RF Orbital Angular Momentum: January 2012

Sunday, January 8, 2012

Time-division multiplexing of the orbital angular momentum of light

Ebrahim Karimi, Lorenzo Marrucci, Corrado de Lisio, and Enrico Santamato

Optics Letters, Vol. 37, Issue 2, pp. 127-129 (2012)

http://dx.doi.org/10.1364/OL.37.000127Abstract

We present an optical setup for generating a sequence of light pulses in which the orbital angular momentum (OAM) degree of freedom is correlated with the temporal one. The setup is based on a single q plate within a ring optical resonator. By this approach, we demonstrate the generation of a train of pulses carrying increasing values of OAM, or, alternatively, of a controlled temporal sequence of pulses having prescribed OAM superposition states. Finally, we exhibit an “OAM-to-time conversion” apparatus that divides different input OAM states into different time bins. The latter application provides a simple approach to digital spiral spectroscopy of pulsed light.

http://www.opticsinfobase.org/ol/abstract.cfm?URI=ol-37-2-127

About this Blog

I believe that OAM may have some unique applications in RF signaling especially for new multi-spectral coding techniques, search for SETI and in the remote detection of bombs, land mines and IEDs.

By combining RF OAM with Nuclear Quadrapole Resonance (NQR) it may be possible to overcome many of the limitations of NQR at the moment for detecting explosives. NQR produces a very weak signal that happens to be in the RF bands of commercial broadcasting. So remote (or even close proximity detection) is a real challenge. The attraction of OAM is the possibility of detecting NQR response to OAM modulated signals at a distance through spatial filtering of the response signal to elminiate common RF interference. Also OAM appears to have no limit to "modulation" power i.e the OAM can be made powerful enough to even create physical resonance as for example the "optical spammer" noted in some of the OAM research. Other resonance stimulation may be possible such as rapidly changing the direction and polarity of the OAM. "Pumping" the NQR sensitive molecules into higher circular vibrational modes with OAM resonance can also be used to enable a secondary OAM RF signal to absorbed, emitted or cross modulated in the detection process. The use of such techniques might enable to detection of explosives at a distance and conceivably even be used to disable explosive devices. This includes atomic bombs which need to use a conventional explosive to ignite the fission core.

An excellent overview of OAM can be found at:
http://www.physics.irfu.se/Publications/Presentations/ThideEtBergman%3ACSC_SETI%3A2008.pdf

RF Orbital Angular Momentum

Sunday, January 8, 2012

Time-division multiplexing of the orbital angular momentum of light

Time-division multiplexing of the orbital angular momentum of light

http://dx.doi.org/10.1364/OL.37.000127Abstract

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