Torsional Mechanical Oscillator Driven by the Orbital Angular Momentum of Sound

Abstract

We demonstrate that the orbital angular momentum of radiating waves can be used to drive a mechanical oscillator, an option that has remained elusive to date on experimental grounds whatever the nature of the waves. This is done using an amplitude-modulated ultrasonic wave interacting with a centimeter-size torsional pendulum. Achieved resonant quantitative measurements of the acoustic radiation torque and material properties set the basis for orbital-angular-momentum-based metrology applications and possibly cooling of the rotational degree of freedom of macroscopic objects.

Underwater acoustic multiplexing communication by pentamode metasurface

“…Due to the similarity between optics and acoustics, OAM in acoustics has been investigated extensively in recent decades. Many efforts on acoustic vortex waves have been reported, including OAM beam formed by active arrays [16] and metamaterials [17][18][19][20][21], OAM beams used for object manipulation [22][23][24][25][26][27], acoustic analogy of the supper radiance of Kerr black holes [28,29] etc. Additionally, acoustic OAM used for communication is also one of the most attractive topics.…”

Acoustic Torsional Mechanical Oscillator Driven by Wave‐Matter Orbital Angular Momentum Transfer with Quality Factor >1000

“…The adjustment of the experimental data with Equation (1) using 𝛾 as the fitting parameter gives Q ≳ 2100, see solid black curve in Figure 3. Moreover, in order to appreciate the improvement with respect to previous work where a 3D printed pendulum was used [13] (L = 30 mm and d = 2.5 mm) a typical data from previous studies using a resin pendulum with l = 4 is added to Figure 3 (blue curve), which gives Q ≈ 10. We thus conclude to an improvement of the quality factor by a factor up to >200.…”

Torsion pendulum driven by the angular momentum of light: Beth’s legacy continues

“…The demonstration of a resonant torsional mechanical oscillator driven by acoustic orbital angular momentum transfer was reported only recently. 58 This was also done in the air, however, via a nondissipative process, using an ultrasonic acoustic field carrying zero angular momentum that reflects off a helical mirror imparting nonzero orbital angular momentum to the reflected field, as illustrated in Fig. 6(b).…”

“…Sketches of torsion pendulum arrangements enabling mechanical detection of the transfer of orbital angular momentum from sound to matter by (a) dissipative and (b) nondissipative means. The inset of panel (b) shows the designed (bottom) and fabricated (top) 3D printed helically corrugated plates acting as a reflective acoustic vortex generator used for experimental demonstration 58 …”