DE102006029035B4 - Apparatus and method for the production and detection in amplitude, phase and polarization of shaped laser pulses - Google Patents

Abstract

Apparatus for producing shaped laser pulses, comprising a pulse shaper, which is traversed by a laser pulse to be formed and has at least one modulator element arranged in the beam path of the laser pulse, wherein
- The pulse shaper is designed to break the laser pulse to be formed into its spectral components, to supply the spectral components of the at least one modulator element and then recombine into a shaped laser pulse and
- The at least one modulator element is designed to adjust the spectral components of the laser pulse in their phase and polarization,
characterized,
in that the pulse shaper (10) additionally has at least one polarizing element (120, 121) arranged in the beam path (S) of the laser pulse (L, L _x , L _y ) and which has a polarization component from the incident laser pulse (L, L _x , L _y ). filters out, has and is designed and provided, by means of the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) and the at least one polarizing element (120, 121) the laser pulse (L ) in amplitude, phase and polarization ...

Description

The The invention relates to a device for producing shaped laser pulses according to the preamble of claim 1, a method of preparation shaped laser pulses according to the preamble of claim 21 and a computer program according to the preamble of claim 36.

such Devices are used in particular for shaping laser pulses a pulse length in the femtosecond range. The application of such laser pulses is the basis various new fields of research, such as femtochemistry, femtobiology, high-field plasma physics or material processing. Pulse generation by means of laser systems is also a current research topic in laser technology. In general, that is through a laser system generated laser pulse while in its form as well as polarization determines the properties of the laser system used and thus established. To change the shape of the laser pulse, a so-called Pulse shaper used by means of which the laser pulse in the context of given by the pulse shaper possibilities and technical Borders can be formed.

One Such pulse shaper is in this case with one or more modulator elements equipped to modulate a laser pulse in the beam path a pulse pulse passing through the laser pulse are arranged. The laser pulse, for example, by an integrated into the device Laser system or an external laser can be generated, falls into the Pulse shaper and is decomposed in this in its spectral components, then fed to the one or more modulator elements and manipulated by these and finally to a shaped laser pulse be reunited. The one or more modulator elements fulfill Here, the function, the spectral components of the laser pulse independently in to adjust their phase and polarization so that one in the desired Way shaped laser pulse results.

A generic device for the formation of laser pulses is for example from the publication A.M. Weiner, D.E. Leaird, J.S. Patel and J.R. Wullert, IEEE J. Quantum Electron. 28 (1992), 908, in which a pulse shaper is described, which is traversed by a laser pulse and the Laser pulse thereby forms in its phase. The pulse shaper has this two optical grids and two cylindrical lenses in the beam path of the laser pulse are arranged so that the incident laser pulse meets and diffracts from a first optical grating and is decomposed into its spectral components. The laser light then proceeds outgoing from the optical grating in different propagation directions, meets a first cylindrical lens, is aligned parallel to it, supplied to first and second modulator elements through a second cylindrical lens focused and through a second optical grating into a single Laser pulse reunited. Due to the Modulatorelemente, as liquid crystal arrays are constructed, the spectral components of the laser pulse are manipulated and in this way the pulse shaper passing, from the spectral Shares composed of laser pulse shaped in phase.

Other Arrangements of a pulse shaper in which the phase and amplitude the laser pulse is modulated, are known and, for example also for a specific structure in the aforementioned publication described. Also pulse shaper, by using a second Modulatorelementes allow a modulation of the phase and polarization, have been realized (see T. Brixner and G. Gerber, Opt. Lett. 26 (2001), 557). However, these have the disadvantage that only one limited Alignment of the major axes in an elliptical polarization the spectral components of the laser pulse is possible by only two perpendicular mutually adjoining directions of the major axis are given can, a rotation of the main axes but not possible. In this way can a pulse shaper by means of phase and polarization modulation only set a narrow subrange of the possible pulse shapes.

Pulse shaper, where simultaneously the phase, amplitude and polarization in the far field can be shaped are not known yet. All known pulse shaper allow only an adjustment of phase and amplitude or phase and polarization (see also L. Polachek, D. Oron and Y. Silberberg, Opt. Lett. 31 (2006), 631) so that by means of such pulse shaper incident laser pulses only modulated with respect to a part of their characteristic parameters can be. Physical processes governed by such a partially modulated Laser pulses are controlled or stimulated in this way are not to influence optimally. Furthermore, at the present time known Pulse shapers a targeted adjustment of the laser pulse for optimal Adaptation to the desired Application difficult or impossible. In particular, no method is known with which a targeted, parametric pulse shaping of the physically relevant Parameters of a laser pulse in phase, amplitude and polarization carry out leaves.

From the publication T. Brixner et al., "Femtosecond Shaping of Transverse and Longitudinal Light Polarization", Opt. Letters, Vol. 18, Sep. 15, 2004 are an apparatus and a method for forming laser pulses are known in which an originally transversely polarized laser pulse is formed by interaction with a near field geometry in the near field and thereby also receives a longitudinal polarization component. For this purpose, an arrangement is shown in which a laser pulse is formed by two LCD modulator elements in phase and polarization such that there is a linear or elliptically polarized plane wave, which is incident on the near field geometry and interacts with it.

Out the publication T. Brixner et al., "Adaptive Shaping of femtosecond polarization profiles ", J. Opt. Soc. At the. B, Vol. 20, no. 5, May 2003, a method is known in which in phase and polarization shaped laser pulses with an experimental feedback algorithm ("learning algorithm ") be optimized.

Of the Invention is based on the object, an apparatus and a method to disposal to provide, by means of which an optimal shaping of short laser pulses allows becomes.

These The object is achieved by a device having the features of the claim 1 solved.

According to the invention a device of the type mentioned above additionally at least a arranged in the beam path of the laser pulse polarizing Element containing a polarization component from the incident Laser pulse filters out, and is trained and provided, by means of the at least one modulator element and the at least a polarizing element of the laser pulses in amplitude, phase and polarization independent form each other.

The Device according to the invention thus a pulse shaper, the at least one modulator element and at least having a polarizing element so arranged in the pulse shaper are that a pulse passing through the laser pulse in amplitude, Phase and polarization is modulated. The at least one modulator element and the at least one pulse shaper act on the spectral Shares of the laser pulse, by the pulse shaper the laser pulse divided into its spectral components and the spectral components so sets a laser pulse to be generated in amplitude, phase and polarization is arbitrarily shaped and temporally variable.

The inventive device thus allows the production completely in amplitude, phase and polarization shaped laser pulses. That way, it's all possible potential Shape parameters of the laser pulse and within the available bandwidth set any pulse shapes. Various applications such laser pulses, for example, for investigation and interference of matter properties in the light-matter interaction, in particular the interaction of light fields with solids (white light generation, phonon generation, Laser Induced Plasma Generation, Laserinduced Breakdown Spectroscopy (LIBS), material processing, etc.) arise and can by Use of the device according to the invention improved in their process control or even made possible in the first place.

The At least one modulator element of the device can in particular be formed as an array that can be controlled independently Pixels, which are in a direction perpendicular to the beam path the laser pulse are arranged offset. The pixels of at least a modulator element here are each a spectral component assigned to the laser pulse by the pulse shaper by disassembling the Laser pulses generated spectral components of different pixels supplied and thus manipulated separately by the pixels. By the reunification of the thus manipulated spectral components is then the shaped laser pulse is generated. Fundamental here is that the laser pulse thus in the frequency domain - namely by influencing the individual spectral components of the laser pulse - is formed and on this Way any temporal pulse shapes in the context of technical conditions are adjustable.

The At least one modulator element can advantageously by a or more liquid crystal arrays be educated. Alternatively, it is conceivable, an acousto-optical Modulator or to use a birefringent phase mask.

Advantageously, the pulse shaper is designed as a compressor grid arrangement, which has at least two optical grids for dividing the laser pulse into its spectral components and for reuniting the spectral components to the shaped laser pulse and additionally at least two cylindrical lenses or cylindrical mirror for focusing the laser pulse. The laser pulse is thereby diffracted at the optical gratings, so that the laser pulses are split into their spectral components, which then propagate along different paths in the pulse shaper, fed to the different pixels of the modulator elements and then reunited into the shaped laser pulse. Essential in such Kompressorgitteranord tion is that the spatial arrangement of the optical grating and the cylindrical lenses or mirrors is selected so that the elements of the compressor grid arrangement - with the exception of the modulator elements - the laser pulse with respect to its shape and pulse duration as little or not change.

The At least one modulator element may be provided by one or more modulator elements be formed in the range of a single or in the field of different Fourier planes of one or more compressor grid arrangements of Pulse shaper are arranged. The Fourier plane corresponds in this Connection of the common focal plane of two cylindrical lenses or Cylindrical mirror of the pulse shaper, which is at a distance of the focal length located by the two cylindrical lenses or cylinder mirrors and in which the spectrum of the laser pulse when passing through the as Compressor grid arrangement formed pulse shaper is maximally resolved. The cylindrical lenses or mirrors of the pulse shaper are then arranged that their focal planes coincide in pairs and between two Cylindrical lenses or cylindrical mirrors thus each have a Fourier plane results.

In an advantageous embodiment of the device is the pulse shaper built in series, so that the laser pulse undivided the at least a modulator element and the at least one polarizing element for Adjustment of amplitude, phase and polarization passes through. advantage this variant is that the achievable pulse stability high and the arrangement used is easy to adjust and fix.

different Variants for Such a serial pulse shaper are conceivable.

In a first variant of the serial pulse shaper are at least three modulator elements in succession in the beam path of the laser pulse arranged so that the laser pulse, the at least three modulator elements goes through exactly once. The polarizing element can then be formed, for example, as a polarizer be after a first or a second modulator element is arranged in the beam path of the laser pulse and only one Polarization component of the laser pulse transmits and the polarization component thus filters out of the laser pulse, causing the laser pulse in its amplitude is modulated.

In In a second variant, the pulse shaper has exactly two modulator elements on, wherein the laser pulse, the modulator elements in different Passes through sections twice. The advantageously designed as a polarizer polarizing Element can then be arranged so that the laser pulse after the first Passage through the first modulator element or after the first Pass through the second modulator element passes the polarizer and subsequently in a second pass again the first and second modulator element passes.

In a third variant is also conceivable that the pulse shaper exactly a modulator element that differs from the laser pulse in different Passing sections at least three times, the polarizing Element after the first or second pass through the modulator element is happening.

As a general rule is the laser pulse after passing through the polarizer in its amplitude modulated and is subsequently by the at least one more Modulator element in the beam path then in its polarization set. This is done by appropriate choice of directions the optical axes of the individual pixels of the liquid crystal arrays, which advantageously Aligned perpendicular to the beam path at appropriate angles are. The optical axis of the polarizing element in the Beam path of the laser pulse arranged portion of the modulator element is different from the polarization direction of the laser pulse aligned, and advantageously by an angle of 45 °. The direction the optical axis of the polarizing element following Section of the modulator element thus differs from the Polarization direction of the after the polarizing element linear polarized laser pulse.

