Photonic-crystal-fiber optical diode

Two cascaded hollow-core photonic-crystal fibers with slightly shifted, but still overlapping transmission peaks are shown to function as an optical diode. A short laser pulse with a spectrum falling within the passband of one of the fibers, but outside the passband of the second fiber, experiences spectral broadening due to self-phase modulation as it propagates through the first fiber. A part of its spectrum is then transmitted through the second fiber. An identical short pulse propagating in the opposite direction is blocked by the second fiber with a shifted passband. Such an optical diode can be employed to switch and decouple ultrashort laser pulses within a broad range of laser intensities, including high-intensity laser pulses.