Lasing in liquid crystal systems with a deformed lying helix

Abstract

We report on experimental investigations of the lasing effect in novel chiral liquid crystal (CLC) systems with a deformed lying helix (DLH). The lasing is studied for both odd- and even-order field-induced stop-bands, which are characteristic exclusively of the DLH state. The DLH state is achieved in special CLC cells with periodic boundary conditions, when the surface alignment is flipped between planar and vertical states. The alignment surfaces are prepared using focused ion-beam lithography. In an electric field, such CLC systems undergo an orientational transition, when the initial Grandjean-plane texture with the helix axis perpendicular to the CLC layer is transformed into the DLH state with the helix axis oriented in the plane of the layer. Due to field-induced strong deformation, the DLH system is characterized by a set of photonic stop-bands with a fine spectral structure; namely, on these fine-structured sub-bands, we have observed and studied the low-threshold lasing effect.

Liquid-crystal metasurfaces: Self-assembly for versatile optical functionality

“…Subjecting a self-twisting cholesteric to untwisting homogeneous electric field and inhomogeneous alignment by substrates patterned with stripes commensurate with the helix periodicity [101], it was possible to stabilize a deformed lying helix (DLH) state manifesting itself by a strongly enhanced first-order diffraction and facilitating lasing in the waveguide regime along the LC layer [102].…”

Waveguide Properties of Homogeneously Aligned Liquid Crystal Layers between ITO Electrodes and Thin Alignment Films

“…Along with well-known display applications, liquid crystals (LCs) are of great interest for various photonic devices. These are electrically controlled beam-steering devices and switched gratings [1,2], lenses and arrays of high-aperture lenses [3][4][5][6][7], liquid crystal metasurfaces [8][9][10], as well as liquid crystal light amplifiers and microlasers [11][12][13][14][15][16]. In many cases, the operation of these devices presupposes an effective waveguide mode of light propagation.…”

“…Recently, the waveguide mode was also proposed for the display applications [20]. However, in recent decades, this regime has also become attractive from the point of view of laser generation in liquid crystal layers [14][15][16]. For example, [16] reports a significant decrease in the generation threshold in the LC lasers when using the in-plane geometry utilizing the waveguide mode.…”

“…For example, [16] reports a significant decrease in the generation threshold in the LC lasers when using the in-plane geometry utilizing the waveguide mode. In [14], a relatively low-threshold laser effect in the waveguide mode was obtained using a liquid crystal structure with a deformed lying helix. However, a deformed lying helix structure occurs only in the presence of an electric field, which in turn inevitably implies the existence of electrodes that bound the LC layer and, accordingly, waveguide energy losses in the electrodes.…”