Would you prefer to seize a chemical transformation inside a cell stay? Or perhaps revolutionize microchips’ manufacturing by printing paths in a layer that has a thickness of simply 100 nanometers? These and plenty of different targets can now be achieved with the latest femtosecond laser created by a workforce of scientists led by Dr. Yuriy Stepanenko.
Today, there’s a multitude of laser gentle sources. They every have their traits and totally different purposes, resembling observing stars, treating diseases, and floor micro-machining. “Our objective is to develop new ones,” says Yuriy Stepanenko, head of the workforce of Ultrafast Laser Methods on the Institute of Bodily Chemistry of the Polish Academy of Sciences. “We take care of sources that produce ultrashort pulses of sunshine. Actually very, very brief—femtosecond pulses (that’s part of a second with 15 zeros after the decimal level). That is the dimensions on which, for instance, intracellular chemical reactions happen. To see them, now we have to “take a photograph” on this very brief time. And due to the brand new laser, we will just do that.
“We will additionally use our supply for the very exact elimination of supplies from numerous surfaces with out destroying them,” says the scientist. “We may, for instance, clear the Mona Lisa utilizing this methodology with out damaging the layers of paint. We’d solely take away mud and dust, a layer about 10 nanometers thick,” explains Dr. Stepanenko, one of many authors of a examine just lately revealed within the Journal of Lightwave Expertise.
“However for this form of job, our laser is even reasonably too exact,” notes Dr. Bernard Piechal, co-author of the publication. “For this, you solely want nanosecond pulses, i.e. pulses lasting a thousand instances longer. The latter, nevertheless, wouldn’t have the ability to, for example, draw paths of exactly deliberate depths in ultra-thin supplies, e.g. eradicating gold sprayed on microchips with a exact adjustment of the thickness of the layer being eliminated. However our laser can do that! It could additionally make holes in tempered glass or ultra-thin silicon plates. In these circumstances, a nanosecond laser would both soften the silicon or ‘smash’ the glass as a result of it produces an excessive amount of warmth. An excessive amount of vitality is concentrated domestically in a really small space. Ours works firmly however gently,” grins Dr. Stepanenko.
How was this impact achieved?
“We wished our supply to fulfill two circumstances: it was to be vulnerable to mechanical disturbance to the least attainable extent, and it was to be cell,” explains Dr. Piechal. “We didn’t need to create an enormous, stationary construction.”
Fiber-optic lasers got here to the rescue of the workforce. “This form of laser is mainly an optical fiber enclosed in a hoop. The laser pulse runs inside it with out being uncovered to mechanical disturbances. The optical fiber will be touched, moved, even shaken with out compromising the steadiness of the heart beat. In fact, if the sunshine solely ran spherical in a circle like this, it might be ineffective, so a part of this impulse is directed exterior the loop in a single place within the type of helpful flashes,” explains Dr. Stepanenko.
Right here we come to a different essential parameter of this form of pulsed laser: the frequency with which the pulses seem on the output. In standard designs, this frequency depends upon the size of the fiber optic loop by which the heart beat travels. Its sensible size is a number of dozen meters. Which is rather a lot, isn’t it? What if we wished flashes of sunshine to seem as usually as attainable? This may be executed by decreasing the circumference of the ring by which the pulse travels. Solely that this form of motion has its limits. “In our lasers, the smallest loop provides pulses each 60 nanoseconds, which remains to be too gradual for our wishes,” explains the researcher. How can this frequency be accelerated? That is the place the brand new invention of the workforce from the IPC PAS is available in: a system that enables the essential frequency to be duplicated as if creating harmonic frequencies on the essential frequency of a guitar string.
“We use so-called Harmonic Mode Locking,” explains Dr. Stepanenko. “What’s progressive in our design is that we’re in a position to change this repetition fee in a managed method and choose solely one of many attainable harmonics, the actual one we’d like. You possibly can say that we’re like a guitarist- on an open string, i.e. our loop of the fiber, we acquire a particular frequency ensuing from its size. Once we put our finger precisely in the midst of the string, we get the so-called second harmonic. The pitch will increase by an octave and the vibration frequency doubles. If we put our finger on 1/3 of the size of the string, we get a frequency equal to 3 instances greater than on the open string. In our case, we enhance the frequency of the pulses by turning the knob. We will solely do it in steps, every time getting one other harmonic, simply because the harmonics within the guitar change in steps, however the vary is kind of giant: we will change our gentle harmonics from 2 as much as 19 instances above the essential frequency, i.e. attain a frequency of pulses as much as simply over 300 MHz.
This can be very essential that the obtained frequencies are secure and will be exactly distinguished. If we select a harmonic, all of the others will likely be so damped that their “quantity” will likely be about 10 million instances decrease than that of the chosen one. You possibly can say that we’re producing a pure sound and eliminating all of the background noise. As well as, the upper the frequency, the higher it’s outlined. “We’re the primary to have managed to do that so effectively,” says the researcher proudly.
It’s left to us to attend for the invention to be carried out in additional industrial purposes. Maybe it’ll imply even thinner and lighter laptops for us or higher data of what’s taking place contained in the human physique.
Supply:Extra data: Bernard Piechal et al, Mamyshev Oscillator With a Broadly Tunable Repetition Charge, Journal of Lightwave Expertise (2020). DOI: 10.1109/JLT.2020.3031540
Scientists unveil latest femtosecond laser
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