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Droplet Lasers Could Enable New Generation of Display Technology

Researchers have developed a new laser display system that controls light emission through electrically deformable liquid droplets. Published in Advanced Materials, this work demonstrates precise control over individual laser pixels using a combination of optical pumping and electrical switching.

a) A schematic representation of a flat laser display. b) Schematic representations of a self-standing droplet oscillator that attenuates its Q-factor upon elongation induced by an external electric field. c) A scanning electron microscopic image of the self-standing droplet. d) An array of self-standing droplets. The inset shows the unmagnified image. e) Histograms of the diameter (d, left, n = 167) and interval (right, n = 306) of the droplets. (Source: Advanced Materials)

The system employs ionic liquid droplets measuring 30.8 micrometers in diameter, containing laser dye and deposited via inkjet printing. These droplets achieve densities of 650 per square millimeter when printed onto specially engineered silicon nanopillars with superoleophobic properties, creating a contact angle of 155 degrees.

When optically excited, each droplet functions as a miniature laser with a threshold of 109 microjoules per square centimeter. Applying an electric field transforms the droplets into prolate spheroids, reducing their Q-factor from 2.28×10³ to 1.24×10³ and halting laser emission. The researchers demonstrated switching frequencies between 0.025 and 1 Hz in a functional 2×3 array prototype.

The achieved pixel density matches current commercial 40-inch 8K displays at 220 pixels per inch. However, significant engineering challenges remain, particularly in reducing optical pumping power requirements and addressing laser dye degradation over time. Electromagnetic and fluid dynamics simulations validated the underlying physics of droplet deformation and its effects on optical properties.

Reference

M. Kato, J. Miyagawa, S. Noguchi, N. Takada, S. Baba, S. Someya, A. K. Singh, J.-S. Huang, Y. Yamamoto, H. Yamagishi, Optically Pumped and Electrically Switchable Microlaser Array Based on Elliptic Deformation and Q-Attenuation of Organic Droplet Oscillators. Adv. Mater. 2024, 2413793. https://doi.org/10.1002/adma.202413793