Ge-rich graded-index Si_1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics

Abstract

To cite this version:J-M Ramirez, V Vakarin, J Frigerio, P Chaisakul, D Chrastina, et al.. Ge-rich graded-index Si 1-x Ge x waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics. Optics Express, Optical Society of America, 2017, 25 (6) Abstract:This work explores the use of Ge-rich graded-index Si 1-x Ge x rib waveguides as building blocks to develop integrated nonlinear optical devices for broadband operation in the mid-IR. The vertical Ge gradient concentration in the waveguide core renders unique properties to the guided optical mode, providing tight mode confinement over a broadband mid-IR wavelength range from λ = 3 µm to 8 µm. Additionally, the gradual vertical confinement pulls the optical mode upwards in the waveguide core, overlapping with the Ge-rich area where the nonlinear refractive index is larger. Moreover, the Ge-rich graded-index Si 1-x Ge x waveguides allow efficient tailoring of the chromatic dispersion curves, achieving flat anomalous dispersion for the quasi-TM optical mode with D ≤ 14 ps/nm/km over a ~ 1.4 octave span while retaining an optimum third-order nonlinear parameter, γ eff . These results confirm the potential of Ge-rich graded-index Si 1-x Ge x waveguides as an attractive platform to develop mid-IR nonlinear approaches requiring broadband dispersion engineering.

Ge-rich SiGe photonic-integrated circuits for mid-IR spectroscopy

“…The first experimental characterization of nonlinear refractive index in SiGe alloys confirms the advantages of using Ge-rich SiGe materials [6]. Then the possibility to achieve flat anomalous dispersion waveguides will be shown, opening strong perspectives towards the realization of efficient wideband optical sources [7].…”

“…The waveguide design has been optimized to meet three different requirements: (i) small effective mode area, (ii) good confinement of the optical mode with the Ge-rich material ; (iii) flat anomalous dispersion in a wide spectral range [7]. The final waveguide design is reported in Fig 5.…”

Wideband Ge-Rich SiGe Polarization-Insensitive Waveguides for Mid-Infrared Free-Space Communications

“…For instance, at a wavelength of 3 µm, n Si = 3.43 and n Ge = 4.04. It is worth noting that, for SiGe waveguides, the mode dispersion dominates over the material refractive-index dispersion in the MIDIR [34]. Consequently, the mode-dispersion engineering approach by means of geometric parameter optimization was chosen to obtain the polarization-insensitive and wideband integrated photonic components.…”

“…The ultra-wideband polarization-insensitive building blocks presented here pave the way for the development of high-performance on-chip photonic circuits for next-generation mid-infrared free-space communication systems.lock-in detection [15,16]. Moreover, in order to reach higher MIDIR wavelengths, various photonic platforms were developed, such as III-V materials [17][18][19], chalcogenide [20][21][22][23], and silicon and silicon-compatible materials [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. MIDIR photonic integrated circuits leveraging the mature Si technology have great potential for low-power consumption and low-cost systems that are meant to outperform existing technologies.…”

“…MIDIR photonic integrated circuits leveraging the mature Si technology have great potential for low-power consumption and low-cost systems that are meant to outperform existing technologies. Among the available group IV-compatible MIDIR platforms, silicon germanium (SiGe), and more specifically, Ge-rich SiGe alloys exhibit a compelling combination of flexible material tunability [34], large transparency, wideband operation [35][36][37], and remarkable nonlinear properties [40]. Here, we study the use of the Ge-rich SiGe platform to develop wideband and polarization-independent MIDIR components for free-space communications.Earth atmosphere's absorption spectrum contains two transparency windows in the MIDIR region that are very interesting for free-space communications.…”