Optical testability in semiconductors with density-dependent carrier lifetimes

Jesper Mørk, Rasmus Kjær, M. van der Poel +2 more

Experimental demonstration and theoretical analysis of slow light in a semiconductor waveguide at GHz frequencies slow-down of light by a factor of two in a semiconductor waveguide at room temperature with a bandwidth of 16.7 GHz using the effect of coherent pulsations of the carrier density. The achievable delay is shown to be limited by the short lifetime. The maximum time delay observed reflects an approximately two-fold increase of the group refractive index, corresponding to a time delay of approximately 20 % of the carrier (population) lifetime. The experimental observations are well-explained by a model accounting for the absorption saturation in the waveguide, when using a lifetime that depends on the reverse bias.

Stanley Desmond Smith, Brian S. Wherrett

M.J. Adams, H.J. Westlake, M.J. O’Mahony

Dispersive bistability arising from the carrier-dependence of the refractive index has been observed in semiconductor lasers operated just below threshold with a small injected optical signal. The minimum optical input required for switch-up is as low as 1 μW for InGaAsP amplifiers at 1.55 μm(1) and 1.3 μm(2) (cf 30 μW for GaAs devices(3)). As yet, reliable measurements of the dynamic response are not (4) available, although we predict recovery times to be on the order of carrier lifetimes, ie a few nanoseconds at room temperature. This contribution will review our experimental and theoretical work on 1.55 μm amplifier bistability and set it in the context of other semiconductor bistable optical devices.

Stanley Desmond Smith

Kamel Bencheikh, Alejandro M. Yacomotti, P. Grinberg +4 more

Summary form only given. We implement coherent population oscillation and carrier-induced nonlinear refractive index in a semiconductor active nanocavity to strongly increase the photonic lifetime and manipulate its optical response.The so-called photonic crystal L3 cavity, given by three missing holes in a 2D photonic crystal (2D-PhC), is an emblematic illustration of a nanocavity with strong light confinement due to high-Q resonance and small mode volume [1]. Strong electronic confinement can also be achieved provided the cavity contains active semiconductor nanostructures such as quantum wells (QWs) or dots. These two effects lead to the enhancement of the light-matter interaction and, potentially, to a modification of photonic, electronic and thermal characteristic times. Thus, semiconductor 2D-PhC L3 nanocavities are excellent candidates for the implementation of advanced nonlinear photonic interactions. In this work we study the combined effects of both coherent population oscillation (CPO) and carrier-induced nonlinear dephasing in the photon lifetime of a L3 cavity incorporating 4 InGaAsP/InGaAs QWs. The CPO induces a decrease of the group velocity through a strong dispersion of the refractive index (i.e. slow light effect) while the nonlinear phase shift, if implemented close to the bistability threshold, ends up with a strong slowing down of the optical response. The resulting cavity lifetime strongly depends on the control parameters. It is then possible to actively control the photon lifetime of the nanocavity, to enhance its quality factor, to achieve differential amplification under the slow-light regime and to benefit from frequency pulling During this presentation we will discuss theoretically [1] all these aspects with respect to the role of CPO and dynamical nonlinear responses. We will further present recent experimental results [2] demonstrating the enhancement by two orders of magnitude of the cavity lifetime together with the frequency pulling effect.Γ

Chi C. Sung, C. M. Bowden