We report here a polarization-independent drop filter (PIDF) based on a photonic crystal self-collimation ring resonator (SCRR). Despite of the large birefringence associated with the polarization-dependent dispersion properties, we demonstrate a PIDF based on multiple-beam interference theory and polarization peak matching (PPM) technique. The PIDF performance was also investigated based on finite-difference time-domain (FDTD) technique, with excellent agreement between the theory and the simulation. For the designed drop wavelength of 1550 nm, the polarization-independent free spectral range is about 36.1 nm, which covers the whole optical communication C-band window. The proposed PIDFs are highly desirable for applications in photonic integrated circuits (PICs).

New all-optical NOT and NOR logic gates based on a single ultracompact photonic crystal ring resonator (PCRR) have been proposed. The PCRR was formed by removing the line defect along the GammaM direction instead of the conventional GammaX direction in a square-pattern cylindrical silicon-rod photonic crystal structure. The behavior of the proposed logic gates is qualitatively analyzed with the theory of beam interference and then numerically investigated by use of the two-dimensional finite-difference time-domain method. No nonlinear material is required with less than a 2.2 microm effective ring radius. The wavelengths of the input signal and the probe signal are the same. This new device can potentially be used in on-chip photonic logic-integrated circuits.

Infrared photon dissociation (IRPD) spectra of the NaSO4(-)(H2O)n clusters with up to five water molecules have been studied using quantum chemical calculations. Our calculation reveals that the splitting of the peaks in the ~800-1300 cm(-1) region of the IRPD spectra, which contains the information on S-O bond stretching of the anion, indicates the deviation of the cation from the C(3v) axis as well as the asymmetric distribution of the water molecules. The frequency of the H-bonded O-H stretching peak in the ~2300-3000 cm(-1) window, on the other hand, provides information on the position of the newly added water molecule with respect to the cation. The IRPD technique thus provides abundant structural information on the early stage of the microsolvation and has the potential to become a powerful tool complementary to photoelectron spectroscopy.

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