If only three modulator elements or sections of modulator elements are used in the serial structure, in general the phase, amplitude and polarization can not be set arbitrarily, because when setting an elliptical polarization the main axes of the polarization ellipse can not be aligned freely. A rotation of this main axis is achieved in an advantageous manner in that at least one further (ie second) modulator element or at least one section of at least one modulator element in the beam path of the laser pulse is arranged behind the polarizer element following the optical axis (or axes) ) is oriented perpendicular to the beam path under angle (deviating angles) deviating suitably from the direction of the optical axis of the preceding modulator element or the section of the modulator element (are). In order to achieve any shaping of the laser pulse in phase, amplitude and polarization, preferably two sections of at least one modulator element are irradiated to the polarizing element, wherein the first subsequent to the polarizing element section with its optical axis at 45 ° to that predetermined by the polarizer Polarization direction and the second thereafter irradiated portion is aligned at an angle of 45 ° to the direction of the optical axis of the preceding portion of the modulator element. Thus, at least four sections of one or more modulator elements and a polarizing element are arranged behind one another in the beam path of the laser pulse and allow any desired and independent modulation of the laser pulse in amplitude, phase and polarization.

In an alternative advantageous embodiment is the pulse shaper built in parallel. The pulse shaper then has a beam splitter on, the laser pulse in a first and a second partial pulse divides, wherein the first and second part of each pulse at least a modulator element and at least one polarizing element go through and independently be modulated from each other. In the parallel structure of the Laser pulse thus divided into sub-pulses, which modulates separately from each other and subsequently be brought together to form a whole shaped laser pulse. Advantage of this variant is the simple structure and the physical Intuitive writability of the split in split pulses laser pulse.

Also for the parallel structure again different variants are conceivable. The pulse shaper can have exactly four modulator elements, of which a first and second modulator element in a row in the beam path of the first partial pulse and a third and fourth Modulator element in succession in the beam path of the second partial pulse are arranged. In a further variant, the pulse shaper exactly two modulator elements, which are so in the beam paths of first and second partial pulse are arranged such that the partial pulses each in different sections, the first and second modulator element run through. It is also conceivable that the pulse shaper only one Modulator element, that of the first and second partial pulse is traversed twice in different sections. It is essential here that the partial pulses are in phase and in each case Amplitude are shaped so that they join together the desired, in amplitude, phase and polarization shaped laser pulse.

at an advantageous embodiment of this parallel structure it is conceivable, one of the two partial pulses in the passage through the modulator element additionally to the desired Pulse shaping in the polarization by 90 ° to rotate.

According to one another preferred variant of the parallel construction occurs in contrast to the serial structure no polarization dependent beam attenuation at Grid on, and it gets a higher intensity usable especially at high modulation resolution. It is at the parallel pulse shaper in the beam path of the first or the second Partial pulse is a polarizing the first or the second partial pulse rotating Element provided, for example, by a λ / 2 plate or a periscope is formed and a rotation of the polarization causes the first or the second partial pulse by 90 °. The polarizing element is preferred after the last grid in the beam path of the Laser pulse arranged to a polarization-dependent beam attenuation at To avoid lattice.

The polarizing element is advantageous as a polarizing beam splitter formed, the a first polarization component of the first or second partial pulse transmitted and a second, vertical to the first directional polarization component of the first or second Partial pulse reflected. The first and second partial pulses then fall perpendicular to each other on the polarizing beam splitter so a the polarizing beam splitter is the first polarization component of the first or second sub-pulse and transmits the second polarization component of the other partial pulse reflected and by spatial superposition of the polarization components both partial pulses combined to form a shaped laser pulse.

at the different variants of the serial or parallel pulse shaper can advantageous reflective elements, in particular in the form of mirrors, be provided, which reflect the laser pulse so that the laser pulse or its spectral components, the modulator elements in the space provided Go through sections. Steer the reflective elements and thus define the beam path of the laser pulse.

Furthermore The object is also shaped by a method of generating Laser pulses with the features of claim 21 solved.

According to the invention, it is provided in the method that by means of the at least one modulator Lementes and at least one arranged in the beam path of the laser pulse polarizing element that filters out a polarization component of the incident laser pulse, the laser pulse in amplitude, phase and polarization is formed independently. In this case, the method can be carried out in particular using the device described above, which forms the laser pulse in amplitude, phase and polarization using at least one modulator element and at least one polarizing element, wherein - as explained above - uses both a parallel and serial structure of the pulse shaper can be.

The inventive method is in particular for forming ultrashort laser pulses in the femtosecond range can be used and opened versatile uses. For example, laser pulses shaped by the method can be used to investigate multi-photonic interactions in which the individual transition dipole moments of molecules differ in their direction. Any modulation of polarization, in particular the free adjustment of the directions of the major axis at an elliptical polarization can be advantageous, for example when the transition dipole moments involved in a physical process a molecule, which are to be controlled by means of shaped laser pulses, not aligned parallel or perpendicular to each other (eg at Excitation in more complex molecules or at Umisomerisierungen) and thus for an effective excitation Laser pulse with differently oriented polarization directions is required. By modulating the amplitude, phase and polarization can then optimally shaped the laser pulse and optimally the adapted to be stimulated molecules be to accurately affect the wave packet dynamics within of the molecules to enable although larger, for example biological molecules (Proteins, nucleotides, etc.) with their complex excitation spectra can be examined with such generated laser pulses to molecule-specific information about their wave packet dynamics, electronic structure or the like to obtain. By means of the method according to the invention can hereby the dynamics up to structural changes and to the deliberate bond breaking of such molecules, and also Enantiomers of multi-chiral biological molecules optimized, elliptically polarized laser pulses are influenced and converted become. About that In addition, there is also a use of such shaped laser pulses for medical Applications conceivable, whereby by using specially shaped Laser pulses z. B. in the area of the eye or the skin targeted changes the molecular structure can be brought about.

One further possible Field of application of such shaped laser pulses results in the transmission of information, the information being by shaping the amplitude, phase and polarization encoded as a function of time in the laser pulse and by transmission of the laser pulse transmitted to a receiver becomes. The transferable in a laser pulse Quantity of information is here among other things by the design the modulator elements determined. It would even be conceivable to use pulse shaping devices high resolution the fundamental limit of influencing every single laser mode to achieve and thus the maximum possible information content the laser pulse for information transmission exploit.

Prefers be carried out of the method modulator elements used in independently of each other controllable pixels are articulated along a perpendicular arranged offset to the beam path of the laser pulse direction are and for adjusting the spectral components of the laser pulse through Predeterminable control parameters are controlled. Every pixel of the at least a modulator element is in this case a spectral component of Assigned laser pulses and forms a spectral portion of the laser pulse at additional Use of at least one polarizing element in amplitude, Phase and polarization. By means of the driving parameters, at Use of liquid arrays Voltage values to drive the pixels, then becomes for each Pixel a phase difference between two polarization components given the polarization of the spectral associated with the pixel Proportion of the laser pulse determined. By shaping the spectral Shares the laser pulse is thus formed in the frequency domain, which within the available Bandwidth arbitrary time-varying pulse shapes adjustable are.

to Forming the laser pulse can the course of the amplitude, phase and polarization of the laser pulse be given as a function of time, from this the driving parameters for controlling the pixels of the at least one modulator element be determined and the pixels of the at least one modulator element be controlled with the drive parameters. In particular, can in this way the course of the amplitude, phase and polarization the laser pulse are given parametrically as a function of time, by specifying subpulses then composing the train shaped laser pulse.

The method thus allows user-selectable parametrically defined pulse shapes of the laser pulse in terms of amplitude, phase and polarization realize in which intuitively understandable and physically relevant parameters, especially subpulse defining parameters such as sub-pulse intensities, distances, chirps, phase differences and polarizations and spectral phase, amplitude and polarization patterns, etc. within the apparatus limits can be specified and adjusted. This allows the production of ultrashort laser pulses, the analysis of chirp dependencies, phase-coupled pump-probe measurements, measurements dependent on the parameters of the generated subpulses, measurements depending on the polarization type, direction and the elliptical eccentricity, measurements depending on spectrally adjusted frequency patterns selective excitation of vibration levels or the like. An essential advantage of the parametric specification of the laser pulse to be set is the use of intuitively understandable, physically relevant parameters as well as the ease of use and the simplicity, which allows a specification of highly complex pulse shapes by specifying a few parameters to define the subpulses.

The Determination of the control parameters from the given as a function of time courses the amplitude, phase and polarization, which is the pulse shape of the laser pulse describes is done for the serial and the parallel structure of the pulse shaper, respectively by using modulation functions that modulate the Laser pulses in dependence specify the drive parameters and are dependent on the structure of the pulse shaper. By reversing the modulation functions are off as a function the time specified pulse shape the required control parameters for the Pixels of the modulator elements used can be determined uniquely.

In a further advantageous embodiment of the method is the In amplitude, phase and polarization shaped laser pulse to interact with a substance - for example to excite a substance - used, detects an excitation signal generated by the interaction and optimized based on the excitation signal of the shaped laser pulse. On In this way, the shaped laser pulse is thus determined on the basis of an excitation signal. So optimized due to a specific application and thus the for the Application optimally shaped laser pulse set.

Prefers the optimization is done iteratively by setting initial values for the control parameters become the excitation signal generated by the thus shaped laser pulse is detected and the driving parameters iterative for optimization the laser pulse are adjusted based on the excitation signal. The iterative optimization can also be based on the parametrically predetermined and the course of the amplitude to be adjusted as part of the optimization, Phase and polarization of the laser pulse made as a function of time become. The use of the parametric specification of the laser pulse allows such a significant limitation of the search space, since not the whole bunch of the drive parameters themselves is varied and optimized, but on the sizes to be optimized a few, the laser pulse descriptive parameter is reduced, which the number of required iterations and thus the optimization time can be significantly reduced. For example, in this way an optimization of the laser pulse as a function of the time interval, Alignment or amplitude between the laser pulse forming Subpulses or the polarization of the subpulses possible.

The iterative optimization may be in an advantageous embodiment in particular by means of an evolutionary algorithm.

at Using the pulse shaper described above, polarization-dependent and / or frequency-dependent Effects occur, for example, due to the properties of the used optical grating and / or the cylindrical lenses or mirrors of the pulse shaper are conditional. In an advantageous embodiment of the method is therefore provided, such polarization dependencies and frequency dependencies by an adaptation of the activation parameters of the at least one Correct modulator element.

The Task is about it in addition, by a computer program with the features of the claim 36 solved, to control the modulator elements in the implementation of previously described method is a user setting the desired Pulse shape allows to convert the pulse shape into the one to be used Actuates parameters and an optimization of the pulse shape in terms allows a measurement signal. The computer program for controlling the optical system provides thus an interface that is simple and easy to use Handling of the device for producing shaped laser pulses guaranteed.

