The fixed frequency and phase relation between the comb teeth allows the application of techniques known from optical combs. Experimental demonstrations have shown mechanical frequency combs exist in different mechanical systems 10, 15, 16, 17, 18, 19, 20, 21, 22, 23, and have explored connections to well-known concepts in nonlinear dynamics such as bifurcations 15, 18, 24, 3- or 4-wave mixing 14, 17, 25, 26, and symmetry-breaking 27. The ideas behind this field began in nonlinear dynamics, where it was realized that mixing in coupled oscillators may lead to a series of sidebands 14, which can be regarded as a frequency comb if there exists a fixed phase relation 12 between these sidebands. But in the last few years, a new paradigm of frequency combs has appeared, which are completely mechanical in nature: phononic frequency combs 11, 12, 13, also called acoustic or mechanical frequency combs. Recent developments in optomechanics have expanded methods to create optical frequency combs by interactions with mechanical resonators 6, 7, 8, 9, 10. The fixed frequency and phase relations between the many different tones of a comb have revolutionized fields such as astronomy 3 or cosmology 4, and allowed tests of fundamental physics with atomic clocks 4, 5. Over the last quarter century, optical frequency combs have become key tools for metrology, timing and spectroscopy 1, 2, and are indispensable in many laboratories around the world. This highlights the overtone frequency comb as the straightforward future for applications in sensing, metrology and quantum acoustics. This combination of effects results in an easy-to-use mechanical frequency comb platform that requires no precise alignment, no additional feedback or control electronics, and only uses a single, mW continuous wave laser beam. The periodic optical field also creates an optothermal parametric drive that requires no additional power or external frequency reference. These overtones share a fixed frequency and phase relation, and constitute a mechanical frequency comb. The periodic optical field modulates the dielectrophoretic force on the membrane at the overtones of a membrane’s motion. We demonstrate a straightforward mechanism to create a frequency comb consisting of mechanical overtones (integer multiples) of a single eigenfrequency, by monolithically integrating a suspended dielectric membrane with a counter-propagating optical trap. So far, their main challenge has been strict requirements on drive frequencies and power, which complicate operation. You now know how to create a 2D waving flag in After Effects, and it’s as simple as animating rectangle merging paths with your flag layer.Mechanical frequency combs are poised to bring the applications and utility of optical frequency combs into the mechanical domain. In the viewer, move the position of the Flag up slightly from the original flag to create the offset part of the flag.Twirl open the duplicated layer, change the Merge Paths Mode from Subtract to Intersect.Type Command + D to duplicate the layer. An offset makes that part of the flag appear closer to the viewer, making the 2D flag look three dimensional! In this step, you’ll duplicate the flag layer, change the mode so that the flag within the rectangle shows on screen, and bump up the height in the viewer to create an offset. Now that’s what you call magic! Step 5: Offsetting the Wave
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