Surfaces -defined as the interfaces between solids and liquids- have attracted much attention in optics and biology, such
as total internal reflection imaging (TIRF) and DNA microarrays. Within the context of optofluidics however, surfaces
have received little attention. In this paper, we describe how surfaces can define or enhance optofluidic function. More
specifically we discuss chemical interfaces that control the orientation of liquid crystals and the stretching of individual
nucleic acids, diffractive and plasmonic nanostructures for lasing and opto-thermal control, as well as microstructures
that read pressure and form chemical patterns.
We demonstrate optofluidic evanescent dye lasers based on two types of solid distributed feedback (DFB) grating
cavities- the first order linear DFB gratings which gives in-plane laser emitting and second order circular DFB gratings
which gives surface laser emitting. For both of them, the laser mode is confined within the waveguide and experience
optical gain via evanescent wave coupling with the dye solution. Benefitting from the solid waveguide cores, stable and
narrow linewidth laser output were observed with a large tolerance of fluid refractive indices, which prove the feasibility
of integrating fluid evanescent gain dye laser into passive waveguide circuit.
We introduce a novel tuning mechanism based on pressure actuating force, which can enable a broad spectrum of
tunable elastomeric optofluidic devices. Thanks to the flexibility of the Polydimethylsiloxane (PDMS) material, the local
deformation inside PDMS chip can be generated by filling the compressed air/liquid into the embedded channels. Such
tuning method turns out to be very simple for fabrication and control, also being compatible with microfluidic chips. To
this end, we have demonstrated the pressure mediated tunable optofluidic gratings, tunable optofluidic laser, and
microfluidic 2×2 optical switch.
We present a pressured mediated tunable optofluidic dye laser with novel cavity. The dye laser chip was fabricated with Polydimethylsiloxane (PDMS) via replica molding and has none nano-features. It comprises a liquid waveguide and micro-scale air-gap chambers which function as mirrors to provide feedback. The lasing wavelength was determined by the interference of the reflected beams from the two PDMS-air interfaces of the air-gap chamber acting as Fabry-Perot etalon, while the tuning was realized by varying the width of the air-gap by applying air pressure. The lasing with linewidth of 3 nm and tuning range of 14 nm was demonstrated.