Electrically variable gradient index liquid crystal lens is developed that uses flat uniform liquid crystal layer and electrodes. The spatial modulation of the electric field across the lens aperture is obtained by the modulation of the effective dielectric constant of an integrated doublet lens structure. The dielectric constants of two materials, composing the doublet, are chosen to be different at electrical driving frequencies, while their optical refractive indexes are the same, hiding thus the structure from the optical point of view. This "hidden layer" approach decouples the electrical and optical functions of that structure, increases significantly the performance of the lens and enables new functionalities. The technical performance and various driving schemes of the obtained lens are presented and analyzed.

A mobile phone camera with an innovative electrically tunable liquid crystal lens (TLCL) concept is demonstrated. We first report the comparative theoretical and experimental analyses of the performance of a traditional "modal control" TLCL versus a TLCL using a floating (unpowered) transparent electrode (FTE). It is shown that the appropriate choice of voltage and frequency values of the driving electric signal may improve significantly (almost twice) the optical quality of the lens using the FTE. Exceptionally low spherical aberrations of the lens (< λ/10 for up to 10 diopters of optical power) and high modulation transfer functions of a mobile phone camera (using those lenses for autofocus function) are demonstrated in a very simple operation mode (frequency tuning of the lens' optical power at a fixed driving voltage). The capacity of the camera to perform high quality long distance photography and near distance bar code recognition within a short autofocus convergence time are demonstrated.

We report a strong spectral broadening of femtosecond pulses propagating in a single-mode As-S glass fiber of 1.5 m length. The pump pulse spectrum is broadened by a factor of five when the input power is grown up to 16.4 mW. The broadened spectra are nearly symmetric and self-phase modulation is believed to be the dominant nonlinear effect responsible for this process.

Additional electrical impedance is introduced in a liquid crystal lens by adding a floating (nonconnected) electrode. This enables excellent optical quality in a very simple operation mode (frequency tuning of the lens' optical power at a fixed driving voltage). The comparative analysis of this lens confirms its suitability for mobile imaging applications.

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