On-chip hollow waveguides
Hollow waveguides (both fiber-based and chip-based) have been the subject of extensive research in the past couple decades, owing to their ability to guide light within a gas- or liquid-core medium. This ability makes hollow waveguides important enablers for nonlinear optics, sensing, and atomic spectroscopy, as well as many other applications. While air-core photonic crystal fibers are commercially well established, techniques for creating air-core waveguide networks on chips are less developed. Traditionally, on-chip hollow waveguides are fabricated using either wafer-bonding or sacrificial etching techniques, typically limiting the size and complexity of the air-core networks that can be easily created.
We have developed an approach for creating complex air-core waveguide networks on chips, by exploiting thin-film delamination buckling. By engineering the stress of thin-film multilayer mirrors, and by introducing patterned regions of low adhesion within the multilayers, we are able to produce a variety of air-core Bragg waveguide structures in parallel. These structures include hollow waveguides with axial variations in core size, enabling dispersive (tapered) structures and novel types of waveguide-based reflectors and microcavities.
Various material systems have been used, but most of our current work employs Si/SiO2-based mirrors for operation in the near infrared or Ta2O5/SiO2-based mirrors for operation in the near-visible range.
References
- M. H. Bitarafan, C. A. Potts, and R. G. DeCorby, "Cutoff-based dual-taper reflectors in on-chip hollow waveguides," Opt. Express 25, 5101-5106 (2017).
https://doi.org/10.1364/OE.25.005101 - A. Melnyk, C. A. Potts, T. W. Allen, and R. G. DeCorby, "Visible range hollow waveguides by guided buckling of Ta 2 O 5 /SiO 2 multilayers," Appl. Opt. 55, 3645-3649 (2016).
https://doi.org/10.1364/AO.55.003645