Voltage dependence of microsecond switching in a nematic optical phase modulator

Abstract

A study of the temporal response of a biased planar nematic liquid crystal to short (∼10 μs) voltage pulses is presented. The resulting optical phase shift varies quadratically with time during the first 2 μs after switching the voltage on and then linearly. A theoretical model is developped starting from the Leslie-Ericksen theory which describes the investigated phase modulation in the microsecond time scale.

Active Q-Switching of a Solid State Laser Using Nematic Liquid Crystal Modulators

“…These modulators are rather fast (few nanoseconds) but require high driving voltages of typically several kilovolts. Recently, fast electro-optical switching with planar nematic liquid crystals using multipass and also Fabry-Ptrot modulators has been also reported [5,6]. By using short driving pulses of only 15OV, we achieved microsecond switching times for nematic planar cells (NPC) and even submicrosecond switching in case of nematic Fabry-Perot modulators (NFPM).…”

Submicrosecond switching with a Fabry–Perot interferometer containing a nematic liquid crystal

“…It is instructive to compare the switching times obtained with the multipass phase modulator 11,16 and the technique developed in the present work. Using a phase modulator of thickness d 1 ϭ22 m at 28°C with Nϭ3 passes, V 0 ϭ1.13 V, and V T ϭ69 V we obtained experimentally t /N ϭ4.0 s. On the other hand, with a Fabry-Perot interferometer at the same temperature, the same voltages V 0 , V T , and slightly larger cell thickness (d 2 ϭ26 m͒ we obtained t /F ϭ2.6 s. Since the switching time is proportional to the cell thickness in both cases, it follows from these experiments that…”

“…It is interesting to note that a similar relation can also be obtained for the multipass phase modulator. 11 The similarity is perfect, if the finesse in Eq. ͑14͒ is replaced by the number N of light passes for a corresponding multipass modulator.…”

Fast phase modulation using dual‐frequency nematic liquid crystals

“…Typical values of the rotational viscosity for the 2f-LCM are in a range of 0.4-0.7 Pa-sec. In the case of nonchiral LCs, the free-energy density F is expressed in terms of both the elastic and electric-field energy densities as follows: (6) where K ii are the elastic modules attributed to different types of deformations. The electric-field contribution is expressed in terms of electric displacement D z , which remains independent of z due to the negligible conductivity of the LC.…”

“…It is well known that nematic liquid crystals (NLCs) can be used as phase retarders in adaptive optics. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] The fieldcontrolled optical phase modulation realized in such devices appears as a result of field-driven NLC director (optical axis) reorientation. For instance, in LC cells with planar alignment, the initial director field distribution can be switched by an electric field to the homeotropic state, when the optical axis becomes normal to the LC layer.…”