RESUMO
We describe and demonstrate a method to induce a single-sideband serrodyne-like optical frequency shift in an all-fiber device. The time-varying phase-shift is generated by cross-phase modulation in a nonlinear fiber. Unlike electro-optic based serrodyne methods, which require a high-fidelity and high-bandwidth analog electrical ramp modulation signal, the proposed optical method uses a simple pulsed pump and can be made simultaneously both low-loss and polarization-independent. We demonstrate the technique by shifting a 1550 nm optical signal 150 MHz in a 1.5 dB insertion-loss polarization-independent frequency shifter and show a pathway to multi-GHz shifting frequencies.
RESUMO
High speed and high sensitivity time-of-flight lidar is demonstrated by judiciously choosing the repetition rates of a pulsed optical source and the gate rate of a GHz gated single photon detector. Sub-mm ranging can be performed in sub-ms time scales at low received powers. We also demonstrate a method to extend the unambiguous measurement range by simultaneously transmitting multiple optical pulse rates and measuring the return signal with a single detector.
RESUMO
Dynamic optical nonlinearities are investigated with a dual-beam (pulsed-pump, cw probe) Z-scan technique. Monitoring of probe transmission after strong pump excitation permits determination of time-varying parameters such as nonlinear refraction n(I, t) and absorption alpha(I, t). Continuous time resolution provides an efficient means of measuring and distinguishing fast and slow nonlinear mechanisms such as electronic, free-carrier, and thermal effects observed in semiconductors. We demonstrate this technique in CdTe and measure bound-electronic refraction; two-photon absorption; free-carrier refraction, absorption, and diffusion; thermal refraction and temperature changes; and related time constants.
