A quantum-well-intermixing process for wavelength-agile photonic integrated circuits

Wavelength-agile photonic integrated circuits are fabricated using a one-step ion implantation quantum-well intermixing process. In this paper, we discuss, the issues in processing optimized widely tunable multisection lasers using this technique and present the results achieved using this process. This quantum-well intermixing process is general in its application and can be used to monolithically integrate a wide variety of optoelectronic components with widely tunable lasers.     

Tunable sampled-grating DBR lasers using quantum-well intermixing

Widely tunable lasers are key components for wavelength division multiplexing fiber optic networks. They reduce cost in sparing, enable dynamic networking applications, and present opportunities for future monolithically integrated wavelength division multiplexing components. The sampled-grating distributed Bragg reflector (SGDBR) laser is ideal for these purposes. The authors present a centered quantum-well SGDBR laser which uses quantum-well intermixing in order to improve device characteristics over previous designs. The mode overlap is improved by 50% over the offset quantum-well design, improving the modal gain. Current injection tuning in the intermixed material is demonstrated for the first time; the maximum modal group index change was measured to be 1%.     

Photocurrent spectroscopy for quantum-well intermixed photonic integrated circuit design

Photocurrent spectroscopy is used to characterize band edges in quantum-well intermixed InGaAsP material lattice matched to InP. The band edge absorption data is used as a design tool to predict the dc performance of electroabsorption modulators, and is shown to agree well with data obtained from actual devices. In addition, we demonstrate the presence of an exciton peak in InGaAsP quantum wells, and present its evolution as a function of quantum-well intermixing and reverse bias voltage.     

Widely tunable negative-chirp SG-DBR laser/EA-modulated transmitter

Ten Gb/s low power penalty (<0.5 dB) error-free transmission was achieved through 75 km using a high-performance sampled-grating (SG) distributed Bragg reflector (DBR) laser/EAM transmitter. Large signal chirp measurements show negative chirp operation across the entire tuning range of the devices. An integration-oriented quantum-well-intermixing (QWI) process was employed for the realization of these devices.     

CW operation of 1.55-/spl mu/m bipolar cascade laser with record differential efficiency, low threshold, and 50-/spl Omega/ matching

By electrically segmenting an InP ridge laser and series-connecting the segments, we have created the first highly scalable bipolar cascade lasers. We report room-temperature continuous-wave operation of 12-stage lasers with a record 390% differential efficiency and 2.8-mA threshold, as well as three-stage lasers with 50-/spl Omega/ input impedance and 118% efficiency.     

High efficiency widely tunable SGDBR lasers for improved direct modulation performance

We report on two novel approaches to improve the differential quantum efficiency (DQE) of widely tunable 1.55-/spl mu/m lasers: the bipolar cascade sampled grating distributed Bragg reflector (BC-SGDBR) laser and the gain-levered SGDBR (GL-SGDBR) laser. Each is fabricated on a robust InGaAsP/InP photonic integrated circuit platform. The lasers demonstrate improved direct modulation performance over conventional SGDBR lasers. The BC-SGDBR laser was also monolithically integrated with a semiconductor optical amplifier and photodetector receiver in order to perform wavelength conversion. Error free wavelength conversion at 2.5 Gb/s and improvements in conversion efficiency are demonstrated.     

Decentralized high-dose cytostatic treatment with autologous stem cell support]

In the past high-dose chemotherapy with autologous stem cell support in the treatment of certain types of cancer, was centralized to two hospitals in Norway. Almost three years ago it was decided that the treatment should be offered by all five university hospitals. In the northernmost university hospital of Norway, Troms?, peripheral stem cells were harvested from 29 patients after successful mobilization with chemotherapy and granulocyte colony-stimulating factor (G-CSF). After high-dose chemotherapy, more than 2 x 10(6) CD34-positive stem cells/kg were transplanted in 24 patients and a sign of reconstitution of bone marrow function was achieved with mean time for neutrophils > 0.5x10(9)/l, 9.8 days and for platelets > 20x10(9)/l, 10.8 days. No treatment-related deaths have occurred. Transplantation of selected CD34-positive stem cells has been performed in one patient. Recovery was comparable to the recovery of patients who had undergone transplantation with unselected products. This indicates that even small centres performing as few as ten procedures per year may offer high-dose chemotherapy with autologous stem cell support safely and successfully.     

Macromolecule analysis based on electrophoretic mobility in air: globular proteins

Globular proteins ranging in molecular mass from 5.7 to 669 kDa were separated and analyzed using an aerosol technique based on the electrophoretic mobility of singly-charged molecular ions in air. The ions were produced by electrospraying and drying 100-nm-diameter droplets of a liquid suspension of the proteins, using ionized air to remove the droplet charge due to the spray process. The electrophoretic mobility was measured using a modified commercial continuous-flow differential mobility analyzer operated near atmospheric pressure. An unmodified commercial condensation particle counter was used for detection. The concentrations analyzed ranged from 0.02 to 200 μg of protein/mL of buffer, with a liquid sample flow rate of approximately 50 nL/min. Sampling time of 3 min was used for each complete distribution measured. The electrophoretic mobilities measured were determined entirely from air flow rates, apparatus geometry, and applied potentials. Results were expressed as electrophoretic mobility equivalent diameters using a Millikan formula.     

Diatom frustules as a biomaterial: effects of chemical treatment on organic material removal and mechanical properties in cleaned frustules from two <Emphasis Type="Italic">Coscinodiscus</Emphasis> species

The three-dimensional structure of silica diatom frustules offers a great potential as nanoporous material for several nanotechnological applications, but the starting point for these applications is the ability to obtain clean frustules with sufficient mechanical strength and intact structure. Here, frustules from the diatoms Coscinodiscus centralis Ehrenberg and Coscinodiscus wailesii Gran et Angst are characterized with respect to their structural integrity, content of residual organic biomaterial and their mechanical properties after two cleaning methods using either hydrogen peroxide as oxidizing agent or a combination of a surfactant (sodium dodecyl sulphate) and a complexing agent. Fluorescence microscopy and energy dispersive spectroscopy (SEM/EDS) analysis revealed clear differences regarding the amount of organic residual within the frustules depending on the cleaning process, with little organic material left after the oxidizing method. This method, however, induced a partial cracking of the frustules suggesting an embrittlement due to the cleaning. Nanoindentation confirmed this and showed that the oxidizing method resulted in more brittle frustules compared to the surfactant/complexing method. More efficient cleaning of organic biomaterial may result in more fragile frustules, and the choice of cleaning method must be based on the planned application.