DE102008022680A1 - Method for time-resolved detection of photons for analyzing processes of semiconductor structures, involves continuously or discontinuously changing acceleration of electrons in z-direction between beginnings of consecutive linear images - Google Patents

Abstract

The method involves accelerating electrons released from a photomultiplier in x and y directions. Acceleration of the electrons in y-direction is changed as function of the time. The electrons are detected in spatially resolved manner by an imaging element (10) extending in the y direction and z direction. The x, y and z directions form an angle between 10 degree and 170 degree. Detection patterns are stored by the element during an imaging period. The acceleration of the electrons in the z-direction is continuously or discontinuously changed between beginnings of consecutive linear images. An independent claim is also included for a measuring arrangement for time-resolved analysis of electromagnetic fields, comprising a distance camera.

Description

The The invention relates to a method for the time-resolved detection of photons, a method for the statistical investigation of an electromagnetic Feldes, a stretching camera and a measuring arrangement for time-resolved examination an electromagnetic field.

The Examination of electromagnetic emissions will be in many areas The physics used to gain knowledge about the emitting object and in this process to win. More recently, this is increasingly important investigation methods, which on the one hand have a high sensitivity, up to the detection of single photons, on the other hand a high one time resolution Offer. The latter is z. For example the investigation of processes in semiconductor structures like quantum filaments or Interesting quantum dots because there are processes such as electron-hole recombination Expire on a timescale in the ps range. To get out of the emitted photons Findings about to gain the underlying processes, it is therefore necessary to apply a measurement method that has a time resolution of the order of magnitude allowed.

In this as well as in other fields, an object of particular interest is the statistical behavior of the emissions, which can be described in particular by the intensity autocorrelation function or correlation function of the second order. This is defined as G (2) (τ) = ⟨I (t + τ) I (t)⟩ ⟨I (t) ⟩²

Here I (t) denotes the intensity at time t. From the above correlation function can be in principle quantum mechanical effects such as "bunching" or "anti-bunching", d. H. the tendency to pairwise or single arrival of photons, read. Leave these effects also read from the photon number correlation function, which instead the intensity, the number of detected photons at time t with that correlated at the time t + τ. In the statistical limit case, the two functions essentially go into each other, because the intensity quantum mechanically interpreted as detection probability is. For this reason in the following conceptually not between the two functions. Metrology is about the detection single photons at high time resolution. However, this forms in usually the basis of a statistical coverage of a variety of photons, which corresponds to the determination of intensities.

To The state of the art is the intensity autocorrelation function typically with the HBT structure (after HANBURY BROWN and TWISS) certainly. Such a structure, however, only allows temporal resolutions in the Range about 500 ps, what for the detection of short-term correlations is completely inadequate. It is be noted in this context that, although in principle by statistical Evaluation of a large number of individual measurements of the resulting Error can be reduced, but many measurements take time. ever longer but the measurements continue, the more difficult are external parameters, which influence the measurement, keep it stable. Therefore, a time-resolved investigation an electromagnetic field and in particular the determination its intensity autocorrelation function with a resolution of a few picoseconds according to the prior art not possible.

In front In this background, it is the object of the invention to take measures propose to measure the time dependence of an electromagnetic Field on a timescale of a few picoseconds.

The Task is solved by a method according to claim 1 and claim 16, by a stretching camera according to claim 19 and by a measuring arrangement according to claim 23.

Of the Term of the electromagnetic field refers in particular here Light fields, as well as the term photon, in particular light particles designated. The methods and devices presented in the following can be applied in principle to other frequency ranges.

At the inventive method to the time-resolved Detection of photons become within one imaging period created a plurality of linear images. Figure period refers to the period from the beginning of the first linear illustration until the end of the last linear illustration. Each linear illustration includes in this case a detection of the photons by means of a photomultiplier. As a photomultiplier in this context, each device denotes, from the by irradiation of a photon a plurality triggered by electrons becomes. Such devices are known in the art and typically comprise a photocathode from which by means of the photoeffect at least a primary one Electron is dissolved, and a secondary electron multiplier by successively knocking out further electrons the number the same greatly increased becomes. The amplification factor is typically of the order of magnitude of 1000. In this first process step, therefore, an incoming one Photon to release at least a few hundred electrons.

