PROCEEDINGS ARTICLE | February 27, 2015
Proc. SPIE. 9365, Integrated Optics: Devices, Materials, and Technologies XIX
KEYWORDS: Refractive index, Femtosecond phenomena, Silica, Waveguides, Cladding, Particles, Laser ablation, Solids, Light wave propagation, Liquids
We present a new method to form liquid-core optofluidic waveguides inside hydrophobic silica aerogels. Due to their
unique material properties, aerogels are very attractive for a wide variety of applications; however, it is very challenging
to process them with traditional methods such as milling, drilling, or cutting because of their fragile structure. Therefore,
there is a need to develop alternative processes for formation of complex structures within the aerogels without
damaging the material. In our study, we used focused femtosecond laser pulses for high-precision ablation of
hydrophobic silica aerogels. During the ablation, we directed the laser beam with a galvo-mirror system and,
subsequently, focused the beam through a scanning lens on the surface of bulk aerogel which was placed on a three-axis
translation stage. We succeeded in obtaining high-quality linear microchannels inside aerogel monoliths by
synchronizing the motion of the galvo-mirror scanner and the translation stage. Upon ablation, we created multimode
liquid-core optical waveguides by filling the empty channels inside low-refractive index aerogel blocks with highrefractive
index ethylene glycol. In order to demonstrate light guiding and measure optical attenuation of these
waveguides, we coupled light into the waveguides with an optical fiber and measured the intensity of transmitted light as
a function of the propagation distance inside the channel. The measured propagation losses of 9.9 dB/cm demonstrate the
potential of aerogel-based waveguides for efficient routing of light in optofluidic lightwave circuits.
