DE202011110732U1 - Optical arrangement for laser interference structuring of a sample with beam guidance of the same path length - Google Patents

Abstract

Optical arrangement for laser interference structuring of a sample (P) with a beam splitter (1) onto which a laser beam (1) can be irradiated along an optical main axis (H) of the arrangement and with which the laser beam (1) irradiated thereto into a transmitted partial beam (t1) and a reflected partial beam (rl) can be divided, the reflected partial beam preferably being able to be reflected at an angle of 90 ° to the main axis (H), and a first positioning mirror (2t) arranged in the beam path of the transmitted partial beam (t1) and one in the beam path of the the two positioning mirrors (2t, 2r) for reflecting the two partial beams (tl, rl) to a common target point (Z) and are arranged and aligned such that the optical path length of the both sub-beams (tl, rl) between the beam splitter (1) and the common target point (Z) is the same.

Description

The present invention relates to an interference structure of an optical system for laser interference structuring, that is, to an optical arrangement for laser interference patterning of a sample.

Optical arrangements for laser interference patterning of samples are already known from the prior art. That's how it shows US 6,549,309 B1 a structure for generating holographic patterns on a sample in which the sample is irradiated with an interference pattern (the structuring then takes place in that, as in the present invention, at the locations of the interference maxima a sufficient beam intensity leads to the removal of material) , In this arrangement, a laser beam is split into two sub-beams by means of a semipermeable beam splitter, wherein both sub-beams have a different geometric path or a different optical path length to impinge on the sample to be patterned. However, this different optical path length of the two partial beams can lead to a reduction of the structuring efficiency (see below).

Moreover, an arrangement with a diffractive beam splitter is known from the prior art, where the split beams are brought together again via lenses ( A. Lasagni, P. Shao, J. Hendricks, CM Shaw, D. Martin and S. The Direct Production of Periodic Patterns with Sub-wavelength Structural Structures on Poly (3,4-Ethylene dioxythiopene) -poly (styrenesulfonates) thin films using femtosecond laser interfering patterning, Applied Surface Science 256 (2010) 1708-1713 ). The disadvantage here, however, is that the transmission component of the split beam must be blocked and thus a lot of beam energy of the input beam is lost. In addition, high energy densities can easily lead to destruction of the diffractive optics. Also, a large-scale editing is not possible.

As already indicated, the lack of consideration of the geometric path difference, ie the different optical path length of the two partial beams after splitting by means of a beam splitter in the first-mentioned prior art generally leads to a reduction of the structuring efficiency. If, in addition, the angles of incidence of the two partial beams on the surface of the sample to be structured are unequal, that is, Θ ₁ ≠ Θ ₂ , then this can additionally lead to asymmetrical and / or inhomogeneous structures. Therefore, it is usually necessary that the angles of incidence of the two partial beams are equal to the sample (Θ ₁ = Θ ₂ ).

4a shows a schematic representation of the beam path in a two-beam interference of the two partial beams in the prior art, if the geometric path difference of the two partial beams is not taken into account. If it is assumed that Θ ₁ = Θ ₂ = Θ, then the difference in the optical path length of the two partial beams, ie the path difference Δ, corresponds exactly to the difference between the geometric path lengths n · (L ₁ + L ₂ ) and n · (L ₃ + L ₄ ), where n is the refractive index of the medium in which the propagation of the laser radiation takes place. Thus, assuming the same angle of incidence (Θ = Θ ₁ = Θ ₂ )

With L ₁ = (L ₃ + L ₅ ) tanΘ and L ₄ = L ₅ tanΘ follows:

4b to 4d show the corresponding time delay (as a function of L ₃ ), with the two laser pulses corresponding to the partial beams (using pulsed laser radiation, as is customary in the Laserinterferenzstrukturierung) impinge on the surface to be structured or the substrate (this normal conditions are assumed that is, n = 1). P is the period of the interference structures that are structured in the surface of the sample. In the in the 4b to 4d shown dependence of the time delay of the impingement of the laser pulses of the two partial beams of L ₃ (shown in each case the ratio of the difference .DELTA.t in the pulse duration and the pulse duration τ) can be seen that with increasing L ₃ , the time difference and the time delay greater becomes. In addition, the laser pulse duration τ has a strong influence on the time shift of two pulses of the two partial beams. The shorter the laser pulses, the greater the time difference when hitting the sample (for example metal substrate). With a pulse duration of τ = 10 ns; a coherence length of L _k = 3m and a geometric retardation of, for example, Δ = 3 cm, the later pulse occurs approximately 33 ps later than the first pulse, which corresponds to a time difference of 0.3%. With pulse durations of τ = 1 ns or τ = 0.1 ns, the time difference increases by a factor of 10 (3%) or 100 (30%).

It is therefore an object of the present invention to provide an optical arrangement for laser interference patterning of a sample, which reduces the structuring efficiency as well as unsymmetrical and / or inhomogeneous ones Avoiding structures, so in general leads to an improved interference structuring.

