Multifunctional integrated photonics in the mid-infrared with suspended AlGaAs on silicon

Abstract

The microscale integration of mid-and longwave-infrared photonics could enable the development of fieldable, robust chemical sensors, as well as highly efficient infrared frequency converters. However, such technology would be defined by the choice of material platform, which immediately determines the strength and types of optical nonlinearities available, the optical transparency window, modal confinement, and physical robustness. In this work, we demonstrate a new platform, suspended AlGaAs waveguides integrated on silicon, providing excellent performance in all of these metrics. We demonstrate low propagation losses within a span of nearly two octaves (1.26 to 4.6 µm) with exemplary performance of 0.45 dB/cm at λ = 2.4 µm. We exploit the high nonlinearity of this platform to demonstrate 1560 nm-pumped second-harmonic generation and octave-spanning supercontinuum reaching out to 2.3 µm with 3.4 pJ pump pulse energy. With mid-IR pumping, we generate supercontinuum spanning from 2.3 to 6.5 µm. Finally, we demonstrate the versatility of the platform with mid-infrared passive devices such as low-loss 10 µm-radius bends, compact power splitters with 96 ± 1% efficiency and edge couplers with 3.0 ± 0.1 dB loss. This platform has strong potential for multi-functional integrated photonic systems in the mid-IR. arXiv:1905.01380v1 [physics.app-ph] 3 May 2019 have suitable optical transparency [23], and strong optical nonlinearities are also required for the generation or broadening of frequency combs in the mid-IR [15]. While significant Kerr nonlinearity is present in silicon, germanium and chalcogenide materials, they lack intrinsic second-order optical nonlinearities for highly efficient frequency conversion [6,7,24,25] and electro-optic modulation [26].Alternatively, group III-V materials possess many desirable properties for multi-functional integrated photonic systems including a high refractive index, strong second-and third-order optical nonlinearities, and wide optical transparency windows into the LWIR. A practical advantage of these materials is the ability to grow a chemically selective etch stop underneath a high-quality epitaxial device (donor) film, enabling wafer or chip-bonding film transfer techniques for heterogeneous integration [27,28]. This has enabled high-index-contrast III-V waveguides on other substrates such as oxidized silicon and sapphire [29][30][31][32][33]. However, to take full advantage of the broad transparency window supported by III-V semiconductors, it is necessary to pursue alternative geometries such as air-clad suspended waveguides. But even this approach requires a degree of caution, as most materials readily form surface oxide layers that also introduce absorption. Undercut etching has been used to suspend GaAs waveguides engineered for mid-IR difference frequency generation [34]. While this represents a promising step in the development of nonlinear mid-IR photonics with III-V materials, many issues remain, such as the propagation loss in the mid-IR region, atmospheric stabilit...

Broadband supercontinuum generation in nitrogen-rich silicon nitride waveguides using a 300 mm industrial platform

“…Recently, efforts have been made to develop SCG on-chip. High nonlinearities have been achieved, e.g., in chalcogenide glasses [5] or III-V materials [6,7]. However, these materials are not appropriate for large scale and low-cost production of compact electronics and photonics devices due to their lack of complementary-metaloxide-semiconductor (CMOS) compatibility.…”

Mid-Infrared Supercontinuum and Frequency Comb Generations by Different Optical Modes in a Multimode Chalcogenide Strip Waveguide

“…The pulse duration T0 = 240 fs and peak power P0 = 2 kW, which are moderate values to model the typical trends of dynamics along the variation of λ0=2.5, 3, and 3.5 μm. Such laser sources centered at the three wavelengths are available from the previous works [52]- [54]. By using the dispersion and nonlinearity parameters of TE00, TE10, and TE20 modes, respectively, the spectral and temporal profiles of the SCs generated at the output point of the waveguide are shown in Fig.…”

On-chip polarization rotator for type I second harmonic generation

“…High conversion efficiency SHG has recently been demonstrated in GaAs [14][15][16] and AlGaAs 17 waveguides using form birefringence phase matching 18,19 and in periodically-poled LiNbO 3 20,21 waveguides using quasiphase matching. Additionally, AlGaAs platforms [22][23][24][25] have demonstrated frequency combs and supercontinuum generation with high efficiency. Type I SHG in either GaAs or AlGaAs is a promising platform for efficient SHG from 2 µm to 1 µm because of the strong χ (2) nonlinearity 26 and small mode sizes.…”