The idea underlying the invention will be illustrated below with reference to the figures th embodiments will be explained in more detail. Show it:

1 a schematic representation of an apparatus for producing a shaped laser pulse;

2A -D schematic representations of four different embodiments of a serial pulse shaper;

3A -B graphical representations of two polarization ellipses;

4A -B plots the horizontal and vertical polarization components as a function of the adjusted phase difference for the uncorrected and the corrected case;

5A -B schematic representations of two different embodiments of a parallel pulse shaper;

6 a schematic representation of a detector for detecting shaped laser pulses;

7A -B plots of polarization ellipses of two prepared and detected shaped laser pulses;

8th a graphical representation of the optimization factor for a phase and amplitude optimized laser pulse and in amplitude, phase and polarization optimized laser pulse on the example of the ionization of NaK;

9A -H plots different laser pulses shaped in amplitude, phase and polarization;

10 a schematic representation of the flow of a method for determining the driving parameters based on parametric operator inputs using a pulse shaper with a serial structure according to 2A -D;

11 a schematic representation of the flow of a method for determining the driving parameters based on parametric operator inputs using a pulse shaper with a parallel structure according to 5A -Federation

12 a graphical representation of an interactive user interface of a computer program for controlling the device according to 1 ,

1 shows a device 1 for making shaped laser pulses L ', which is a laser system 30 for generating a laser pulse L to be formed, a pulse shaper 10 for shaping the laser pulse L into a shaped laser pulse L 'and a detector 20 for detecting and detecting the shaped laser pulse L '. The laser system 30 in this case generates the unshaped laser pulse L, its amplitude, phase and polarization by the laser system 30 is determined and not modulated and whose pulse length is preferably in the femtosecond range. The unshaped laser pulse L is here by the laser system 30 emits and hits a first beam splitter 41 which partially transmits and partially reflects the laser pulse L, the reflected part being a reference pulse L _R via a mirror 40 to the detector 20 passes and the transmitted part of the laser pulse L via another mirror 40 into the pulse shaper 10 incident. In the pulse shaper 10 The laser pulse L is formed in amplitude, phase and polarization and then as a shaped laser pulse L 'via another beam splitter 42 emitted and thus reaches an application in which the shaped laser pulse L 'is used for example for the excitation of molecules. Through the beam splitter 42 , which partially reflects the shaped laser pulse L 'and partially transmits and, for example, can also be designed as a folding mirror, passes through the pulse shaper 10 shaped laser pulse L 'to the detector 20 and is detected by this, wherein the detector 20 measures and records the shape of the laser pulse L 'determined by amplitude, phase and polarization as a function of time.

The basic concept of the invention is that a laser pulse L is formed to be variable in time, in amplitude, phase and polarization, wherein the shaping by the pulse shaper 10 takes place, which is designed such that an unshaped laser pulse L in the pulse shaper 10 occurs in the pulse shaper 10 is processed and while passing through the pulse shaper 10 is modulated in amplitude, phase and polarization. The pulse shaper 10 is designed so that it can be used in particular for ultrashort laser pulses L in the femtosecond range is and a shaping of such laser pulses L allows.

Various embodiments of such a pulse shaper are conceivable. 2A - 2D show different embodiments of a serial pulse shaper, while in 5A and 5B two pulse shaper arrangements are shown with a parallel structure.

The illustrated arrangements for pulse shaping use a compressor grid arrangement (also referred to as a zero dispersion compressor) in which a laser pulse L through optical gratings 101 . 102 fanned out and bundled again and cylindrical lenses 111 . 112 in the beam path S at a distance 2F are arranged to each other. The laser pulse L thus has after its passage through the pulse shaper 10 Ideally, if the shaping by the sections of the modulator elements a, b, c, d, e, f or ax, ay, bx, by and the polarizer 120 . 121 is neglected, the same shape and duration as at the beginning. An influence of the laser pulse L thus does not take place - except for a real intensity attenuation.

The shaping of the laser pulse L as it passes through the pulse shaper 10 takes place solely through the sections of the modulator elements a, b, c, d, e, f and the polarizer 120 . 121 , The sections of the modulator elements a, b, c, d, e, f may, for example, be constructed as liquid crystal arrays which are perpendicular to the beam path S and parallel to the propagation plane spanned by the beam path S, respectively into individual pixels a1, a2, a3, ... or b1, b2, b3, ... or c1, c2, c3, ... (or d1, d2, d3, ...) are structured. The pixels a1, a2, a3, etc. are each assigned a spectral component of the laser pulse L, so that each pixel a1, a2, a3, etc. forms a spectral portion of the laser pulse L and the different pixels a1, a2, a3, etc. allow a separate manipulation of the spectral components of the laser pulse L.

at the liquid crystal arrays these are birefringent structures arranged in cell-shaped pixels, the nematic liquid crystals use, which align themselves by the action of an applied voltage and thus the refractive index of the structures or the individual pixels the structures for change a polarization component of the incident laser pulse L. On this way, the polarization components of the laser pulse L or its spectral components, a phase difference is impressed, by means of which the phase and polarization of the spectral components of the laser pulse is set.

In 2A - 2D are initially serially formed pulse shaper 10 illustrated in which a laser pulse L in the pulse shaper 10 is incident, moves along its beam path S through the pulse shaper and emitted as a shaped laser pulse L '.

The serial pulse shaper 10 according to 2A here has a first optical grating 101 , Cylindrical lenses 111 . 112 Modulator elements a, b, c, a polarizing element in the form of a polarizer 120 and a second optical grating 102 on. The incident, unshaped laser pulse L strikes the first optical grating 101 whose grating lines are perpendicular to the propagation plane of the laser pulse L defined by the beam path S, and is passed through the first optical grating 101 decomposed into its spectral components. The spectral components are diffracted differently depending on their wavelength, so that the optical grating 101 causes a fanning of the spectral components of the laser pulse L, which then starting from the optical grating on the first cylindrical lens 111 meet and from the cylinder lens 111 be deflected so that behind the cylinder lens 111 all spectral components in the direction of the beam path S, thereby causing the cylindrical lens 111 at a distance of the focal length F, measured at the central frequency ω _{0 of} the laser pulse L, behind the optical grating 101 is arranged. From the cylindrical lens 111 the spectral components of the laser pulse L in each case in the direction of the beam path S are focused in the Fourier plane and get there to a first modulator element a, go through the first modulator element a, meet the polarizer 120 which polarizes the spectral components of the laser pulse L in one direction and thereby modulates the amplitude, and then passes through a second and third module element b, c. Alternatively, the polarizer can also be arranged between the second and third modulator element.

After the modulator elements b, c, the spectral components arrive at the second cylindrical lens 112 , be through the second cylindrical lens 112 on the second optical grating 102 at a distance F behind the second cylindrical lens 112 blasted and through the second optical grating 102 in turn collimated into a beam-shaped bundled, now shaped laser pulse L '.

Since the modulator elements a, b, c and the polarizer 120 are arranged directly one behind the other and each one of the focal length F corresponding distance to the first and second cylindrical lens 111 . 112 have, are the modulator elements a, b, c and the polarizer 120 in the Fourier plane between the cylindrical lenses 111 . 112 in which the spectral components of the laser pulse L due to the finite Strahlra of the original laser pulse L are maximally resolved.

mit der Phase φ = 0.5(ϕ_a + ϕ_b + ϕ_c), der Transmission T = cos²[0.5ϕ_a], der Phasendifferenz Δφ = ±π/2 und den Amplituden A_x = cos[0.5ϕ_a]cos[0.5(ϕ_b – ϕ_c)] und A_y = cos[0.5ϕ_a]sin[0.5(ϕ_b – ϕ_c)] der Komponenten des Laserpulses. Die durch das Hauptachsenverhältnis beschriebene Elliptizität B/A der eingestellten Polarisation des Laserpulses L', die durch die Differenz der von den Flüssigkristallarrays eingestellten Phasenverzögerungen Δϕ = ϕ_b – ϕ_c des Laserpulses L bestimmt ist, entspricht dabei B/A = |tan[Δϕ/2]|. Für den Fall, dass der Polarisator 120 nach dem zweiten Modulatorelement b angeordnet ist, erhält man

mit der Phase φ = 0.5(ϕ_a + ϕ_b + ϕ_c), der Transmission T = cos²[0.5(ϕ_a – ϕ_b)], der Phasendifferenz Δφ = ±π/2 und den Amplituden A_x = cos[0.5(ϕ_a – ϕ_b)]cos[0.5ϕ_c] und A_y = cos[0.5(ϕ_a – ϕ_b)]sin[0.5ϕ_c], wobei ϕ_a, ϕ_b und ϕ_c die Phasenverzögerungen der jeweiligen Pixel der einzelnen Modulatorelemente a, b, c bezeichnen. Die Elliptizität B/A der eingestellten Polarisation des Laserpulses L', die durch die Phasenverzögerung Δϕ = ϕ_c des Flüssigkristallarrays c des Laserpulses L bestimmt ist, entspricht dabei B/A = |tan[Δϕ/2]|In order to achieve a modulation of the phase, amplitude and polarization of the laser pulse L by the modulator elements a, b, c, it is conceivable and advantageous to align the optical axes of the modulator elements a, b, c differently, for example alternately. It is conceivable, for example, an alignment of the optical axes in the xy plane (see 2A ) with angles of + 45 °, -45 °, + 45 ° relative to the x-axis. For this alignment of the optical axes, the modulation of the laser pulse L for such a serial construction with the polarizer between the first and second modulator element can be mathematically described by the following equations:

with the phase φ = 0.5 (φ _a + φ _b + φ _c ), the transmission T = cos ² [0.5φ _a ], the phase difference Δφ = ± π / 2 and the amplitudes A _x = cos [0.5φ _a ] cos [0.5 (φ _b - φ _c )] and A _y = cos [0.5φ _a ] sin [0.5 (φ _b - φ _c )] of the components of the laser pulse. The ellipticity B / A of the set polarization of the laser pulse L 'described by the principal axis ratio, which is determined by the difference of the phase delays Δφ = φ _b -φ _{c of} the laser pulse L set by the liquid crystal arrays, corresponds to B / A = | tan [Δφ . / 2] | In the event that the polarizer 120 is arranged after the second modulator element b, one obtains

with the phase φ = 0.5 (φ _a + φ _b + φ _c ), the transmission T = cos ² [0.5 (φ _a - φ _b )], the phase difference Δφ = ± π / 2 and the amplitudes A _x = cos [ 0.5 (φ _a - φ _b )] cos [0.5φ _c ] and A _y = cos [0.5 (φ _a - φ _b )] sin [0.5φ _c ], where φ _a , φ _b and φ _{c are} the phase delays of each Designate pixels of the individual modulator elements a, b, c. The ellipticity B / A of the set polarization of the laser pulse L ', which is determined by the phase delay Δφ = φ _{c of} the liquid crystal array c of the laser pulse L, corresponds to B / A = | tan [Δφ / 2] |

Other embodiments of the serial pulse shaper 10 are in 2 B to 2D shown. In 2C is a pulse shaper 10 with four modulator elements a, b, c, d shown one behind the other in the beam path S of the laser pulse L. In 2 B and 2D are two realizable with already commercially available Doppelflüssigkristallarrays embodiments of a pulse shaper 10 represented, in which the laser pulse L passes through the pulse shaper in the forward and reverse directions and thereby repeated from the optical gratings 101 . 102 is bent or collimated.

At the in 2 B illustrated embodiment, the incident laser pulse L passes through a mirror 140 first on the optical grating 101 and is diffracted so that the spectral components of the laser pulse L fanned out and on one half of a cylindrical lens 111 falls, which aligns the spectral components parallel to each other. The spectral components then pass through a first section a, b of a first and second modulator element, through a second cylindrical lens 112 focused and collimated again by the second optical grating. The thus reunited laser pulse L then passes through a arranged in the beam path S of the laser pulse L polarizer 120 , is through mirrors 140 reflected and incident angle, in turn, on the optical grating 102 , which splits the laser pulse into its spectral components and these to a second half of the cylindrical lens 112 prevented. The cylindrical lens 112 aligns the spectral components so that the spectral components pass through a second section c, d of the second or first modulator element, then through the cylindrical lens 111 and through the optical grating 101 are reunited to then be emitted as a shaped laser pulse L '. The optical axes of the two liquid crystal arrays of the respective dual-liquid arrays are each perpendicular to each other at + 45 ° and -45 ° to the x-axis.