The above object of the invention is achieved by an optical arrangement according to claim 1. Advantageous embodiments of the invention can be found in the dependent claims. Hereinafter, the present invention will be described first generally, then with reference to several embodiments. The individual features realized in the exemplary embodiments in combination with one another do not have to be realized exactly in the manner shown in the exemplary embodiments (in particular the positioning and / or alignment of individual optical elements of the arrangement) within the scope of the patent claims can also be realized in other ways. In particular, individual ones of the features or optical elements shown can also be omitted or else positioned and / or aligned or combined with other optical elements in another way.

The basic idea of the present invention is to position and align the individual optical elements of the arrangement used for beam guidance in such a way that a time difference between laser pulses of the two partial beams impinging on the sample is avoided. The individual optical elements of the arrangement are thus aligned and arranged so that the optical path length of the two partial beams is the same, so that no geometric path difference of the two partial beams exists. In addition, the individual optical elements of the arrangement according to the invention and the sample are aligned and positioned so that the same angles of incidence (relative to the surface normal of the sample to be processed) are realized for the two partial beams incident on the sample.

An essential optical element of the arrangement here is first a semipermeable beam splitter, with which the laser beam used for structuring (eg produced by means of a Nd: YAG laser), generally pulsed laser pulse (pulse duration eg between 0.01 and 100 nanoseconds), in the two partial beams, hereinafter also referred to as transmitted and reflected partial beam is divided. The two partial beams are then, as described in more detail below, guided by means of individual mirrors so that an optical path difference between the two partial beams is avoided.

For the purposes of the present invention, a mirror is to be understood as meaning any optical element capable of deflecting laser beams in their direction (for example by reflection). Likewise, in the context of the present invention, reflecting a (partial) beam generally means any deflection of this beam, irrespective of which concrete physical process (at the optical element used therefor) ultimately leads to this deflection. Correspondingly, a transmission of a (partial) beam through a used optical element (in particular: beam splitter) means that at least a part of the corresponding laser beam penetrates this optical element without changing direction.

The present invention thus describes an optical arrangement for laser interference structuring, in which the same path lengths of the partial beams are realized by a specific positioning of mirrors, so that the time delay of the overlapping of pulses of different partial beams is zero. This is particularly important for laser systems with shorter pulse durations, since the time delay, which represents a critical value when hitting the sample, in particular for very short laser pulses ( 4b - 4d ), is minimized.

Moreover, the present invention also achieves an improvement in the contrast between the interference maxima and minima. The contrast is the intensity difference between interference maxima and minima in the overlap of two pulses. For the ideal case (time delay is equal to zero) the following applies: intensity _maxima = 2 × intensity _output beam (before the beam splitter 1) and intensity _minima = 0.

The optical arrangement according to the invention can be used for the direct interference patterning of samples of a wide variety of structures (for example of metal substrates, plastic substrates or also semiconductor substrates) from different fields of application (such as the solar industry, the automotive industry, medical technology, optics or sensor technology). In addition, a wide variety of structuring applications are conceivable, in particular in the field of electronics or aircraft engineering.

An optical arrangement according to the invention for laser interference structuring comprises a preferably semipermeable beam splitter onto which a laser beam can be irradiated along an optical main axis of the arrangement and with which this laser beam can be split into a transmitted (transmitted) sub-beam and a deflected (reflected) sub-beam. The reflected partial beam is preferably reflected or deflected by the beam splitter at an angle of 90 ° to the main axis. The arrangement further comprises one in the beam path of the transmitted sub-beam arranged first positioning mirror and arranged in the beam path of the reflected sub-beam second positioning mirror. The two positioning mirrors are arranged (3D position in space) and aligned (3D orientation in space), that they divert the two partial beams to a common target point (in which then the component to be structured can be arranged), so reflect. The arrangement and alignment takes place (as shown below with reference to examples) so that the optical path length of the two partial beams between the beam splitter and the common target point of the two partial beams is the same.

As described in more detail below, in the beam path of the two partial beams between the beam splitter and the target point further optical elements which deflect or reflect the partial beams, which are referred to as deflecting mirrors, can be added. However, the two positioning mirrors are those mirrors in the beam path that cause the last deflection of the partial beams towards the common target point. In general (but this need not be so), the positioning mirrors are arranged stationary, but with respect to that surface which causes the deflection of the partial beams, variable (that is, they allow a different orientation of the mirror surface in space). In contrast to this (however, this need not be so), the optionally used further deflecting mirrors are usually both stationarily positioned and provided with a fixed, non-variable orientation of their mirror surfaces in space (fixed orientation of the mirror surface). The change in the orientation of the mirror surface of the positioning mirror can be realized for example by means of a corresponding motor control. The stationary positioning of the positioning mirror and / or the deflection mirror can be realized by means of a flat base plate on which the individual mirrors can be screwed.

