Electrically controllable laser based on cholesteric liquid crystal with negative dielectric anisotropy

Abstract

This work examines a planar cholesteric liquid crystal ͑CLC͒ cell with a negative dielectric anisotropy, doped with laser dye, as an electrically tunable one-dimensional photonic crystal laser device. The lasing wavelength is demonstrated to be tunable by applying a voltage. Additionally, lasing can be switched on and off changing the frequency of the applied voltage. Wavelength tuning caused by the shift of the reflection band of CLC is attributed to the electrohydrodynamical effect in the negative dielectric cell.

Thermal tuning band gap in cholesteric liquid crystals

“…In recent years, significant progress has been made in the use of cholesteric liquid crystals (CLCs) as passive polarising elements in laser cavities [1][2][3][4][5][6][7][8][9][10]. CLC materials with a pitch comparable to the optical wavelength can be regarded as a class of one-dimensional photonic crystals exhibiting a wider band gap and narrower line widths for modes closer to the band edge.…”

Simultaneous red–green–blue reflection and wavelength tuning from an achiral liquid crystal and a polymer template

“…However, a marked deterioration in the quality of the macroscopic helix can result due to the presence of EHDIs. [13,14] There have also been a number of reports on wavelength tuning using polymer-stabilized N*LCs; [15][16][17][18][19][20][21] however, it should be noted that this too involved a Helfrich deformation and a deterioration of the structure was observed. Consequently, direct electrical control of the N*LC using such methods does not generally permit a smooth change of the reflected wavelength as the quality of the periodic structure is not maintained.…”

Liquid-crystal photonic applications

“…116,117 Voltage tuning may seem to be an easy way, but it is not because an applied voltage will cause a distortion of the helical structure and thus will prevent lasing. 118 Therefore, one must resort to certain tricks to achieve voltage tuning, such as negative dielectric chiral materials 119 or by using smectic LC. 120 Two other classes of liquid-crystal lasers can be identified in which there is no intrinsic chirality or periodicity in the liquid-crystal.…”