In contrast to the structure according to 2 B in which the laser pulse L is the pulse shaper 10 in each case goes once in the outward and once in the return direction, the laser pulse L in the structure according to 2D in Hin, Rück- and again in execution and additionally passes through the polarization-changing element 142a , which is designed as λ / 2 plates with optical axis less than 22.5 ° to the x direction. The polarization-changing elements can also be advantageous 142b (eg a λ / 2 plate with optical axis below 22.5 °) and 142c (eg, a λ / 2 plate with optical axis less than 45 °) according to 2D be used to the Po To balance larisationsabhängigkeit the lattice diffraction.

Also in the arrangements according to 2 B respectively. 2D are the cylindrical lenses 111 . 112 at a distance 2F to each other, wherein the modulator elements a, b, c, d, e, f in the common Fourier plane of the cylindrical lenses 111 . 112 are arranged so that it is also in the structures according to 2 B and 2D is about compressor grid arrangements.

The following is a pulse shaper 10 according to 2 B described mathematically, in which the modulator elements a, b, c, d are aligned with their optical axes in + 45 °, -45 °, -45 °, + 45 ° to the x-axis. The modulation of the laser pulse L for such a serial structure can be described by the following equations:

In these equations, E _{x, out} , E _{y, out represent} the complex components of the electric field of the shaped laser pulse L 'at a frequency ω, ie for a spectral component of the laser pulse L', in the x-direction (horizontal component) y-direction (vertical component). The phase φ of the laser pulse L ', the transmission T, the polarization determining phase difference Δφ between the vertical and horizontal components of the shaped laser pulse L' and the amplitudes A _x , A of the components of the laser pulse From this, φ = 0.5 (φ _a + φ _b + φ _c + φ _d ), T = cos ² [0.5 (φ _a - φ _b )], Δφ = ± π / 2 and A _x = cos [0.5 (φ _a - φ _b )] cos [0.5 (φ _c - φ _d )] and A _y = cos [0.5 (φ _a - φ _b )] sin [0.5 (φ _c - φ _d )], where φ _a , φ _b , φ _c and φ _d denote the set phase delays of each of the frequency ω associated pixels of the modulator elements a, b, c, d and their sections a, b, c, d respectively. The ellipticity describing major axis ratio B / A of the set polarization ellipse of the laser pulse L ', by the difference of the liquid crystal arrays (with the optical axes at + 45 ° and -45 ° to the horizontal) set phase delays Δφ = φ _c - φ _{d of} the Laser pulse L is determined, this corresponds to B / A = | tan [Δφ / 2] |.

oder in anderer Form

mit den Hauptachsen A ≤ |E_xmax| und B ≤ |E_ymax| und den maximalen Amplituden A₁ = A₂ des elektrischen Feldes unter +45° und –45° zur horizontalen Richtung. Eine solche Polarisierungsellipse ist in 3A dargestellt.If only three modulator elements a, b, c or four modulator elements a, b, c, d aligned in + 45 °, -45 °, -45 °, + 45 ° are used, then the amplitude, phase and polarization of the laser pulse L can be used Although modulated independently. However, the orientation of the adjustable elliptical polarization is limited by the fact that the major axes of the polarization ellipse are fixed in their direction and can not be rotated. In the cases described in Equations (1) to (3), the major axes of the adjustable polarization ellipse are always aligned in a horizontal or vertical direction, so that the mathematical description of the associated polarization ellipses, which the so-called Jones vector traverses in the electric field, is:

or in another form

with the main axes A ≤ | E _xmax | and B ≤ | E _ymax | and the maximum amplitudes A ₁ = A _{2 of} the electric field at + 45 ° and -45 ° to the horizontal direction. Such a polarization ellipse is in 3A shown.

Such a serial pulse shaper 10 thus allows a modulation of amplitude, phase and polarization. However, the polarization is not yet fully universally modulatable, since the major axes of the polarization ellipse can not be aligned in any way. This is due to the fact that the amplitudes A ₁ and A _{2 of} the components of the laser pulse can not be adjusted independently of each other and are thus the same (see 3A ).

Also conceivable for this case of limited modulation are embodiments in which only one modulator element with three sections is used and the laser pulse L is guided through mirrors through the sections of the modulator element. The disadvantage of such an arrangement is that the number of necessary diffractions on the optical gratings 101 . 102 would increase and the Polarisationsab dependence of the optical grating 101 . 102 would therefore have a stronger impact. It is also conceivable to use a plurality of separate compressor grid arrangements, each having one or two modulator elements, which are successively passed through by the laser pulse L. It is also conceivable to align the optical axes of the sections a, b, c, d of the at least one modulator element in the same way and to arrange polarization-rotating elements in the beam path S of the laser pulse L.

As described, pass three consecutive sections at least a Modulatorelementes with the polarizer behind the first or second section out to a shaping in phase, amplitude and polarization perform. Any shaping, in particular for arbitrary adjustment the directions of the big ones Main axis of the polarization ellipse, however, is as above explained, not possible.

In order to allow any shaping of all laser pulse parameters, at least four independent manipulations of the laser pulse L by a modulator elements with several independent sections a, b, c, d, e, f or more independent modulator elements a, b, c, d, e, f necessary, whose optical axes are aligned in a certain way to each other. Different possibilities for the alignments of the optical axes of the at least four modulator elements a, b, c, d, e, f or their sections a, b, c, d, e, f are conceivable, for. B. at angles of 45 °, -45 °, 0 °, 90 ° to the x-direction when the polarizer 120 is disposed between the first and second sections a, b (see 2C ), or below 45 °, -45 °, 45 °, 0 °, when the polarizer 120 between the second and third section b, d of the modulator element is arranged. It is essential that after the polarizer 120 at least two further sections c, d or modulator elements c, d are irradiated. The optical axis of the first section c is in each case at an angle of 45 ° to the polarization direction of the polarizer 120 and the optical axis of the second section d is set at an angle of 45 ° to the previous section.

mit der Phase φ = 0.5(ϕ_a + ϕ_b + ϕ_c + ϕ_d), der Transmission T = cos²[0.5ϕ_a], der Phasendifferenz Δφ = ±π/2 + ϕ_d und den Amplituden A_x = cos[0.5ϕ_a]cos[0.5(ϕ_b – ϕ_c)] und A_y = cos[0.5ϕ_a]sin[0.5(ϕ_b – ϕ_c)]. Auf diese Weise ist eine beliebige Modulation des elektrischen Feldes in Phase, Amplitude und Polarisation unter beliebiger Ausrichtung der Hauptachsen der Polarisierungsellipse möglich.The mathematical description for a pulse shaper 10 in which the polarizer 120 is installed after the first section a of the at least one modulator element and the alignment of the optical axes has been selected to 45 °, -45 °, 45 °, 90 ° to the x-direction is described below. In this case, one obtains for the polarization components of the electric field

with the phase φ = 0.5 (φ _a + φ _b + φ _c + φ _d ), the transmission T = cos ² [0.5φ _a ], the phase difference Δφ = ± π / 2 + φ _d and the amplitudes A _x = cos [0.5φ _a ] cos [0.5 (φ _b - φ _c )] and A _y = cos [0.5φ _a ] sin [0.5 (φ _b - φ _c )]. In this way, any modulation of the electric field in phase, amplitude and polarization under any orientation of the major axes of the polarization ellipse is possible.

With the currently commercially available Doppelflüssigkristallarrays can advantageously in 2D illustrated structure for arbitrary modulation, in which one passes through three times through the sections of the double liquid crystal array can be realized. The polarizer 120 is installed between the first and second passage. At least one polarization-rotating element 142a , which is arranged directly in front of the modulator elements a, b, c, d, e, f representing double fluid array and irradiated in the third pass, provides for a rotation of the polarization of the laser pulse L by 45 ° in the third pass.

Conceivable is also, several separate compressor arrangements each with one to use three modulator elements, one after the other from the Laser pulse L be traversed. Furthermore, the optical axes of the at least four sections a, b, c, d, e, f of the at least one Modulatorelementes aligned and polarization rotating Elements in the beam path S of the laser pulse L can be arranged.

A disadvantage of arrangements in which the laser pulse L, the pulse shaper 10 is repeated in the back and forth direction, is that the number of diffraction at the optical gratings 101 . 102 increases and the polarization dependence of the optical grating 101 . 102 thus more powerful.

As described above, basically any shaping of the amplitude, phase and polarization of the laser pulse L and thus any shaping of the laser pulse L is possible. However, the formability of the laser pulse is dependent on the design of the pulse shaper 10 and in particular the orientation of the modulator elements a, b, c, d, e, f. If z. B is a pulse shaper 10 used with modulator elements a, b, c, d whose optical axes are aligned in the xy plane at + 45 °, -45 °, -45 °, + 45 °, or If only three modulator elements a, b, c or sections a, b, c of modulator elements are used for shaping the spectral components, then the polarization of the laser pulse L can not be set as desired since the direction of the main axes of the polarization ellipse is not rotated in the case of an elliptical polarization can be. If, however, the fourth modulator element d or the fourth passed through section d is aligned in a suitable manner, a free shaping of all parameters of the laser pulse L is fundamentally possible.

If the refractive indices of the optical and perpendicular axes the modulator elements a, b, c, d for all voltage settings differ from each other, it is the exact modulation especially at very short laser pulses necessary, to each modulator element a, b, c, d each one another, with its optical axis perpendicular to add aligned modulator element. This extra Modulator elements then resemble the otherwise occurring temporal Displacements of the pulse components.

The laser pulse L is before incidence in the pulse shaper 10 in its amplitude, phase and polarization direction determined by the laser system. As a rule, the laser pulse L is initially linearly polarized and is preferably oriented so that it is aligned in the x direction (see FIG 2A ) is polarized and so on the first optical grating 101 , whose grid lines are also directed in the y direction, is incident. A polarization-dependent diffraction of the laser pulse L at the first grid 101 at the first diffraction is excluded in this way. When passing through the pulse shaper 10 However, the polarization of the laser pulse L is modulated so that the laser pulse L or its spectral components can assume a circular, elliptical or linear polarization and the second optical grating 102 in turn be bent and collimated. The diffraction of these polarized spectral components on the second optical grating 102 can be polarization-dependent, so that a correction is required.

The polarization dependent For example, diffraction can be achieved by using glass plates that be placed under the Brewster angle in the beam path S, balanced, as in T. Brixner and G. Gerber, Opt. Lett. 26 (2001) 557. However, this leads to a reduction in intensity of the entire laser pulse. To avoid this attenuation, the polarization-dependent diffraction the laser pulse L also advantageous in the generation of pulse shapes, d. H. into the drive parameters for controlling the individual pixels a1, a2, a3, ... etc., to be included.

