The Laserlab-Europe Talk “Multi-pass cells – quasi-guiding systems for laser pulse post-compression and advanced nonlinear optics” by Christoph Heyl (DESY) has taken place on 13 December 2023.
Nonlinear multi-pass cells (MPCs) have brought exciting opportunities to the field of ultrafast optics, ranging from major advances in post-compressed ultrafast lasers to novel frequency conversion schemes. As a hybrid concept bridging free-space and guided-wave nonlinear optics, MPCs overcome several limitations of traditional nonlinear optics approaches. Here, I discuss the underlying principles and possibilities of nonlinear MPCs, as well as selected recent results.
#nonlinear #optics #laser #mpc #multipasscells #ultrafast #ultrafastoptics
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The Laserlab-Europe Talks consist of a series of online seminars and panel discussions proposed and organised by our community on specific topics (thematic or research-specific) and provide a platform for regular information exchange and knowledge sharing.
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DESY Deutsches Elektronen-Synchrotron: @DeutschesElektronenSynchrotron
I’m really honored to um for this opportunity here to present um in this um laserlb Europe seminar here online and I’m very happy to see many participants joining today and I will be speaking about multipass Sals as announced already and um yeah I call them basically quasi
Guiding guiding systems which we use for post compression and nonlinear Optics as you will see in the presentation today let me start but before jumping into the topic a very quick intro um my group is the group of ultra fonic research and Innovation a group hosted both at Daisy
Mainly at Daisy but also at helos instit Yer in Germany both institutes in Germany and we have a focus here on current research topics namely addressing really quality guided nonlinear Optics in particular in multipass cells then Ultra Force laser developments mainly for secondary Photon and particle sources and yeah a new
Topic which is not part of this talk today gas bace sonop phonics I briefly mention it the Outlook of this presentation um the B presented today is yeah carried out was carried out by my group and also in very close collaboration with the DC laser Science and Technology Group many of the works
Here um have been jointly conducted yeah let me start then to jump here right into the topic with a short motivation Ultra fast lasers if you look at ultrafast Laser Technology um there are in particular two very important sources the tanium safire laser a laser which provides Ultra short laser pulses
But at very limited average power on the other hand we have terbium laser systems providing very high average power reaching up into the kilowatt regime but the PSE duration is rather limmited um to not very short durations we’re speaking about hundreds of HTO seconds here if we look a bit and of
Course there is opcpa Technologies available as well and a couple of more systems if we look a bit back there has been a prediction in um I think this paper came out in 2014 that opcpa would mature to much much higher average powers and um the develop further in this direction this
Has certainly happened and there have been great achievement over the last couple of years this direction but I would say nowadays there is another very attractive approach and this is the approach I will be discussing in this presentation among other things today and namely the approach just taking
Taking the turum system and directly post compressing such systems by utilizing very large compression factors um and efficient efficient compression schemes and in particular this combination of very efficient compression and large compression factors has been really um receiving a boost over the last couple of years by this multipass post compression
Technology which we review in this um recent review published in in Optica yeah let me let me move on and um move over to a very short intro into what is a multi passel I suppose many of you probably know this technology but a short review here is is needed imagine
We have two we have two mirrors two concave mirrors typically facing each other and we have Ultra short laser pulse bouncing many times back and forth between um these mirrors we can now introduce a nonlinear medium between these two mirrors such as a gas or a solid plate medium glass plate for
Example and in this in this nonlinear medium the laser pulse can undergo self phace modulation thereby spectrally broadening its spect by broadening its spectral content and afterwards we can post compress this laser pulse um using a compressor this principle has been widely applied now to various laser
Systems but in particular um to the atum laser platform very importantly here is particular when we speak about itum lasers and large compression factors but in general for post compression it is important to consider that we while gaining large nonlinear faces large B integrals we need to find a way to
Mitigate to avoid and the beam to collapse spatially this is done to for example traditionally by us utilizing guiding structures such as fibers and here in this particular case we use this quasi guiding scheme the multipass cell it actually has similar properties I will explain them a bit later why this is the
Case um key features of such multipar cells have been shown to be very high power compatibility large compression factors which are support supported very high efficiencies they support excellent beam qualities they are adaptable to very large parameter ranges and maybe most interestingly at least depending on the application um they really feature
Advanced amplitude and phase control option again I will come back also to that topic later in my presentation um if we look at parameters I’m showing you here an overview published in our um in our recent review paper and in this in this overview you see essentially in in in red dots here