The triggered from the photomultiplier After being triggered, electrons are accelerated in a first direction (hereinafter: x-direction) and in a second direction (in the following: y-direction). The acceleration preferably takes place in an electric field that is generated by at least one capacitor per x or y direction. The field and thus the acceleration of the electrons can be controlled by the voltage applied to the capacitor.

Essential is that the acceleration in y-direction as a function of time changed becomes. A typical change takes place continuously, in particular linearly, but there are also other z. B. discontinuous, gradients conceivable. However, it is crucial that the time course of the Change known is. The acceleration in the x direction preferably becomes constant over time held, a temporal change the same is conceivable.

The Electrons accelerated in this way are subsequently detected spatially resolved. Detection takes place by means of an imaging element which is in the x-direction is spaced from the photomultiplier and that in the y-direction as well in a third direction (hereinafter: z-direction). According to the invention include x-, y- and z-direction each with an angle between 10 ° and 170 °, d. H. no two of these directions even come close together. The spacing of the imaging element from the photomultiplier provides for this, that the electrons before hitting the imaging element undergo a deflection in the y-direction, which due to the time-dependent acceleration also time-dependent is, depending on when the electrons were triggered.

When Imaging element in this case each component is called, the Impact of the electrons a spatial localizable signal, in particular optically or electrically generated. For this purpose, such a component preferably has a serving for detection surface on, so a kind of detection screen.

That the imaging element extends in the y and z directions, means not necessarily, that it has a detection surface serving in the by the said directions spanned yz plane lies. Such surface may also differ from the said level and may in particular domed be educated. However, an alignment in the yz plane is prefers.

Farther At least one detection pattern will be detected by the imaging element while the recording time. The term "store" in this context means the points on the imaging element at which electrons are detected at the end of the recording time, based on the state of the imaging element are detectable. This falls in particular, an afterglow of an imaging element, by the impact of the electrons is excited to shine.

The Designation "Linearabbildung" should not linear relationship in the mathematical sense suggest, but therefore, that the time variable Deflection in the y-direction to a shift of the detection point on the imaging element along a line.

According to the invention will now between the beginning of two successive linear images an acceleration of the electrons in the z-direction changed. This can as in the acceleration in the x and y direction by means of the electrical Field of a capacitor made. This can be the acceleration be changed continuously or discontinuously. A discontinuous change can in particular between the end of a linear illustration and the Beginning of the subsequent linearabbildung done. In any case it is preferable that the change acceleration in the same direction (ie either always increase or always reducing the acceleration) and still preferred each time by the same amount.

By this procedure will be in the course of recording time the yz level in scanned z direction, d. H. Electrons that at the same time, measured at the beginning of each linearab, but within various linear images were triggered hit the picture element not offset at the same point, but in the z-direction against each other.

Consequently results in a total areal Detection pattern, in which in the y-direction of the sequence one each Linear illustration is apparent while in the z direction each other next to each other arranged the detection pattern of the individual linear images are. The detection pattern thus has a line-like structure on, in which the individual lines of each linear illustration correspond.

With the method according to the invention, it is possible to carry out a temporally high-resolution detection of photons. With suitable imaging elements, temporal resolutions of less than 10 ps, preferably even less than 5 ps, particularly preferably less than 3 ps, can be achieved. For this purpose, on the one hand a sufficient spatial resolution of the imaging element is required, on the other hand, a sufficiently rapid change in the acceleration in the y-direction. A linear illustration can here z. B. within a few 10 picoseconds to we nanoseconds, which can be done with current components.

critical Advantage of the method, however, is that at high time resolution longer chronological course of the carried out Measurement is stored on the imaging element. That is, if for example, at a time resolution of 5 ps, a linear image 3 ns takes and 20 linear images are created, is at the end the recording time the information from a period of 60 ns at the time resolution mentioned stored on the imaging element. The mentioned period must not connected be. This depends depending on whether the linear illustrations follow each other without interruption. In any case, data from a period that is available measured by the time resolution long, as measured by the time scale on which external parameters change, however is very short. Therefore, the data obtained in this way are due to external parameter changes unaffected.

It is unnecessary in the process according to the invention, the to evaluate the resulting detection patterns at the same speed, with which it arises. Rather, an evaluation may be after the end the last linearab education done. This represents another Advantage is because a continuous reading even with modern Electronics would not be possible with the specified speed.

