A document discusses overcoming efficient optical coupling to high orbital momentum modes by slightly bending the taper dispersive element. This little shape distortion is not enough to scramble the modes, but it allows the use of regular, free-beam prism coupling, fiber coupling, or planar fiber on-chip coupling with, ultimately, 100 percent efficiency.
The Bessel-beam wave- guide is bent near the contact with the coupler, or a curved coupler is used. In this case, every Bessel-beam mode can be successfully coupled to a collimated Gaussian beam. Recently developed Bessel-beam waveguides allow long optical delay and very high dispersion. Delay values may vary from nanoseconds to microseconds, and dispersion promises to be at 100 μs/nm. Optical setup consisted of a red laser, an anamorphic prism pair, two prism couplers, and a bent, single-mode fiber attached to prisms. The coupling rate increased substantially and corresponded to the value determined by the anamorphic prism pair.
This work was done by Anatoliy Savchenkov, Vladimir Iltchenko, Andrey Matsko, Thanh Le, Nan Yu, and Lute Maleki of Caltech for NASA's Jet Propulsion Laboratory.
NPO-45440
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Efficient Coupler for a Bessel Beam Dispersive Element
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Overview
The document discusses a significant advancement in optical technology, specifically focusing on an efficient coupler for Bessel-beam dispersive elements developed by NASA's Jet Propulsion Laboratory. Bessel-beam waveguides are noted for their ability to provide long optical delays and high dispersion, with delay values ranging from nanoseconds to microseconds and dispersion rates reaching up to 100 μs/nm. However, previous coupling techniques faced challenges, particularly with fiber-to-fiber coupling, which had an unacceptable efficiency of –30 dB for practical applications.
To address these limitations, the document proposes a new coupling technique that enhances the efficiency of coupling a free Gaussian beam to a Bessel beam waveguide. The proposed methods involve bending the Bessel beam waveguide near the coupler or utilizing a curved coupler. This innovative approach allows for successful coupling of every Bessel beam mode to a collimated Gaussian beam, significantly improving the coupling rate.
The optical setup used for the demonstration includes a red laser, an anamorphic prism pair, two prism couplers, and a bent single-mode fiber attached to the prisms. The results indicate a substantial increase in the coupling rate, aligning with the values determined by the anamorphic prism pair. This experimental demonstration effectively resolves the challenges associated with optical coupling to very small Bessel beam tapers.
The document is part of NASA's Technical Support Package (NPO-45440) and is intended to disseminate aerospace-related developments that have broader technological, scientific, or commercial applications. It emphasizes the importance of compliance with U.S. export regulations and provides contact information for further inquiries regarding research and technology in this area.
In summary, the document highlights a breakthrough in optical coupling techniques for Bessel-beam waveguides, showcasing a practical solution to enhance efficiency and broaden the applicability of these advanced optical systems. This advancement holds promise for various fields, including telecommunications, imaging, and other areas where precise optical manipulation is crucial.
