HOME / PRESENTATIONS /

Nan Shen

Manipulation of Single Cells with Sub-cellular Precision Using Femtosecond Laser Pulses, at Photonics West, Commercial and Biomedical Applications of Ultrafast Lasers IV (San Jose, CA), Wednesday, January 23, 2002:
talk_422.pdf
Femtosecond laser pulses centered at 800 nm are used to manipulate sub-cellular structures inside live and fixed cells. Using only a few nanojoules of laser pulse energy, we are able to selectively disrupt individual mitochondria in live bovine capillary epithelial (BCE) cells, and cleave single actin fibers in the cell cytoskeleton network of fixed human fibro-blast cells. We tightly focus femtosecond laser pulses using high numerical aperture (NA) microscope objectives to create high laser intensity in the sub-micrometer-sized focal volume. Laser energy is absorbed through non-linear... Read more about Manipulation of Single Cells with Sub-cellular Precision Using Femtosecond Laser Pulses
Photodisruption in biological samples using femtosecond laser pulses, at Photonic West Conference (San Jose, CA), Tuesday, January 23, 2001:
talk_367.pdf
Tightly focused femtosecond laser pulses can be absorbed nonlinearly inside biological materials, vaporizing tissue in the focal volume. High intensity is achieved at the focus with relatively low energy, minimizing collateral damage and unwanted heat deposition. We focus 100-fs laser pulses using a high numerical aperture microscope objective in the bulk of the skin tissue, disrupting micrometer-sized regions up to 100 mm beneath the sample surface. When the laser beam is focused even deeper into the sample, we observe the formation of filaments in the skin bulk rather than spherical sub-... Read more about Photodisruption in biological samples using femtosecond laser pulses
Photodisruption in turbid tissues with ultrashort laser pulses, at Photonics West 2000 (San Jose, CA), Tuesday, January 25, 2000:
talk_331.pdf
We investigate the potential of femtosecond laser pulses for photodusruptive surgery on the surface and in the bulk of turbid tissue. Human epidermis cultures, mouse skin, and pig skin were used as tissue models. We use nonlinear absorption of tightly focused 100-fs laser pulses to vaporize tissue in the focal volume. By focusing the pulse in the bulk of the skin, we can vaporize 10-µm diameter regions up to 100 µm beneath the surface with minimal damage to the surrounding tissue. This technique offers exciting possibilities for clinical dermatology applications, such as tattoo removal and... Read more about Photodisruption in turbid tissues with ultrashort laser pulses
Molecular orientation in Langmuir monolayers studied by surface second harmonic generation, at APS Centennial Meeting 1999 (Atlanta, GA), Tuesday, March 23, 1999:
talk_266.pdf
We used surface second harmonic generation (SHG) to study molecular orientation in a smectic-C liquid-crystal Langmuir monolayer at an air/water interface. The molecules under investigation are 4-octyl-4'-(3-carboxytrimenthyleneoxy) azobenzene (8AZ3). Because water is inversion symmetric, the SHG signal comes only from the surface. Furthermore, the magnitude of the surface SHG signal depends on the orientation of molecules, which makes SHG a sensitive probe of the phase of the monolayer. We measured the response of the SHG signal as we compressed the monolayer from a smectic-C phase to a more... Read more about Molecular orientation in Langmuir monolayers studied by surface second harmonic generation