Electrically tunable laser based on oblique heliconical cholesteric liquid crystal.
A cholesteric liquid crystal (CLC) formed by chiral molecules represents a self-assembled one-dimensionally periodic helical structure with pitch [Formula: see text] in the submicrometer and micrometer range. Because of the spatial periodicity of the dielectric permittivity, a CLC doped with a fluorescent dye and pumped optically is capable of mirrorless lasing. An attractive feature of a CLC laser is that the pitch [Formula: see text] and thus the wavelength of lasing [Formula: see text] can be tuned, for example, by chemical composition. However, the most desired mode to tune the laser, by an electric field, has so far been elusive. Here we present the realization of an electrically tunable laser with [Formula: see text] spanning an extraordinarily broad range (>100 nm) of the visible spectrum. The effect is achieved by using an electric-field-induced oblique helicoidal (OH) state in which the molecules form an acute angle with the helicoidal axis rather than align perpendicularly to it as in a field-free CLC. The principal advantage of the electrically controlled CLCOHlaser is that the electric field is applied parallel to the helical axis and thus changes the pitch but preserves the single-harmonic structure. The preserved single-harmonic structure ensures efficiency of lasing in the entire tunable range of emission. The broad tuning range of CLCOHlasers, coupled with their microscopic size and narrow line widths, may enable new applications in areas such as diagnostics, sensing, microscopy, displays, and holography.
Liquid Crystal Institute, Kent State University, Kent, OH 44242.|Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
Jie
J
Xiang
Liquid Crystal Institute, Kent State University, Kent, OH 44242.|Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
Andrii
A
Varanytsia
Liquid Crystal Institute, Kent State University, Kent, OH 44242.|Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
Fred
F
Minkowski
Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3UE, Scotland, United Kingdom.
Daniel A
DA
Paterson
Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3UE, Scotland, United Kingdom.
John M D
JM
Storey
Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Aberdeen AB24 3UE, Scotland, United Kingdom.
Corrie T
CT
Imrie
Liquid Crystal Institute, Kent State University, Kent, OH 44242; olavrent@kent.edu mpalffy@kent.edu.|Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
Oleg D
OD
Lavrentovich
Liquid Crystal Institute, Kent State University, Kent, OH 44242; olavrent@kent.edu mpalffy@kent.edu.|Chemical Physics Interdisciplinary Program, Kent State University, Kent, OH 44242.
Peter
P
Palffy-Muhoray
cholesteric liquid crystals; electric tunability; heliconical structure; lasing