Direct laser interference patterning

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Video in TIB AV-Portal: Direct laser interference patterning

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Direct laser interference patterning
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This video shows how a pulsed nanosecond laser beam can be used for the modification of a surface with structures on the micron scale in a single shot on an area of mm2. As a start interference is explained with examples of water waves and light. For the light a laser beam is split into two beams which are recombined on the surface to be patterned. The structures are detected by diffraction from the formed surface pattern. Atomic force microscopy is used to image the surface. This technique can be used for the structuring of single molecule layers, catalysts, surfaces of metals, semiconductors and polymers.
Keywords photo
Dietary supplement Surface science Zunderbeständigkeit
Thin film Soap
Surface science Korngrenze Soap Reflexionsspektrum
Water Drainage basin
Spring (hydrology) Drainage basin
Chemical experiment Wasserwelle <Haarbehandlung>
Screening (medicine) Wasserwelle <Haarbehandlung>
Chemical experiment
Water Homocysteine
Set (abstract data type)
Sample (material) Chemical experiment Flüssiger Stickstoff Screening (medicine) Mineral
Sample (material) Paste (rheology) Water quality
Surface science Chemical experiment Crystallographic defect Regulatorgen Periodate Electronic cigarette
Area Surface science Chemical experiment Glasses Addition reaction Reflexionsspektrum
Process (computing) Crystallographic defect
Sample (material) Surface science Chemical experiment
Area Sample (material) Karst Periodate
Anomalie <Medizin> Area Metal Surface science Nomifensine Reaction mechanism Materials science Transport Gemstone Polymer Periodate Process (computing)
it is we knew we would like to introduce use the technique of hearts laser the theories which allows us to bet on the surface with flights us on the might of scale with a single a cell phones can see the set up here but before we go into the details of the set up we would like to do some special features. of interference.
for the demonstration of interference we need first intensive white light source which we switch on all white line into fear is a phenomenon that can be identified by collop appearance of thin films a well known example of white light interference is to college appearance of soap bubbles.
it's as you can see here we get home phone calls from the surface of these bubbles the reason for this column appearance is to reflection on both sides of the bubbles and these two reflected beams interfere with each other in the for rice to enhanced.
reflection of certain colleagues are reduced reflection of certain costs in the first experiments but the soap bubbles we observe to interference have to waste which were reflected from the two interfaces of to soap bubble and which were traveling in the same direction but now we would like to switch to an.
and where the teams are traveling across an angle and we would like to see to interference which happens then but before we would like to see how we do this experiment we do this experiment in a water basin where really excite the travelling waif by dipping a metal sheet into the water.
and it's who can see by the spring audi dipping week side a periodic way for traveling all along the water basin.
after we changed from the linear rich to the v. shaped rich we can see that very close to the rich still leo waves are excited but now we have a into action regime in the in the actual regime we can see interference and this interference.
is shown in maxime us which are fixed in position at certain directions.
we would like to repeat the experiment that we have done with water waves before now with an optical with and therefore we use a laser and split these laser into two beams by the help of a beam splitter one of the been struggling to was dismissed or in this reflected back the other was traveling to the other and it's also.
reflected back to what our observation screen it's interesting to know how to have a look on the to individual beams as they are reflected saab look the first beam in we can see a circle a pattern of the laser beam they not block the other one and opened the first and you can see a very similar appearance of that to individual beans but if we.
open boast beam summer tenuously we can see a change of the pattern from homo genus around shape to a shape where we have individual lines in the center you to interference and this is interference which we also have seen in our water brave experiment before and which we now can use foreign next six.
government. now we are back on all possible as the experimental set off we have learned in the last experiment that we need to be means to form an interference pattern and now we're left to look in detail how we do that in this experiment to form such a laser petal father actual pet on the experiment view was a pulse laser of high intensity.
the which is a need to need a necklace or of ten on a second possible and the beam of five hundred thirty two nanometers what a screen light is coming in from decide in this going to us this been split and then to be missed divided in have been passing through and have been reflected in these two beams are going to these minerals. and then tomorrow's reflect the beam two votes the actual sample position in order to show the beam line we blow in some liquid nitrogen and now we can see.
the beams past thing here through the beam splitter and being split into two beams and they into beams are going along to works the sample. we have seen the actual set up now and we can calculate from the distance of america's and the distance to water sample that the beauty of which we would expect will be somewhere in the five microns range five michael is something which we can see anymore so the question is how would we.
recognised as such a pattern would be on the surface. for that purpose i would like to remind going to affect which is called the fractional due to know from every cd years will see wonderful collop light on on the cd you're to defect shun off the grating have to see the end you can see that if you reflect the laser beam from such a grating you. the debt more than one spot in your can see three teams are reflected from the surface you to deflection deflection itself it's also an interference if we form a grating of a small period we will find additional deflection and that's what we do now we erred in additional regulate.
for which to i switch on now and now you can see on the side of the experimenter reflection from this red laser from the surface and this red list of will hit exactly the same area on the surface that we will hit with the parts laser and if additional spots appeared there.
we are sure that we formed a grating on the surface. now everything is ready for the extra experiment but we have to use of course lays of security glass us because we will use now a high intensity of the laser beam in contrast to before where the intensity was very low.
the defection peden shows arse that we successfully made the creating but the details of the great team and its profile can only be started with the atomic force microscope.
we are in atomic force microscope lap and i asked martin to perform a measurement of the sample we made with delays interference this is done by atomic force microscope were a very fine tip is scanned across the surface and the actual position off the tip is smashed in be can display.
it is actual position and such the topography of to sample on our money toward we can see here now to talk a fee of to sample that we struck by a pulse laser interference first three observe a period of roughly five microns and we can see a low areas which are brownish and yellow high area us soil.
obviously material was transported from the brown area us towards the high yellow area us and we can explain this process by a lot to our transport of liquid from the area out where it's brown out to watch the area which is yellow not the technique of parslow as an interview in spending of surfaces.
this is a very flexible method it works on a variety of different materials like metal semiconductors and polymers. we can make very different periods on the surface from three hundred to five hundred microns stone to three to five hundred nanometers just by our relation of the angle between their merits of nevertheless to physical mechanism behind are not well understood and therefore we are currently performing timers. of measurements because we know that the movement of liquids are in both there and baby may play a major role but still we don't have a complete understanding of the ongoing process as.