Gain and noise properties of InAs/InP quantum dash semiconductor optical amplifiers

Semiconductor optical amplifiers (SOAs) based on nanostructure gain media such as quantum dots (QD) and quantum dashes (QDASH) have several basic characteristics which offer significant performance improvements over commonly used quantum well (QW) or bulk amplifiers. Among these are broadband optical gain bandwidth (which is two to three times broader than that of QW/bulk gain media), fast gain dynamics, large saturation powers, and low a parameter and population inversion factor. Originally, these properties have been demonstrated for QD/QDASH SOAs operating at 1000 nm and 1300 nm. However, it is imperative that QD/QDASH SOAs operating at 1550 nm be materialized in order for them to have the expected impact on fiber-optic communication. Operation at 1550 nm has been achieved using InAs / InP QD and QDASH laser structures. In this paper the unique gain and noise properties of InAs / InP QDASH SOAs operating at 1550 nm will be presented. Specifically, cross-gain-modulation, four-wave-mixing and chirp measurements which explore the complex spectral cross relaxation dynamics of these SOAs will be described and highlighted in the context of simultaneous, distortionless, high bit-rate multiwavelength data amplification, as well as wideband / high-speed optical signal processing applications. Also, an experimental study of the gain and noise in saturated QDASH SOAs will be described together with a theoretical analysis comprising both coherent and incoherent gain phenomena. The impact of the partially inhomogeneously broadened gain spectrum, fast population pulsation dynamics, α parameter and wetting layer density of states on the noise characteristics will be discussed.