Variable optical delay using population oscillation and four-wave-mixing in semiconductor optical amplifiers

Abstract

We investigate variable optical delay of a microwave modulated optical beam in semiconductor optical amplifier/absorber waveguides with population oscillation (PO) and nearly degenerate four-wave-mixing (NDFWM) effects. An optical delay variable between 0 and 160 ps with a 1.0 GHz bandwidth is achieved in an InGaAsP/InP semiconductor optical amplifier (SOA) and shown to be electrically and optically controllable. An analytical model of optical delay is developed and found to agree well with the experimental data. Based on this model, we obtain design criteria to optimize the delay-bandwidth product of the optical delay in semiconductor optical amplifiers and absorbers.

Theory of Optical-Filtering Enhanced Slow and Fast Light Effects in Semiconductor Optical Waveguides

“…We theoretically analyze the slow and fast light effects in SOA structures due to CPO effects by using a wave mixing description [5], [6]. Wave mixing in active semiconductor waveguides has contributions from carrier density depletion, carrier heating (CH), spectral hole burning (SHB), as well as two-photon absorption (TPA) and Kerr effects [22].…”

“…Similarly, gain saturation is governed by the carrier (pump) signal, corresponding to . By assuming, without loss of generality, the input electric field to be real and defining the input conditions as (4) then a general analytical solution to (2) can be obtained for an SOA with given device length (details in Appendix) (5) The common complex amplification factor is (6) and the gain grating related complex amplification factor is (7) Here, and indicate the real and imaginary part of , respectively. The integrals are determined by the input and output optical power of the SOA, which can be calculated by solving the CW optical power propagation equation for the SOA numerically [5], [6].…”

“…This effect relies on the beating between two externally injected laser beams, or a single intensity-modulated laser beam with sidebands, which leads to oscillations of the electron density in the medium, which in turn alter the effective index seen by the optical signal. In general, the effect can therefore be described as a wave mixing phenomenon, where interactions between the frequency components are mediated by the complex susceptibility, which in semiconductor structures has contributions from various carrier dynamical processes [5], [6]. It has by now been experimentally demonstrated that light-speed control can be realized by CPO effects in a number of different semiconductor structures, i.e., bulk, quantum well (QW) or QD semiconductor optical amplifiers (SOAs) [6]- [10], electro absorbers (EAs) [5], and integrated SOA-EA pairs [11], [12].…”

“…However, the maximum phase shift and bandwidth will be limited by different effects [14]. In both SOAs and EAs, the carrier lifetime sets an important limit [5], [6]. For absorbing media, the residual loss further limits the achievable delay [6].…”

“…In both SOAs and EAs, the carrier lifetime sets an important limit [5], [6]. For absorbing media, the residual loss further limits the achievable delay [6]. The amplified spontaneous emission (ASE) limits the available SOA gain, and hence the phase change, in long amplifiers [15].…”