Advantageously, the arrangement according to the invention is designed so that a surface portion of the sample to be structured at the target point can be positioned (eg via a sample holder on the base plate) that the incidence angle of the two partial beams are the same: the two angles between the surface normal on this The surface section of the sample on the one hand and the partial beam section incident on this surface section by means of the respective positioning mirror on the other hand are thus identical (Θ _r = Θ _t , in which case "r" for the reflected partial beam deflected by the beam splitter and "t" for the partial beam left by the beam splitter or transmitted partial beam is available).

In a further advantageous variant, the two positioning mirrors are arranged and aligned so that the optical path length between the beam splitter and the impact position on the respective positioning mirror is the same for the transmitted and the reflected partial beam and that for the transmitted and the reflected partial beam, the optical path length is also the same length between this impact position and the common target point.

In principle, however, this need not be the case: the two positioning mirrors can also be arranged so that the path lengths (in the reflected and in the transmitted partial beam) between the beam splitter and the positioning mirror are of different lengths, in which case this different length is caused by corresponding path length differences on the distance between the respective positioning mirror and the common target point is compensated again.

In this case, if necessary, the sample orientation and positioning in the room must be adjusted so that the two angles of incidence Θ _r and Θ _t are identical to the sample surface to be structured in the two partial beams.

As already indicated, at least one deflecting mirror deflecting the relevant partial beam is advantageously arranged in the beam path of at least one of the partial beams between the beam splitter and the positioning mirror. Advantageously, at least one deflecting mirror is present between the beam splitter and the positioning mirror both in the beam path of the reflected partial beam and in that of the transmitted partial beam.

In a further advantageous variant of the beam splitter and the deflection mirror are arranged and aligned so that for several, preferably for all of the deflection mirror, the angle between the respective incident partial beam portion (in the reflected and / or in the transmitted partial beam) and the normal to the mirror surface (of the Beam splitter and / or the respective deflection mirror) is identical. In addition, the arrangement is preferably designed such that this angle is 45 ° for several, preferably for all deflecting mirrors and preferably also for the beam splitter.

In a further advantageous arrangement according to the invention, both partial beams (ie the reflected as well as the transmitted partial beam) are guided in parallel at least in sections between the beam splitter and its respective positioning mirror, preferably in a section prior to its impact on the respective positioning mirror. It is likewise advantageous to use both partial beams between the beam splitter and its respective positioning mirror at least in sections, preferably completely in exactly one plane spanned by the two partial beams (which is then generally parallel to a flat base plate on which the individual mirrors are mounted). It is then possible to orient the mirror surface of the positioning mirror in the space such that the common target point lies outside this plane (eg above this plane on the side opposite the base plate). However, it is also conceivable to arrange and align the positioning mirrors such that the common target point lies in this plane.

Further specific arrangements according to the present invention can be found in the dependent claims 8 to 10, wherein particularly advantageous these inventive arrangements, each realize all mentioned in these claims individual features in combination, are described in the following embodiments.

Advantageously, the arrangement according to the invention is further provided with the laser beam generating laser (which can also be mounted on the base plate to be in fixed spatial relation to the other optical elements of the arrangement). In this case, in particular a pulsed laser with a pulse duration in the range between 0.01 ns and 100 ns can be used, which finally irradiates the laser beam onto the beam splitter. However, it is also conceivable to use a continuous laser. Advantageous laser types are solid-state lasers (neodymium-YAG, neodymium-doped glass (Nd: glass) and ytterbium-doped glasses and ceramics), argon ion lasers, copper vapor lasers (metal vapor lasers) or Ti sapphire lasers with wavelengths in the infrared (eg 1064 and 800 nm ), in the visible (eg 532 and 514.5 nm) or in the UV range (eg 355, 351 or 266 nm).

Of course, in addition to the already mentioned optical elements any other optical elements in the beam path of the laser before hitting the beam splitter (in particular focusing lenses and / or aperture) or in the partial beam path of the reflected and / or the transmitted laser beam be present (if the latter equality the two optical path lengths do not destroy).

The optical arrangement according to the invention will be described below with reference to three exemplary embodiments.

Showing:

1a and 1b a first arrangement according to the invention in supervision ( 1a ) as well as in 3D view ( 1b ).

2 a second inventive arrangement in plan view.

3 a third arrangement according to the invention in supervision.

1a shows a plan view of the plane which is spanned by the beam paths of the transmitted and the reflected partial beam between the beam splitter and the impact on the respective positioning mirror of the (transmitted or reflected) partial beam path. This plane is parallel to a base plate to which the individual optical elements are fixed in 1a not shown, see this 1b ,

The optical arrangement 1a . 1b includes a pulsed Nd: YAG laser 5 which generates a pulsed laser beam 1 and along the main axis H of the arrangement (parallel to the base plate 4 , compare 1b) radiates. Centered on the main axis H is in the laser beam l first a lens-diaphragm combination 6 formed, with which the laser beam l on the semi-transparent beam splitter 1 the arrangement, which is also centered on the main optical axis H, is coupled. Instead of 6 Lenses may also be after 3t-2 and 3r be formed, or even after 1 (one between 1 and 3r , and the 2nd between 3t-1 and 3t-2 ); in both cases two lenses are necessary.

