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We propose and demonstrate a method of “z-microscopy” by utilizing an array of 45°-tilted micro mirrors arranged along the axial direction. Image signals emitted from different axial positions can be orthogonally reflected by the corresponding micro mirrors and spatially separated for parallel detection, essentially converting the more challenging axial imaging to a lateral imaging problem. Each micro mirror also provides optical sectioning capability due to its finite dimension. Numerical analysis shows that nearly diffraction limited axial resolution can be achieved. Experimental demonstration of z-imaging of fluorescent microspheres is also presented.

We report a second-order nonlinear nanoprobe for characterizing ultrafast optical near fields. The proposed nanoprobe comprises second harmonic nanocrystals attached to a carbon nanotube, which is in turn attached to a silica fiber taper. We demonstrate in situ pulse characterization directly in the air core of a photonic crystal fiber. Further, it is shown that nanoprobes containing a single nanocrystal in the tip of the nanotube can be fabricated by auxiliary focused ion beam nanomilling. These results indicate that the proposed nanoprobe can open an avenue for probing the evolution of ultrafast optical fields in complex three-dimensional micro-or nanostructures. (C) 2010 American Institute of Physics. [doi:10.1063/1.3532112] National Science Foundation_ECCS0925591, ECCS0644488, DBI0649866, ECCS0547475, 0335765 Pennsylvania State University Materials Research Institute Nanofabrication Laboratory

Near-field scanning can achieve nanoscale resolution while ultrashort pulse diagnostic tools can characterize femtosecond pulses. Yet currently it is still challenging to nonperturbatively characterize the near field of an ultrashort optical pulse with nanofemtoscale spatiotemporal resolution. To address this challenge, we propose to develop a nonlinear nanoprobe composed of a silica fiber taper, a nanowire, and nonlinear fluorescent spheres. Using such a nanoprobe, we also report proof-of-principle characterization of femtosecond optical pulse through interferometric autocorrelation measurement.

We report on a simple approach to obtain spectrally smoothed supercontinuum (SC) by using unstably mode-locked femtosecond laser pulses. The spectrum smoothing effect is due to the averaging of the supercontinua generated in a nonlinear photonic crystal fiber by modulated pulses. Theoretical analysis based upon solving the generalized nonlinear Schrodinger equation is presented, which qualitatively agrees well with the experimental observation. Finally, the application of the smoothed SC to broadband coherent anti-Stokes Raman scattering spectroscopy is demonstrated, which can result in a relatively smooth nonresonant background and suppress spurious peaks.

The authors report on a supercontinuum tweezer which combines tweezing with broadband (∼3000cm−1) coherent anti-Stokes Raman scattering (CARS) spectroscopy by taking advantage of the high spatial coherence and broad bandwidth of pulsed supercontinuum generated in a nonlinear photonic crystal fiber. Polarization-discriminated and time-resolved CARS is investigated to suppress the nonresonant four-wave-mixing background.