Abstract
The development of Ge and SiGe chemical vapor deposition techniques on silicon wafers has enabled the integration of multi-quantum well structures in silicon photonics chips for nonlinear optics with potential applications to integrated nonlinear optics, however research has focused up to now on undoped quantum wells and interband optical excitations. In this work, we present model calculations for the giant nonlinear coefficients provided by intersubband transitions in hole-doped Ge/SiGe and Si/SiGe multi-quantum wells. We employ a valence band-structure model for Si1-xGex to calculate the confined hole states of asymmetric-coupled quantum wells for second-harmonic generation in the mid-infrared. We calculate the nonlinear emission spectra from the second-order susceptibility tensor, including the particular vertical emission spectra of valence-band quantum wells. Two possible nonlinear mid-infrared sensor architectures, one based on waveguides and another based on metasurfaces, are described as perspective application.
Highlights
Mid-infrared (MIR) photonics is receiving considerable attention due to the variety of envisaged applications in medical diagnostics [1], biochemistry studies [2,3], chemical analytics [4], and environmental monitoring for safety and security [5]
We present an application study for MIR emission sensors based on secondharmonic generation (SHG) in hole-doped multi quantum wells (MQW) made of Ge/SiGe and SiGe/Si whose band offset of 0.5 eV enables MIR applications, unlike Ge/SiGe electron-doped MQWs that have an offset around 0.1 eV [31]
The paper is organized as follows: in Section 2 the silicongermanium heterostructure material platform is introduced and three specific heterostructure designs are described; in Section 3, a model for the giant nonlinearity of intersubband transitions (ISBTs) in the valence band of group-IV heterostructures is presented and SHG spectra are calculated; in Section 4, the feasibility of epitaxial material growth is discussed; in Section 5, two nonlinear MIR sensor architectures based on waveguide chips and plasmonic metasurfaces are proposed
Summary
Mid-infrared (MIR) photonics is receiving considerable attention due to the variety of envisaged applications in medical diagnostics [1], biochemistry studies [2,3], chemical analytics [4], and environmental monitoring for safety and security [5]. InGaAs/AlInAs heterostructures (In1-xGaxAs wells and Al1-xInxAs barriers) on InP substrates [17,18,19,27] This material system represents an ideal platform for nonlinear MIR photonics because it can be approximated with the ideal single-parabolic band model; it features a band offset of 0.5 eV, quite higher than MIR photon energies of interest for molecular sensing; it has a high refractive index of 3.6 useful for strong mode-confinement in waveguides; and it can operate as active gain material to compensate for pump depletion and free-carrier losses [19]. The paper is organized as follows: in Section 2 the silicongermanium heterostructure material platform is introduced and three specific heterostructure designs are described; in Section 3, a model for the giant nonlinearity of ISBTs in the valence band of group-IV heterostructures is presented and SHG spectra are calculated; in Section 4, the feasibility of epitaxial material growth is discussed; in Section 5, two nonlinear MIR sensor architectures based on waveguide chips and plasmonic metasurfaces are proposed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
