Anti-Stokes photoluminescence from colloidal CdSeS/ZnS quantum dots (QDs) is observed. The QDs were inserted into the core of wider-bandgap SiO2/Si3N4/SiO2 structure by thin film deposition and confirmed as promising nanoemitters for laser cooling due to efficient anti-Stokes emission. The nanoemitters were optically pumped by semiconductor lasers coupled to the waveguides using free-space optics. A direct evidence of local optical cooling in the waveguide structure has been demonstrated with a luminescence thermometry based on the detection of photoluminescence signal phase change versus power of the pumping laser, using a lock-in amplifier.
Biomolecules can exhibit low-lying vibrational modes in the THz region which are detectable in transmission
given a strong molecular dipole moment and optical depth, and a spectrometer of adequate sensitivity. The nucleic
acids are particularly interesting because of applications such as label-free gene assay, bio-agent detection, etc. However
for nucleic acids, sample preparation and THz coupling are of paramount importance because of the strong absorption by
liquid water and the small concentration of molecules present in physiological solutions. Concentration methods
become necessary to make the THz vibrational modes detectable, either by concentrating the nucleic-acid sample itself
in a small volume but large area, or by concentrating the THz radiation down to the volume of the sample. This paper
summarizes one type of the first method: nanofluidic channel arrays for biological nucleic acids; and two types of the
second method: (1) a circular-waveguide pinhole, and (2) a
circular-waveguide, conical-horn coupling structure, both for
DNA crystals. The first method has been demonstrated on a very short artificial nucleic acid [small-interfering (si) RNA
(17-to-25 bp)] and a much longer, biological molecule [Lambda-phage DNA (48.5 kbp)]. The second method has been
demonstrated on small (~100 micron) single crystals of DNA grown by the sitting-drop method.
We demonstrate imaging interferometric microscopy (IIM) for binary objects in two dimensions. Combining multiple exposures with different off-axis illumination configurations together with interferometric restoration of the zero-order beam during dark-field conditions, IIM provides high lateral resolution at low numerical apertures (NA). It retains the large field-of-view, long working distance and large depth-of-field of a low-NA imaging system. Also we include a first demonstration of imaging of a phase mask. All these properties are increasingly important for in semiconductor mask metrology. IIM relies on image processing to reconstruct the image; we present the processes necessary to obtain the combined image. Finally we compare the experiment with a simple Fourier optics model.
Using the principle of imaging interferometry we resolve structures with a relatively low NA microscope objection which could not be resolved in the conventional illumination setup. We show experimental results for the cases of 700- and 4000-nm period gratings. We compare these results with theoretical simulations and estimate the maximum resolution potential. Also we evaluate further advantages of our approach, such as field of view and working distance.