Ferrofluid-based optofluidic switch using femtosecond laser-micromachined waveguides

We present a portable optofluidic switch using a ferrofluid plug in a commercially produced microfluidic chip with waveguides added via femtosecond laser micromachining (FLM). FLM enabled the one-step fabrication of highly reproducible, perfectly aligned integrated waveguides orthogonally crossing an existing microfluidic channel. In the "ON" state for each output, the ferrofluid plug is outside the intersection and input light arrives at the output with relatively small loss. In the "OFF" state, the plug is inside the intersection and the input light is absorbed. The same plug is used to turn ON and OFF several parallel waveguides with contrast ratios of 22 dB or better. In addition, the plug is driven periodically using an electromagnet combined with a permanent magnet for frequency-dependent characterization. Photodiode data show high contrast up to 50 Hz and linear frequency response up to 1 KHz. (C) 2015 Optical Society of America