Fig. 1. (a) Refractive index dispersion of the Ge22Sb18Se60 glass film measured using ellipsometry; inset schematically depicts the waveguide structure. (b) Simulated GVD of GeSbSe waveguides with varying widths (W) and a fixed core thickness H=400  nm.

Fig. 2. (a) Top-view optical micrograph of the zigzag GeSbSe waveguides; (b) SEM cross-sectional image of a 0.95  μm (W)×0.4  μm (H) GeSbSe waveguide. (c) Experimental setup of on-chip SC generation and sensing. (d) Block diagram of home-built femtosecond laser module (OC, optical coupler; WDM, wavelength division multiplexer; SA, graphene saturable absorber; PC, polarization controller).

Fig. 3. SC spectra in GeSbSe waveguides: (a) SC spectra from waveguides with different widths W; when W=0.95  μm, the zero-dispersion point of the waveguide coincides with the pump wavelength; (b) SC generation of GeSbSe waveguides with the optimal geometry (W=0.95  μm, H=0.4  μm) and varying lengths; (c) SC spectra from a 21 mm long GeSbSe waveguide (W=0.95  μm, H=0.4  μm) at different pump power levels. The power quoted here represents the average optical power coupled into the waveguide.

Fig. 4. (a) SC spectra measured on GeSbSe waveguides of different lengths L when immersed in chloroform; the triangle marks the optical absorption at 1695 nm calibrated using a benchtop UV-Vis spectrometer for an equivalent waveguide path length L=21  mm; (b) SC spectra taken on a 21 mm long GeSbSe waveguide immersed in CHCl₃–CCl₄ solutions of varying volume concentration ratios; (c) measured peak absorption at 1695 nm versus the GeSbSe waveguide length used in the experiment. The linear relation indicates that the classical Lambert’s law is obeyed; the inset shows the mode profile simulated by finite difference method.