The Procedure simplifies significantly when the accelerations in the three directions mentioned and the resulting distractions independently done from each other. This is fulfilled when the three directions approximately orthogonal to each other. Therefore, in a preferred embodiment the method according to the invention the x, y and z directions in each case an angle between 80 ° and 100 °, preferably between 89 ° and 91 °.

As already explained, is a big Advantage of the procedure the length of the period due to the majority of the linear illustrations can be reproduced the imaging element. The length of this Period increases with the number of linear figures. on the other hand have to the individual "lines" spatially from each other be separable, which limits the number of linear images. Therefore it is advantageous that within a mapping period between 10 and 100, preferably between 20 and 70, more preferably between 30 and 60 linear images are created.

Of the Period within which a linear drawing is created can in the method according to the invention be varied within a relatively wide range. however increases due to the spatial given by the imaging element resolution by a short linear imaging time the temporal resolution. Therefore Advantageously, a Li nearabbildung each within 20 ps to 20 ns, preferably within 1 ns and 5 ns.

A special variant of the method results when the reaction of a medium is examined for a suggestion. In this case let the photons be separated from the medium within a short time Period, typically of a few nanoseconds, after the stimulation be detected with high time resolution detect. Here is It is particularly advantageous that the excitation of a medium synchronized is performed with at least one linear image. Here, "synchronized" does not mean inevitably, the beginning or end of the suggestion and the beginning of the said Linearabbildung coincide in time. In this context is especially to consider within a 1 ps period, a photon as well as an electrical one Signal in a circuit travels only 0.3 mm, which is why the transit times to be considered here are. A vote on this However, to carry out a task that the expert due to his Can solve knowledge. In any case, however, the term "synchronized" means that the time interval between the beginning (or end) of the suggestion and beginning of at least one linearablet set and known is. Here you can following a suggestion one or more linear images, d. H. it is Z. B. conceivable, in each case an excitation with every second, third etc. synchronized linear imaging performed. A possibility the synchronization is that the linear representation after Start of the suggestion is started, and offset by the duration, the photons for need the distance from the excited medium to the photomultiplier.

For special short-term processes it is preferred in this context that synchronized with each linear illustration each a suggestion of Medium performed becomes. Here then corresponds to each "line" of the detection pattern the Emissions that occur in response to a single stimulus are. The evaluation of all recorded linear images can for one be used for statistical analysis.

by virtue of the very high time resolution and the associated short imaging period is suitable the procedure especially for suggestions, which in turn very short time respectively. Such a suggestion leaves in particular by means of a pulsed laser perform. With Such lasers can be pulse durations in the range of femtoseconds (and below), which makes it ideal for short-term suggestions are.

It is preferred in the present Verfah used an imaging element comprising a phosphor element. Here, phosphorus element refers to a component which is excited when hitting fast electrons to emit a light signal. Such phosphor elements are known from the prior art and usually have a two-dimensional surface structure. They typically exhibit afterglow after electron excitation during a decay time, which persists during the imaging periods characteristic of the process. In this way, such an element ensures storage of the detection pattern during the imaging period. A typical phosphor element is based on the use of P43 phosphor, consisting of gadolinium oxysulfide and terbium. When using P43 phosphor occurs afterglow of a few milliseconds.

If It is it to read out several detection patterns one after the other advantageous if no remains of a previous pattern due afterglow of the phosphor element are more present, if a new imaging process is started. For a particularly fast sequence the individual imaging processes Therefore, it is preferable that the phosphor element used has a cooldown of less than 20 μs. A phosphor element, that satisfies this condition, can be prepared using P46 phosphorus consisting of yttrium aluminate and cerium.

Around the light intensity of the detection pattern for To increase an even more efficient evaluation is in a further development the method provided that the photomultiplier used a Double-layer microchannel plate includes. Microchannel plates are out known in the art. These include a plate of semiconductor material, between their faces in the operating state a voltage is applied. The plate is interspersed from a variety of channels with a diameter of the order of magnitude a few um and a distance from each other in the same order of magnitude. Each of the channels, the opposite the perpendicular to the faces are arranged inclined, works as a secondary electron multiplier. A allows such micro-channel plate at a spatial resolution in the μm range an electron multiplication by three tens of zenith. This multiplication can be increased to six orders of magnitude by adding two microchannel plates be arranged one behind the other, thereby forming a double-layer microchannel plate receives.

