P. A. Harten

Ultrafast modulation with subpicosecond recovery time in a GaAs/AlGaAs nonlinear directional coupler

All‐optical modulation is observed at room temperature in a GaAs/AlGaAs multiple quantum well nonlinear directional coupler using femtosecond pulses. The origin of the ultrafast (<500 fs) recovery of the device is attributed to the optical Stark effect.

Noise in a dual dye jet hybridly mode-locked near infrared femtosecond laser

Abstract The noise properties of a near infrared hybridly mode-locked dye laser system operating in the 100 fs pulse regime are investigated. Two closely spaced cavity length values near the zero mismatch point are identified which produce distinctly different pulses. These pulse trains and the pump laser pulse train are examined in the time and frequency domains for the purpose of determining their usefulness for the study of ultrafast physical processes. The differences in pulse energy fluctuation, pulse width fluctuation, and intensity autocorrelation of the two modes of operation are explained in terms of cavity detuning effects.

Optical switching and propagation effects in nonlinear GaAs MQW waveguides

We summarize our ultrafast switching results in GaAs multiple quantum well directional couplers and report on coherent pulse propagation in single strip-loaded GaAs multiple quantum well waveguides. The transmitted pulse shape is measured by sum frequency generation cross-correlation and compared with calculations based on the coupled semiconductor Bloch and Maxwells equations.

Subpicosecond All-Optical Modulation Using The Optical Stark Effect In A Nonlinear Directional Coupler

All-optical modulation in a GaAs/AlGaAs multiple quantum well nonlinear directional coupler is observed at room temperature using femtosecond pulses. The ultrafast (< 1 ps) response and recovery of the device is attributed to the optical Stark effect. All-optical switching in various nonlinear optical devices is of interest because of its possible application in high-speed photonic switches. In semiconductor devices, which exploit the relatively large optical nonlinearities near a semiconductor bandedge, the source of the nonlinearity is typically the presence of free carriers photoexcited by a temporally short pump (i.e. control) beam. Previously we have demonstrated all-optical switching both in a GaAs/AlGaAs multiple quantum well (MQW) nonlinear etalon, as well as in a MQW nonlinear directional coupler (NLDC) using real carrier excitations to generate the nonlinearities. In both cases the device has a response which follows the pulse, and a recovery time which was limited to ≈10ns by the recombination and the diffusion of the photo-generated carriers. Recently, the operation of a nonlinear etalon with a subpicosecond recovery time was demonstrated. This was accomplished by using femtosecond pulses tuned in the semiconductors transparency region to generate instantaneous nonlinearities which were present only while the pump travelled through the etalon. In this case the source of the optical nonlinearity was the now well known optical Stark effect. Here we report the first observation of ultrafast switching, including < 1ps recovery time, in a GaAs/AlGaAs NLDC. We believe the optically-induced temporally-short index change responsible for this fast switching is generated by the optical Stark effect.