Fabrication and characterization of high-contrast mid-infrared GeTe_4 channel waveguides

Abstract

We report the fabrication and characterization of high index contrast (Δn≈0.9) GeTe4 channel waveguides on ZnSe substrate for evanescent-field-based biosensing applications in the mid-IR spectral region. GeTe4 films were deposited by RF sputtering and characterized for their structure, composition, transparency, and dispersion. The lift-off technique was used to pattern the waveguide channels. Waveguiding from 2.5-3.7 and 6.4-7.5 μm was demonstrated, and mode intensity profile and estimated propagation losses are given for the 3.5 μm wavelength.

Optical quality ZnSe films and low loss waveguides on Si substrates for mid-infrared applications

“…They were then developed in AZ726 MIF developer for 2 min to create an undercut profile. GeTe 4 was then deposited on these patterned samples by RF sputtering at 40W sputtering power and 15 mTorr sputtering pressure [21]. The photoresist was then lifted off by soaking the samples in acetone, leaving the 20 µm wide GeTe 4 channels on the ZnSe film surface.…”

“…In our earlier work, GeTe 4 chalcogenide waveguides on bulk ZnSe substrates were demonstrated in both the MWIR and LWIR regions. Ductile dicing was used to prepare the end facets as conventional end facet polishing was unsuitable due to the soft and brittle nature of chalcogenide materials [21]. MIR waveguides fabricated on Si substrates would have the advantage that silicon is a plentiful, high quality low-cost material and can be readily cleaved along crystalline planes, avoiding end facet polishing.…”

Complex refractive index spectra of whole blood and aqueous solutions of anticoagulants, analgesics and buffers in the mid-infrared

“…This could be achieved for ATR-FTIR spectroscopy using an evanescent waveguide sensor, which is effectively a compact and ultrasensitive ATR element 4 . Techniques for fabricating such mid-infrared devices have been developed by our group 5 and by others 6 – 10 , but these devices have not yet been used for characterising the composition of human-derived materials such as blood.…”

Mid-infrared GeTe4waveguides on silicon with a ZnSe isolation layer

“…Moreover, it is important that these materials should be compatible with existing semiconductor fabrication technology to enable integration of electronics and photonics together on a single chip. In our previous work, we have demonstrated the fabrication and characterization of chalcogenide GeTe 4 waveguides on bulk ZnSe substrates, where the end facets of the waveguides were prepared using ductile dicing that left the sample end-facet with a staircase -like pattern [9,10]. Cut end facets are also inconvenient due to practical difficulties encountered in characterizing the waveguides optically; for example, it is difficult to collect light from the output of the waveguide using a fibre or by free space optics, as the contribution of scattered light from the rough cut cannot be avoided.…”