In many cases is it desirable to selectively detect photons of a given frequency. Therefore In an embodiment of the method, an interference filter is used The photons pass through before detection. such Filters that due to interference effects only radiation of a narrow frequency or wavelength range let through, are known from the prior art. Hereby can to a background emissions are filtered out. It is hereby but also possible specifically a certain frequency component of the emissions of a medium to investigate, for. For example, the issue of a particular type owned by electron-hole recombination.

Around the evaluation of the temporarily stored on the phosphor element To make detection patterns even more efficient, it is in one Further development of the procedure provided that subsequent to the performing the linear images a readout of the phosphor element takes place. Such readout is preferably carried out by means of a CCD camera which is arranged on the phosphor element. Such a CCD camera provides the recorded pattern is already available in digital form and is therefore good for the integration into a fast, digital processing process. in principle could the reading also with a conventional camera with a photo plate o. However, such a procedure is not preferred, since it is particularly further processing of the recorded data difficult.

in the Further can the read-out data is stored on a data medium. Hereby designated disk in addition to volatile Save (such as the main memory of a PC) all Types of non-volatile Save, such as floppy disks, CDs, magnetic tapes, hard drives, flash memory. However, these are memories with short write access times preferred as these ensure that the CCD camera is particularly fast for another shot is. The storage of the data is advantageous for a further evaluation and allows a computerized Evaluation.

In order to ensure an even more efficient process, in a development of the method, the readout of the phosphor element is synchronized with the execution of the linear images. This means that the read-out of the phosphor element is automatically initiated by a certain time interval after the end of the last linear image. For a fast processing, the mentioned time interval should be set as short as possible, whereby the accuracy of the setting must ensure that the last linear recording is actually completed. This synchronization is important to ensure that the decay time of the phosphor element does not elapse before reading. On the other hand, this contributes to several temporally successive recordings of detection patterns, to avoid unnecessary delays.

The described method leaves in a special way to the statistical investigation of an electromagnetic Insert field. Here, at least one procedure for time-resolved detection performed by photons. However, it is preferred that a plurality of such process sequences are carried out, each creating a plurality of linear images, of which each one provides a detection pattern. The obtained in this way Multiple detection patterns provide a broad basis for statistical Evaluation. To determine the correlation function, the read out Signals computer-aided evaluated. Suitable here is z. B. a commercial PC. The whole procedure This must be done within a period of time in which experience has shown that the external parameters to stay stable. To the collection as possible Often, it is therefore preferable to use the individual detection patterns preferably to record quickly in quick succession.

through of the described method can in particular by the computer-aided evaluation determines a correlation function of the electromagnetic field become. The determination of the correlation function from the given Data is a task that can be performed with suitable software from a computer, z. As a PC performed can be. In this area, the present method is the state the technique, for. B. the HBT method, far superior because time resolution in single-digit picosecond range can not be achieved with conventional methods are.

The Method for determining the correlation function, as well as the other methods according to the invention, is preferably with a time resolution of less than 10 ps, on preferably less than 5 ps, more preferably less than 3 ps.

For the inventive method A modified stretching camera can be used. How out known in the art, such a camera comprises a Photomultiplier, means for accelerating electrons released from the photomultiplier in a first direction (x-direction) and means for accelerating of the electrons in a second direction (y-direction) with a temporally changeable Acceleration. These elements have already been described above. Furthermore, the streak camera includes a phosphor element for the detection of electrons in the x-direction is spaced from the photomultiplier and that in the y-direction as well in a third direction (z-direction) extends.

As already explained, allowed to the directions do not approximate coincide and simplifies a substantially orthogonal alignment the evaluation of the detection patterns. Hence include the camera described the x-, y- and z-direction with each other each an angle between 10 ° and 170 °, preferably between 80 ° and 100 °, especially preferably between 89 ° and 91 °.

The inventive camera however, is modified in so far as it additionally has means for accelerating of electrons in the z-direction, which are designed so that they can exert on the electrons a temporally variable acceleration.

