Abstract

We describe a means of communication in which a user with no external receiver hears an audible audio message directed only at him/her. A laser transmits the message, which is encoded upon a modulated laser beam and sent directly to the receiver’s ear via the photoacoustic effect. A 1.9 μm thulium laser matched to an atmospheric water vapor absorption line is chosen to maximize sound pressure while maintaining eye-safe power densities. We examine the photoacoustic transfer function describing this generation of audible sound and the important operational parameters, such as laser spot size, and their impact on a working system.

© 2019 Optical Society of America

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References

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  1. A. G. Bell and S. Tainter, “Photo phone-transmitter,” U.S. patent2,354,96A (December14, 1880).
  2. W. F. Rush, J. E. Huebler, and P. Lysenko, “Photoacoustic speaker and method,” US patent4,641,377 (February3, 1987).
  3. S. Gallagher, “Non-Lethal Weapon: DOD seeks to use lasers to create shouting will-o-the-wisp,” 2018, https://arstechnica.com/tech-policy/2018/03/non-lethal-weapon-dod-seeks-to-use-lasers-to-create-shouting-will-o-the-wisp/ .
  4. A. H. Frey, J. Appl. Physiol. 17, 689 (1962).
    [Crossref]
  5. J. C. Lin and Z. Wang, Health Phys. 92, 621 (2007).
    [Crossref]
  6. S. Egerev, Acoust. Phys. 49, 51 (2003).
    [Crossref]
  7. “Audio Spotlight by Holosonics—Focused Audio Technology,” https://www.holosonics.com/ .
  8. “LRAD Mass Notification & Life Safety Systems Archives,” LRAD, https://www.lradx.com/product_categories/lrad_mass_notification_systems/ .
  9. R. W. Haupt and K. D. Rolt, Lincoln Lab. J. 15, 3 (2005).
  10. C. M. Wynn, S. Palmacci, M. L. Clark, and R. R. Kunz, Appl. Phys. Lett. 101, 184103 (2012).
    [Crossref]
  11. R. M. Sullenberger, M. L. Clark, R. R. Kunz, A. C. Samuels, D. K. Emge, M. W. Ellzy, and C. M. Wynn, Opt. Express 22, A1810 (2014).
    [Crossref]
  12. Laser Institute of America, “American National Standard for Safe Use of Lasers,” (American National Standards Institute, 2007).
  13. A. C. Tam, Rev. Mod. Phys. 58, 381 (1986).
    [Crossref]

2014 (1)

2012 (1)

C. M. Wynn, S. Palmacci, M. L. Clark, and R. R. Kunz, Appl. Phys. Lett. 101, 184103 (2012).
[Crossref]

2007 (1)

J. C. Lin and Z. Wang, Health Phys. 92, 621 (2007).
[Crossref]

2005 (1)

R. W. Haupt and K. D. Rolt, Lincoln Lab. J. 15, 3 (2005).

2003 (1)

S. Egerev, Acoust. Phys. 49, 51 (2003).
[Crossref]

1986 (1)

A. C. Tam, Rev. Mod. Phys. 58, 381 (1986).
[Crossref]

1962 (1)

A. H. Frey, J. Appl. Physiol. 17, 689 (1962).
[Crossref]

Bell, A. G.

A. G. Bell and S. Tainter, “Photo phone-transmitter,” U.S. patent2,354,96A (December14, 1880).

Clark, M. L.

Egerev, S.

S. Egerev, Acoust. Phys. 49, 51 (2003).
[Crossref]

Ellzy, M. W.

Emge, D. K.

Frey, A. H.

A. H. Frey, J. Appl. Physiol. 17, 689 (1962).
[Crossref]

Haupt, R. W.

R. W. Haupt and K. D. Rolt, Lincoln Lab. J. 15, 3 (2005).

Huebler, J. E.

W. F. Rush, J. E. Huebler, and P. Lysenko, “Photoacoustic speaker and method,” US patent4,641,377 (February3, 1987).

Kunz, R. R.

Lin, J. C.

J. C. Lin and Z. Wang, Health Phys. 92, 621 (2007).
[Crossref]

Lysenko, P.

W. F. Rush, J. E. Huebler, and P. Lysenko, “Photoacoustic speaker and method,” US patent4,641,377 (February3, 1987).

Palmacci, S.

C. M. Wynn, S. Palmacci, M. L. Clark, and R. R. Kunz, Appl. Phys. Lett. 101, 184103 (2012).
[Crossref]

Rolt, K. D.

R. W. Haupt and K. D. Rolt, Lincoln Lab. J. 15, 3 (2005).

Rush, W. F.

W. F. Rush, J. E. Huebler, and P. Lysenko, “Photoacoustic speaker and method,” US patent4,641,377 (February3, 1987).

Samuels, A. C.

