Response Of Semiconductor Optical Amplifiers Research Articles

The response of semiconductor optical amplifiers containing lateral composition modulation in the quantum wells

Tensile strained quantum wells are used to change the polarization sensitivity of semiconductor optical amplifiers. However, lateral composition modulation (LCM), which is present in the quantum wells of the device, is shown to impact the device performance. A broadening of the spectral gain is seen as recombinations from the conduction band to the heavy hole band in the In-rich regions of the LCM. This additional component to the gain from the quantum well will reduce the device gain efficiency at a specific wavelength for a given current, or it may be used to broaden the gain spectrum of an individual quantum well.

Analysis of the Dynamic Responses of SOA Wavelength Converters Using Linear Frequency Resolved Gating Technique

This letter demonstrates the applicability of the linear frequency resolved optical gating technique for the complete characterization of the fast dynamic response of semiconductor optical amplifiers (SOAs) when operating as wavelength converters. We have investigated both the cross-gain modulation and cross-phase modulation responses to short pump signals, using an SOA Mach-Zehnder interferometer in a pump-probe configuration. A blind deconvolution algorithm has then been used to retrieve the electric field profiles of both the signal and the gate function.

Theoretical study on ultrafast response of semiconductor optical amplifier

We proposed a novel method to analyze the propagation of sub-picosecond optical pulses through semiconductor optical amplifiers(SOA), fully considering spectral dispersion of ultrashort pulses. A reasonable model is established via sampling the pulses simultaneously in time domain and frequency domain. Based on the established model, we observed an evident shift of the pulse spectrum, which agrees well with the experiment results in literature. Further, the relationship is discussed respectively between the value of shift and several external conditions, including wavelength, energy, width of the pulse, length of SOA and injected current. Gain suppression induced by ultrafast nonlinearities including carrier heating, spectral hole burning and two-photon absorption is described in detail, employing two-beam configuration. The simulated results give good guidance to the improvement of ultrafast dynamic characteristics of SOAs.

Variation of Carrier Lifetime during the Dynamic Response of Semiconductor Optical Amplifier to Ultra-short Optical Pulse

Article Variation of Carrier Lifetime during the Dynamic Response of Semiconductor Optical Amplifier to Ultra-short Optical Pulse was published on June 1, 2004 in the journal Journal of Optical Communications (volume 25, issue 3).

A time-domain computer simulator of the nonlinear response of semiconductor optical amplifiers

We present a computer simulator of semiconductor optical amplifiers. The nonlinear input-output response of the device is characterized in terms of a complex gain, representing the accumulated gain and wavevector change of the propagating field across the active waveguide. We account for the gain saturation induced by stimulated recombination and by the perturbation of the carrier quasi-equilibrium distribution within the bands. A rigorous elimination of the spatial coordinate allows us to reduce the description of the amplifier dynamics to the solution of a set of ordinary differential equation for the complex gain. If the waveguide internal loss is negligible, the spatial inhomogeneity of the complex gain is implicitly yet exactly taken into account by the reduced model. The accuracy of the reduced model is the same for models based on the direct solution of the set of partial differential equations describing the interaction between the optical field and the active semiconductor waveguide, but the model is computationally much simpler. To preserve the input-output characteristics of the model, we include the amplified spontaneous emission noise in the device description by an equivalent signal applied to the device input and amplified by the saturated gain. At the expense of a minor increase of the program complexity, the waveguide internal loss may also be included. We report on the comparison between the output of the simulator and the results of four-wave mixing experiments in various pump-signal configurations. Good agreement is obtained.

Separation of coherent and incoherent nonlinearities in a heterodyne pump-probe experiment

We demonstrate that the transient coherent nonlinearity (coherent artifact) affecting the pump-probe response of semiconductor optical amplifiers can be experimentally separated from the incoherent transient. The technique is based on measuring the mirror component of the coherent artifact which is a background-free four--wave mixing signal at a different frequency with respect to the transmitted probe in a heterodyne detection scheme. Measurements on amplifiers of different length reveal strong deviations from the commonly expected symmetric shape of the coherent artifact in case of long waveguides.

Modelling and experimental measurements of the switching behaviour of semiconductor optical amplifiers

A numerical model for the analysis of the switching response of semiconductor optical amplifiers is presented. Output phase and output power behaviour can be derived. This model considers the amplifier longitudinal nonuniformity related to the variation of the carrier and photon density along the device. Auger recombination and spontaneous and stimulated emissions are included in the model. The gain is considered via the parabolic band approximation. The carrier density distribution appears to play a key role in the amplifier behaviour since the computed results exhibit differences from uniform models. The dynamic evolution of the local carrier and photon density can be derived. This information will prove extremely useful in applications other than switching. The results for various rising and falling steps of electrical current are compared with experimental measurements. Good agreement is obtained for both the phase and the power response, supporting the validity of the model. The device chirping characteristics are analysed and discussed.