Light-controlled change in the helical pitch and broadband tunable cholesteric liquid-crystal lasers

This paper presents an overview of the results obtained in recent investigations of the control over the helical pitch under irradiation and the use of these data for the design of compact broadband tunable lasers based on dye-doped cholesteric liquid crystals. It is demonstrated that a reversible change in the lasing frequency can be achieved upon exposure to two low-power light-emitting diodes. Another alternative approach to the generation of tunable laser radiation in the visible and ultraviolet spectral regions (370–680 nm) in a specially designed cell with a cholesteric liquid crystal that is doped with several dyes and possesses a helical pitch gradient is considered.