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Pseudomagnetic fields for sound at the nanoscale.

Brendel, Christian; Peano, Vittorio; Painter, Oskar J; Marquardt, Florian.

Proc Natl Acad Sci U S A ; 114(17): E3390-E3395, 2017 04 25.

Article in English | MEDLINE | ID: mdl-28400518

ABSTRACT

There is a growing effort in creating chiral transport of sound waves. However, most approaches so far have been confined to the macroscopic scale. Here, we propose an approach suitable to the nanoscale that is based on pseudomagnetic fields. These pseudomagnetic fields for sound waves are the analogue of what electrons experience in strained graphene. In our proposal, they are created by simple geometrical modifications of an existing and experimentally proven phononic crystal design, the snowflake crystal. This platform is robust, scalable, and well-suited for a variety of excitation and readout mechanisms, among them optomechanical approaches.

Nonlinear optical phenomena in silicon waveguides: modeling and applications.

Lin, Q; Painter, Oskar J; Agrawal, Govind P.

Opt Express ; 15(25): 16604-44, 2007 Dec 10.

Article in English | MEDLINE | ID: mdl-19550949

ABSTRACT

Focus Serial: Frontiers of Nonlinear Optics

Several kinds of nonlinear optical effects have been observed in recent years using silicon waveguides, and their device applications are attracting considerable attention. In this review, we provide a unified theoretical platform that not only can be used for understanding the underlying physics but should also provide guidance toward new and useful applications. We begin with a description of the third-order nonlinearity of silicon and consider the tensorial nature of both the electronic and Raman contributions. The generation of free carriers through two-photon absorption and their impact on various nonlinear phenomena is included fully within the theory presented here. We derive a general propagation equation in the frequency domain and show how it leads to a generalized nonlinear Schrodinger equation when it is converted to the time domain. We use this equation to study propagation of ultrashort optical pulses in the presence of self-phase modulation and show the possibility of soliton formation and supercontinuum generation. The nonlinear phenomena of cross-phase modulation and stimulated Raman scattering are discussed next with emphasis on the impact of free carriers on Raman amplification and lasing. We also consider the four-wave mixing process for both continuous-wave and pulsed pumping and discuss the conditions under which parametric amplification and wavelength conversion can be realized with net gain in the telecommunication band.

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