All optical components described below are on the in 1b shown base plate made of steel 4 firmly screwed, thus firmly positioned on the latter. Apart from the two positioning mirrors described in detail below 2r and 2t is also the orientation of all optical elements relative to the base plate (in particular, if available, their laser beam deflecting surfaces or mirror surfaces) fixed as described below, that is fixed immutable.

The semi-transparent beam splitter 1 is aligned relative to the main axis H so that the laser beam l at an incident angle of α ₁ 45 ° incident on the surface of the semi-transparent beam splitter. By this orientation of the beam splitter 1 is the incident laser beam l in a transmitted partial beam tl (behind the beam splitter 1 first along the main axis H continues) and at an angle of 90 ° to the main axis and parallel to the base plate 4 ( 1b ) Reflected partial beam rl divided.

In the beam path of the reflected partial beam rl is seen in the beam direction behind the beam splitter 1 at the distance a from the main axis H a deflection mirror 3r arranged and aligned so that the beam splitter 1 at 90 ° from the main axis H wegreflektierte partial beam section at an angle of α _3r = 45 ° to the surface of this deflection mirror 3r incident. The on the deflection mirror 3r incident beam section of the reflected partial beam rl is thus deflected by an angle of 90 °, leaves the deflection mirror 3r thus parallel to the main axis H, but at a distance a thereof. The parallel to the main axis H extending, at the deflection mirror 3r deflected partial beam section of the reflected partial steel rl finally hits the second positioning mirror 2r , which is seen along the main beam direction H spaced from the deflection mirror 3r and also at a distance a from the main axis H is arranged.

As with the beam splitter 1 is the deflecting surface or the mirror surface at the deflection mirror 3r perpendicular to the surface of the base plate 4 aligned (this also applies to the other subsequently described deflection mirror 3t-1 and 3t-2 in the beam path of the transmitted partial beam tl).

Im through the beam splitter 1 transmitted sub-beam tl is spaced from the beam splitter 1 viewed in the beam direction along the main beam axis H centered on the latter initially a front deflecting mirror 3t-1 arranged. Also, this deflecting mirror is fixed to the base plate 4 screwed so that both its position and the orientation of its mirror surface in space is fixed. The mirror surface is oriented so that the incident beam portion of the transmitted partial beam tl is incident at an angle of 45 ° to the mirror surface and viewed at an angle of 90 ° to the main beam axis H of the latter in the direction of the mirrors 3r . 2r in the reflected partial beam rl opposite side of the main beam axis H is reflected away. For the angle of incidence of this mirror α _3t-1 is thus α _3t-1 = 45 °.

In the beam path of the transmitted partial beam tl after the front deflecting mirror 3t-1 is at a distance a from the main beam axis (on the two mirrors 3r . 2r opposite side of the main beam axis H) a rear deflecting mirror 3t-2 arranged. Also, this mirror is in terms of its positioning and the arrangement of its mirror surface in space (perpendicular to the base plate 4 ) by screwing to the base plate 4 unchangeable. The orientation of the mirror surface of the deflecting mirror 3t-2 is set so that the front deflecting mirror 3t-1 reflected beam portion of the transmitted partial beam tl at an angle α _3t-2 = 45 ° to the deflection mirror 3t-2 is incident, so at 90 ° at the mirror 3t-2 is reflected and the latter parallel to the main beam direction H, but at a distance from the same leaves, before finally on the (in the direction of the main beam direction H seen) spaced from the rear deflecting mirror 3t-2 arranged first positioning mirror 2t in the transmitted partial beam path tl falls.

Also the first positioning mirror 2t is in terms of its positioning in the room by screwing to the base plate 4 fixed, but allows (as with the second positioning mirror 2r by a motor control, not shown here) a variable orientation of the mirror surface in space. The first positioning mirror is (seen along the main beam axis H) at the same height as the second positioning mirror 2r and, as well as this (but on the opposite side of the main beam axis H) at a distance a from the main beam axis H arranged.

Seen in the beam direction along the main axis H follow in the illustrated arrangement thus first the laser 5 , spaced from the laser-aperture combination 6 , spaced from it (at the same height, but laterally offset from each other) of the beam splitter 1 as well as the deflection mirror 3r the reflected partial beam rl, spaced therefrom (at the same height, but laterally offset from one another), the two deflection mirrors 3t-1 and 3t-2 in the transmitted partial beam path tl and spaced therefrom and at the same height (but laterally offset from one another on both sides of the main axis H), the two positioning mirrors 2r and 2t ,

Instead of the combination 6 can also fade after 3t-2 and 3r be present after 1 (one between 1 and 3r , and the 2nd between 3t-1 and 3t-2 ), or after 2t and 2r (In all cases two apertures are necessary).

