Liquid crystal lasers

Researchers at the Centre of Molecular Materials for Photonics and Electronics (CMMPE) (part of the Department's Photonics Research Group) are leading the way towards the development of extremely high colour resolution laser displays using liquid crystal laser technology.

Laser displays are new to the market, and are currently being developed by a number of electronics manufacturers. In a laser display, pixels of light emission are generated from three separate red, green and blue (RGB) laser sources. They therefore have a much narrower spectral linewidth compared to the relatively broadband RGB sources from other display technologies, including CRT, plasma, LCD and even the latest organic light-emitting diode (OLED) displays. When these three narrow linewidth red, green and blue sources are combined in a laser display, they offer unprecedented depths of colour resolution over competing display technologies.

The liquid crystal laser is based on a similar device architecture as a conventional liquid crystal display. Liquid crystals are fast becoming an alternative medium for use as the feedback structure for a wide variety of miniature laser devices. Certain liquid crystal phases, in particular the chiral nematic phase, spontaneously self-organize to form a helical structure with a periodic refractive index. When combined with a gain medium, such as a fluorescent dye, the chiral liquid crystal provides sufficient feedback to generate lasing within a device of thicknesses less than a human hair. Unlike most conventional semiconductor lasers, the emission wavelength of a liquid crystal laser can be dynamically tuned using an applied voltage to alter the degree of periodicity of the macroscopic molecular structure. A further merit of this technology is that the emission can be chosen to be at any desired wavelength across the visible range through careful control, chemically, of the macroscopic material properties. A gradient in the periodicity of the liquid crystal structure can therefore be formed, which gives rise to simultaneous different emission wavelengths across the device. Such a feature is not readily achievable with existing laser technologies.

Liquid crystal lasers, however, are not merely restricted in their use to laser displays. Researchers at CMMPE are also developing applications for their use in infra-red medical diagnostic tools, telecommunication devices and holographic projection.

Source: Cambridge University News