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The ability to detect small metallic nanoparticles by optical microscopy inside environmentally relevant species may have a wide impact for ecotoxicology studies. Here, we demonstrate four-wave mixing microscopy on individual small gold nanoparticles inside the hepatopancreas of Oniscus Asellus, a terrestrial isopod, which ingests metals found in the soil. After the exposure to food containing 10 nm radius gold nanoparticles, hepatopancreas tubules were collected, and nanoparticles were imaged by four-wave mixing microscopy with high contrast, locating them with sub-cellular resolution in the volume, despite the significant light scattering from these multi-cellular organs. Notably, the ultrafast dynamics of the four-wave-mixing non-linearity of gold nanoparticles resonantly excited and probed at their localized surface plasmon allows them to be distinguished from other metal deposits in the hepatopancreas, which manifest as a long-lived photothermal contrast. Our findings bring unexpected insight into the location of gold nanoparticles in relation to the cell types forming the hepatopancreas. Considering its simplicity, volumetric imaging capabilities, specificity, and compatibility with living cell studies, four-wave mixing microscopy holds great potential to investigate the fate of metal nanoparticles inside biological systems.

We present the rime-resolved optical characterization of InAs/InGaAs self-assembled quantum dots emitting at 1.3 mu m at room temperature. The photoluminescence decay time varies from 1.2 (5 K) to 1.8 ns (293 K). Evidence of thermalization among dots is seen in both continuous-wave and time-resolved spectra around 150 K. A short rise time of 10+/-2 ps is measured. indicating a fast capture and relaxation of carriers inside the dots. (C) 2000 American Institute of Physics.

We report on a spectroscopic technique named intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) employed for sensitive trace-gas detection in the mid-infrared spectral region. It is based on a combination of QEPAS with a buildup optical cavity. The sensor includes a distributed feedback quantum cascade laser emitting at 4.33 mu m. We achieved a laser optical power buildup factor of similar to 500, which corresponds to an intracavity laser power of similar to 0.75 W. CO2 has been selected as the target molecule for the I-QEPAS demonstration. We achieved a detection sensitivity of 300 parts per trillion for 4 s integration time, corresponding to a noise equivalent absorption coefficient of 1.4 x 10(-8) cm(-1) and a normalized noise-equivalent absorption of 3.2 x 10(-10) W cm(-1) Hz(-1/2). (C) 2014 AIP Publishing LLC.

We report on the linewidth narrowing of a room-temperature mid-infrared quantum cascade laser by phase-locking to a difference-frequency-generated radiation referenced to an optical frequency comb synthesizer. A locking bandwidth of 250 kHz, with a residual rms phase-noise of 0.56 rad, has been achieved. The laser linewidth is narrowed by more than 2 orders of magnitude below 1 kHz, and its frequency is stabilized with an absolute traceability of 2 x 10(-12). This source has allowed the measurement of the absolute frequency of a CO2 molecular transition with an uncertainty of about 1 kHz. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4799284]

The role of p-type doping on the carrier dynamics of epitaxially grown InAs/GaAs quantum dots QDs has been discussed intensively in recent literature. Via the incorporation of p-doping, QDs are positively charged by a built-in hole reservoir. These systems are not only of fundamental interest to study, e.g., carrier spin dynamics, but also received increasing attention for their application in optoelectronic devices with improved performances. InAs/GaAs QD lasers incorporating p-doping were shown to exhibit temperature insensitive threshold current 1 and linewidth enhancement factor, 2 high peak modal gain, 3 and high modulation bandwidth. 4

Using evanescent field coupling via frustrated total internal reflection, we measured whispering-gallery optical resonances of polystyrene microspheres held in aqueous buffer by optical tweezers, as a function of the distance from the planar coupling substrate. An intrinsic Q factor of 4×106 was found for a microsphere of 30 μm diameter, indicating the potential of such microresonators for highly sensitive biomolecular detection. These measurements provide an upper limit of 2×10−7 for the imaginary part of the complex refractive index of polystyrene at 770 nm wavelength.