The two with respect to the orientation of their mirror surface in space variable positioning mirror 2r and 2t are now (with respect to the main axis H seen) mirror-symmetrically oriented so that the parallel to the main axis H on the positioning mirror 2r . 2t incident partial beam sections rl and tl are deflected at identical angles β _r = β _t towards a plane perpendicular to the base plate, the main axis H comprehensive plane reflected or reflected (reflected beam sections rla in the reflected partial beam rl and tla in the transmitted partial beam tl). The mirror surfaces of the positioning mirror 2r and 2t are there, as in 1b are oriented so that the sub-beam sections rla and tla are out of that of the transmitted sub-beam sections tl between beam splitters 1 and positioning mirror 2t and the reflected sub-beam portions rl between beam splitters 1 and positioning mirror 2r clamped, parallel to the surface of the base plate 4 extending plane to one above this level (ie, on the opposite side of the base plate side of this plane) lying common target point Z are reflected out. As 1a indicates in supervision, which cuts from the base plate outgoing surface normal through the common target point Z the major axis H.

By not shown here (a variable orientation of the sample P to be structured in space enabling), mounted on the base plate sample holder, the surface to be structured sample P in the target point Z are arranged and oriented so that the angle of incidence of the two at the positioning mirrors 2t . 2r reflected partial beam sections rla and tla are equal to this sample surface. It thus applies Θ _r (angle of incidence of the reflected partial beam rl on the sample surface to be structured) = Θ _t (corresponding angle of incidence in the transmitted partial beam tl).

Due to the above-described symmetrical alignment of the two positioning mirrors 2r and 2t to the plane perpendicular to the baseplate 4 and by the main beam axis H for the path lengths rla = tla. Due to the above-described arrangement of the deflection mirror 3r . 3t-1 and 3t-2 , the two positioning mirrors 2r and 2t and the beam splitter 1 are also the path lengths between the beam splitter 1 and positioning mirror 2t in the transmitted partial beam tl and between the beam splitter 1 and positioning mirror 2r identical in the reflected partial beam rl. This ensures that the path lengths until the impingement of the beam pulses of the laser beam l on the sample surface P are identical for both partial beams.

The reference symbol N here denotes the surface normal N on the surface of the sample P to be structured (the angles Θ _r and Θ _{t are} measured between the latter and the incident sub-beams).

1b shows the concrete construction of the optical arrangement of the first embodiment and the attachment of all the above-described optical elements to the base plate 4 , Good to see is the beam path of the partial beam sections in the reflected as well as in the transmitted partial beam in the region between the beam splitter 1 and hitting the mirror surface of the two positioning mirrors 2r and 2t in a plane parallel to the base plate 4 before both partial beams are finally directed by these positioning mirrors to the common target point Z above this plane. By symmetrically occurring variation of the orientation of the mirror surface of the two positioning mirrors 2r . 2t During machining (by means of the motor control) or the two deflection angles β _r and β _t , the common target point Z can be moved along a straight line in space, so that a corresponding longitudinal structuring of the suitably held sample P can take place.

As 1b shows are in the transmitted beam path tl between the rear deflecting mirror 3t-2 and the positioning mirror 2t and in the reflected beam path rl between the deflection mirror 3r and the positioning mirror 2r one focusing lens each 7 and a panel 8th arranged. The use of focusing lenses 7t and 7r is optional. The optical apertures 8t and 8r are screens that primarily serve to adjust the partial beams to ensure their parallelism (eg to the base plate). As far as they are not needed for processing, they can be removed.

1a and 1b show an inventive interference structure of an optical system, which here comprises a beam splitter, two (variable) positioning mirror and four (rigid) deflection mirror. The distances between 1 and 3r such as 3t-1 and 3t-2 ( 1a ) are dependent on the desired period of the interference structure. The incident laser beam l is coupled into the structure via the lens-diaphragm combination (here also only a lens or a diaphragm can be used), which strikes the semipermeable beam splitter 1 and is separated into the two partial beams tl and rl (reflection angle 45 ° at the beam splitter). The transmitted tl and the reflected rl part of the radiation are applied to the deflection mirrors 3r . 3t-1 and 3t-2 steered, each at an angle of 45 ° relative to the main beam direction H fixed to the base plate 4 are mounted. The two parallel to the surface of the base plate 4 and the main axis H and mutually parallel sections in the transmitted and in the reflected beam path are finally on the two positioning mirrors 2r . 2t to the sample P, where they interfere at equal angles of incidence Θ _r = Θ _t relative to the surface normal N.

As a result of the positions and orientations of the individual optical elements shown, it is thus possible to realize identical path lengths for both partial beams. Thus, the beams at the deflecting mirrors and at the beam splitter are always reflected by 45 °. This results in each case a path that is the same size for both partial beams. The two positioning mirrors are then used to precisely adjust the partial beams to the sample to be processed, whereby finally Θ _t = Θ _{r is} achieved and asymmetries and inhomogeneities in the interference structure at the object can be avoided.

