We demonstrate a non-mechanical on-chip optical beam steering device using the photonic crystal waveguide with a double periodic structure that repeats the increase and decrease of hole diameter. Guided slow light in this waveguide is radiated to be a light beam. Slow light shows strong dispersion, which allows a deflection angle of approximately 10 times that of a normal diffraction grating. We fabricated the device using complementary metal oxide semiconductor process and observed a beam deflection angle of 24° in the longitudinal direction with maintaining the divergence angle of 0.3° when the wavelength was changed by 27 nm. Four such waveguides were integrated, and one of them was selected by a Mach-Zehnder optical switch. Then, the lateral beam steering was obtained when a cylindrical lens was placed above these waveguides. By combining the longitudinal and lateral beam steering, the collimated beam was scanned two-dimensionally with 80 × 4 resolution points.
We report what we call co- and counter propagating slow-light systems based on the high nonlinearity in Si lattice-shifted
photonic crystal waveguides (LSPCWs). The intense slow-light pulse, as a control pulse, efficiently generates
two-photon absorption and carrier plasma effects, which tunes the dispersion characteristics of the LSPCWs and
spectrum of copropagating or counter-propagating slow-light pulse, as a signal pulse. Using the control pulse, we
succeeded in experimentally demonstrating adiabatic wavelength conversion and its enhancement, delay tuning of up to
10 ps with a response time <10 ps, and temporal pulse compression of factor 9.9 in the signal pulse. Furthermore, we
discussed theoretically the collision and reflection of the signal pulse counterpropagating against the control pulse
through the photonic-bandgap shift, resulting in a large Doppler shift. Considering the detail of these phenomena, we
clarified the relation and difference between the adiabatic wavelength conversion, cross-phase modulation, and Doppler
shift, which have been unclear so far.
We demonstrated ultrafast delay tuning of slow-light pulse with a response time < 10 ps. This is achieved using two
types of slow light: dispersion-compensated slow light for the signal pulse; and low-dispersion slow light to enhance the
nonlinear effect of the control pulse. These two slow light are generated simultaneously in lattice-shifted photonic crystal
waveguides, arising from flat and straight sections of the photonic band, respectively. The control pulse blue-shifts the
signal pulse spectrum, through dynamic tuning and cross-phase modulation caused by the plasma effect of two-photonabsorption
carriers. This changes the delay by up to 10 ps only when the two pulses overlap within the waveguide, and
enables an ultrafast tuning that is not limited by the carrier lifetime. Using this, we succeeded in the delay tuning of one
target pulse within a pulse train with 12 ps intervals.