Multiwave out-of-normal band-edge lasing in cholesteric liquid crystals

Abstract

Highly efficient twisted nematic liquid crystal polarization gratings achieved by microrubbing Appl. Phys. Lett. 101, 041107 (2012) A polarization-independent liquid crystal phase modulation using polymer-network liquid crystals in a 90° twisted cell J. Appl. Phys. 112, 024505 (2012) Fast switchable grating based on orthogonal photo alignments of ferroelectric liquid crystalsWe have investigated the lasing effect in dye-doped cholesteric liquid crystals, where the photonic stop-band for light propagating along the helical axis coinciding with the layer normal is strongly shifted to longer wavelengths with respect to the luminescence band of the dye. In the absence of overlapping of the photonic and luminescence bands, the well-known lasing effect along the normal at the stop-band edges is forbidden. However, the lasing is still allowed for out-of-normal directions, for which the photonic band is shifted to shorter wavelengths corresponding to the luminescence band. Despite of the out-of-normal light propagation, the positive feedback necessary for the lasing is still available in a case of the monodomain cholesteric layer, when its thickness is much less than the optical pumping aperture. We have observed a significantly increased energy threshold for the out-of-normal lasing modes despite they are characterized by lower threshold gain compared to the modes propagating along the helix axis. The increased energy threshold is explained in terms of continuous distribution of the lasing emission over a large angular sector and energy leakage caused by the leaky lasing into the substrates. V C 2012 American Institute of Physics. [http://dx.

Mode coupling by scattering in chiral nematic liquid crystal ring lasing

“…The emission wavelength in the color cone lasing is blue shifted for increasing inclination angle, corresponding to the blue shift of the LWE with the inclination angle. Laser light that is trapped inside the CLC layer may also appear in leaky modes in the glass, for inclination angles close to 90° as investigated by Palto et al [11].…”

Rotatable Diffraction Gratings Based on Cholesteric Liquid Crystals with Phototunable Helix Pitch

“…[1][2][3][4][5][6][7][8][9][10][11] CLC materials possess a unique supramolecular helical structure predetermining their optical properties. Their periodic helical supramolecular structure and high sensitivity to the external fi elds make them very promising stimuli-responsive materials for different applications in photonics, electrooptics, display technology, creation of optical sensors, and other applications.…”

Optically pumped mirrorless lasing. A Review. Part II. Lasing in photonic crystals and microcavities

“…[54][55][56][57] and termed as a colour-cone lasing. Detailed theoretical and experimental investigations of the off-axis Bragg lasing has recently been performed by Palto et al [58] and Pennick et al [59]. One of the important conclusions following from Ref.…”

“…One of the important conclusions following from Ref. [58] is that the off-axis lasing mode, together with a waveguide mode W g and so-called quasi-in-plane leaky (QIPL) modes, are the most important mechanisms competing with the conventional in-axis Bragg laser mode for the emission power. The W g -mode is based on the effect of total internal light reflection and thus takes place only if the refractive index of substrates is lower than at least one of the refractive indices n  or n  of a LC for the angles of light propagation larger than a corresponding threshold angle of the total internal reflection.…”