CN101201457A - Large multiplying power beam expander for high power laser system - Google Patents

Abstract

The invention provides a beam expander of large magnification for a laser system of high power and consists of a first convex lens, a filtration hole, a concave lens and a second convex lens sequentially; the first convex lens, the filtration hole, the concave lens and the second convex lens share the same optical axis; the filtration hole is arranged on the back focus of the first convex lens; the position of the components meets the following relations, wherein, L1 is the space between the filtration hole and the concave lens; L2 is the space between the concave lens and the second convex lens; f0, f1 and f2 are respectively the focus of the first convex lens, the concave lens and the second convex lens; beta is the beam expanding ratio of the beam expander. The invention has the advantages of simple structure, low cost and large regulating range.

Description

The big multiplying power beam expander that is used for high power laser system

Technical field

The present invention relates to Laser Devices, particularly a kind of big multiplying power beam expander that is used for high power laser system.

Technical background

In contemporary optics, laser application particularly, beam expander is a kind of beam converter commonly used.The expansion bundle structure that two kinds of structures are arranged usually: structure of falling Kepler and the structure of falling the Galileo.The structure of falling Kepler as shown in Figure 1, beam expander is little focal length convex lens and a coaxial formation of connecting of big focal length convex lens, and the focus in object space of little focal length convex lens overlaps with the rear focus of big focal length convex lens, then expands the ratio that beam ratio equals two focal lengths of lens.If will increase the expansion beam ratio, just must increase the focal length of big focal length convex lens, perhaps reduce the focal length of little focal length convex lens.For the beam expander of big expansion beam ratio, two convex lens spacings can be very big, generally all needs long lens barrel, and beam expander device commonly used generally all is that a kind of expansion beam ratio is only arranged, and this is very inconvenience in application.

For high power laser system, because its output power is big, the monochromaticity height need carry out big multiplying power and expand bundle under vacuum condition before laser output, all will add an aperture simultaneously in beam expander inside and constitute spatial filter, improved output beam quality.As shown in Figure 2, the structure of falling Kepler is done as a whole being sealed within the vacuum after adding aperture, and expanding beam ratio can not become again, and expands beam ratio greatly and mean long lens barrel; The structure of falling the Galileo causes beam quality to descend owing to can not constitute the spatial filter structure, and wavefront is wayward.

Summary of the invention

The objective of the invention is to overcome above-mentioned the deficiencies in the prior art, a kind of big multiplying power beam expander that is used for high power laser system is provided, characteristics of the present invention are: for one group of lens determining, the expansion beam ratio of this structure is by regulating lenticular spacing adjustable continuously in can realizing on a large scale; The 2nd, for the expansion beam ratio of giving provisioning request, the selection of scioptics focal length can be found a minimum spacing, saves the space than common beam expander.

Technical solution of the present invention is as follows:

A kind of big multiplying power beam expander that is used for high power laser system, constitute by first convex lens successively, filtering aperture, concavees lens and second convex lens with optical axis, described filtering aperture is positioned at the back focus of first convex lens, and following relationship is satisfied in the position of said elements:

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{f_0{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\mathrm{\&beta;}}{f_2}-f_1$ ${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=f_2-{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+\frac{f_1{f}_2}{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_0\mathrm{\&beta;}}$

Wherein: L ₁Be the spacing of filtering aperture and concavees lens, L ₂Be the spacing of the concavees lens and second convex lens, f ₀, f ₁And f ₂Be respectively the focal length of first convex lens, concavees lens and second convex lens, β is the expansion beam ratio of beam expander.

The bore r of described first convex lens ₀Should be more than or equal to the input beam bore; The bore r of described concavees lens ₁By r ₀, f ₀, L ₁Common decision, and satisfy r ₁〉=L ₁r ₁/ f ₀The bore r of described second convex lens ₂Expansion beam ratio β and r by system requirements ₀Decision, and satisfy r ₂〉=β r ₀

Technique effect of the present invention:

Because the adding of concavees lens is improved the range of adjustment that expands the bundle multiplying power under the finite space, the selection of concavees lens and convex lens can be implemented under the prerequisite of identical expansion beam ratio and utilizes minimum axial space; In addition, add a small filter in the beam expander of the present invention, played the effect of beam shaping.The present invention is simple in structure, and cost is low, and range of adjustment is big, can be applied to the expansion bundle of high power laser system.

Our experiments show that:

The expansion beam ratio of the big multiplying power beam expander of the present invention is by regulating lenticular spacing adjustable continuously in can realizing on a large scale; For given expansion beam ratio, the selection of scioptics focal length can search out a minimum spacing, saves the space than common beam expander.

Big multiplying power beam expander of the present invention is applied in the high power laser system, be with first convex lens, filtering aperture and concavees lens as being packaged in the laser system under the overall vacuum condition, focal length selection by second convex lens and concavees lens and different expansion beam ratio in distance adjustment between second convex lens can obtain in a big way so.

By the light path principle of reversibility as can be known, be inverted this structure and can be used for the light beam bundle that contracts.

Description of drawings

Fig. 1 is common beam expander structural representation.

Fig. 2 is a beam expander commonly used in the existing superpower laser.

Fig. 3 is the structure and the parameter synoptic diagram of the big multiplying power beam expander in the high power laser system of the present invention.

Fig. 4 is the tunable feature of the expansion beam ratio of beam expander of the present invention.

Fig. 5 is the tunable feature that beam expander of the present invention is applied to expand in the high power laser system beam ratio.

