“…Unfortunately, it is not always useful for mid-IR liquid-sensing applications, where coupling to active or passive on-chip components on the wavelength-scale is needed. For avoiding those limitations of metalbased mid-IR plasmonics, lower-plasma-frequency materials have been demonstrated, including highly-doped epitaxial semiconductors (Taliercio and Biagioni, 2019;Ehlers and Mills, 1987;Gómez Rivas et al, 2004;Ginn et al, 2011;Law et al, 2012;N'tsame Guilengui et al, 2012;Augel et al, 2016;Frigerio et al, 2016;Pellegrini et al, 2018), such as Ge, Si, III-Vs (e.g., GaP and GaN) or II-VIs (Barker, 1968;Harima et al, 1998;Streyer et al, 2014;Zhong et al, 2015;Taliercio and Biagioni, 2019), transparent conductive oxides (Zhong et al, 2015;Castellano, 2022), silicides (Soref et al, 2008;Naik et al, 2013;Zhong et al, 2015), transition metal nitrides (Zhong et al, 2015) and graphene (Fei et al, 2012;Grigorenko et al, 2012;Zhong et al, 2015;Constant et al, 2016). However, they mainly fit to Si-photonics integration or to implementation into CMOS-structures and lack simple fabrication and implementation protocols, compatible with mid-IR technology.…”