, 22-fourier transform lens, 23-fourier spectra face.

Embodiment

The present invention is further illustrated below in conjunction with accompanying drawing and embodiment.

The structural representation of coherent array laser inverse Dammann grating beam-combining aperture filling device of the present invention as shown in Figure 1, as seen from the figure, coherent array laser inverse Dammann grating beam-combining aperture filling device of the present invention, be made of coherent laser array 11, spectrum distribution phase plate 12, fourier transform lens 13 and contrary Darman raster 14 with optical axis successively, described spectrum distribution phase plate 12 and contrary Darman raster 14 are positioned over respectively on the object plane and frequency plane of described fourier transform lens 13.

Limited the aplanatic array of light spots that the arrangement mode of described coherent laser array 11 spacing that particular diffraction order time produces on the back focal plane fourier spectra face 23 of fourier transform lens during with Darman raster 21 beam splitting equates distributes identical, can be designed as one dimension periodic array or bidimensional periodic array.

Described Darman raster 21 is a kind of gratings that can produce the position distribution of particular diffraction order number of times purpose periodicity pure phase, Darman raster 21 is placed on fourier transform lens 22 front focal planes, incident light irradiation through certain amplitude, on fourier spectra face 23, obtain the isocandela of the limited number that spacing equates and have the array light field of certain PHASE DISTRIBUTION, as shown in Figure 2.

Described Darman raster 21 is positioned on the front focal plane of fourier transform lens 22, and described fourier spectra face 23 is the back focal plane of fourier transform lens 22.

Described spectrum distribution phase plate 12 is phase-plates that the PHASE DISTRIBUTION according to Darman raster 21 light field on fourier spectra face 23 is made into.

Described contrary Darman raster 14 be a pure phase position grating, with the PHASE DISTRIBUTION of Darman raster 21 are complex conjugate relationship, Darman raster 21 and all can be two-value or many-valued pure phase position grating against Darman raster 14.

Described coherent laser array 11 is positioned on the front focal plane of fourier transform lens 13, and described contrary Darman raster 14 is positioned on the back focal plane of fourier transform lens 13.

The function declaration of Darman raster is as follows:

Darman raster is the typical binary diffractive optic element of a kind of generation particular diffraction order number of times purpose, before Darman raster placed fourier transform lens, through the light-wave irradiation of certain amplitude, the aplanatic array of light spots that obtains the equal limited number of spacing on the back focal plane of fourier transform lens distributes.

Darman raster 21 is a kind of pure phase position gratings, and its transmittance function is:

Wherein: T _x, T _yThe cycle and the center that are respectively x, y direction Darman raster with Δ x, Δ y are shifted, and have inferior periodic phase structure in 21 cycles at Darman raster

The spectrum of the desirable two-dimentional Darman raster of diffraction M * N level point is that Fourier transform is:

In the formula: f _x, f _yBe spatial frequency, C _M, C _NBe constant, H (f _x, f _y) be the high order diffraction item,

For odd number M, N has m=0, and ± 1, ± 2 ..., ± (M-1)/2, and n=0, ± 1, ± 2 .., ± (N-1)/2,

For even number M, N has m=0, and ± 1, ± 3 ..., ± (M-1), and n=0, ± 1, ± 3 ..., ± (N-1).

Therefore, H (f under the ideal design _x, f _y) ≈ 0, Darman raster 21 can produce the array of light spots that the inferior light intensity of given M * N order of diffraction equates, phase place is certain on fourier spectra face 23, so can be different diffraction level time corresponding PHASE DISTRIBUTION

Be made into spectrum distribution phase plate 12, and the PHASE DISTRIBUTION of Darman raster 21 is got complex conjugate can obtain contrary Darman raster 14.

The process of closing the beam orifice filling based on the coherent array laser against Darman raster is as follows:

The array distribution light field of supposing phase-locked coherent laser array 11 is:

$e_1(x,y)=e_s(x,y)**\underset{m}{\overset{M}{\mathrm{\Σ}}}\underset{n}{\overset{N}{\mathrm{\Σ}}}\mathrm{\δ}(x-m{T}_{\mathrm{\α}})\mathrm{\δ}(y-n{T}_{\mathrm{\β}}),---\left(3\right)$

Wherein: e _s(x y) is unit laser beam optical field distribution, T _α, T _βThe cycle of array beams.The transmittance function of spectrum distribution phase plate 12 is:

So the coherent laser array adds the light field behind the spectrum distribution phase plate, be the fourier transform lens 13 of f through focal length after, the optical field distribution on back focal plane is:

$E_2(x,y)=\frac{1}{\mathrm{j\λf}}\frac{F_{f_x=\frac{x}{\mathrm{\λf}},f_y=\frac{y}{\mathrm{\λf}}}\left\{e_s(x,y)\right\}}{C_M{C}_N}[g_D(-x)g_D(-y)-F_{f_x=\frac{x}{\mathrm{\λf}},f_y=\frac{y}{\mathrm{\λf}}}\{H(f_x,f_y)\left\}\right],---\left(5\right)$

Wherein: $F_{f_x=\frac{x}{\mathrm{\λf}},f_y=\frac{y}{\mathrm{\λf}}}\left\{\right\}$ Be the Fourier transform operator.

The output light field that obtains after coherent array closes the beam orifice filling after the contrary Darman raster 14 of adding on the back focal plane of fourier transform lens 13 carries out phase compensation is:

e ₂(x，y)＝g _D*(-x)g _D*(-y)E ₂(x，y)， (6)

Wherein: g _D ^*The g of (-x) _D ^*(-y) is contrary Darman raster optical field distribution function, and " * " represents complex conjugate.

