![]() Lasers of this and even higher power classes are used, for example, for material processing, in fusion research, or for the latest particle accelerators. In their experiments, the researchers used an infrared laser pulse with a peak power of 20 gigawatts, which corresponds to the power of around two billion LED bulbs. The team sees great potential in the technique for high-performance optics. "Fortunately, we are in the ultrasound range, which our ears don't pick up." "We are moving at a sound level of about 140 decibels, which corresponds to a jet engine a few meters away," explains scientist Christoph Heyl from DESY and the Helmholtz Institute Jena, who is leading the research project. Credit: Science Communication Lab for DESYįor the first test, the scientists had to turn their special loudspeakers way up. The laser beam interacts with this grating and is deflected without contact. In this animation, a laser light beam passes between a loudspeaker-reflector array that creates a grating of air. Significantly higher efficiencies should be possible in the future, according to numerical models. In the first laboratory tests, a strong infrared laser pulse could be redirected in this way with an efficiency of 50 percent. "The properties of the optical grating are influenced by the frequency and intensity-in other words, the volume-of the sound waves." ![]() "However, deflecting light by diffraction grating allows much more precise control of the laser light compared to deflection in the Earth's atmosphere," says Schrödel. In a way that is similar to how differential air densities bend the light in the Earth's atmosphere, the density pattern takes on the role of an optical grating that changes the direction of the laser light beam. With the help of special loudspeakers, the researchers shape a pattern of dense and less dense areas in the air, forming a striped grating. student at DESY and Helmholtz Institute Jena. "We've generated an optical grating with the help of acoustic density waves," explains first author Yannick Schrödel, a Ph.D. This depends on the spacing of the grating and the wavelength of the incident light.The innovative technique uses sound waves in order to modulate the air in the region where the laser beam is passing. ![]() I 0 is the maximum intensity λ is the wavelength of the light and a is the slit width.ĭiffraction grating is an optical component having a periodic structure which can split and diffract light t several beams travelling in different directions. Where is the total phase angle, it can be related to the deviation angle, Is the angle at which destructive interference occurs. Intensity minima will occur if this path length difference is an integer number of wavelengths. At this angle all the light from the top half of the slit will get cancelled with the light from the bottom half to produce a dark band. This causes destructive interference to occur because the path difference between the top and the middle of the slit is half of the wavelength. Let at an angle θ, the path difference between the top and bottom of the slit is a wavelength. The dark bands are caused when the light from the top half of the slit destructively interferes with the light from the bottom half.Ĭonsider a slit of width ‘a’. The pattern formed on a screen consists of a broad central band of light with dark bands on either side. The secondary wavelets spread out and overlap each other interfering with each other to form a pattern of maximum and minimum intensity. Diffraction is due to the superposition of such secondary wavelets. ![]() Huygens considered each point along a wave front to be the source of a secondary disturbance that forms a semi-circular wavelet. When waves pass through a gap, which is about as wide as the wavelength they spread out into the region beyond the gap. This phenomenon is termed as diffraction. When a wave train strikes an obstacle, the light ray will bend at the corners and edges of it, which causes the spreading of light waves into the geometrical shadow of the obstacle. Spectrometer, diffraction grating element and mercury vapor lamp. To calculate the wavelength of the other prominent lines of mercury by normal incidence method. To determine the number of lines per millimeter of the grating using the green line of the mercury spectrum.Ģ.
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