Self-phase modulation has been observed for ultrashort pulses of wavelength 800nm propagating through a 1 cm-long Ta2O5 rib waveguide. The associated nonlinear refractive index n2 was estimated to be 7.23x10-19 m2/W, which is higher than silica glass by more than one order of magnitude. Femtosecond time of flight measurements based on a Kerr shutter configuration show that the group velocity dispersion is small at a wavelength of 800 nm, confirming that dispersion may be neglected in the estimation of n2 so that a simplified theory can be used with good accuracy.
This communication introduces a digital design for tunable microfluidic optical fiber devices. In these systems, multiple, independently controlled microfluidic plugs are pumped into or out of overlap with a fiber structure to modulate its transmission characteristics. The devices described here use eight plugs, eight electrowetting pumps and a corresponding set of molded planar recirculating microchannels to control the depth of the narrowband loss feature associated with a long period fiber grating. Optical measurements illustrate the digital and relatively fast operation of this type of microfluidic fiber device.
Nonlinear reflection and diffraction measurements have been performed on a GaAs/AlGaAs photonic-crystal waveguide patterned with a square lattice: The basis in the two-dimensional unit cell consists of rings of air in the dielectric matrix. The measured angles of diffracted second-harmonic beams agree with those predicted for nonlinear diffraction conditions. Results for second-harmonic intensities as a function of incidence angle, polarization, and pump wavelength show that the reflected second-harmonic signal is dominated by the crystalline symmetry of GaAs, whereas nonlinear diffraction is determined by the photonic-crystal structure
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