The intensity of the laser pulse components (L _x , L _y ) diffracted at the optical gratings is polarization-dependent and causes a deviation of the adjusted ellipticity of the polarization from the desired ellipticity. This effect usually increases when using gratings with shorter lattice spacing and thus greater spectral splitting and higher resolution, which in practice limits the modulation resolution. The effect of polarization-dependent diffraction is in 4A by way of example, in which the measured intensities of the horizontal polarization component L _{h of} the shaped laser pulse L ', the vertical polarization component L _v and the entire shaped laser pulse L' graphically over the phase difference set between the polarization components L _h , L _v (using a pulse shaper 10 according to 2C ) are shown. As can be seen, the maximum values of the intensities of the polarization components L _h , L _{v are} not identical, but deviate from each other by approximately 15%, which is due to the polarization dependence of the diffraction at the optical gratings 101 . 102 is conditional. From the measured intensities (I _h = (cos [Δφ / 2]) ² and I _v = C (sin [Δφ / 2]) ² ) of the two polarization components L _h , L _v (where the constant C is the ratio of the maximum values of the Intensities of the polarization components L _h , L _v and referred to in 4A the case shown is 0.85), the ellipticity can be determined analytically as follows.

This corresponds to that after the pulse shaper 10 according to 2C occurring ellipticity of the shaped laser pulse L ', in the thus by the last grid 102 modified polarization-dependent diffraction is included in the determination of ellipticity. Accordingly, the ratio of the two diffracted polarization directions C = I _vmax / I _{hmax is} determined and thus the ellipticity is calculated as a function of the phase difference. In the adjustment of the phase difference, which results in the control parameters for the pixels a1, a2, a3,..., Etc. of the modulator elements a, b, c, d, the diffraction effects are thus taken into account and the phase difference adjusted so that the desired Ellipticity is obtained. In this way, any ellipticity can be adjusted without weakening, which is advantageous over the use of under the Brewsterwin In the latter case, the intensity of the laser pulse in the beam must be reduced.

multipliziert wird. Diese Funktion wird als Korrektur bei der Bestimmung der Ansteuerungsparameter für die Modulatorelemente a, b, c, d bzw. deren Pixel a1, a2, a3, ..., etc. berücksichtigt und sorgt für eine Angleichung der Intensität beider Polarisierungskomponenten. In 4B sind die gemessenen Intensitäten der horizontalen und vertikalen Polarisierungskomponente L_h, L_v sowie des gesamten Laserpulses L bei Verwendung der Korrektur dargestellt.The occurring polarization dependence of the intensity of the laser pulse emerging from the pulse shaper can advantageously be corrected by setting the activation parameters described below in such a way that no more polarization dependence occurs. For this purpose, the intensity of the stronger component is attenuated to the value of the lower by a suitable adaptation of the amplitude modulation by the set transmission with the function

is multiplied. This function is taken into account as a correction in the determination of the activation parameters for the modulator elements a, b, c, d or their pixels a1, a2, a3, etc., and ensures an equalization of the intensity of both polarization components. In 4B the measured intensities of the horizontal and vertical polarization components L _h , L _v and the entire laser pulse L are shown using the correction.

In 5A and 5B are two embodiments of an alternative, parallel pulse shaper 10 in which, in contrast to the pulse shaper according to 2A - 2D , a laser pulse L is divided into two partial pulses L _x , L _y and the partial pulses then in a parallel manner the pulse shaper 10 to be shaped in amplitude, phase and polarization.

The laser pulse L falls in this case in the pulse shaper 10 and is through a beam splitter 141 divided into two equally strong partial pulses L _x , L _y , which then at different angles of incidence on a first optical grating 101 steered and through the optical grid 101 to be bent. The optical grid 101 splits the partial pulses L _x , L _y respectively into the spectral components, which pass through a first cylindrical lens 111 be aligned in parallel, each pass through a first and second modulator element ax, bx or ay, by, through a second cylindrical lens 112 be focused and collimated by a second optical grating to form two shaped partial pulses L _x ', L _y '. The one shaped partial pulse L _y 'is then passed through a phase retarder in the form of a λ / 2 plate 142 steered and rotated by this in its polarization direction by 90 °. Both partial pulses L _x ', L _y ' are finally a polarizing element in the form of a polarizing beam splitter 121 which transmits a first polarization component and reflects a second, perpendicular to the first polarization component. In the in 5A and 5B In the case illustrated, the two partial pulses impinge on the polarizing beam splitter at a spatial angle of 90 ° to one another 121 , wherein the first partial pulse L _y 'almost completely reflected and the second partial pulse L _x ' is almost completely transmitted. The polarizing beam splitter 121 thus unites the two partial pulses L _x ', L _y ' again to a common, shaped laser pulse L ', which is then emitted from the pulse shaper.

In the parallel pulse shaper 10 according to 5A Four separate modulator elements ax, ay, bx, by are used in two different, respectively compressor arrangements, while in the pulse shaper 10 according to 5B two modulator elements each having two different sections ax, ay and bx, by are used in a compressor arrangement. In the latter way, the structure can be simplified and made inexpensive. It is essential here that both partial pulses L _x , L _y pass through two modulator elements ax, bx, or ay, by, respectively, and are shaped in this way.

In the parallel pulse shaper 10 according to the embodiments of 5A and 5B Thus, two partial pulses L _x , L _y are modulated separately and brought together again unshaken. The electric field E (x, y, z) = E _x e _x + E _y e _y (with the unit vectors e _x and e _y ) of the laser pulse L is determined by superposition of the electric fields of the two partial pulses L _x , L _y , wherein for each of the frequency ω associated pixels of the modulator elements respectively the two equations e x (x, y, z) = A x cos (ωt - kz + φ x ) (9) and e y (x, y, z) = A y cos (ωt - kz + φ y ) (10) where ω denotes the frequency, k the wave vector and φ _x , φ _y the respective phases of the partial pulses L _x , L _y .

Characterized in that the laser pulse L is split into two partial pulses L _x , L _y , which pass through the modulator elements ax, bx, ay, by parallel, the partial pulses L _x , L _y are modulated independently of one another in amplitude and phase, wherein the shaped laser pulse L 'then by combining the two partial pulses L _x , L _y by the polarizing beam splitter 121 is formed. This then results in a total formed in amplitude, phase and polarization laser pulse. The spatial intensity profiles of the two beam paths S of the two partial pulses L _x , L _y should be as equal as possible, which in the case of an asymmetrical profile is a direct difference between the number of reflections on mirrors 140 . 141 . 143 presupposes. The polarization dependence of the optical gratings 101 . 102 plays, in contrast to the serial structure, in the parallel pulse shaper 10 No matter, since the polarization direction of the first partial pulse L _x 'only after passing through the second optical grating 102 by means of the λ / 2 plate 142 is turned. This allows the use of optical gratings 101 . 102 with shorter lattice spacing, which thus a greater spectral splitting and thus a higher spectral resolution in the Fourier plane between the cylindrical lenses 111 . 112 enable.

The fact that the partial pulses L _x , L _y are modulated separately in the parallel arrangement requires the parallel pulse shaper 10 a high accuracy in the temporal and spatial superimposition of the partial pulses L _x , L _y after the respective passage through the modulator elements ax, bx, ay, by and thus an exact adjustment of the arrangement. Fluctuations in the length of the beam paths S can be reduced, for example, with a construction that is stable against vibration, through and through a surrounding housing to avoid air circulation, so that the interferometric stability and thus a high pulse accuracy is obtained. The spectral intensities of the partial pulses as a function of the different beam paths S can be adjusted by adjusting the transmission of the modulator elements ax, bx, ay, by. In addition, apparatus-related phase differences between the beam paths (path differences, dispersion through lenses, etc.) can be compensated by a phase mask written on the modulator elements, so that the partial pulses L _x , L _y in their temporal shape not by the apparatus design (with the exception of the modulator elements ax, bx, ay, by). This can be advantageously realized by the use of an optimization algorithm for finding an optimal phase adjustment, wherein the destructive interference signal between the partial pulses L _x , L _{y is} minimized and thus a precise production of the desired pulse shapes is possible.

By integration to a parallel pulse shaper, as in 5B is shown, a more compact structure can be achieved, in which the two optical beam paths S in spatial proximity to each other and path differences due to vibration and air circulation are thus kept low. It is also advantageous to ensure the interferometric phase constancy between the partial pulses L _x ', L _y ' by active stabilization in order to compensate for temporal changes between the beam paths S. This could be done, for example, by detecting, evaluating and optimizing an interference signal caused by interference of the unused for the application polarizing components on the polarizing beam splitter 121 is generated, namely by the polarizing beam splitter 121 transmitted component of the first partial pulse L _x 'and by the polarizing beam splitter 121 reflected component of the second partial pulse L _y ', which in 5A and 5B from the polarizing beam splitter 121 perpendicular to the beam path of the shaped laser pulse L '(in the plane of the drawing) are emitted vertically upwards. One of the two beam paths S in the pulse shaper 10 is for this purpose then (eg with mounted on a piezo element, along a direction of displacement V adjustable mirrors 143 ) so that a constant interference pattern can be set. The advantage of optimizing this interference signal is that the shaped laser pulse L 'is not disturbed and attenuated by additional optical elements in the beam path and the shape of the shaped laser pulse L' can be kept constant by means of active stabilization with regard to interference phenomena, for example in the spectrum.

mit der Transmission des geformten Laserpulses L' T = 0.5(cos²[0.5(ϕ_ax – ϕ_bx] + cos²[0.5(ϕ_ay – ϕ_by)]), der Phasendifferenz Δφ = 0.5((φ_ax + ϕ_bx) – (ϕ_ay + ϕ_by)) und den Amplituden der Teilpulse L_x', L_y' A_x = cos[0.5(ϕ_ax – ϕ_bx)] und A_y = cos[0.5(ϕ_ay – ϕ_by)], wobei ϕ_ax, ϕ_bx und ϕ_ay, ϕ_by die Phasenverzögerungen der einzelnen, der Frequenz ω zugeordneten Pixel der Modulatorelemente bzw. -abschnitte ax, bx und ay, by bezeichnen. Die Phasendifferenz Δφ und die Amplituden A_x und A_y bestimmen die elliptische Form und somit die Polarisation des Laserpulses L':

The electric fields of the through the parallel pulse shaper 10 modulated partial pulses L _x ', L _y ' are given by:

with the transmission of the shaped laser pulse L 'T = 0.5 (cos ² [0.5 (φ _ax - φ _bx ] + cos ² [0.5 (φ _ay - φ _by )]), the phase difference Δφ = 0.5 ((φ _ax + φ _bx ) - (φ _ay + φ _by )) and the amplitudes of the partial pulses L _x ', L _y ' A _x = cos [0.5 (φ _ax - φ _bx )] and A _y = cos [0.5 (φ _ay - φ _by ) ], where φ _ax, φ _bx and φ _ay, φ _by the phase delays of the individual, the frequency ω associated pixels of the modulator elements or sections ax, bx and ay, by call. the phase difference Δφ and the amplitudes A _x and A _y determine the elliptical shape and thus the polarization of the laser pulses L ':

The polarization ellipse is then in the direction of its major axes and its ellipticity, as in 3B shown, freely adjustable.

The device 1 for producing shaped laser pulses L 'according to 1 also has a detector 20 for detecting the shaped laser pulses L ', which in a possible embodiment in FIG 6 is shown.

in principle can for the detection of the circumstances In complex manner shaped laser pulses L 'different techniques used become. It is essential, however, that for the detection of in arbitrarily formed in its polarization laser pulse L 'of the laser pulse L' in at least three Polarization directions is measured. This is necessary since the polarization ellipse of the shaped laser pulse L 'in principle arbitrary can be aligned. First of all it is clear that the main axes are not rotated and thus fixed, so is the measurement only sufficient polarization directions.

