KIF5B plays important roles in dendritic spine plasticity and dendritic localization of PSD95 and FMRP in the mouse cortex in vivo.

Kinesin 1 (KIF5) is one major type of motor protein in neurons, but its members' function in the intact brain remains less studied. Using in vivo two-photon imaging, we find that conditional knockout of Kif5b (KIF5B cKO) in CaMKIIα-Cre-expressing neurons shows heightened turnover and lower stability of dendritic spines in layer 2/3 pyramidal neurons with reduced spine postsynaptic density protein 95 acquisition in the mouse cortex. Furthermore, the RNA-binding protein fragile X mental retardation protein (FMRP) is translocated to the proximity of newly formed spines several hours before the spine formation events in vivo in control mice, but this preceding transport of FMRP is abolished in KIF5B cKO mice. We further find that FMRP is localized closer to newly formed spines after fear extinction, but this learning-dependent localization is disrupted in KIF5B cKO mice. Our findings provide the crucial in vivo evidence that KIF5B is involved in the dendritic targeting of synaptic proteins that underlies dendritic spine plasticity.

Real-time Fourier-domain optical vector oscilloscope.

To meet the constant demands of high-capacity telecommunications infrastructure, data rates beyond 1 terabit per second per wavelength channel and optical multiplexing are widely applied. However, these features pose challenges for existing data acquisition and optical performance monitoring techniques because of bandwidth limitation and signal synchronization. We designed an approach that would address these limitations by optically converting the frequency limit to an unlimited time axis and combining this with a chirped coherent detection to innovatively obtain the full-field spectrum. With this approach, we demonstrated a real-time Fourier-domain optical vector oscilloscope, with a 3.4-terahertz bandwidth and a 280-femtosecond temporal resolution over a 520-picosecond record length. In addition to on-off keying and binary phase-shift keying signals (128 gigabits per second), quadrature phase-shift keying wavelength division-multiplexed signals (4 × 160 gigabits per second) are simultaneously observed. Moreover, we successfully demonstrate some high-precision measurements, which indicate them as a promising scientific and industrial tool in high-speed optical communication and ultrafast optical measurement.

Near-infrared double-illumination optical-resolution photoacoustic microscopy.

Label-free chemical bond imaging is of great importance in biology and medicine. Photoacoustic imaging at the third near-infrared windows (1600-1870 nm, near-infrared-III) provides a stable molecular vibrational imaging tool for lipid-rich tissue owing to the first overtone transition of the CH bond at 1.7 µm. However, lacking high-energy pulsed laser sources at 1.7 µm and the strong water absorption significantly limit the signal-to-noise ratio of the lipid imaging, especially for thin lipid tissues. To circumvent this barrier, we develop near-infrared-III double-illumination optical-resolution photoacoustic microscopy (DIOR-PAM) for improving the sensitivity of label-free lipid imaging. Using the same laser, DIOR-PAM can enhance the sensitivity by nearly 100%, which we prove in the Monte Carlo simulation. We experimentally demonstrated 50% ~ 100% sensitivity enhancements on nonbiological and biological lipid-rich samples.

Real-time transition dynamics and stability of chip-scale dispersion-managed frequency microcombs.

Femtosecond mode-locked laser frequency combs have served as the cornerstone in precision spectroscopy, all-optical atomic clocks, and measurements of ultrafast dynamics. Recently frequency microcombs based on nonlinear microresonators have been examined, exhibiting remarkable precision approaching that of laser frequency combs, on a solid-state chip-scale platform and from a fundamentally different physical origin. Despite recent successes, to date, the real-time dynamical origins and high-power stabilities of such frequency microcombs have not been fully addressed. Here, we unravel the transitional dynamics of frequency microcombs from chaotic background routes to femtosecond mode-locking in real time, enabled by our ultrafast temporal magnifier metrology and improved stability of dispersion-managed dissipative solitons. Through our dispersion-managed oscillator, we further report a stability zone that is more than an order-of-magnitude larger than its prior static homogeneous counterparts, providing a novel platform for understanding ultrafast dissipative dynamics and offering a new path towards high-power frequency microcombs.

Real-time dynamics and cross-correlation gating spectroscopy of free-carrier Drude slow-light solitons.

Optical solitons-stable waves balancing delicately between nonlinearities and dispersive effects-have advanced the field of ultrafast optics and dynamics, with contributions spanning from supercontinuum generation to soliton fission, optical event horizons, Hawking radiation and optical rogue waves, among others. Here, we investigate picojoule soliton dynamics in silicon slow-light, photonic-bandgap waveguides under the influence of Drude-modeled, free-carrier-induced nonlinear effects. Using real-time and single-shot amplified dispersive Fourier transform spectroscopy simultaneously with high-fidelity cross-correlation frequency resolved optical gating at femtojoule sensitivity and femtosecond resolution, we examine the soliton stability limits, the soliton dynamics including free-carrier quartic slow-light scaling and acceleration, and the Drude electron-hole plasma-induced perturbations in the Cherenkov radiation and modulation instability. Our real-time single-shot and time-averaged cross-correlation measurements are matched with our detailed theoretical modeling, examining the reduced group velocity free-carrier kinetics on solitons at the picojoule scale.

All-optical picoseconds logic gates based on a fiber optical parametric amplifier.

All-optical XOR-, OR-, NOT-, and AND-gate were demonstrated for 10 Gb/s return-to-zero on-off keying (RZ-OOK) signals using a single experimental setup. This setup can be set to output different logic by altering input power, state-of-polarization, center frequencies of input optical signals, and/or input bitstreams. Full-width at half-maximum pulsewidth of the input and the output signals were less than 5.1 ps in all cases showing a possibility of higher data rate operation at 80Gb/s or beyond.