Multipass cells and blue dots other post compression schemes and um we show here very clearly that in particular if we look at high peak power and high average power sorry it was too quick and the red dots perform pretty nicely same for power efficiency for the efficiency of
The system for compression ratios we can see that um these systems reach despite reaching very large compression factors even still very high efficiencies exceeding even 90% And this is of course very attractive parameter that has attracted many researchers and and has really led to a spread of this
Technology in the ultra fast laser Community to illustrate this and without going here being here too Global I I focus here just on our Institute Daisy in Hamburg in Germany and here we see a map of the DC campus in which I Mark um Laboratories which which host Ultra fast
Laser systems um and I’m adding now basically to this to this map which is a few years old already um more recent developments developments which has happened over the last three years in which um which I indicate here in yellow basically multipass systems that have been installed or that are currently
Under development and by while presenting this I’m already seeing that um there are laps missing because this this um slide is already half a year old so I need to update that yeah but it really what I want to show here it really shows the progress on Ultra Laser
Technology using this multipass cell option and it shows it here on DC campus but I think this is an example for um a trend that we see in the ultra fast laser Community worldwide yeah what I’m showing you here is not only works not only Labs of course by by my group but
But by many other groups contributing and groups with which we are also collaborating here on campus and yeah another indication here if you count um papers that contain the the the word multi parel or that focus on this technology um even only looking at Journal papers will reach very large
Counts um over the last few years that have been published on this topic already we also have been publishing quite a few things and just briefly mention that that here and I will now basically in the next um in the next few slides show you some selected results
From the the the results achieved on this topics over the last um yeah about three years I will start with a quick um a quick intro into into this nonlinear Optical quasy guiding systems and explain a bit the some basic features and why they are very attractive not
Only for post compression my second my my main main first topic here namely post compression and then um but also for the second topic here namely multipass cell based nonlinear Optics I will briefly show you first a few examples for post compression systems which we have which we are currently
Working on or have been working on recently and then also two examples for General non Optics performed in multi passels but let me start very basic here and look at the multi passel as a very special system nonlinear Optics is typically if you look back into the history of nonlinear Optics is typically
Performed either in a free space geometry or in wave guide wave gate features very large interaction length it features to some extent um amplitude and pH control wi dispersion engineering for example and some limited high power high energy compatibility well actually very limited here free space Optics on
The other hand feature only very short non nonlinear interaction length due to the fraction limiting this spectral amplitude and phe control is not easily possible here but of course very high powers are feasible the multi passel which is here represented as a sort of unfolded schemes of many lens of of a
Lens array essentially um is yeah optically very similar to a multi passel this multi passel here is featuring basically nice properties of both previous themes and thereby actually therefore actually being very powerful there’s another way to see this if you think about a basic nonlinear Optical processes can be sface modulation or
Another nonlinear Optical process where certain laser PSE enters um a medium and then another laser PSE is emitting the medium if we have such a process and now imagine we could Pro we could divide this process into many slices and we could now after each slice tune amplitude and phase within this process
That would be a very powerful mean of means of controlling nonlinear Optical process if we at the same time also can make sure that this process happens in a guiding geometry well that would be even better and would even give larger flexibility on tuning and optimizing this process but I mean what I’m
Explaining you is what a multipass cell can do if we take into account dispersion engineering and not only dispersion but also amplitude engineering Concepts that can that we can apply for example by um by a clever miral design or other means inserting um filters or similar systems into the multi
Cell yeah so this is a short intro here why why I believe that this this this system is really powerful and can will lead to many more things than just self-face modulation based processes in the future um and it can really provide a means to overcome efficiency limits
Band limits faal beam quality limits and many other limitations in nonlinear for nonlinear Optical processes let me move on and jump right into a few examples on laser piles post compression I’m starting with an example um for laser lasers developed here for the free electron laser facility in hurg
Flesh lasers where that are being used as pump rope lasers we speak about free electron lasers I have to introduce here that many experiments at certain systems are being carried out in a pump rope fashion when Optical laser PSE is being used in connection with an with a free electron
Laser PSE and x-ray pulse for example and then a controlled delay leads to a pump prob scheme such lasers then in particular if you consider a large variety of different experiments that might be targeted at such facilities and such Optical laser pses need to be yeah or laser systems need to be high
