Enhanced second-harmonic generation in AlGaAs/Al_xO_y tightly confining waveguides and resonant cavities

Abstract

We demonstrate second-harmonic generation (SHG) from sub-micrometer-sized AlGaAs/AlxOy artificially birefringent waveguides. The normalized conversion efficiency is the highest ever reported. We further enhanced the SHG using a waveguide-embedded cavity formed by dichroic mirrors. Resonant enhancements as high as approximately 10x were observed. Such devices could be potentially used as highly efficient, ultracompact frequency converters in integrated photonic circuits.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

“…However, harmonic generation using the sub-wavelength structures reported thus far relies on field enhancements associated with localized surface plasmon resonances or collective resonances and requires exquisite fabrication techniques 1,[4][5][6][7] .…”

GaAs/AlOx Nonlinear Waveguides for Infrared Tunable Generation

“…Indeed, a smoother AlAs/air lateral interface is supposed to improve oxidation kinetics, allowing a better flux of H 2 O toward the ridge core and a better release of reaction products. It is worth comparing the above roughness values with those recently reported for strongly confining AlOx waveguides obtained by e-beam lithography + chlorine plasma etching (Scaccabarozzi et al, 2006). In this case, a 6 nm rms roughness is measured on the ridge sidewalls suggesting that, in spite of recent improvements, plasma-assisted etching does not provide yet the same surface quality as wet etching.…”

Second Harmonic Generation in AlGaAs Nanowaveguides

“…However, this cannot be easily achieved in an arbitrary geometry due to the inherent material dispersion. For momentum conservation to be satisfied, bulk birefringent crystals (such as BBO and KTP) [2,3] as well as waveguide geometries (in polymers [4], LiNbO 3 [5,6], and semiconductors [7][8][9][10][11]) have been successfully used. The latter solution has recently gained a significant amount of scientific attention, resulting in the development and improvement of several phase-matching techniques in waveguiding structures.…”

“…Of particular importance for this paper, SHG has been previously realized in isotropic AlGaAs by way of modal phase-matching (MPM) [7,8], quasi-phase-matching (QPM) [8][9][10], or artificial birefringence [8,11]. Unfortunately, most of the proposed solutions require costly and complex fabrication procedures.…”

“…Unfortunately, most of the proposed solutions require costly and complex fabrication procedures. In particular, they include (i) the introduction of additional thin oxidized layers of Al (in the core region of the waveguides) in order to break the isotropy of GaAs and induce artificial birefringence [11]; (ii) periodic domain orientations or quantum well intermixing [8][9][10] for QPM; or (iii) multi--step etching of "M-shaped" waveguides for MPM [7,8]. In addition, even more advanced photonic structures in the form of the Bragg reflector waveguides [16], ring resonators [17], and waveguide couplers [18] suitable for SHG have also been investigated.…”