2 shows a second embodiment of the invention, which basically as in in 1a . 1b shown case, so that only the differences are described below.

Im in 2 The case shown was the rear deflecting mirror 3t-2 omitted in the transmitted beam part, so that both in the reflected rl, as well in each case exactly one (rigid) deflecting mirror about the transmitted t1 partial beam path 3r respectively. 3t is available. The deflection mirror 3t In the transmitted partial beam path tl is thereby aligned and positioned as the front deflecting mirror 3t-1 in the first embodiment (angle of incidence α _3t = 45 °).

In the case shown are the elements 5 . 6 . 1 and 3r designed, arranged and oriented as in the first embodiment. Seen along the main radiation direction H spaced from the laterally offset elements arranged 1 and 3r in the present case, however, are the two positioning mirrors 2r and 2t at the same height as the single deflecting mirror 3t positioned the transmitted partial beam path. The deflection mirror 3t is positioned centered on the main beam axis H, while the two positioning mirror 2r and 2t as in the 1a . 1b shown case on both sides of the main beam axis H at a distance a from the same are positioned.

In the present case of 2 then there is no symmetrical orientation of the two positioning mirror 2r and 2t to the passing through the main beam axis H, perpendicular to the base plate 4 (not shown here) aligned plane. Thus, β _r ≠ β _t applies here, the orientation of the two positioning mirrors 2r . 2t in such a way that, in turn, the path lengths from the point of incidence of the two partial beams on their respective positioning mirrors to the point of incidence at the target point Z on the sample surface P are the same length (the sample P being oriented again so that Θ _r = Θ _t ). The angle β _t is thus here an acute angle, whereas the angle β _{r is} an obtuse angle.

Since not only the path lengths rla and tla between positioning mirror and sample are identical, but also the path lengths between the beam splitter 1 and the place of impact on the respective positioning mirror (via the two deflecting mirrors 3r and 3t ), is thus as in 1a . 1b Case shown the optical path length of the two partial beams rl and tl identical.

3 Finally, shows a third embodiment, which basically as well as in 2 shown second embodiment is realized, so that in turn only the differences from the in 2 will be described (the arrangement of the elements 5 . 6 and 1 centered on the main beam axis H takes place as in 2 ).

In the 3 The arrangement shown now only requires the two (variable) positioning mirror 2r and 2t , but no additional (rigid) deflection mirror. The first positioning mirror 2t in the transmitted partial beam path tl is centered on the main beam axis H spaced from the beam splitter 1 arranged (instead of the deflecting mirror 3t in 2 ). At the same distance from the beam splitter 1 is laterally spaced from the main beam axis H, the second positioning mirror 2r the reflected partial beam path rl arranged (at the position of the deflection mirror 3r in 2 ).

The two positioning mirrors 2r and 2t (or their reflective surfaces) are now oriented in space and the sample P is positioned and oriented by the sample holder, not shown, that not only the distances between the beam splitter 1 and first positioning mirror 2t (along the major axis H) and between beam splitters 1 and second positioning mirror 2r (perpendicular to the main axis H) are identical, but also the distances tla between the first positioning mirror 2t and common target point Z in the transmitted partial beam and rla between the second positioning mirror 2r and common target point Z in the reflected partial beam. (Again, the two positioning mirrors steer 2t and 2r the respective partial beams out of the plane spanned by the beam sections r 1 and t 1 between the beam splitter and the respective positioning mirror onto the common target point Z lying above this plane)

By the two identical path sections rl and tl on the one hand and rla and tla on the other hand and the appropriate orientation of sample P and mirror surfaces 2r . 2t Thus, not only is = _r = Θ _t ensured, but also an identical optical path length of both partial beams.

In the case shown, the sections between the beam splitter 1 and positioning mirror 2t . 2r However, this does not have to be the case: If different path lengths are selected in this respect, a suitable positioning of the sample P in the space by means of a sample holder not shown here enables such that the different lengths of the first sections in front of the mirrors by correspondingly different lengths of second track sections tla and rla are compensated for again after the mirrors, as well as a total of identical optical path lengths in the transmitted and in the reflected partial beam. (With suitable orientation of the elements 2r . 2t and P in space, the condition Θ _r = Θ _t can be additionally maintained.)