Efficient highly reliable easy transportable across large experimental halls and they need to allow great parameter flexibility we have been here at D installing a couple of such systems now based on a exactly a multi parel concept where we start with a PC laser then apply nonlinear spectral broadening
In multi passels and um after transporting the beam to a user end station where experiments are carried out optional weight length control schemes can be applied and then the system the pulses are delivered to a user end station let me show you one example here a very particular example
We are not don’t we have not used a standard multipass cell but a very particular one namely cell multipass cell that is essentially a hybrid solution between a hybrid between a multiplate and a multi multipath um spectral broadening scheme here we used more than one p um duration input pulses
That we send into to this multipass cell spectrally broaden them and by passing multiple class plates placed inside one multipass cell and then reaching larger and larger spectral broadening factors as we increase the energy the multiple plates here are being used for increasing the maximum B inter that we
Can achieve per pass through the system which is limited to small values if we have a single blate in the system only and we have been reaching here particular work by m colleagues um Marco Sidle and my former colleague an aniseti um they have been reaching here yeah
Very short pulse durations by employing actually a double scheme double multi parel approach cascaded multi parel approach and where they went all the way from 1.2 P seconds down into a sub 10 10to seconds a very similar system then the one I’m showing you here and with similar results but containing only a
Single stage has been installed as a permanent laser and one of the three electron laser beam lens here at flesh in hurg and this is an example of a system where you see that such multipass cells are not only good for proof of principal demonstrations but for actual um
Everyday operation as the system has been operated almost three years already in a more or less 247 operation mode and it’s not now being used as permanent um facility laser here in Hamburg let me move on and switch topic from electron laser pump rope placers where we use this multiplus cell scheme for
Post compression to another very attractive topic also an important topic here at Daisy in Hamburg namely laser plasma acceleration a plasma acceleration without really going into any details here is a process where essentially a plasma weight is being used for accelerating alrons over very short distances to very high energies
Reaching easily into the mega electron vol even Giga electron VA energy range and was the main with the main feature that very compact accelerators can be built the challenge and Big Challenge in this in the field has been since long time that very intense lasers are required here which typically run only
At limited repetition rates and this has been a bottleneck for really building application relevant laser plasma accelerators there have been a few reports on using F cycle pses for such laser plasma acceleration experiments and now with the new technology that we have available for extreme post compression we are actually reaching a
Regime but we can think of using atum systems so really high average power lasers convert them to very short pass durations and use these systems for laser plasma acceleration this is one of the topics we’re also addressing here at the DC and I want to briefly cover here
In my talk a few years back in 2020 they already showed that it is possible as to um compress in two cascaded gas fil multipass cells laser Pulses from the P of second regime down to the fuse cycle regime um at that point this was a principal demonstration that had reached
Only low efficiencies and sub mle levels very far from the terawatts we need the terawatt range that we need for laser plasma acceleration meanwhile a few other groups have nicely catched up here on this technology and in particular the group of um against liper in in y and O
Pin here also in Hur they have reached very nice demonstrated very nice systems in again using um for each system two cascaded multipass cells in one system here reaching compression factors 29 at almost one mle at the output but reaching the F cycle regime and the second example down here compression
Dror 33 at the micr level pulses but also reaching very short pass duration so very promising examples that show the powerful this power show that illustrate this powerful technology um we have now aimed at boosting this compression Factor further and at the same time pushing the energy
In order to reach um close to the terawatt regime which is required for laser plasma acceleration and this is what I’m going to show you in the next slide where we basically aim at more than 100 compression Factor while operating at multi mle levels you see a
View here onto the system that we have currently under operation in our laboratory and you will now see a few some data on what we have recorded so far before a quick reminder what are we utilizing here we utilize two cascaded multipass cells one filled with argon
One filled with neon and both actually completely assembled um using as key ingredient dialectric mirrors that provide very high efficiency for the entire post compression process yeah I’m also showing the key people involved in this experiment and then a view into the second multipass cell this is actually a
Real photograph of an operating of an operating F cycle multipass cell illustrating that we’re generating many colors in this cell so sending in invis a invisible um one micron laser we convert this laser into a colorful broad spectrum the key results that we have reached here without going too much into details
