A spatial light modulator that uses scattering in a cholesteric liquid crystal

Area of Science:

• Materials Science
• Optoelectronics

Background:

• Cholesteric liquid crystals exhibit strong light scattering in their random-domain texture.
• Electric field application can induce phase transitions in liquid crystals.

Purpose of the Study:

• To develop a polarizer-free spatial light modulator (SLM) utilizing the electric-field-induced phase transition of cholesteric liquid crystals.
• To characterize the performance and transmission range of the developed SLM.

Main Methods:

• A 20x20 pixel array of indium-tin-oxide electrodes was fabricated on a glass substrate.
• Cholesteric liquid crystal (5 μm helical pitch) was sandwiched between glass plates with a 20 μm gap.
• Electrical voltage (7-27 V) was applied to individual pixels to control light transmittance.

Main Results:

• The SLM transitioned from a scattering translucent state to a transparent homeotropic phase upon voltage application.
• Pixel transmittance was controllable from 0% to 40% within the 7-27 V range.
• The modulator demonstrated a wide transmission range from ultraviolet (350 nm) to infrared (>800 nm).

Conclusions:

• The developed cholesteric liquid crystal SLM operates without polarizers, offering efficient light modulation.
• Its broad spectral transmission and polarizer-free operation make it suitable for controlling lamp spectra in spectroscopy.