In In other embodiments, the stretching camera comprises a double-layer microchannel plate or a phosphorous element with a decay time below 20 μs, which is preferred Includes P46 phosphorus.

The Inventive stretching camera can in a measuring arrangement for the time-resolved examination of an electromagnetic Field are integrated. Such a measuring arrangement further comprises a CCD camera for reading the phosphor element. It understands itself that in this case forms are included, in which the CCD camera is integrated into the stretching camera. To be in operating condition a delay-free To ensure particularly reliable evaluation of detection patterns is synchronized with a change the acceleration of the electrons in the z-direction a readout of the phosphor element automatically triggered. This usually means that an automated controller guaranteed that after passing through the acceleration in z-direction up to an end value, which corresponds to the beginning of the last linear representation, and the lapse of an additional period for the Create the last linear image, a corresponding readout he follows. Such a controller may be integrated into the drafting camera. Alternatively, an external control is conceivable that both the acceleration the electrons in the stretching camera, as well as the read-out process controlled by the CCD camera.

As already explained is often a selective detection of photons more specific Wavelength desired. To For this purpose, the measuring arrangement by an interference filter added which is arranged to the photomultiplier so that he shields from photons of other frequency ranges. Again, this is In turn, it is conceivable that an interference filter in the stretching camera is integrated.

Preferably, the measuring arrangement also includes a computer for storing and evaluating data that can be transmitted by the CCD camera. As already explained, the evaluation of the data read by the CCD camera is thereby performed made much more efficient.

in the The following details of the invention with reference to an embodiment explained with reference to the figures. This shows

1 a schematic representation of a perspective view of an embodiment stretching camera according to the invention; such as

2 a diagram of the essential elements of a measuring arrangement according to the invention and the processes running between them.

At the in 1 shown stretching camera 1 is a phosphorus element in a vacuum tube (not shown) 11 arranged from P46 phosphor, which is formed flat and extends along a second y and a third z-direction. The said directions are in this case orthogonal to one another and to a first x-direction. Along this x-direction is the phosphor element 11 from a photomultiplier 3 spaced, which is a photocathode 4 and a double-layer microchannel plate 5 includes. Relative to the x-direction between photomultiplier 3 and phosphorus element 11 are a first pair of capacitor plates 6 and a second pair of capacitor plates 7 arranged. In this case, the first pair of capacitor plates extends 6 in the xz plane and serves to generate a y-directional electric field, while the second pair 7 extends in the xy-plane and serves to generate a running in the z-direction electric field. About power supplies (not shown), the voltages and thus the electric fields between the plates of a respective pair 6 . 7 be varied. Another pair of electrodes (not shown) serves to build up a time-constant electric field in the x-direction, which crosses the fields running in the y- or z-direction.

Meets a photon 100 on the photocathode 4 , it triggers there a primary electron, which in turn in the two layers of the double-layer microchannel plate 5 dissolves a large number of secondary electrons. The secondary electrons are directed through the x-directional electric field in the direction of the phosphor element 11 accelerated. Depending on the strength of the y-and z-directional electric fields, they experience a different acceleration in the corresponding directions. This in turn leads to different impact points on the surface of the phosphor element 11 , In the figure, a possible path of the impact point is indicated by the dashed line. With respect to the imaging element in the present structure, the y-direction represents the vertical, the z-direction represents the horizontal.

At the beginning of a first linear formation, both the y-acceleration and the z-acceleration are set to a minimum value, whereby the impact point in a first position 20 lies. A vertical trigger is used to start the first linear mapping, whereby within 2 ns the y-acceleration is continuously increased to a maximum value while the z-acceleration is kept constant. As a result, the impact point moves to a second position 21 which is shifted from the first position in the y-direction. Subsequently, y-acceleration is reset to the minimum value and the z-acceleration is increased by a predetermined amount, whereby the impact point in a third position 22 is relocated. The camera 1 is now ready for the beginning of the second linearab education. This is triggered by the vertical trigger, which again increases the y-acceleration to its maximum value within 2 ns, bringing the impact point into a fourth position 23 emigrated. The process described is continued, with the area of the phosphor element being line by line 11 is scanned.