Essentially show compression from PC from a p second about down to the fuse cycle regime and to really see what is happening we we have to play a trick we have to zoom in into our plot here both in on the intensity scale and also on
The time scale and to make actually all the pulses visible so in in in red here you see the ingoing laser pulse which is yeah fairly not really visible on this blot but you you have seen now when scaled in how this PSE looks like initially and then the PSE after the
First compression cell is in blue and the blue area and then in the blue line is the few cycle PSE coming out after the second multi passel following and compression via dispersive mirrors we reaching 6 mle at sub 10 F seconds with the system and we have actually a peak
Power regime at reaching 0.3 about 0.3 tatt which is a regime which already support should support um mega electron volt laser plasma acceleration I’m also showing you on a second plot here very similar data but now recorded not using a frog frequency resoled Optical gating
As used for the first plot but using a third order autocorrelator to investigate the temporal PSE contrast of such a post compressed piles you see here in blue the piles coming out of the laser truly speaking not a very high contrast but this laser system has actually never been optimized for
Extremely high contrast um temperal contrast and then you see and the output of the second of the first multipass cell and the output beyond the second multi pass cell and we clearly see that Temple contrast if we normalize it to essentially we normalize this data here to the
Peak of the main laser pulse the the temple contrast is increasing over a large range which is expected as the peak power is increasing at each compression stage but this is yeah and clearly clearly I’m showing here large scales on the PC range this data is not resolving
The weak pre and post passes which you see in the linear scale here which of are of course present from when we post compress pulses let me move on um yeah maybe quick summary here we have here demonstrated really mle multi Mill class the turum laser pulse compression very
More than a factor of 100 reaching in reaching yeah approaching the the terab power regime um and at the same time demonstrated temporal PSE contrast Improvement a few words here on energy scaling very interesting topic is for further boosting this up in Peak power energy scaling and here we Face the
Limitation that multi are typically Limited in length and Laboratory as well and um we can show it has been shown for example in the paper displayed down here that the system length if we scale standard multipar cell system in length supports linearly with increasing length more and more PSE energy limited
Essentially by um by effects like laser induced Dage schold of the miral as the main effect and maybe um ionization as a secondary effect and this is a very linear scaling actually sorry this is this is the other paper this is a paper which describes um already a few years
Back from um my postdoc time which describes um linear scaling in gas Cas nonlinear Optics and this can be very well applied for this theme Here the question is now how can we go beyond this linear scaling regime um you end up with very large systems this is a big
Problem here as for example with this system here is shown from and Trump s scientific where more than 10 met long MPC was used to compress um more than one actually 200 mle laser pulses this is a very very impressive number but the system is really large and therefore not
Very practical so alternative scaling approaches are really needed there have been a couple of papers discussing them and I don’t have the time here to go through all of the approaches that have been proposed so far I want to quickly um summarize one approach which is an
Approach which we have been looking into this is an approach which considers Market cells which are not just made out of two um mirrors but which are using more mirrors we considering here for example a So-Cal B TI geometry and B geometry is essentially geometry that we
Use at least four mirrors and in this four mirror configuration we can consider that the beam path from focusing mirror one to focusing mirror two is not the same and as the returning beam path from Mirror to to mirror one as typically the case for standard multipass cells if we have these two
Nonidentical path um that exist in multi such a multipath cell we can plot a stability diagram for a for a multi cell and we see actually large regimes um appearing in in this stability diagram so you see on the diagonal line and this is basically the normalized length on
Length one and length two and you see on the DI on the diagonal line where L1 is equal to L2 the standard multipel configurations and the stability range um reaching here from zero to the maximum length of a standard multiple cell configuration but we can now go outside the standard regime and really
Explore different regimes for um for for multipel post compression and interestingly there are regimes which support much higher energies on the same footprint in particular if we employ um folding geometry and geometries and we can use that if we make sure that the laser beams are not just just tightly focused between the
Mirrors but if utilize sections in the multipass cell which are close to quim um yeah illustration here again of the corresponding lens arase of two these two regimes without going um more into details here I want to briefly mention that we are yeah working on this topic
Obviously we have been publishing an a theoretical proposal paper here and we also have done experimental tests by now I’m showing you here some preliminary data actually not not the best data as I just learned from the student arber was working on that topic there’s already
Better data available but you get to see the preliminary data and which will be hopefully published very soon of a very compact multi parel of only um 40 cmet length supporting 8 MJ which is quite a reent quite nice achievement and in particular it is a very nice achievement
