ABSTRACT
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ABSTRACT
Electrical injection lasers emitting in the 1.3 µm wavelength regime based on (GaIn)As/Ga(AsSb)/(GaIn)As type-II double "W"-quantum well heterostructures grown on GaAs substrate are demonstrated. The structure is designed by applying a fully microscopic theory and fabricated using metal organic vapor phase epitaxy. Temperature-dependent electroluminescence measurements as well as broad-area edge-emitting laser studies are carried out in order to characterize the resulting devices. Laser emission based on the fundamental type-II transition is demonstrated for a 975 µm long laser bar in the temperature range between 10 °C and 100 °C. The device exhibits a differential efficiency of 41 % and a threshold current density of 1.0 kA/cm2 at room temperature. Temperature-dependent laser studies reveal characteristic temperatures of T0 = (132 ± 3) K over the whole temperature range and T1 = (159 ± 13) K between 10 °C and 70 °C and T1 = (40 ± 1) K between 80 °C and 100 °C.
ABSTRACT
Ultrafast femtosecond timescale dynamics in Vertical External Cavity Surface Emitting Lasers (VECSELs) have recently been employed to achieve record average power and duration mode-locked pulses by employing different types of saturable absorbers and Kerr Lens elements. Microscopic many-body dynamics are expected to dominate when attempting to push pulse durations below 100 fs. We present a preliminary microscopic simulation of ultrafast mode-locking in order to expose the role of hot carrier distributions in establishing ultrafast mode-locking.
ABSTRACT
The development of a disposable amperometric immunomigration sensor for the detection of triazine pesticides in real samples is presented. Thick film electrodes printed on PVC were used as strip-type transducers. Monoclonal antibodies against atrazine and terbutylazine served as biorecognition element. For the generation and amplification of the signal, hapten-tagged liposomes entrapping ascorbic acid as a marker molecule were chosen. A capillary gap and a wicking filter membrane strip served as migration zone. For signal detection on a graphite electrode, liposomes were lysed by Triton X-100 and the released ascorbic acid was quantified at a potential of + 300 mV vs printed Ag/AgCl. Signal response time was 1-3 min, and sensitivity of measurements in tap water was below 1 microgram l-1 of atrazine and terbutylazine. Atrazine determinations in soil extracts correlated well with standard procedures based on ELISA and HPLC.