The detector 20 according to 6 , which is formed as a so-called cross-correlation structure, has a polarization-rotating element in the form of a λ / 2 plate 250 and a polarizing element in the form of a polarizer 220 on, which are arranged in the beam path S of the shaped laser pulse L '.

For measuring a polarization component of the shaped laser pulse L 'in a certain polarization direction, the polarizer becomes 220 vertically aligned and the optical axis of the λ / 2 plate 250 adjusted so that the polarization direction of the laser pulse L 'to be measured by the action of the λ / 2 plate 250 is rotated in the vertical direction. In order to measure the vertical direction of polarization, the λ / 2 plate is thus aligned vertically, so that no rotation of the polarization of the shaped laser pulse L 'takes place, while for recording the horizontal polarization direction, the optical axis of the λ / 2 plate at an angle of - 45 ° to the vertical direction (to rotate the polarization by 90 ° from horizontal to vertical). In this way, each one of the intensity of the shaped laser pulse L 'in a polarization direction indicating linear polarization component of the shaped laser pulse L' is filtered out by a mirror 240 and a lens 260 on an interaction element 270 For example, a BBO crystal focuses and interacts in the interaction element 270 with a reference pulse L _R , which, as in 1 represented, may be diverted from the unshaped laser pulse L and mirrors 240 , A delay line for readjusting the beam path in the form of along the direction of displacement V adjustable mirror 243 and a lens 260 the interaction element 270 is supplied.

By the interaction of the shaped laser pulse L 'and the reference pulse L _R in the interaction element 270 An interaction signal K, which corresponds to the cross-correlation signal of a polarization component of the shaped laser pulse L 'and of the reference pulse L _R, is produced. The interaction signal K thus generated is transmitted via another lens 260 and another mirror 240 to an evaluation unit for detecting and evaluating the interaction signal K representing spectrometer 280 which detects the interaction signal K and derives from the interaction signal K the intensity of the polarization component and thus the polarization direction of the shaped laser pulse L '. The measurement is repeated for at least two (advantageously at least three) different polarization components and the amplitude, phase and polarization, in particular also the polarization ellipse of the shaped laser pulse L ', determined as a function of time from the measured intensities.

The detector according to 6 is designed so that in each case the intensity of a linear polarization component of the shaped laser pulse L 'in a polarization direction as a function of time is measured in temporally successive measurements, the λ / 2 plate 250 is rotated by a certain angle between the measurements, a second polarization direction is measured and the process is repeated until the desired polarization directions of the shaped laser pulse L 'are detected. In principle, the measurement of the individual polarization directions can be automated, automatically measuring a predetermined number of polarization directions of the laser pulse L 'as a function of time and determining the temporal shape of the laser pulse L' therefrom. Since the different directions of polarization are detected in separate measurements, the temporal correspondence of the measurements must be accurately determined when evaluating the measurements to determine the shape of the shaped laser pulse L '.

In the evaluation of the measured polarization directions must in principle by the λ / 2 plate 250 resulting phase shift of π be deducted to determine the polarization ellipse of the laser pulse L 'as a function of time. The described use of λ / 2 plates provides reliable results for sufficiently long pulses, while deviations may occur in extremely short pulses with appreciable changes in amplitude within a wavelength, but which can be achieved by using z. B. polarization rotators can be avoided.

In a pulse shaper 10 in which the major axes of the polarization ellipse are not twisted, the elliptical shape of the laser pulse L 'can be determined from the measured horizontal and vertical polarization components of the shaped laser pulse L' since the major axes of the ellipse are aligned along the horizontal and vertical directions (see 3A ). For this, the intensities are to be determined in a retrieval method. The major axis ratio B / A is now determined from the root of the ratio of the intensities of the vertical and horizontal polarization components that uniquely determine the elliptical shape of the laser pulse L '.

In any orientation of the polarization ellipse, the shape of the laser pulse L 'is indeed determined by the recording of intensity and phase in the horizontal and vertical polarization direction. However, phases and in particular phase differences between the individual polarization components can only be determined very inaccurately. Therefore, the laser pulse L 'should still be recorded in at least one further polarization direction (for example at an angle of 45 °) in order to use the intensities I _h , I _v and I _{45 of} the three polarization components as the function of the polarization ellipse of the laser pulse L' the time over the main axes A, B and the angle γ of the main axis to the horizontal, which result in:

The polarization ellipse and the projection on any axis (at an angle θ) are described by the following equations:

The ellipse parameters A, B and γ can also be found analogously by a numerical fit of the experimentally obtained intensities of the polarization components to equation (15). Thus, the polarization ellipse of the electric field can be determined for each point in time within the laser pulse L ', and the shape of the laser pulse L' can be represented graphically by plotting the polarization ellipse over time (see FIG 7A and 7B ).

Around to get the sense of circulation of the polarization ellipse, either the (hard-to-find) phase difference can be used, it can be a λ / 4 plate be used in the laser beam, or it may be among the various Directions recorded spectra are compared with simulated spectra, whereby the sense of circulation is fixed.

Two polarization ellipses M of a laser pulse L 'detected by the detector at a specific time are shown graphically in FIG 7A and 7B shown. The predetermined polarization ellipses T, which are set on the pulse shaper, are shown in dashed lines, the additionally assigned respective parameters ellipticity B / A and the main axis angle γ being indicated. By determining the polarization ellipses at each point in time of the laser pulse L ', the laser pulse L' can then be represented in a three-dimensional manner as a function of the time t, such as in FIG 9B shown.

Through the pulse shaper 10 according to 2A - 2D or 5A and 5B For example, the laser pulse L can be shaped in amplitude, phase and polarization in a time-dependent manner. The time-dependent shaping takes place by manipulating the spectral components of the laser pulse L separately, the pixels a1, a2, a3, etc. of the modulator elements a, b, c, d, e, f, ax, ay, bx, by be assigned to the spectral components for this purpose and the spectral components are thus adjusted in their polarization. The pixels a1, a2, a3,... Etc. are in this case controlled by control parameters which, when liquid crystal arrays are used, correspond to voltage values applied to the pixels a1, a2, a3, Polarizing component of the incident laser pulse L effect. The control parameters are set once and then not changed during the pulse duration of the laser pulse L.

different Methods for determining the drive parameters are here conceivable. On the one hand, the determination of the activation parameters as part of an iterative optimization process possible. For example can initially a distribution of control parameters for control the pixels a1, a2, a3, ... etc of the modulator elements a, b, c, d, e, f or ax, ay, bx, by, the laser pulse thus formed L 'in one application, for example, to excite a molecule, used therefrom an excitation signal (fitness) can be detected and by adaptation the drive parameter iteratively optimizes the excitation signal become. In this way, the iterative for a particular application determined optimal control parameters.

For example In this way, the shaped laser pulse L 'can be determined by means of a random initial setting Activation parameters are used for the ionization of molecules, wherein detects an excitation signal in the form of an ion signal (fitness) and iteratively optimized. The adaptation of the control parameters can happen by accidental crossover and mutation as part of an evolutionary algorithm, at the shaped laser pulses L on the received ion signals (Fitness) of the desired cluster / molecule be and the resulting ions in an ionic optics by electrostatic fields subtracted, selected with a quadrupole mass spectrometer and detected in an electron multiplier become. Only a certain number of laser pulses L 'with the best fitness is then reused to turn new by crossing the elements To generate driving parameters and further optimize. This iterative process will continue until fitness fails more changes and thus an optimally shaped laser pulse L 'is found.

In 8th An optimization factor is shown as a function of the iterations during such an optimization. The optimization factor indicates the ratio of the intensities of the measured excitation signal and the excitation signal obtained with an unshaped laser pulse L. Shown is an optimization process using the example of a free optimization of amplitude, phase and polarization of a laser pulse L 'for the ionization of NaK, wherein in the case shown, a serial pulse shaper 10 according to 2 B and the ionization of NaK in the molecular beam has been optimized by excitation with a laser pulse L 'shaped in amplitude, phase and polarization as well as for comparison with a laser pulse modulated only in phase and amplitude. The illustrated learning curves show a considerable increase and convergence within about 70 iterations. It can be seen that the optimization by means of the laser pulse L 'shaped in amplitude, phase and polarization leads to a better optimization factor and thus a more effective laser pulse compared with the laser pulse formed only in phase and amplitude.

Around the drive parameters for generating a shaped laser pulse To pretend L 'is also conceivable, the pulse shape of the laser pulse to be generated parametrically as a function of time and from the parametric specifications the driving parameters required to generate the laser pulse L ' determine. In this way it is possible, the laser pulse L 'on for a Users simple and clear Way to define and indicate or, as part of an optimization process, significantly restrict the search space.

The In this case, parameters predeterminable by a user can be particularly intuitive understandable parameters be. For example, a user may specify sub-pulses which a laser pulse is to be composed and which is controlled by subpulse intensities, distances, chirps, -phase differences, ellipticities, -helizitäten and main axis angles are defined. The subpulses set in In this context, individual elementary pulses that combines can be and thus give the entire laser pulse. In addition, a user can specify spectral phases, amplitude and polarization patterns, from which then by means of the control parameters a corresponding Laser pulse L 'generated becomes.

Examples of laser pulses L 'produced in this way are shown in FIG 9A to 9H indicated, in 9A . 9C . 9E and 9G the progressions of intensity, ellipticity and major axis angle are given as a function of time for four different laser pulses L ', while in 9B . 9D . 9F and 9H the respectively associated generated laser pulses L 'are shown in a three-dimensional representation over the transverse xy plane and the time t. It show here 9A . 9B elliptical subpulses, which are aligned perpendicular to each other, 9C . 9D an elliptical and a circular subpulse, 9E . 9F elliptical subpulses that are at an angle of 30 ° to each other and 9G . 9H elliptical subpulses that are at an angle of 45 ° to each other.

Using the pulse shaper 10 are thus in amplitude, phase and polarization arbitrarily shaped laser pulses L 'adjustable. For determining the drive parameters for the serial pulse shaper according to 2A - 2D is advantageously described in the following and in 10 used in a concise manner.

First, a user selects pulse parameters such as. B. subpulse distances, intensities, chirps, phase differences and direction of rotation (helicity), ellipticity or the like for the laser pulses to be generated L 'forming sub-pulses (step 512 ). The sub-pulses may in this case have, for example, a gaussian shape in time.

die jeweilige Maximalamplitude in beiden Komponenten zu

errechnet (oder alternativ mit der Differenz der Phasenverzögerungen Δϕ = ±2 arctan(BA ) zu

beide Formulierungen sind mathematisch äquivalent). Die einzelnen Unterpulse werden dann gesondert für beide Komponenten kombiniert und so die elektrischen Felder beider Komponenten des gesamten Laserpulses L' ermittelt. Auf diese Weise werden E_x,out(t) und E_y,out(t) (E komplex) des gesamten Laserpulses L' bestimmt und mittels Fourier-Transformation daraus direkt die spektralen elektrischen Feldkomponenten E_x,out(ω) und E_y,out(ω) abgeleitet, die die spektralen Anteile des Laserpulses L' angeben.Subsequently, the respective maximum intensity of the two components of the electric field from the total intensity of the subpulse and the ellipticity is calculated for each subpulse (step 512 ). For each subpulse this is about the relationship

the respective maximum amplitude in both components

calculated (or alternatively with the difference of the phase delays Δφ = ± 2 arctane ( B A ) to

both formulations are mathematically equivalent). The individual subpulses are then combined separately for both components, thus determining the electric fields of both components of the entire laser pulse L '. In this way E _{x, out} (t) and E _{y, out} (t) (E complex) of the entire laser pulse L 'are determined and by means of Fourier transformation directly from the spectral electric field components E _{x, out} (ω) and E _{y , out} (ω), which indicate the spectral components of the laser pulse L '.

