Two-way wavelength conversion for visible and infrared signal pulses

Two-way wavelength conversion was achieved for visible and infrared signal pulses by using a phosphorescent disk. When a visible (530 nm) or infrared (980 nm) laser beam was focused on the disk, absorbed photons created bright spots that emitted both visible and infrared phosphorescence (upconversion and downconversion). Although the phosphorescence lasted for 1 ms, a pulse signal of 1 MHz (1 μs period) was detected successfully by circulating the bright spots on the disk (a time–space conversion method). In comparison with downconversion, upconversion was easier to achieve for high-frequency signals, since the two-photon absorption process prevented overlapping of adjacent spots by restricting the phosphorescence spot size.