Resonant nonstationary amplification of polychromatic laser pulses and conical emission in an optically dense ensemble of neon metastable atoms

Experimental and numerical investigation of single-beam and pump-probe interaction with a resonantly absorbing dense extended medium under strong and weak field-matter coupling is presented. Significant probe beam amplification and conical emission were observed. Under relatively weak pumping and high medium density, when the condition of strong coupling between field and resonant matter is fulfilled, the probe amplification spectrum has a form of spectral doublet. Stronger pumping leads to the appearance of a single peak of the probe beam amplification at the transition frequency. The greater probe intensity results in an asymmetrical transmission spectrum with amplification at the blue wing of the absorption line and attenuation at the red one. Under high medium density, a broad band of amplification appears. Theoretical model is based on the solution of the Maxwell-Bloch equations for a two-level system. Different types of probe transmission spectra obtained are attributed to complex dynamics of a coherent medium response to broadband polychromatic radiation of a multimode dye laser.Comment: 9 pages, 13 figures, corrected, Fig.8 was changed, to be published in Phys. Rev.

Assessment of single cell viability following light-induced electroporation through use of on-chip microfluidics

The high throughput electroporation of single cells is important in applications ranging from genetic transfection to pharmaceutical development. Light-induced electroporation using optoelectronic tweezers (OET) shows promise towards achieving this goal. However, cell viability following light-induced electroporation has yet to be shown. Here we present a novel OET device which incorporates microfluidic channels in order to assess the viability of single cells following light-induced electroporation. Monitoring of single cell electroporation and viability is achieved through the use of fluorescent dyes which are exchanged using the integrated fluidic channels. The successful reversible electroporation of HeLa cells is shown

Metallic nanoparticle manipulation using optoelectronic tweezers

We report on trapping of single and multiple spherical gold nanoparticles with 60 to 250 nm diameters using optoelectronic tweezers (OET). Thanks to the low optical intensities required for stable trapping (20 muW over 1.7 mum spot), we estimate the temperature increase in OET-trapped nanoparticles due to absorption to be DeltaT < 0.1degC, making OET-trapped nanoparticles suitable for biological imaging and sensing applications. In addition, we observe translational velocities of 68 mum/s and demonstrate trapping of both single and multiple nanoparticles in a single trap

NanoPen: light-actuated patterning of nanoparticles

We introduce NanoPen, a novel technique for flexible, real-time reconfigurable, and large-scale light-actuated patterning of single or multiple nanoparticles such as metallic spherical nanoparticles, semiconducting and metallic nanowires, and carbon nanotubes