Researchers are using structured light on a chip in another photonics breakthrough

May 17, 2023

(Nanowerk News) In everyday life we ​​experience light in one of its simplest forms – rays or optical rays. However, light can exist in much more exotic forms. Thus, even blocks can be formed into a spiral; the so-called vortex beam, endowed with unusual properties. Such rays can make dust particles spin, just as they actually move along an intangible spiral.

This mode of light with additional structure is called “structured”, and even more exotic forms of structured light can be achieved in artificial optical materials – metamaterials, in which several light waves combine and combine to create the most complex forms of light.

In their two most recent works, published back-to-back in journals Science Advances (“Photonic Dirac cavity with spatially varying mass terms”), And Natural Nanotechnology (“Optical mode-dependent properties guided by adiabatic trapping potentials in photonic Dirac metasurfaces”), City College of New York researchers from Alexander Khanikaev’s group have created structured light on a silicon chip, and are using this additional structure to gain new, unprecedented function and control. Channels for guiding structured light – a silicon photonic chip prototype with information encoded in an optical mode spinning structure. (Image: Dr. Svetlana Kiriushechkina)

For this purpose, two-dimensional optical metamaterials, which are referred to as metasurfaces, and house special types of structured light rotating like vortex beams have been created. Through experiments conducted in Khanikaev’s laboratory at The City College, the researchers demonstrated a new type of trap to constrain structured optical modes and direct them on the chip.

In them Science Advances working, the researchers demonstrated that, by slowly changing the pattern of the metasurface in two directions, one can create an optical resonator that traps structured light and emits it. Interestingly, this underlying structure gives rise to an unusual pattern of emitted light – an optical vortex beam.

Applies a similar slow change to the pattern in one direction, as reported in Natural Nanotechnology work, the researchers have created a waveguide for structured light. This channel allows guiding the optical signal while maintaining the internal structure of light. Thus, it is similar to the flow of current in a cable, if we can have a cable with two types of charges.

Interestingly, such currents have become of immense interest in electronics recently, and a whole new class of electronic devices, commonly called spintronic or valleytronic, has been envisioned. In such devices, it is not the flow of charge by itself that will transfer the signal, but the spins or troughs of electrons, which promise many advantages over conventional electronic devices.

Khanikaev’s work envisages a similar concept, but with light instead of electrons. However, in contrast to electronic systems, optics and photonics have one significant advantage – optical modes do not decoherence to the same extent as electrons, which can be vital for quantum technologies. The demonstration by Khanikaev’s group could be useful for quantum applications for several reasons. Thus, additional optical mode structures can be used to encode quantum information in the form of quantum bits. This information can then be transported on a chip or emitted into free space to communicate quantum information between remote systems.

Moving in this direction, Khanikaev’s group is currently working to implement these ideas with structured light quantum states and realize quantum logic in their photonic nanostructures.

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