Versatile hot-embossing of chalcogenide glasses for integrated optics

Spectroscopic sensing, by vibrational absorption, in the mid-infrared (IR) allows detection of molecular type, and quantity, and has applications across many sectors such as medical, environmental, manufacturing, security, energy production. Chalcogenide glasses are transparent across the mid-IR spectral region and suitable for fabricating as optical circuits for integrated optical sensors. Low optical loss, chalcogenide glass monomode waveguide are one of the building blocks of such integrated circuits. We have been developing the simple, yet scalable, route of hot-embossing to fabricated these, here we review progress in using hot-embossing to make single mode, low loss waveguides in chalcogenide glasses as follows: (i) As40Se60/Ge17As18Se65 (at. %) core/cladding rib waveguides fabricated in a one-step process by hot embossing two As40Se60 fibres sandwiched between a silicon mould and a planar Ge17As18Se65 glass substrate. This results in a series of replicated thin-film rib structures on glass and optical characterization at 1.55 µm reveals single mode waveguide propagation, in agreement with numerical modeling. [1] (ii) Single-mode optical rib waveguides operating at telecommunication wavelength are successfully patterned in a thermally evaporated chalcogenide glass thin film on a chalcogenide glass substrate. Ellipsometry is used to measure the refractive index dispersion of the presses film As40Se60 and substrate Ge17As18Se65. [2] (iii) Analogous patterning is demonstrated of low optical loss, single-mode optical rib waveguide in a radio-frequency sputtered chalcogenide glass thin film on a chalcogenide glass substrate. Waveguide 4-6 µm wide and 1.9 ±0.1 µm high are fabricated with optical loss of <0.78 dB/cm for the TE mode and < 0.81 dB/cm for the TM mode at 1550 nm. [3] the paper will conclude with a call for standardising, across the community, the measurement and interpretation of optical loss in novel glass planar waveguides, as we currently find some discrepancies