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 6549309 B1 [0002]

Cited non-patent literature

• A. Lasagni, P. Shao, J. Hendricks, CM Shaw, D. Martin and S. The Direct Production of Periodic Patterns with Sub-wavelength Structural Structures on Poly (3,4-Ethylene dioxythiopene) -poly (styrenesulfonates) thin films using femtosecond laser interfering patterning, Applied Surface Science 256 (2010) 1708-1713 [0003]

Claims (11)

Optical arrangement for the laser interference structuring of a sample (P) with a beam splitter ( 1 ), on which a laser beam (l) along a main optical axis (H) of the arrangement is einstrahlbar and with which this irradiated laser beam (l) in a transmitted partial beam (tl) and a reflected partial beam (rl) can be divided, wherein the reflected partial beam preferably with an angle of 90 ° to the main axis (H) is reflected, and a in the beam path of the transmitted partial beam (tl) arranged first positioning mirror ( 2t ) and in the beam path of the reflected partial beam (rl) arranged second positioning mirror ( 2r ), whereby the two positioning mirrors ( 2t . 2r ) for reflecting the two partial beams (t1, r1) onto a common target point (Z) and arranged and aligned such that the optical path length of the two partial beams (t1, R1) between the beam splitter ( 1 ) and the common target point (Z) is the same. Optical arrangement according to the preceding claim, characterized in that a surface portion of the sample (P) to be structured is positionable at the target point (Z), preferably positionable by means of a positioning unit such as a sample holder such that the two angles (θ _r , θ _t ) between the surface normal (N) on this surface portion on the one hand and by means of the respective positioning mirror ( 2t . 2r On the other hand, part-beam portions (tla, rla) irradiated to this surface portion are identical (θ _r = θ _t ). Optical arrangement according to one of the preceding claims, characterized in that the two positioning mirrors ( 2t . 2r ) are arranged and aligned such that for both partial beams (t1, r1) the optical path length between the beam splitter ( 1 ) and the impact position on the respective positioning mirror is the same length and that for both partial beams (tl, rl) the optical path length (tla, rla) between the impact position on the respective positioning mirror and the common target point (Z) is the same length. Optical arrangement according to one of the preceding claims, characterized in that in the beam path at least one of the partial beams (tl, rl) between the beam splitter ( 1 ) and positioning mirror ( 2t . 2r ) at least one deflection beam deflecting the partial beam by reflection ( 3t . 3r ), wherein in each case at least one such deflecting mirror is arranged both in the beam path of the reflected partial beam (rl) and in the beam path of the transmitted partial beam (tl). Optical arrangement according to the preceding claim, characterized in that the beam splitter ( 1 ) and the deflection mirrors ( 3t . 3r ) are arranged and aligned such that for at least two, preferably for all deflecting mirrors ( 3t . 3r ) the angle between the respective incident partial beam section and the normal to the mirror surface is identical, preferably furthermore for at least two, preferably for all deflecting mirrors ( 3t . 3r ) and also preferred for the beam splitter ( 1 ) Is 45 °. Optical arrangement according to one of the preceding claims, characterized in that both partial beams (tl, rl) between the beam splitter ( 1 ) and their respective positioning mirror ( 2t . 2r ) at least in sections, preferably in a section before impinging on the respective positioning mirror ( 2t . 2r ), parallel guided or guided. Optical arrangement according to one of the preceding claims, characterized in that both partial beams (tl, rl) between the beam splitter ( 1 ) and their respective positioning mirror ( 2t . 2r ) are guided or guided at least in sections, preferably completely, in exactly one plane spanned by the two partial beams (t1, r1), before they can be guided either by the two positioning mirrors ( 2t . 2r ) are reflectable on the target point (Z) not lying in this plane or can be reflected on the target point (Z) also lying in this plane. Optical arrangement according to one of the preceding claims, characterized in that in the beam path of the transmitted partial beam (tl) between the beam splitter ( 1 ) and the first positioning mirror ( 2t ) exactly two deflecting mirrors ( 3t-1 . 3t-2 ) and in the beam path of the reflected partial beam (rl) between the beam splitter ( 1 ) and the second positioning mirror ( 2r ) exactly one deflection mirror ( 3r ) are arranged and aligned, wherein preferably at least one, several or all of the following features are / are realized: The front seen in the beam direction (FIG. 3t-1 ) of the two deflection mirrors in the beam path of the transmitted partial beam (tl) is positioned on the main optical axis (H). • The rear (seen in the beam direction) 3t-2 ) of the two deflection mirrors in the beam path of the transmitted partial beam (t1) and the deflection mirrors ( 3r ) in the beam path of the reflected partial beam (rl) are positioned on both sides of the main axis (H) at an identical distance (a) from the main axis (H). • The partial beam sections between the rear ( 3t-2 ) Deflecting mirror and the first positioning mirror ( 2t ) in the beam path of the transmitted partial beam (tl) on the one hand and between the deflection mirror ( 3r ) and the second positioning mirror ( 2r ) in the beam path of the reflected partial beam (rl) on the other hand run parallel to each other and on both sides of the main axis (H) parallel to this and at an identical distance (a) from this. • For all three deflection mirrors ( 3t-1 . 