Femtosecond dynamics of the nonlinear anisotropy in polarization insensitive semiconductor optical amplifiers

Abstract

The nonlinear response of polarization insensitive semiconductor optical amplifiers shows that anisotropy may be induced as a function of intensity. With a hetrodyne pump-probe technique, the nonlinear gain and index components may be polarization resolved as well as time resolved. By extending this measurement technique we measure the dynamic anisotropy directly.

Measurement of the interwell carrier transport lifetime in multiquantum-well optical amplifiers by polarization-resolved four-wave mixing

“…Of particular interest is the finite rate at which the carrier densities in neighboring wells reach equilibrium with one another and with the distribution of unconfined carriers in the barrier region. This process has received considerable attention in recent years [1][2][3][4][5][6][7][8] since it has been associated with nonlinear gain compression, and hence the maximum modulation bandwidth of quantum-well lasers.…”

Quantum-well capture and interwell transport in semiconductor active layers

“…Furthermore, if the carrier density modulation is efficiently transferred into the neighbouring compressive wells, an additional contribution to the TE component of the FWM signal can be generated there. We notice that the use of polarization to discriminate between the contributions from tensile and compressive wells in alternating-strain SOAs has been originally demonstrated in a FWM experiment in [51], and it has also been subsequently employed in a time-domain pump-probe experiment [22]. Figure 5(b) gives a schematic representation of the different processes contributing to the FWM signal field E (s) , which can accordingly be written as…”

“…As a result, it is well suited [47] to study of the ultrafast intraband carrier dynamics associated with optical nonlinearities such as carrier heating and spectral hole burning. It is interesting to point out that FWM can be viewed as the frequency-domain counterpart of pump-probe spectroscopy, which has also been applied to SOAs [22,48]: specifically, while pump-probe experiments measure an impulse response function, FWM gives the corresponding frequency response.…”

“…A remarkable result of these early studies was the prediction of an oscillatory dependence of the capture rate on the QW width. The large body of experimental work that followed [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], based on several different techniques, found measured values for the capture lifetime varying over a wide range, from a fraction to tens of picoseconds, depending on the experimental conditions. Similarly, the predicted oscillations with well width were only observed under appropriate conditions [10,18,21], most notably in the low carrier density regime, where the lifetime broadening of the delocalized single-particle states is small.…”

SOA-based all-optical switch with subpicosecond full recovery

“…Essential for SOA-based all-optical switches operating at ultrahigh repetition rates is absence of a carrier lifetime-imposed-long-lived tail, which prevents pattern effects on the switched data-stream from occurring [8]. Switching of ultrashort optical pulses in an SOA-based nonlinear polarization switch has been investigated in [9] in the context of a fundamental investigation of nonlinear anisotropy in polarizationindependent SOAs. The results in [9] suggest that ultrafast operation in an SOA-based nonlinear polarization switch is not possible due to a long-lived tail in the switch recovery.…”