Embodiment

The invention will be further described below in conjunction with embodiment and accompanying drawing, but should not limit protection scope of the present invention with this.

See also Fig. 3 earlier, Fig. 3 is used for the structure and the parameter synoptic diagram of the big multiplying power beam expander of high power laser system for the present invention.As seen from the figure, the present invention is used for the big multiplying power beam expander of high power laser system, constitute by first convex lens 1 successively, filtering aperture 2, concavees lens 3 and second convex lens 4 with optical axis, described filtering aperture 2 is positioned at the back focus of first convex lens 1, and following relationship is satisfied in the position of said elements:

${\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">L</figure-callout>}}_1=\frac{f_0{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_1\mathrm{\&beta;}}{f_2}-{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_1$

${\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">L</figure-callout>}}_2=f_2-{\mathrm{<figure-callout\; id="1"\; label="f"\; filenames="S2007101719074E00011.png,S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_1+\frac{f_1{f}_2}{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="S2007101719074E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}_0\mathrm{\&beta;}}$

Wherein: L ₁Be the spacing of filtering aperture 2 and concavees lens 3, L ₂Be the spacing of the concavees lens 3 and second convex lens 4, f ₀, f ₁And f ₂Be respectively the focal length of first convex lens 1, concavees lens 3 and second convex lens 4, β is the expansion beam ratio of beam expander.

The bore r of described first convex lens 1 ₀Should be more than or equal to the input beam bore; The bore r of described concavees lens 3 ₁By r ₀, f ₀, L ₁Common decision, and satisfy r ₁〉=L ₁r ₁/ f ₀The bore r of described second convex lens 4 ₂Expansion beam ratio β and r by system requirements ₀Decision, and satisfy r ₂〉=β r ₀

According to the specific requirement that system expands beam ratio, space length to beam expander, be used for the satisfied relation of each parameter of the big multiplying power beam expander of high power laser system in conjunction with the present invention, determine the optimal selection of system.

1, in the lower optical system of power, for given f ₀, f ₁, f ₂, can realize that β's (L) is adjustable continuously.As: f ₀=0.5, f ₁=0.15, f ₂, mainly regulate L at=1.2 o'clock ₁Can obtain large-scale β and change, as shown in Figure 4.

2, in the lower optical system of power, the β for giving provisioning request passes through f ₁, f ₂Suitable selection, can reach L (f ₁, f ₂) minimum value.

3, for high power laser system, with first convex lens 1, spatial filter 2, concavees lens 3 as an overall package in laser system, as the output terminal of laser system.F so ₀, f ₁, L ₁Can not become again, by regulating L ₂Select appropriate f simultaneously ₂Can realize expanding the variation of beam ratio β.As f ₀=0.5, f ₁=0.15, L ₁, expand beam ratio β and f at=1 o'clock ₂, L ₂Variation relation as shown in Figure 5.

The selection of lens opening: the bore r of first convex lens 1 ₀By the decision of input beam bore, can not be less than the input beam bore; The bore r of concavees lens 3 ₁By r ₀, f ₀, L ₁Common decision, and satisfy r ₁〉=L ₁r ₁/ f ₀The bore r of second convex lens 4 ₂Expansion beam ratio β and r by system requirements ₀Decision, and satisfy r ₂〉=β r ₀

Aperture of lens in the system is by the input beam beamwidth and the decision of expansion beam ratio of beam expander.For the lower optical system of power, for lens and space length L ₁, L ₂Selection do not have much requirements.But for high power laser system, the surface of lens generally wants plated film to strengthen necessary optical characteristics, considers the damage threshold of rete and lens, can be to L ₁, L ₂Selection add necessary restriction, this must be noted that in application.

The present invention is used for the big multiplying power beam expander of high power laser system, because the adding of concavees lens, the range of adjustment that expands beam ratio is improved, and the selection of concavees lens and convex lens can be implemented under the prerequisite of identical expansion beam ratio and utilizes minimum axial space; In addition, add a small filter in the beam expander, played the effect of beam shaping.

In a word, the present invention has simple in structure, and cost is low, and the characteristics that adjustable range is big can be applied to high power Expanding of laser system.

Claims (2)

1. big multiplying power beam expander that is used for high power laser system, be characterised in that by first convex lens (1) successively, filtering aperture (2), concavees lens (3) and second convex lens (4) and constitute with optical axis, described filtering aperture (2) is positioned at the back focus of first convex lens (1), and following relationship is satisfied in the position of said elements:

$L_1=\frac{f_0{f}_1\mathrm{\&beta;}}{f_2}-f_1$ $L_2=f_2-f_1+\frac{f_1{f}_2}{f_0\mathrm{\&beta;}}$

Wherein: L ₁Be the spacing of filtering aperture (2) and concavees lens (3), L ₂Be the spacing of concavees lens (3) and second convex lens (4), f ₀, f ₁And f ₂Be respectively the focal length of first convex lens (1), concavees lens (3) and second convex lens (4), β is the expansion beam ratio of beam expander.

2. the big multiplying power beam expander that is used for high power laser system according to claim 1 is characterized in that the bore r of described first convex lens (1) ₀Should be more than or equal to the input beam bore; The bore r of described concavees lens (3) ₁By r ₀, f ₀, L ₁Common decision, and satisfy r ₁〉=L ₁r ₁/ f ₀The bore r of described second convex lens (4) ₂Expansion beam ratio β and r by system requirements ₀Decision, and satisfy r ₂〉=β r ₀

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