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Normal incidence InAs/In0.15Ga0.85As dots-in-a-well (DWELL) detectors are reported in which the peak operating wavelength was tailored from 7.2 to 11 μm using heterostructure engineering of the DWELL structure. Using an optimized design, a detector with a spectral response spanning the long-wave infrared atmospheric window (8–12 μm) is obtained. Spectral response peaks were observed at λp=10.3 μm and 11.3 μm under positive and negative bias, respectively. These peaks are attributed to bound-to-bound transitions from the InAs quantum dot to the InGaAs well.

Hole drift velocities in n-type In0.53Ga0.47As have been determined experimentally for the first time. Measured values of the frequency response of transit-time-limited InGaAs p-i-n photodiodes were fit with the theoretical response using hole velocity as the only free parameter. Measurements over field strengths from 54 to 108 kV/cm showed the drift velocity to be relatively constant at (4.8±0.2) 106 cm/s, indicating that velocity saturation has occurred at field levels below 54 kV/cm.

mission system based on three polarization channels multiplexing technique. Polarization channels can be received by a simple alignment of the polarization analyzer. The BER better than 10 Ϫ9 was achieved. Transmission quality was not as good as for two channels PDM systems. This results from relatively small value of polarization isolation. ACKNOWLEDGMENTSThe author thanks R&D Polish Telecom for providing the JDSU Optical Network Testers.