Leland Stanford Junior University

Jonathan R Kurz

Martin M Fejer

Ming-Hsien Chou

An apparatus and method for nonlinear frequency mixing of light waves relying on a nonlinear material having a nonlinear coefficient d and a waveguide fabricated in the nonlinear material. The waveguide is equipped with a quasi-phase-matching (QPM) grating extending along the length of the waveguide and endowed with an asymmetry of the nonlinear coefficient d along the width of the waveguide. The transverse asymmetry is chosen to establish a mode overlap for nonlinear frequency mixing between different transverse width modes of light. The transverse asymmetry can be odd or else neither odd nor even so as to establish mode overlap for frequency mixing between even transverse width modes and odd transverse width modes. The QPM grating can have single or multiple grating stripes that can be staggered, interleaved, angled and otherwise altered to achieve the transverse asymmetry establishing a mode overlap for frequency mixing between even transverse width modes and odd transverse width modes.

Apparatus and method for quasi-phase-matched nonlinear frequency mixing between different transverse width modes

A method and a nonlinear frequency mixer employing the method to generate at least one output light from at least one input light with the aid of a quasi-phase-matching (QPM) grating for quasi-phase-matching the input and output light involved in a nonlinear frequency mixing operation such as three-wave mixing, four-wave mixing or other nonlinear operation mediated by a susceptibility of the nonlinear optical material. The QPM grating has a beam-modifying pattern with features for wave front shaping. More specifically, the features shape the wave fronts of the output light by diffraction or phase front shaping to thereby modify its propagation. This modification of propagation can be used to steer, focus, defocusing, split and/or collimate the output light. The features themselves can have various geometric shapes and sizes, even on the order of the wavelength of the output light, and they can include domains exhibiting a nonlinear optical susceptibility &#x3c7;, such as the second-order susceptibility &#x3c7;, domain edges, and/or spacings between such domains.

Nonlinear frequency mixer using quasi-phase-matching gratings having beam-modifying patterns

A compensated nonlinear optical frequency mixer for compensating the walk-off produced by group velocity mismatch (GVM) between interaction waves. The compensated mixer has a first mixing region in which the interaction waves participate in a non-linear optical mixing process and where walk-off occurs between the interaction waves due to GVM. The compensated mixer is equipped with a frequency selective coupling and time delay structure located after the first mixing region for eliminating the walk-off produced between the interaction waves in the first mixing region by guiding the waves in arms whose lengths differ by a re-synchronization length. A second mixing region is located after the frequency-selective coupling and time delay structure, such that when the waves emerge in phase from the frequency selective coupling and time delay structure they continue to interact efficiently in the second mixing region. The compensated nonlinear optical frequency mixer of the invention can by used to compensate for GVM in frequency mixing operations involving a material's &khgr; susceptibility.

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Jonathan R Kurz