Slowing sub-picosecond laser pulses with 0.55 mm-thick cholesteric liquid crystal

Extraordinarily thick well-aligned planar cholesteric liquid crystal (CLC) cells with low scattering loss have been successfully fabricated using a field-assisted self-assembly technique. These cells exhibit excellent 1D photonic crystal properties such as photonic bandgap and strong group velocity dispersion at the band edges and enable several all-optical ultrafast laser pulse modulation operations. In particular, we report an experimental observation of the clear separation of ~1 ps between the normal and slow 600 fs light pulses after traversing a 0.55 mm-thick CLC. With simple optimization procedures, such as tuning the photonic band-edge and laser wavelength, and use of more appropriate laser pulse duration and bandwidth, one could realize a much larger effect. These extraordinarily thick CLCs have previously also demonstrated their capabilities for direct compression, stretching and recompression of sub-picosecond pulses, and thus present themselves as promising compact, all-optical and versatile alternatives to existing materials for slow-light production and ultrafast pulse modulation operations.