Because we use here multi mirror geometry which um which EX um scaling energy scaling options which go beyond the standard linear scaling of length versus energy and therefore really put nice hopes up here for high energy multi pulse post compression systems in the future okay since time is really um
Moving moving fast I need to advance here to the second topic namely leaving um post compression and moving over to multipar Cel based nonlinear Optics I’m going back to my initial scheme illustrating um the the Bey that we have if we use the multi pastel and combine it with dispersion engineering and one
Very nice work that has been appeared just very recently by published by the group of oine and actually uses such a multi pastel um for not not self modulation but for second time one generation and very interestingly using clever dispersion engineering tricks you can the bring group here has shown that
It is possible to efficiently convert a laser beam into its second harmonic um in a geometry where actually a single pass R crystal is not even necessarily face match so you can use quy face matching tricks to boost the efficiency of our M generation process here this
Was done in the Pro of principle scheme for very long laser pulses and where the efficiency actual efficiency record reached um was uh yeah I think you see the data here around around 60 to 70% but the which is maybe not not not surpassing if
I’m not wrong here um the the the the typical values one can even reach for narrow band with lasers in a single pa geometry but this is not the main point of the paper the main point of the paper really is you can use clever and dispersion engineering and boost non-f
Match geometries thereby having a quy face matching geometry for essentially a free space or quasy guided Optical Arrangement this really Pro puts up hope for many more frequency conversion schemes that can be exploited via interesting dispersion engineering let me conclude this topic here by mentioning that we also working on on
Exactly this topic and we are at the moment really um carrying out research on dispersion tuning in very broad band withd second harmonic generation multi you see some very preliminary data which I don’t want to comment any further but I can tell you already we have um very
Promising results here that show that dispersion engineering really can um play a big role for second time morning generation processes and respectively other processes as well that’s by the way one paper also published by us and co-workers and by the group of Franchesca cigari on this persing in
Multi passes not for second time morning generation but for um post compression okay now another topic um Beyond simply post compression that I want to discuss here briefly which is going from second monic generation over to back to cell phace modulation but not selfless modation for spectral broadening but for something
Else if we look at spectral broadening process we typically get a symmetric spectrum because the laser pulse that we use for spectral broadening is symmetric and time therefore mapping out a symmetric um spectrally broadened um frequency if we use laser pares which are not symmetric in time and this could
Be in extreme cases a triangular or yeah Sawtooth shaped laser pulse then we should also get a very asymmetric Spectra broadening process this is the case um and we have shown that this is possible a very important ingredient here is again dispersion engineering especially if we use shape l P we have
To make sure and want to use a dedicated shape to control a process in a certain way we need to make sure that the laser PSE keeps its temporal shape throughout the generation throughout the passes many passes through the multi passel and this can be done at least to some extent
If we use a dispersion balance multi passel this is what we have been setting up and using a homebuilt erbium laser system and which a CPA laser system and shown here on the top row which we then have complemented with a pulse shaper that we use for shaping
This this triangular or this s shaped laser pulse and then we have also complemented system by um multi passel after the CPA um units then a spectral filter and the compressor behind if we do this we can actually start to tune the output spectrum of such a laser system this is Illustrated
Here so essentially we use a shaper send the laser P into a multi pass system and then after applying a filter we can get a spectral filter we can get a laser PSE out which is centered at a different Central frequency you see the measured experimental data here was the input
Spectrum showing in red and the green output Spectrum um before and after filtering as well as the corresponding measured the temple pulse structures we can by flipping the face and we can shift the Spectrum or shift the tuning from one side from one spectral direction to the other spectral
Direction and really play with the output spectral Center cental Central wavelength and this is really a feature which allows to build Ultra fast laser systems which are not just emitting laser emitting pulses at the central frequency the central wavelengths of the supported by the gain medium but really
Um we can effectively get PES generated outside the gain medium of the band of the gain medium um yeah maybe a few more words on this before I’m already coming to the end of my talk we have been inspired by earlier works by again the group of y libert y
Who have looked at the similar process but actually used the standard spectral broadening system then applied spectral filtering and looked at the temple contrast of basically one side Loop of this spectrum this broaden spectrum by doing so they have identified that such a such as output P after spectral
Filtering here and features extremely nice temporal contrast characteristics inspired by this work and knowing that PES that have undergone nonlinear processes and basically then um PES that exist only of frequency components which were generated in the nonlinear process such PES can really feature very nice temporal PSE contrast
