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Spotlight on Optics

Spotlight on Optics


  • December 2013

Optics InfoBase > Spotlight on Optics > Lasing and waveguiding in smectic A liquid crystal optical fibers

Lasing and waveguiding in smectic A liquid crystal optical fibers

Published in Optics Express, Vol. 21 Issue 25, pp.30233-30242 (2013)
by Karthik Peddireddy, V. S. R. Jampani, Shashi Thutupalli, Stephan Herminghaus, Christian Bahr, and Igor Muševič

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Spotlight summary: As a materials scientist who plies his trade to optical fibers, I never cease to be inspired by the breadth of materials-related opportunities for enabling next generation photonics. The recent work by Peddireddy et al., which stems from a collaboration between Max Planck Institute for Dynamics and Self Organization (Goettingen, Germany), the Stefan Institute (Ljubljiana, Slovenia), and the Faculty of Mathematics and Physics (Ljubljiana, Slovenia), is an excellent case in point.

Entitled "Lasing and waveguiding in smectic A liquid crystal optical fibers", the work employs a self-assembly process inherent to liquid crystals. As a brief primer, thermotropic liquid crystals are anisotropic organic molecules that spontaneously align depending on temperature. Nematic liquid crystals arise when rod-like organic molecules align ('nematic' derives from the Greek for 'thread'). Previous work by others have shown that the (typically) spherical shapes of nematic phases when formed in immiscible fluids can enable a variety of microphotonic devices including resonators, lasers, and whispering gallery mode structures. In this work, smectic-A liquid crystals are employed because their microstructure in this case is of coaxial organization such that precisely sized fibers result. Additionally, the resultant fibers should possess a topological line defect aligned with the fiber’s longitudinal axis which should reduce the likelihood of scattering.

The resultant smectic-A liquid crystalline fibers exhibited strong waveguiding and significant birefringence that enabled low threshold (75 μJ/cm2) whispering gallery mode lasing. Perhaps more interesting than the performance of these proof-of-concept fibers are the possibilities for such soft-matter photonics. Conventional optical electronics are built from hard-matter such as silicon or silica which permit very little post-process tailorability. Organics, in contrast, can be further modified – whether permanently or transiently - thermally, chemically, electronically, or optically. And the guidance of light via the topological line defects might permit an added degree of control over the polarization and phase properties of the propagating light

Further, for those readers who are academics, it is also worth noting that the images of total internal reflection [Figures 3a and 3b] are text-book examples and show that the phenomena can be imaged at smaller dimensions than conventionally depicted.

With any novel work, continued progress is required. In the present work, optical losses could be further improved as could the controlled growth of longer prototypes. That said, a flag in the ground has been staked and the possibilities for such soft matter (or topological) photonic devices is, forgive the pun, bright.

--John Ballato

Technical Division: Optoelectronics
ToC Category: Fiber Optics and Optical Communications
OCIS Codes: (230.3720) Optical devices : Liquid-crystal devices
(230.7400) Optical devices : Waveguides, slab
(140.3948) Lasers and laser optics : Microcavity devices
(230.4555) Optical devices : Coupled resonators
(130.5460) Integrated optics : Polymer waveguides

Posted on December 16, 2013

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