Under desirable design conditions,

$e_2(x,y)=\frac{\sqrt{M}\sqrt{N}}{\mathrm{j\λf}}{F}_{f_x=\frac{x}{\mathrm{\λf}},f_y=\frac{y}{\mathrm{\λf}}}\left\{e_s(x,y)\right\},---\left(7\right)$

So obtain the single light beam output that particular amplitude distributes, thereby the beam orifice of closing of realizing the contrary Darman raster of coherent laser array is loaded.

Need to prove: because the Fourier transform of Gaussian function remains Gaussian function, so array laser during for Gaussian function output laser still be Gaussian beam, its far-field distribution also is a Gaussian beam.Because single-mode laser adopts Gaussian beam to express basically, therefore has height validity.

The present invention is further illustrated below by embodiment:

32 * 32 coherent optical-fiber laser arrays of wavelength 1.55 μ m, each laser instrument output light field are that symmetrical Gaussian type amplitude is $\mathrm{Kexp}(-\frac{{\mathrm{\ξ}}^2}{{\mathrm{\ω}}_{\mathrm{\ξ}}^2})\exp (-\frac{{\mathrm{\η}}^2}{{\mathrm{\ω}}_{\mathrm{\ξ}}^2}),$ Wherein K is a constant, lines up 32 * 32 facing battle array in two perpendicular quadrature directions to wait cycles 100 μ m, symmetry be placed on Darman raster ± 1, ± 3, ± 5, ± 7, ± 9, ± 11, ± 13, ± 15, ± 17, ± 19, ± 21, ± 23, ± 25, ± 27, on ± 29, ± 31 grades the order of diffraction is inferior.Array plane ripple waist width (2 ω _ξ) be 10 μ m, fourier transform lens bore 8.386mm, focal length 20.268mm.

The one dimension of spectrum distribution phase plate 12 phase places distributes as shown in table 1, and this is distributed corresponding to x, y axle, can obtain two-dimensional phase and distribute.The one dimension of the interior phase place of contrary Darman raster 14 one-periods distributes as shown in table 2, and this is distributed corresponding to x, y axle, can obtain two-dimentional Darman raster.The logarithm of catastrophe point is 17 pairs in contrary Darman raster 14 one-periods, wherein a _i, b _iThe coordinate of representing a pair of catastrophe point, coordinate a _i, b _iBetween phase place be 0, coordinate b _i, a _I+1Between phase place be π.

Under desirable design conditions, close filling back, beam orifice optical field distribution and be $\mathrm{kexp}(1-\frac{x^2}{{\mathrm{\ω}}_x^2})\exp (-\frac{y^2}{{\mathrm{\ω}}_x^2}),$ Be the single light beam of a Gaussian distribution of amplitudes, close ripple waist width (2 ω of bundle _x) be 0.314mm.

Table 1 spectrum distribution phase plate 12 one dimension PHASE DISTRIBUTION

The order of diffraction is inferior	-31	-29	-27	-25	-23	-21	-19	-17
									Phase place (π)	0.6047	-0.0347	0.7055	0.6144	0.9885	0.3160	-0.5067	-0.6508
The order of diffraction is inferior	-15	-13	-11	-9	-7	-5	-3	-1
									Phase place (π)	0.7172	0.6638	-0.7662	0.2049	0.2531	0.1088	0.7287	-0.3066
The order of diffraction is inferior	31	29	27	25	23	21	19	17
									Phase place (π)	-0.6047	0.0347	-0.7055	-0.6144	-0.9885	-0.3160	0.5067	0.6508
The order of diffraction is inferior	15	13	11	9	7	5	3	1
									Phase place (π)	-0.7172	-0.6638	0.7662	-0.2049	-0.2531	-0.1088	-0.7287	0.3066

The one dimension of phase place distributes in contrary Darman raster 14 one-periods of table 2

The two-value phase place: 0 and π, the catastrophe point logarithm in the one-period: 17

i	1	2	3	4	5	6	7	8	9
										a i	0	0.08900	0.13340	0.19580	0.23060	0.33010	0.40100	0.44110	0.4840
b i	0.05540	0.11010	0.17320	0.21090	0.24870	0.34820	0.43320	0.46530	0.5
										i	10	11	12	13	14	15	16	17
a i	0.55540	0.6101	0.6732	0.7109	0.7487	0.8482	0.9332	0.9653
										b i	0.58900	0.6334	0.6958	0.7306	0.8301	0.901	0.9411	0.984

Claims (3)

1. coherent array laser inverse Dammann grating beam-combining aperture filling device, it is characterized in that this device is successively by coaxial phase-locked relevant laser array (11), spectrum distribution phase plate (12), fourier transform lens (13) and contrary Darman raster (14) constitute, described spectrum distribution phase plate is the phase-plate that the PHASE DISTRIBUTION according to Darman raster light field on the fourier spectra face is made into, the PHASE DISTRIBUTION of described contrary Darman raster is the complex conjugate of the PHASE DISTRIBUTION of Darman raster, and described spectrum distribution phase plate (12) and contrary Darman raster (14) are positioned over respectively on the object plane and frequency plane of described fourier transform lens (13).

2. coherent array laser inverse Dammann grating beam-combining aperture filling device according to claim 1 is characterized in that described phase-locked relevant laser array (11) is the laser array that is produced by diode laser matrix, laser array, solid state laser array or gas laser array.

3. coherent array laser inverse Dammann grating beam-combining aperture filling device according to claim 1 is characterized in that described phase-locked relevant laser array is the one dimension periodic array, or the two-dimensionally periodic structure array.

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