Electrically tunable laser based on oblique heliconical cholesteric liquid crystal

Area of Science:

• Materials Science
• Optics and Photonics
• Condensed Matter Physics

Background:

• Cholesteric liquid crystals (CLCs) exhibit self-assembled helical structures enabling mirrorless lasing when doped with fluorescent dyes.
• Tuning CLC laser wavelength by chemical composition is possible, but electric field tunability, a highly desired feature, has remained elusive.
• Existing CLC laser tuning methods lack the broad range and electrical control necessary for advanced applications.

Purpose of the Study:

• To achieve electrically tunable laser emission from cholesteric liquid crystals (CLCs) over an unprecedentedly broad spectral range.
• To investigate the mechanism of electric field-induced tuning in CLCs.
• To demonstrate the potential of electrically tunable CLC lasers for various technological applications.

Main Methods:

• Fabrication of CLC lasers incorporating fluorescent dyes.
• Application of an electric field parallel to the helical axis to induce an oblique helicoidal (OH) state.
• Optical pumping of the CLC-OH system to achieve lasing and spectral analysis.

Main Results:

• Realization of an electrically tunable CLC laser with a broad tuning range exceeding 100 nm across the visible spectrum.
• Demonstration that the electric field induces an oblique helicoidal (OH) state, altering the helical pitch.
• Preservation of the single-harmonic structure in the CLC-OH state, ensuring efficient lasing across the entire tuning range.

Conclusions:

• The electric-field-induced oblique helicoidal (OH) state provides an effective method for broad-range electrical tuning of CLC lasers.
• The microscopic size, narrow linewidths, and broad tunability of CLC-OH lasers offer significant advantages over existing technologies.
• These tunable CLC-OH lasers hold promise for advancements in diagnostics, sensing, microscopy, displays, and holography.