We have looked exactly into this we have set up a s AO autoc cator for yeah in this case one about one micr two laser pulses and we have shown as you can see in this plot here that yeah we reach we you compare the the the ingoing the the
Laser parts emitted by the laser in red and the temple contrast of that one and then in blue the temple contrast of the specularly shifted laser pulse in this case you see a large contrast Improvement Although our measurement is actually limited by the dynamic range of the autocorrelator so lightly likely the
Range is even much larger than what we can display here yeah so we can really use such a such a feature here not only for such a method not only for spectral shifting but also for temporal contrast enhancement and really see great potential here for high high field science experiments in particular very
Very high intensities are you used um and where the temple Quast is a very important quantity such as for example for laser plasma acceleration with this this parameter is a very important one and yeah maybe last topic also on this on this experiment here we have not only explored the temple contrast but
Also looked at the coherence properties of such an as asymmetrically shifted laser pulse and by that without really going into details you are yeah welcome to have a look in into our paper um published in Native tonics early this year and um we have we have basically used
The our laser system which is a frequency comp laser system locked this system to a stable CW laser as a reference source and then looked at the coherence by beating the CW laser with the frequency shifted output and also beating the CW laser in comparison um with the with the nonline nearly
Amplified um with Noni portion of the oscillator of the system and by doing such a such a such a an experiment we have actually characterized the phas noise of both um of both the the oscillator effectively and the the the the output after frequency shifting and the comparison shows that there is no
There is only very little um additional phas noise generated in the shifting process such that we can make the claim here that this shifting process is um at least sufficiently coherent to support Herz level coherence measurements yeah this is the the schematic here also add here one picture of the real experiment
Showing that there’s actually heavy heavy and complex Electronics involved into setting up such an experiment which was um mostly carried out by sa Salon my PhD for my PhD student who’s now gradated okay this already brings me to my almost last slide of my talk here with a short summary I have introduced
You opportunities with nonlinear quasy guiding systems or in other words with multiusers speaking mostly about post compression and then also speaking about General nonlinear Optics approaches that we can drive using multipass cell or nonlinear quasi guiding geometries as a short outlook here yeah our works go in multiple directions but including and
Pushing towards higher Peak Powers towards reaching into the terat um Peak power regime and pushing further towards even shorter pulse duration at the same time scaling up the pulse energy a very important scenario for high energy lasers where multi pass cells could prospectively in the future also play an
Important role and then last but not least and very important topic in my opinion explore other nonlinear processes which can heavily benefit from the properties that multipass cells provide I’m showing you here on the right side a little simple illustration here of what how I see the the field of
Multi Parcels at the moment but we have exploited and exploited quite a bit already um namely post compression some wavelengths tuning um a few more topics like second tonic generation which should be above the water level which is just below the water level I have to
Update this blot as well and um but there’s many more processes such as for mixing has been a bit explored already but not much and parametric processes Terra Generation Um beam pulse cleaning approaches whatsoever there can be many more things that we can utilize we can um for using this quas guided nonlinear
Optics approaches and of course all um being useful for various applications in nonlinear Optics which I don’t in in for applications of ultra fast placers which I don’t have to so don’t go into detail here in this talk um yeah again a quick reference here to our um review paper or
Perspective paper also in terms of Outlook we are lining out forther directions in this paper that brings me to my last slide and um I think I’m just in time now almost and um yeah I would like read to thank everyone who has been um involved in the works presented I
Showed you already uh the people involved in in my first slide and um and of course the funding agencies let me conclude here by naming that we doing other things than multipass as well and I’m pointing you towards the very recent publication we explore um what we what we call gas
Phase nonlinear Optics or um g face sonop photonics a new topic where we try to um to control laser passes laser beams contact free directly in gases a very exciting topic which opens many new directions and last but not least position openings in my group we have several positions opened by a new
Project which is going to be started um early next year the Mega E project a project where we aim at a very high powerful Laser Source which then drives an an E Source for Imaging applications and we here searching for posts and PhD students um with various topics covering
Multipass cell development um metric amplification High harmonic generation and a few more there’s also a second project where we are searching for a post talk or PhD student and that is involving Optical fibers to work with mle class laser pares with that let me thank you for your attention