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We compare detailed spatio-temporal propagation simulations with experiments on generation of terahertz (THz) pulses in single filaments with two-color optical excitation, which elucidates the mechanism whereby positively chirped optical pulses lead to the maximum THz yield. The long-wavelength components in the leading edge of the positively chirped 2ω-pulse preserve the overlap with the ω-pulse. The THz yield is extremely sensitive to the temporal overlap: for a 35-fs ω-pulse, the yield decreases by an order of magnitude upon a ω–2ω pulse shift of only 5 fs. [ABSTRACT FROM AUTHOR]

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a primary pest of citrus due to its status as a vector of the citrus disease, huanglongbing. We evaluated the effects of light of specific wavelength and polarization on phototactic behavior of D. citri using a horizontal bioassay arena. Wavelength-associated positive phototaxis was associated with short wavelength UV (350-405 nm) targets whereas little or no responses were seen in longer wavelength targets in the visible spectrum from green to orange (500-620 nm). Distance walked towards the visual target was greater for UV/blue wavelengths (350-430 nm) than for longer wavelengths. Distances walked towards 365 nm light were greater than to white light, and distances travelled to green, yellow and orange light were similar to those in darkness. A reduced light intensity decreased responses to white and UV (365 nm) light. Polarized light was discriminated and D. citri travelled greater distance in response to white vertically polarized light than to horizontally polarized or unpolarized light of equal intensity. Responses to polarized 405 nm light were greater than to unpolarized light, although without an effect of polarization plane. For 500 nm light, there was no difference between responses to polarized or unpolarized light. There was no effect of age on responses to 405 nm light although 1 day old psyllids travelled faster in the presence of 500 nm green compared to 4-7 day old psyllids. Movement in response to UV and relative stasis in response to longer wavelength light is consistent with observed behaviors of settling on foliage for feeding and dispersing out of the canopy when flush needed for reproduction is scarce. [ABSTRACT FROM AUTHOR]

Three-dimensional subsurface imaging through the back side of a silicon flip chip is reported with a diffraction-limited lateral resolution of 166 nm and an axial performance capable of resolving features only 100 nm deep. This performance was achieved by implementing sample-scanned two-photon optical beam induced current microscopy using a silicon solid immersion lens and a peak detection algorithm. The excitation source was a 1530 nm erbium:fiber laser, and the lateral optical resolution obtained corresponds to 11% of the free-space wavelength. [ABSTRACT FROM AUTHOR]