The stretching camera 1 further includes a CCD camera 12 , which, based on the photomultiplier 3 , on the rear side of the phosphor element 11 is arranged. Together with this she forms an image element 10 , It is in this case a silicon CCD camera 12 , which allows read-out frequencies of a few 10 kHz.

In the 1 illustrated stretching camera 1 is used in an attempt to investigate the transition from spontaneous to stimulated emission by means of electron-hole recombinations in quantum dots. For this purpose, a sample comprising an ensemble of quantum dots embedded in a microcavity is excited with a titanium sapphire laser operating in pulse mode at a repetition frequency of 76 MHz. In the quantum dot ensemble, which has a number of discrete energy levels, electron-hole pairs are generated by the laser pulses, which subsequently recombine, with photons 100 a wavelength of 700 nm are emitted. The stretching camera 1 is provided with an interference filter tuned to said wavelength and arranged such that photons emitted from the sample 100 in the photomultiplier 3 be registered. A particularly efficient implementation of the measuring process requires a sophisticated synchronization system, which is described below with reference to FIG 2 is explained.

First, a vertical trigger over a first transmission link 50 in the stretching camera 1 which is tuned to the repetition frequency of the 76 MHz laser. As a result, approximately every 13.2 ns becomes a linear image solved, taking the time of triggering taking into account the transit times of photons 100 and electrical signals is chosen so that it with the earliest possible arrival of photons 100 at the photomultiplier 3 coincides after the respective excitation of the sample.

The signal of the vertical trigger is also transmitted via a second transmission link 51 in a frequency divider 70 as well as via a third transmission connection 52 a syn chrongenerator 71 fed. The frequency divider 70 generates from the 76 MHz signal a horizontal trigger signal with a frequency of approx. 12 kHz. Before this in the streak camera 1 It can be fed in via a fourth transmission link 53 into the synchronous generator 71 fed in, where it is synchronized with the vertical trigger. This generates a synchronized horizontal trigger that has a fifth transmission connection 54 in a horizontal sweep unit 14 (in 1 not shown) of the stretching camera 1 is fed. The horizontal sweep unit 14 When inputting a signal of the synchronized horizontal trigger, it starts to increase the acceleration in the z-direction in the manner described above. The synchronized horizontal trigger which marks the beginning of a recording of a detection pattern is also transmitted over a sixth transmission link 55 into a rectangle generator 72 fed by a via a seventh transmission link 56 transmitted gate signal the stretching camera 1 releases for detection. The gate signal is a square wave whose length is tuned to the time required for recording all linear images.

In this case, 50 linear images are created (in 1 For reasons of clarity, only the path of the impingement point is shown for 10 linear images), resulting in an imaging period of 658 ns. After this time, well below the cooldown of the phosphorus element 11 is about 15 μs, is on the phosphor element 11 a detection pattern emerged, which can now be read out. For this, the horizontal sweep unit sends 14 via an eighth transmission connection 57 a read signal to the CCD camera 12 , which performs the readout process within 66 μs.

The data of the CCD camera 12 be over a ninth transmission link 58 to a PC 80 sent where they are stored. In addition, the CCD camera sends 12 to the PC 80 a reset signal that marks the end of the recording. The computer 80 sends after receiving the data and the reset signal to the horizontal sweep unit 14 over a tenth transmission connection 59 a trigger reset signal, causing the horizontal sweep unit 14 the acceleration in the z-direction is reset to the minimum value and can now be started by a new synchronized horizontal trigger.

The transmission connections 50 . 51 . 52 . 53 . 54 . 55 . 56 . 57 . 58 . 59 may be formed as a cable, waveguide, optical fiber and / or wireless. In this case, the person skilled in the art can select a suitable connection form on the basis of his knowledge.

The recording and reading process takes under 80 μs in total, which means that more than 600,000 linear images can be created within one second. Within a test period, within which external parameters remain stable and which is typically on the order of a few minutes, can therefore from PC 80 Data from some 10 million linear shots are saved. The computer 80 evaluates the data by means of suitable image recognition software and calculates a correlation function of the light field, which has an excellent accuracy due to the time resolution of 5 ps achieved in this case and the large amount of underlying data.