Sullenberger, R. M.

Tainter, S.

A. G. Bell and S. Tainter, “Photo phone-transmitter,” U.S. patent2,354,96A (December14, 1880).

Tam, A. C.

A. C. Tam, Rev. Mod. Phys. 58, 381 (1986).
[Crossref]

Wang, Z.

J. C. Lin and Z. Wang, Health Phys. 92, 621 (2007).
[Crossref]

Wynn, C. M.

Acoust. Phys. (1)

S. Egerev, Acoust. Phys. 49, 51 (2003).
[Crossref]

Appl. Phys. Lett. (1)

C. M. Wynn, S. Palmacci, M. L. Clark, and R. R. Kunz, Appl. Phys. Lett. 101, 184103 (2012).
[Crossref]

Health Phys. (1)

J. C. Lin and Z. Wang, Health Phys. 92, 621 (2007).
[Crossref]

J. Appl. Physiol. (1)

A. H. Frey, J. Appl. Physiol. 17, 689 (1962).
[Crossref]

Lincoln Lab. J. (1)

R. W. Haupt and K. D. Rolt, Lincoln Lab. J. 15, 3 (2005).

Opt. Express (1)

Rev. Mod. Phys. (1)

A. C. Tam, Rev. Mod. Phys. 58, 381 (1986).
[Crossref]

Other (6)

Laser Institute of America, “American National Standard for Safe Use of Lasers,” (American National Standards Institute, 2007).

“Audio Spotlight by Holosonics—Focused Audio Technology,” https://www.holosonics.com/ .

“LRAD Mass Notification & Life Safety Systems Archives,” LRAD, https://www.lradx.com/product_categories/lrad_mass_notification_systems/ .

A. G. Bell and S. Tainter, “Photo phone-transmitter,” U.S. patent2,354,96A (December14, 1880).

W. F. Rush, J. E. Huebler, and P. Lysenko, “Photoacoustic speaker and method,” US patent4,641,377 (February3, 1987).

S. Gallagher, “Non-Lethal Weapon: DOD seeks to use lasers to create shouting will-o-the-wisp,” 2018, https://arstechnica.com/tech-policy/2018/03/non-lethal-weapon-dod-seeks-to-use-lasers-to-create-shouting-will-o-the-wisp/ .

Cited By

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Figures (4)

Fig. 1.
Fig. 1. Delivery of audible messages via photoacoustics. (a) Traditional photoacoustic configuration: 1907.2 nm laser light is absorbed by ambient water vapor. The laser beam is amplitude modulated via an acousto-optic modulator. (b) Dynamic photoacoustic communication amplifies the audible signal. (c) H2O absorptivity near 1.9 μm, with an overlay of the laser emission from our thulium fiber laser.
Fig. 2.
Fig. 2. Results from our tests utilizing the traditional photoacoustic configuration. (a) Transfer functions describing the conversion of eye-safe optical energy at 50% RH into acoustic energy for various laser spot sizes. Markers represent measured data, and lines represent theory [solid = Eq. (2), dashed = Eq. (1)]. (b) Measured photoacoustic signal (in mPa) versus RH. The result shows that signal strength is linear with RH. (c) Demonstration of a photoacoustic communications waveform, 20 kHz to 1 kHz frequency sweep, sent (T) and received (R).
Fig. 3.
Fig. 3. Results from our tests utilizing the dynamic photoacoustic configuration (sweep length=50cm, range=2.5m). (a) Photoacoustic signal heat map, sweep velocity (in Mach #) versus time, for a 5 mm laser spot at target. Waveforms at M=1.05, M=1.00, and M=0.95 are shown to the right of the heat map. Positive and negative values represent compression and rarefaction, respectively. (b) Pressure versus laser spot size. (c) Compression timescale (duration of the leading compressive wave) of dynamic photoacoustic waveform versus spot size. The compression timescale is indicative of the forcing function on the water vapor molecules from the swept laser beam.
Fig. 4.
Fig. 4. Measured spatial extent of the acoustic signal (mVpp) produced via the dynamic photoacoustic configuration at a range of 2.5 m, sweep length of 25 cm, and total propagation distance from start of sweep to receiver of (a) 50 cm and (b) 25 cm. A horizontal position of 0 mm corresponds to Mach 1. Horizontal positions > 0 correspond to sweep speeds > Mach 1, and horizontal positions < 0 correspond to sweep speeds < Mach 1. (c) Simulation of the “separation distance” (Δh) measured at supersonic sweep speeds growing linearly with propagation distance, which agrees with our measured data. (d) Schematic of the spatial measurement.

Equations (2)

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P(r)=βIsafeD1/2Av222fLCPr1/2,
P(r)=βIsafeD2Av28fLCPr1/2(vTpulse)3/2.