116. shaping and steering of surface laser beam carrying orbital angular momentum

Department: Electrical & Computer Engineering
Faculty Advisor(s): Boubacar Kante
Award(s): Honorable Mention

Primary Student
Name: Babak Bahari
Email: bbahari@ucsd.edu
Phone: 858-534-4939
Grad Year: 2019

Steering the beam of a wave source has been demonstrated using mechanical and non-mechanical techniques. While mechanical techniques are bulky and slow, non-mechanical techniques rely on breaking the symmetry of the refractive index profile either using asymmetric structure or injecting a non-uniform current to get appropriate phase profile. To date, most of the light sources only produce relatively simple light beams with spatially homogeneous polarization and planar wave-front. Generation of the complex orbital angular momentum beams usually relies on either bulk devices, such as spiral phase plates, spatial light modulators, and computer-generated holograms, or recently developed planar optical components, including phase modulation?based metasurfaces, q-plates, and silicon resonators. In this contribution, we theoretically and experimentally demonstrated a new type of topological steering of light sources in which the phase offset is provided by Floquet-Bloch phase in periodic structure. It was shown that in periodic structures, there exist singular states with polarization vortex in the radiation region of the band diagram that exhibit diverging quality factor. Thus light sources can operate at these states with lower threshold power. The existence of these singular states are topologically protected, and their momentum are very sensitive to any small perturbations, which is used to control the steering angle. By uniformly controlling some parameters in the system, such as a physical dimension or injecting current uniformly, the beam of the light source steers. Our experimental demonstrations open new paradigm in the implementation of light steering with applications in data communications, optical tweezers, bio imaging and sensing.

Industry Application Area(s)
Electronics/Photonics | Semiconductor

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