Single step optical fabrication of a DFB laser device in fluorescent azobenzene-containing materials

Distributed feedback (DFB) lasers are produced directly in fluorescent azobenzene-containing materials using a single holographic optical step. Surface relief grating capable of producing images in fluorescence microscopy can be holographically formed in a number of materials

Very efficient surface relief holographic materials based on azobenzene-containing epoxy resins cured in films

An extremely high rate of holographic surface relief grating inscription has been achieved in materials based on a solid state ring-opening reaction of an oxirane with amino substituted azobenzenes. A number of effective formulations based on various oxirane derivatives and different aminoazobenzene derivatives has been prepared. For one of the best formulations, a low molecular weight three-armed azobenzene derivative has been separated in a pure form. This three-armed azobenzene derivative exhibited the highest inscription rate

Stable selective gratings in LC polymer by photoinduced helix pitch modulation

A cholesteric mixture based on the nematic liquid crystalline side-chain polymer doped with a chiral-photochromic compound was prepared and used as an active medium for creation of stable polarization selective gratings by phototunable modulation of the helix pitch. Such modulation was fabricated in the polymer mixture by a nonpolarized UV-irradiation with spatially modulated intensity that causes E-Z isomerization of a chiral-photochromic dopant, decreasing its helical twisting power. It was shown that the gratings recorded by UV-exposure through a mask are strongly selective to the handedness of circular polarized light. The studied polymer film forms a right-handed helical structure and, correspondingly, the diffraction of only the right-circularly polarized light was found in the transmittance mode. The maximum diffraction efficiencies were found for the wavelength values between the maxima of selective light reflection. The films obtained open very interesting possibilities for further development of materials with stable gratings operating in the entire visible spectral range. Both the position and the width of the spectral range of an efficient diffraction can be easily controlled by the UV exposure and concentration of the dopant. The materials obtained and methods developed can be used for creation of specific diffraction elements for optics and photonics

Coherent atomic motions in a nanostructure studied by femtosecond x-ray diffraction

Reversible structural changes of a nanostructure were measured non-destructively with subpicometer spatial and subpicosecond temporal resolution via x-ray diffraction (XRD). The spatially periodic femtosecond excitation of a gallium arsenide/aluminum gallium arsenide superlattice results in coherent lattice motions with a 3.5-picosecond period, which was directly monitored by femtosecond x-ray pulses at a 1-kilohertz repetition rate. Small changes (DeltaR/R=0.01) of weak Bragg reflexes (R=0.005) were detected. The phase and amplitude of the oscillatory XRD signal around a new equilibrium demonstrate that displacive excitation of the zone-folded acoustic phonons is the dominant mechanism for strong excitation