The electric field components are then converted into the drive parameters necessary for driving the individual modulator elements a, b, c, d in the form of voltage values (steps 513 to 517 ). The phase delay φ _c (ω) and φ _d (ω) determining the driving parameters are obtained by substituting E _{x, out} (ω), E _{y, out} (ω) and E _in (ω) into the following equations.

nach ϕ_c(ω) und ϕ_d(ω), wobei nur der Realteil verwendet wird, da imaginäre Werte nicht in Ansteuerungsparameter umsetzbar sind. Bei der Verwendung eines Pulsformers 10, bei dem die Hauptachsen der Polarisierungsellipse des einstellbaren Laserpulses L' festgelegt und nicht drehbar sind, führt die Bestimmung der Ansteuerungsparameter zu Imaginärteilen in den Phasenverzögerungen. Durch Einschränkung auf den Realteil werden somit angenäherte Pulsformen erzeugt, die den gewünschten zeitlichen Verlauf nur näherungsweise nachbilden und zusätzlich (kleine) Replika-Pulse aufweisen.These expressions are obtained by switching the modulation function (see, for example, equation (1)) of the electric field for the serial pulse shaper according to FIG 2A - 2C

after φ _c (ω) and φ _d (ω), where only the real part is used, since imaginary values can not be converted into control parameters. When using a pulse shaper 10 in which the principal axes of the polarization ellipse of the tunable laser pulse L 'are fixed and not rotatable, the determination of the drive parameters results in imaginary parts in the phase delays. By restricting to the real part thus approximate pulse shapes are generated, which only approximately simulate the desired time course and additionally have (small) replica pulses.

Alternatively, E _{x, out} (t) and E _{y, out} (t) can also be mathematically simulated by phase modulation in their functional form (resulting in replica pulses in the individual components) and by Fourier transformation into the spectral components E _{x, out} (ω) and E _{y, out} (ω) are converted. By substituting the thus-obtained theoretical components E _{x, out} (ω) and E _{y, out} (ω) into the equations for the phase delays (Equation (20)), then only real values for the phase delays φ _c (ω) and φ _{d are obtained} (ω), since the preselected pulse shapes have been correspondingly pre-limited by intensity normalization and exclusive phase modulation.

When using a pulse shaper 10 in which the main axes of the polarization ellipse of the laser pulse L are fixed and not rotatable as a result of the alignment of the optical axes of the modulator elements a, b, c, d or the use of only three modulator elements a, b, c, as mentioned above, Replica pulses due to the restriction that the transmission T (ω) for both components of the laser pulse L is always the same. Because of this limitation, no simultaneous exact shaping of the sub-pulses in both polarization components of the laser pulse L can take place. An exact, replica-free shaping of the laser pulse L requires an independent adjustment of the transmissions in both components of the laser pulse L.

The use of a fourth modulator element d oriented at 45 ° to the third modulator element c, as described above, eliminates this limitation and allows any parametric modulation of the laser pulse L without replica pulses. The method for setting the pulse shape required for this purpose is analogous to the method described above, wherein only the function for the phase delays (see equation (20)) depends on E _{x, out} (ω), E _{y, out} (ω) and E must be adjusted _in (ω). Thus, the desired pulse shape, in which the main axes of the polarization ellipse are freely adjustable, exactly replicable, without resulting in replica pulses.

On the manner described above is also a parametric shaping a laser pulse L 'im Spectral range possible, at the desired Frequency patterns (eg narrow gauss-shaped peaks with variable intensities and distances in the frequency domain), the shaping in the frequency domain but here on the bandwidth of the laser pulse to be formed L limited is. For example, leave peaks set in the frequency range beneficial for that use, (vibronic) transitions in molecules in the frame to look for an optimization, or certain already known transitions in one To allow (or forbid) optimization or a desired pulse shape. This opens novel possibilities of a targeted influencing of molecular processes.

An analogous, oversight in 11 the illustrated method results when using a parallel pulse shaper 10 according to 5A and 5B ,

oder alternativ:

(beide Beschreibungen sind mathematisch äquivalent).Here, the user first selects the pulse parameters for the parametric definition of the laser pulse L 'to be generated (step 502 ). The user-defined parameters y (alignment of the main axes) and r = B / A (ellipticity) are here converted into the spectral phase difference Δφ and the magnitude of the ratio of the amplitudes A _x and A _{y of} the polarization components of the laser pulse L for each subpulse, the sign the spectral phase difference is determined by the choice of polarization direction and defines the direction of rotation (helicity):

or alternatively:

(both descriptions are mathematically equivalent).

sowie die Phasendifferenz Δϕ zwischen den Phasen beider Komponenten des elektrischen Feldes eingestellt (Schritt 503). Durch Kombination der Unterpulse werden dann E_x,out(t) und E_y,out(t) des gesamten Laserpulses L' ermittelt und daraus mittels Fourier-Transformation E_x,out(ω) und E_y,out(ω) gebildet.For each subpulse then the amplitude ratio

and the phase difference Δφ between the phases of both components of the electric field (step 503 ). By combining the subpulses, E _{x, out} (t) and E _{y, out} (t) of the entire laser pulse L 'are then determined and formed therefrom by Fourier transformation E _{x, out} (ω) and E _{y, out} (ω).

und werden in die die Ansteuerungsparameter definierenden Phasenverzögerungen mittels ϕ_ax = π/2 + ψ(ω) + arccos(R_x(ω)), ϕ_bx = π/2 + ψ_x(ω) – arccos(R_x(ω)), ϕ_ay = π/2 + ψ_y(ω)+ arccos (R_y(ω)) und ϕ_by = π/2 + ψ_y(ω) – arccos(R_y(ω)) umgerechnet. Die mittels der so bestimmten Ansteuerungsparameter modulierten Teilpulse L_x', L_y' ergeben dann nach der Zusammenführung den gewünschten geformten Laserpuls L'.Filter functions for the partial pulses L _x ', L _y ' are then calculated from the components of the electric field (step 504 to 508 ) and derived therefrom the control parameters, which are then used to control the modulator elements ax, bx, or ay, by (see 5A and 5B ). The filter functions H _x , H _y (complex), with the amplitude factors R _x , R _y and the phase factors ψ _x , ψ _y , are given by

and are included in the phase delays defining the drive parameters by means of φ _ax = π / 2 + ψ (ω) + arccos (R _x (ω)), φ _bx = π / 2 + ψ _x (ω) - arccos (R _x (ω) ), φ _ay = π / 2 + ψ _y (ω) + arccos (R _y (ω)) and φ _by = π / 2 + ψ _y (ω) - arccos (R _y (ω)). The partial pulses L _x ', L _y ' modulated by means of the thus determined activation parameters then yield the desired shaped laser pulse L 'after the merger.

Also any one desired by the user temporal or spectral course of the pulse shape (eg with regard to the polarization direction, the ellipticity or the phase characteristic) within the pulse or subpulse can be presented with the Methods for the serial and the parallel structure can be realized. The user can do this the pulse shape (for example, by entering a functional Context or setting of any polynomial form) according to his wishes shape.

Advantageously, the method for determining the drive parameters for the serial and the parallel pulse shaper is hereby implemented by means of a computer program that calculates the drive parameters from the user inputs and modulator elements for generating the ge Wanted laser pulse L 'drives. The computer program can be designed so that a user is the input of sub-pulse parameters for defining the laser pulse forming subpulses is made possible by, for example, the position, the energy, the phase, the ratio of the major axes B / A, the direction of rotation (helicity), the angle of the major axis relative to the horizontal, a linear, quadratic or cubic chirp of the respective subpulse can be entered, from which the pulse shape of the laser pulse L 'to be generated is calculated and displayed (in particular in three-dimensional form, analog 9A - 9H ), the drive parameters are determined and the pulse shaper 10 controlled in this way.

• – sind oben links Unterpulsparameter einzugeben, nämlich die Position, Energie, konstante Phase, Verhältnis der Hauptachsen B/A, Umlaufrichtung (Helizität), Winkel der großen Hauptachse relativ zur Horizontalen, linearer, quadratischer und kubischer Chirp für die jeweiligen Unterpulse,
• – besteht oben rechts die Möglichkeit, sich die Variation eines eingestellten Parameters des Laserpulses, beispielsweise den Winkel der großen Hauptachse zur Horizontalen (Major Axis Angle) in Form eines Meßsignals anzeigen zu lassen und
• – werden unten die aus den Parametern errechneten dreidimensionalen Pulsformen dargestellt, wobei auch andere Darstellungen der Pulsform wie z. B. die zeitliche oder spektrale Intensität, Amplitude, Phase oder dergleichen ausgewählt werden können.

12 shows an interactive user interface of such a computer program, by means of which the shape of the laser pulse to be formed L can be input. The user interface provides an easy-to-use input mask for the user, whereby the user inputs the parameters for the specification of the laser pulse, outputs the time variation of a set parameter for the laser pulse in the form of parameter scans, and displays the simulated shaped laser pulses in different representations , In the in 12 displayed input mask

• - Enter sub-pulse parameters at the top left, namely the position, energy, constant phase, ratio of the major axes B / A, helical direction, angle of the major axis relative to the horizontal, linear, quadratic and cubic chirp for the respective subpulses.
• - There is the possibility to see the variation of a set parameter of the laser pulse, such as the angle of the major axis to the horizontal (Major Axis Angle) in the form of a measured signal, and
• - Below are calculated from the parameters calculated three-dimensional pulse shapes, with other representations of the pulse shape such. B. the temporal or spectral intensity, amplitude, phase or the like can be selected.

The Input mask thus allows an instructive comparison with the after activation of the pulse shaping device and implementation of the Detection indeed measured pulse shape of the laser pulse, which in the user interface also can be represented.

Conceivable and also advantageous is an iterative optimization of the generated Laser pulses L 'means the parametric definition of the laser pulse L 'make. In this way, the Search space and thus the number of required iterations considerably be reduced. For example, such an optimization can take place by iteratively the distance between sub-pulses and / or the orientation adapted and optimized the polarization ellipses of the subpulses becomes. As a result, the optimization can then be physically immediate interpretable parameters, which also draw conclusions allow the respective application. For example, it is conceivable that by means of the optimization determined polarization directions of the different sub-pulses of the laser pulse L 'on the orientation of the laser pulse L 'excited molecules closed back can be.

The presented invention is not on the previously described embodiments limited. In particular, arrangements are conceivable which, in terms of the used Bandwidth and resolution are optimized by pulse shaper with a larger number of modulator elements and / or pixels per modulator element. To this Way you can longer Pulse shapes are produced, giving a more accurate stimulation and influence of a molecular system over a longer period of time allows.

