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Electrically controllable liquid crystal random lasers below the Fréedericksz transition threshold
Chia-Rong Lee1, Jia-De Lin, Bo-Yuang Huang
1Institute of Electro-Optical Science and Engineering and Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan. crlee@mail.ncku.edu.tw
Optics Express
|March 4, 2011
Summary
Researchers demonstrate electrically controllable random lasers below threshold voltage in dye-doped liquid crystal cells. Adjusting voltage below threshold alters lasing intensity and energy thresholds by controlling liquid crystal order and photon scattering.
Area of Science:
- Photonics
- Materials Science
- Condensed Matter Physics
Background:
- Random lasers offer unique properties due to feedback from scattering media.
- Controlling random laser output is crucial for practical applications.
- Dye-doped liquid crystals (DDLCs) are promising gain media for tunable lasers.
Purpose of the Study:
- To investigate the electrical control of random lasers below threshold voltage in DDLCs.
- To explore the influence of azo-dye addition on this electrical controllability.
- To elucidate the underlying physical mechanisms governing the observed phenomena.
Main Methods:
- Fabrication of dye-doped liquid crystal cells with and without azo-dye.
- Experimental measurements of random laser characteristics (intensity, threshold) under varying applied voltages below the Fréedericksz transition.
- Analysis of liquid crystal orientational order and photon scattering properties.
Main Results:
- Electrical control of random laser intensity and energy threshold achieved below threshold voltage.
- Increasing applied voltage below threshold decreases lasing intensity and increases energy threshold.
- Azo-dye addition narrows the effective voltage range for this control.
Conclusions:
- Below-threshold electric fields effectively reduce spatial fluctuations in liquid crystal order, enhancing photon diffusion and decreasing scattering.
- This mechanism explains the observed decrease in lasing intensity and increase in energy threshold.
- The study establishes a novel method for tuning random laser properties using electric fields in DDLCs.
