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The electrodes in a carrier-injection-based digital optical switch are separated by a gap of less than 1μm. Good switch performance requires minimal current spreading and effective electrical isolation of these two electrodes without perturbing the underlying guided optical fields. Two methods of such isolation are modeled and experimentally compared. One is the etching of an e-beam-defined 0.5-μm-wide trench down to an etch stop layer, and the other is the implanting of oxygen ions using the electrodes as a shadow mask. Electrical simulation results suggest that injected current magnitudes and carrier concentration profiles are similar with both the trench and the ion implant, and so they should be equally effective in preventing current flow between the two branches. However, experimental results show that ion implantation produces better switching contrasts of greater than 20dB. We attribute this to the fact that implantation using the electrodes as a shadow mask results in an injected carrier distribution that more accurately reproduces the shape of the overlying electrode.The electrodes in a carrier-injection-based digital optical switch are separated by a gap of less than 1μm. Good switch performance requires minimal current spreading and effective electrical isolation of these two electrodes without perturbing the underlying guided optical fields. Two methods of such isolation are modeled and experimentally compared. One is the etching of an e-beam-defined 0.5-μm-wide trench down to an etch stop layer, and the other is the implanting of oxygen ions using the electrodes as a shadow mask. Electrical simulation results suggest that injected current magnitudes and carrier concentration profiles are similar with both the trench and the ion implant, and so they should be equally effective in preventing current flow between the two branches. However, experimental results show that ion implantation produces better switching contrasts of greater than 20dB. We attribute this to the fact that implantation using the electrodes as a shadow mask results in an injected carrier distribu...

Hexagonal lattice photonic crystal microcavities with modified single missing air-hole defects were fabricated in suspended InAs∕InP quantum dot membranes. The cavity modes predicted from finite-difference time-domain simulations are observed in photoluminescence measurements. The resonant energies of the defect modes are tuned across the band gap of the photonic crystal through modifications of the size and position of the inner ring holes surrounding the defect. Up to a 20-fold enhancement of the quality factor of the modes are observed as they are tuned across the band gap, with measured Q values of up to 6000.

Quantum dot laser diodes with up to five well-defined electronic shells are fabricated using self-assembled quantum dots (QDs) grown by molecular beam epitaxy. At 77 K, we tune the lasers from the first to the fourth excited state of the QDs by varying the cavity length, this covers a wavelength range from 869 to 963 nm. At room temperature, we obtain lasing from the second to the fourth excited state covering the 938 to 984 nm wavelength range. For high injection currents, a large part of the QD ensemble contributes at once to the stimulated emission yielding a lasing emission linewidth having a full width at half maximum of 25 nm. By increasing the energy spacing between the QD energy level contributing to the lasing and the wetting layer energy levels, improved thresholds at higher temperatures are observed, leading to lasing below 100 A/cm2 at room temperature.Quantum dot laser diodes with up to five well-defined electronic shells are fabricated using self-assembled quantum dots (QDs) grown by molecular beam epitaxy. At 77 K, we tune the lasers from the first to the fourth excited state of the QDs by varying the cavity length, this covers a wavelength range from 869 to 963 nm. At room temperature, we obtain lasing from the second to the fourth excited state covering the 938 to 984 nm wavelength range. For high injection currents, a large part of the QD ensemble contributes at once to the stimulated emission yielding a lasing emission linewidth having a full width at half maximum of 25 nm. By increasing the energy spacing between the QD energy level contributing to the lasing and the wetting layer energy levels, improved thresholds at higher temperatures are observed, leading to lasing below 100 A/cm2 at room temperature.

An airbridge technique was developed and subsequently employed to fabricate mesoscopic devices, such as parallel quantum point contacts. The airbridge technique mainly involves two different electron sensitive polymers, polymethylglutarimide and polymethyl methacrylate. The airbridge was patterned by electron beam lithography and metal lift-off with bilayer resist. Conductance measurements were performed on the devices at low magnetic fields. The results confirmed both the presence of the elliptical antidot as a negative voltage was applied to the center gate, as well as the nonintrusive nature of the airbridge technique.

A method for stitching error compensation in electron beam lithography by multipass writing of the pattern in the areas spanning the field boundaries is described. This method does not require reducing the write current or changing beam dwell time and was used to correct artificial stitching errors which were deliberately introduced in a layout. SOI-based photonic waveguides with intentional stitching errors of predefined amplitudes and orientation were fabricated. The number of the errors along the waveguides was chosen to produce a measurable optical effect. A corrected version of the same layout was fabricated on the same chip. The optical losses were measured for both the TE and TM polarizations and compared to the results of finite difference time domain simulations. Measurements of optical losses for the waveguides after correction show a clear improvement.