Claims (25)

A method for the time-resolved detection of photons by producing a plurality of linear images within an imaging period, respectively by - detecting the photons by means of a photomultiplier, - accelerating electrons released from the photomultiplier in a first direction (x-direction) and a second direction ( y-direction), wherein the acceleration in the y-direction is changed as a function of time, - spatially resolved detection of the electrons by means of an imaging element, which is spaced in the x-direction from the photomultiplier and in the y-direction and in a third direction (z-direction), wherein the x-, y- and z-direction each include an angle between 10 ° and 170 °, and - Saving a detection pattern by the imaging element at least during the imaging period are created, characterized in that between the beginning of each two consecutive He linear illustrations an acceleration of the electrons in the z-direction is changed continuously or discontinuously. A method according to claim 1, characterized in that the x-, y- and z-direction each with an angle between 80 ° and 100 °, be preferably between 89 ° and 91 °. Method according to claim 1 or 2, characterized that within a mapping period between 10 and 100, preferred between 20 and 70, more preferably between 30 and 60 linear images to be created. Method according to one of claims 1 to 3, characterized each linear map is within 20 ps to 20 ns, preferably within 1 ns and 5 ns. Method according to one of claims 1 to 4, characterized in that synchronized with at least one linear image excitation of a medium for the emission of photons ( 100 ) is carried out. Method according to claim 5, characterized in that that synchronized with each linear education each a suggestion carried out of the medium becomes. Method according to claim 5 or 6, characterized that the excitation is carried out by means of a pulsed laser. Method according to one of claims 1 to 7, characterized in that the imaging element ( 10 ) a phosphorus element ( 11 ). Method according to claim 8, characterized in that the phosphorus element ( 11 ) has a cooldown of less than 20 μs. Method according to claim 8 or 9, characterized in that the phosphorus element ( 11 ) P46 phosphorus. Method according to one of claims 1 to 10, characterized in that the photomultiplier ( 3 ) a double-layer microchannel plate ( 5 ). Method according to one of claims 1 to 11, characterized in that the photons ( 100 ) pass through an interference filter before detection. Method according to one of claims 8 to 12, characterized in that subsequent to the implementation of the linear images, a read-out of the phosphor element ( 11 ) he follows. Method according to claim 13, characterized in that that the read-out data is stored on a data medium. Method according to one of claims 13 or 14, characterized in that the readout of the phosphor element ( 11 ) is synchronized with the implementation of the linear images. Method for statistical analysis of an electromagnetic Field with the steps - Perform at least a method sequence, preferably a plurality of method sequences, after one of the claims 1 to 15 - computer-aided evaluation the read out signals. Method according to claim 16, characterized in that that by means of the evaluation, a correlation function of the electromagnetic Field is determined. Method according to one of claims 1 to 17, characterized that it is preferred with a temporal resolution of less than 10 ps below 5 ps, more preferably below 3 ps. Stretching camera with - a photomultiplier, - means for accelerating electrons released from the photomultiplier in a first direction (x-direction), - means for accelerating the electrons in a second direction (y-direction) with a temporally variable acceleration and - a phosphor element for detecting the electrons, which is spaced in the x-direction from the photomultiplier and which extends in the y-direction and in a third direction (z-direction), wherein the x, y and z directions each with an angle between 10 ° and 170 °, preferably between 80 ° and 100 °, more preferably between 89 ° and 91 °, characterized by means ( 7 ) for accelerating the electrons in the z direction, wherein the means ( 7 ) are designed so that the electrons can be accelerated in time variable. Stretching camera according to claim 19, characterized by a phosphor element ( 11 ) with a cooldown of less than 20 μs. Stretching camera according to claim 19 or 20, characterized in that the phosphor element ( 11 ) P46 phosphorus. Stretching camera according to one of claims 19 to 21, characterized in that the photomultiplier ( 3 ) a double-layer microchannel plate ( 5 ). Measuring arrangement for the time-resolved examination of an electromagnetic field with a stretching camera according to one of the claims 19 to 22 and - a CCD camera for reading the phosphor element, characterized in that synchronized with a change in the acceleration of the electrons in the z direction, a readout of the phosphor element ( 11 ) is automatically triggered. Measuring arrangement according to claim 23, characterized by an interference filter. Measuring arrangement according to one of Claims 21 to 24, characterized by a computer ( 80 ) for storing and evaluating data transmitted by the CCD camera ( 12 ) are transferable.