1

contraption

10

pulse shaper

101 102

grid

111-112

cylindrical lens

120

polarizer

121

polarizing beamsplitter

140

mirror

141

beamsplitter

142, 142a, 142b, 142c

Polarization Wheeling element

143

Adjustable mirror

20

detector

220

polarizer

240

mirror

243

Adjustable mirror

250

Phasenretardierer

260

lens

270

Interaction element

280

evaluation

30

laser system

40

mirror

41 42

beamsplitter

a, b, c, d, e, f

modulator element or section of a modulator element

ax, ay, bx, by

modulator element or section of a modulator element

a1, a2, a3

pixel

b1, b2, b3

pixel

c1 c2, c3

pixel

d1 d2, d3

pixel

A ₁ , A ₂ , A _x , A _y

amplitude

F

focal length

e

electrical field

K

Interaction signal

L

unformed laser pulse

L '

molded laser pulse

L _R

reference pulse

L _x , L _y

unformed part pulse

L _x ', L _y '

molded part pulse

L _h

horizontal polarization component

L _v

vertical polarization component

M

measured polarization ellipse

S

beam path

t

Time

T

theoretical polarization ellipse

V

displacement direction

x, y

axes

Claims (36)

Apparatus for producing shaped laser pulses, comprising a pulse shaper, which is traversed by a laser pulse to be formed and has at least one modulator element arranged in the beam path of the laser pulse, wherein - the pulse shaper is designed to divide the laser pulse to be formed into its spectral components, the spectral components be supplied to the at least one modulator element and then recombine into a shaped laser pulse and - the at least one modulator element is designed to adjust the spectral components of the laser pulse in phase and polarization, characterized in that the pulse shaper ( 10 ) additionally at least one in the beam path (S) of the laser pulse (L, L _x , L _y ) arranged polarizing element ( 120 . 121 ), which filters out a polarization component from the incident laser pulse (L, L _x , L _y ), and is designed and provided by means of the at least one modulator element (a, b, c, d, e, f, ax, ay, bx , by) and the at least one polarizing element ( 120 . 121 ) to shape the laser pulse (L) in amplitude, phase and polarization independently. Device according to claim 1, characterized in that in that the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) as a liquid crystal array is trained. Device according to Claim 1 or 2, characterized in that the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) as an acousto-optic modulator or as a birefringent one Phase mask is formed. Device according to at least one of the preceding claims, characterized in that the pulse shaper ( 10 ) includes at least one compressor grid array comprising at least two optical grids ( 101 . 102 ) for the decomposition of the laser pulse (L, L _x , L _y ) into its spectral components and for the reunification of the spectral components to the shaped laser pulse (L ') and additionally at least two cylindrical lenses ( 111 - 112 ) or cylindrical mirror for focusing the laser pulse (L, L _x , L _y ). Device according to at least one of the preceding claims, characterized in that the at least one modulator element is formed by one or more modulator elements (a, b, c, d, e, f, ax, ay, bx, by) which are in the range of a single or in the region of different Fourier planes of one or more compressor grid arrangements of the pulse shaper ( 10 ) are arranged. Device according to at least one of claims 1 to 5, characterized in that in the pulse shaper ( 10 ) in a serial structure, the at least one modulator element is formed by one or more modulator elements (a, b, c, d, e, f, ax, ay, bx, by), the laser pulse (L) in each case once or in different sections of the Modulator elements (a, b, c, d, e, f, ax, ay, bx, by) passes through several times. Device according to at least one of claims 6, characterized in that in the pulse shaper ( 10 ) in a serial structure of the laser pulse (L) at least three different sections of one or more modulator elements (a, b, c, d, e, f, ax, ay, bx, by) passes through. Apparatus according to claim 6 and 7, characterized in that the pulse shaper ( 10 ) is formed in a serial structure, by exactly four successively in the beam path (S) of the laser pulse (L) arranged portions of the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) the laser pulse (L) in amplitude, phase and polarization. Device according to at least one of claims 6 to 8, characterized in that the polarizing element ( 120 ) is arranged in the beam path (S) of the laser pulse (L) such that the laser pulse (L) subsequently passes through at least a portion of a modulator element (a, b, c, d, e, f, ax, ay, bx, by) , Device according to Claim 9, characterized in that the optical axis of the post-polarizing element ( 120 ) in the beam path of the laser pulse (L) arranged portion of the modulator element (a, b, c, d, e, f, ax, ay, bx, by) differs in their orientation from the polarization direction of the laser pulse (L). Device according to claim 9 or 10, characterized in that the optical axis of the post-polarizing element ( 120 ) in the beam path of the laser pulse (L) arranged portion of the modulator element (a, b, c, d, e, f, ax, ay, bx, by) perpendicular to the beam path (S) at an angle of 45 ° to the polarization direction of the laser pulse ( L) is aligned at the location of the modulator element (a, b, c, d, e, f, ax, ay, bx, by). Device according to claim 10 or 11, characterized that afterwards at least one further section of a modulator element (a, b, c, d, e, f, ax, ay, bx, by) in the beam path (S) of the laser pulse (L) is arranged, whose optical axis is different from the direction the optical axis of the preceding section of a modulator element (a, b, c, d, e, f, ax, ay, bx, by) differs. Device according to claim 12, characterized in that that afterwards at least one further section of a modulator element (a, b, c, d, e, f, ax, ay, bx, by) in the beam path (S) of the laser pulse (L) is arranged, whose optical axis perpendicular to the beam path (S) at an angle of 45 ° to Direction of the optical axis of the preceding modulator element (a, b, c, d, e, f, ax, ay, bx, by) is aligned. Device according to at least one of claims 1 to 5, characterized in that the pulse shaper ( 10 ) in parallel construction a beam splitter ( 141 ), which divides the laser pulse (L, L _x , L _y ) into a first and a second partial pulse (L _x , L _y ), and a combining element which reassembles the partial pulses into the shaped laser pulse L '. Apparatus according to claim 14, characterized in that in the pulse shaper ( 10 ) in parallel construction in each case at least one modulator element (ax, ay, bx, by) and at least one polarizing element ( 121 ) in the beam paths (S) of the first and second partial pulse (L _x , L _y ) for modulating the partial pulses (L _x , L _y ) is arranged. Apparatus according to claim 14 or 15, characterized in that the at least one module Gate element by one or more modulator elements (ax, ay, bx, by) is formed, which pass through the first and second partial pulse (L _x , L _y ) once or in different sections of the modulator elements (ax, ay, bx, by) several times , Device according to at least one of claims 14 to 16, characterized in that in the beam path (S) of the first or the second partial pulse (L _x , L _y ) an element rotating the polarization of the first or the second partial pulse (L _x , L _y ) ( 142 ) is provided. Device according to at least one of claims 14 to 17, characterized in that the polarizing element ( 121 ) is arranged and provided, the first and second partial pulse (L _x , L _y ) to the shaped laser pulse (L ') together. Apparatus according to claim 18, characterized in that the polarizing element as a polarizing beam splitter ( 121 ) is formed, which transmits a first polarization component of the first or second partial pulse (L _x , L _y ) and a second, perpendicular to the first directed polarization component of the first or second partial pulse (L _x , L _y ) reflected. Apparatus according to claim 19, characterized in that the first and second partial pulse (L _x , L _y ) perpendicular to each other on the polarizing beam splitter ( 121 ) come so that the polarizing beam splitter ( 121 ) transmits the first polarization component of the first or second partial pulse (L _x , L _y ) and the second polarization component of the other partial pulse (L _x , L _y ) reflected and by spatially superimposing the polarization components, the partial pulses (L _x , L _y ) to the formed Laser pulse (L ') combined. A method for producing shaped laser pulses, in which a laser pulse to be formed is decomposed into its spectral components and the spectral components are supplied to at least one modulator element arranged in the beam path of the laser pulse and subsequently combined to form a shaped laser pulse, wherein the at least one modulator element comprises the spectral components in its Phase and polarization adjusts, characterized in that by means of the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) and at least one in the beam path (S) of the laser pulse (L) arranged polarizing Element ( 120 . 121 )), which filters out a polarization component from the incident laser pulse (L, L _x , L _y ), the laser pulse (L) in amplitude, phase and polarization is formed independently. Method according to claim 21, characterized in that the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) in independent mutually controllable pixels (a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3) arranged along a direction perpendicular to Beam path of the laser pulse (L) directed direction staggered and to adjust the polarization of the spectral components of the laser pulse (L) controlled by predeterminable control parameters become. A method according to claim 22, characterized in that by means of the drive parameters for each pixel (a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3) a phase difference is predetermined which corresponds to the polarization components of the Pixel (a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3) associated with the spectral component of the laser pulse (L, L _x , L _y ) for setting the polarization is impressed. Method according to at least one of claims 21 to 23, characterized in that for shaping the laser pulse (L) the course of the amplitude, phase and polarization of the laser pulse (L) is given as a function of time (t), from this the control parameters and the pixels (a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3) of the at least one modulator element (a, b, c, d, ax, ay, bx, by) are controlled with the drive parameters. Method according to Claim 24, characterized that the course of the amplitude, phase and polarization of the laser pulse (L) as a function of time (t) by a specification of the laser pulse (L) forming sub-pulses are given. Method according to claim 24 or 25, characterized that the subpulses are indicated by specifying subpulse intensities, subpulse spacings, subpulse chords, Subpulse phase differences and / or sub-pulse polarizations specified become. Method according to at least one of claims 24 to 26, characterized in that the laser pulse (L ') by default of shaped spectral phase, amplitude and / or polarization patterns becomes. Method according to at least one of Claims 21 to 27, characterized in that it is used to control a serial pulse shaper ( 10 ) is designed to form laser pulses (L '). Method according to at least one of Claims 21 to 28, characterized in that it is used to control a parallel pulse shaper ( 10 ) is designed to form laser pulses (L '). Method according to at least one of claims 21 to 29, characterized in that the shaped laser pulse (L ') for interaction used with a substance, an excitation signal generated by the interaction measured and optimized the shaped laser pulse (L ') based on the excitation signal becomes. Method according to claim 30, characterized that optimization is done iteratively by setting initial values for the driving parameters for controlling the pixels (a1, a2, a3, b1, b2, b3, c1, c2, c3, d1, d2, d3) of the at least one modulator element (a, b, c, d, ax, ay, bx, by) given by the thus formed laser pulse (L ') generated excitation signal is measured and the driving parameters iterative for optimization of the shaped laser pulse (L ') be adjusted by the excitation signal. Method according to claim 30 or 31, characterized that the iterative optimization of the laser pulse (L ') by adaptation the predetermined time course of the amplitude, phase and polarization of Laser pulses (L), from which the activation parameters are calculated, he follows. Method according to at least one of claims 30 to 32, characterized in that the iterative optimization means an evolutionary one Algorithm is done. Method according to at least one of claims 21 to 33, characterized in that polarization dependencies and / or frequency dependencies of the optical gratings used ( 101 . 102 ) and / or cylindrical lenses ( 111 - 112 ) or cylindrical mirror can be corrected by adjusting the drive parameters. Method according to at least one of claims 21 to 34, characterized in that the shaped laser pulse (L ') for transmission of information is used. Computer program for carrying out the method according to one the claims 21 to 35, characterized in that the computer program the at least one modulator element (a, b, c, d, e, f, ax, ay, bx, by) according to the method according to one of the claims 21 to 35 controls.