3t-2 . 3r ), the angle between the incident partial beam portion and the normal to the mirror surface is identical and is 45 °. • The deflection mirror ( 3r ) of the reflected sub-beam (rl), the rear ( 3t-2 ) of the two deflecting mirrors in the beam path of the transmitted partial beam (tl) and the two positioning mirrors ( 2r . 2t ) have the same distance (a) from the major axis (H) as seen with respect to the point of incidence of the radiation. • In the beam direction along the main axis (H) are seen first on the main axis (H) of the beam splitter ( 1 ) and at the same height laterally offset from the main axis (H) on a first side thereof the deflection mirror ( 3r ) of the reflected partial beam (rl) before then spaced therefrom on the main axis (H) of the front deflecting mirror ( 3t-1 ) and at the same height laterally offset from the main axis (H) on a second, the first side opposite side of the main axis (H) of the rear deflecting mirror ( 3t-2 ) are positioned and finally spaced therefrom laterally offset to the main axis (H) on the first side of the second positioning mirror ( 2r ) and on the second side at the same height the first positioning mirror ( 2t ) are positioned. Optical arrangement according to one of the preceding claims 1 to 7, characterized in that in the beam path of the transmitted partial beam (tl) between the beam splitter ( 1 ) and the first positioning mirror ( 2t ) exactly one deflection mirror ( 3t ) and in the beam path of the reflected partial beam (rl) between the beam splitter ( 1 ) and the second positioning mirror ( 2r ) exactly one deflection mirror ( 3r ) is arranged and aligned, wherein preferably at least one, several or all of the following features is / are realized: The deflecting mirror (FIG. 3t ) in the beam path of the transmitted partial beam (tl) is positioned on the main optical axis (H). • The deflection mirror ( 3r ) in the beam path of the reflected partial beam (rl) is positioned laterally offset from the main axis (H) on a first side thereof. • The partial beam sections between the beam splitter ( 1 ) and the deflection mirror ( 3r ) in the beam path of the reflected partial beam (rl) on the one hand and between the deflection mirror ( 3t ) and the first positioning mirror ( 2t ) in the beam path of the transmitted partial beam (tl) on the other hand parallel to each other and perpendicular to the main axis (H). • For both deflecting mirrors ( 3t . 3r ), the angle between the incident partial beam portion and the normal to the mirror surface is identical and is 45 °. • The deflection mirror ( 3r ) of the reflected partial beam (rl) and the two positioning mirrors ( 2r . 2t ) have the same distance (a) from the major axis (H) as seen with respect to the point of incidence of the radiation. • In the beam direction along the main axis (H) are seen first on the main axis (H) of the beam splitter ( 1 ) and at the same height laterally offset from the main axis (H) on a first side thereof the deflection mirror ( 3r ) of the reflected sub-beam (rl) before, then spaced therefrom and at the same height on the main axis (H) of the deflection mirror ( 3t ) of the transmitted partial beam (tl), offset laterally from the main axis (H) on the first side thereof the second positioning mirror ( 2r ) and offset laterally from the main axis (H) on a second, the first side opposite side of the main axis (H) of the first positioning mirror ( 2t ) are positioned. Optical arrangement according to one of the preceding claims 1 to 7, characterized in that neither in the beam path of the transmitted partial beam (tl) between the beam splitter ( 1 ) and the first positioning mirror ( 2t ), nor in the beam path of the reflected partial beam (rl) between the beam splitter ( 1 ) and the second positioning mirror ( 2r ) Deflection mirrors are present, whereby preferably at least one, several or all of the following features are / are realized: The first positioning mirror (FIG. 2t ) is positioned on the main optical axis (H). • The second positioning mirror ( 2r ) is positioned at a distance from the major axis (H). • The two positioning mirrors ( 2r . 2t ) have the same distance from the beam splitter with respect to the point of incidence of the radiation ( 1 ). • In the beam direction along the main axis (H) are seen first on the main axis (H) of the beam splitter ( 1 ) and at the same height laterally offset from the main axis (H) on a first side thereof the positioning mirror ( 2r ) of the reflected sub-beam (rl), before then spaced therefrom and on the main axis (H) of the positioning mirrors (rl) 2t ) of the transmitted partial beam (tl) is positioned. Optical arrangement according to one of the preceding claims, characterized in that the positioning mirrors ( 2r . 2t ) are arranged in a stationary position, but with movable, for example by means of motors to different orientations in space adjustable mirror surfaces, preferably on a base plate ( 4 ), and / or that one of, preferably a plurality of, preferably all of the deflection mirrors in a stationary position and with a fixed orientation of its mirror surface (s) in the Space is / are arranged, preferably on the base plate ( 4 ) is / are arranged. Optical arrangement according to one of the preceding claims, characterized by a laser ( 5 ), in particular a pulsed laser having a pulse duration in the range between 0.001 ns and 1000 ns, for irradiating the laser beam (1) onto the beam splitter ( 1 ) and / or one in the laser beam (l) in front of the beam splitter ( 1 ) arranged lens ( 6 ) and / or diaphragm with which the incident laser beam (1) on the beam splitter ( 1 ) and / or in that the sample (P) is arranged at the target point or can be arranged.

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