Mid-infrared Nonlinear optics in SiGe waveguides
L. Carletti
1
, D. Allioux
1
, P. Ma
2
, Y. Yu
2
, B. Luther-Davies
2
, S. Madden
2
, D. Hudson
3
, M. Sinobad
4
, D. J. Moss
4
, M. Brun
5
,
S. Ortiz
5
, P. Labeye
5
, S. Nicoletti
5
, R. Orobtchouk
1
, C. Monat
1
, and C. Grillet
1
1. University of Lyon, Institut des Nanotechnologies de Lyon, Ecole Centrale de Lyon, 36 Avenue Guy de Collongue, 69134 Ecully, France
4. School of Electrical and Computer Engineering, Royal Melbourne Institute of Technology, Victoria 3001, Australia
5. CEA-Leti MINATEC Campus, 17 rue des Martyrs 38054 GRENOBLE Cedex 9, France
Christian.grillet@ec-lyon.fr
Abstract: Comprehensive mid-IR nonlinear measurements of SiGe waveguides performed in the
picosecond and femtosecond regime and compared to numerical calculations are reported.
Nonlinear properties of SiGe waveguides in the mid-IR are extracted.
OCIS codes: (130.4310) Nonlinear; (130.3120) Integrated optics devices; (130.3060) Infrared;
1. Introduction
The interest in expanding the spectral window of operation of group IV photonics towards the mid-infrared (mid-
IR), which corresponds to wavelengths between 2 and 10 m, is rapidly growing. The strong appeal of this particular
spectral range derives from a vast range of potential applications such as chemical and biological sensing, active
imaging, tissue ablation, secure free-space communication, and multiwavelength light sources [1,2]. The mid-IR
region has also been welcomed as a promising future regime for silicon based nonlinear photonic devices. The
nonlinear loss phenomenon of two-photon absorption, that limits nonlinear optical applications in the near-infrared
region, vanishes at these wavelengths [2,3], thus opening the door to photonic devices with new capabilities such as
parametric waveguide amplifiers with positive net gain [4]. However, it has recently been shown [5], that under
some experimental conditions, e.g. using picosecond pulses, nonlinear losses in the mid-IR can still be significant.
The free carriers generated by multi-photon absorption can have a strong impact through free-carrier absorption
(FCA) and thus limit some applications for which a strong nonlinear response is required, as for example
supercontinuum generation [5].
The silicon-on-insulator (SOI) material platform has attracted significant interest to implement on-chip
integrated waveguides operating in the mid-IR thanks to the possibility of a CMOS compatible fabrication process.
However, the increasing absorption of the silica cladding layer of the SOI at wavelengths longer than 3.5 m may
limit the useful wavelength range of this material platform. It is therefore crucial to explore other material platforms.
In this context, SiGe alloys on Si are seen as an attractive alternative platform to SOI for applications in the mid-IR
due to their expected lower propagation losses and higher nonlinear response [6,7].
Recently [8], we reported SiGe/Si waveguides with propagation losses as low as 0.5dB/cm at a wavelength of
4.75 m. Here, we experimentally investigate the nonlinear response of these SiGe waveguides in the mid-IR
including nonlinear transmission and self-phase modulation (SPM) using picosecond [8] and femtosecond optical
pulses centered at wavelengths between 3 and 5 m.
2. Waveguides fabrication and experimental setup
The SiGe/Si step index ridge waveguides consist of a Si
0.6
Ge
0.4
core surrounded by a Si cladding (Fig.1(a)). The
devices were fabricated at CEA-Leti on a CMOS fabrication line.
1.4 m
2 m
SiGe Core
(a) (b)
Fig. 1: (a) SEM image of a SiGe waveguide with an inset showing the SiGe core surrounded by Si cladding. (b) Experimental setup used for the
transmission experiments.
59
ME1.3 (Invited)
9:30 AM - 10:00 AM
978-1-4799-7468-9/15/$31.00 ©2015 IEEE