Device performance and wavelength tuning behavior of ultra-short quantum-cascade microlasers with deeply etched Bragg-mirrors

The fabrication and characteristics of edge-emitting quantum-cascade (QC) lasers and microlasers with monolithically integrated deeply etched semiconductor-air Bragg-mirrors based on GaAs is reported. We observe a reduction of the threshold current density by 25% and an increase of the operation temperature by 23 K to a maximum of 315 K for 800 /spl mu/m long devices by employing Bragg-mirrors. Devices with ultra-short cavities of about 100 /spl mu/m (/spl sim/40 times the wavelength) operate up to 260 K. At 80 K, these devices show threshold currents as low as 0.63 A and output levels up to 56 mW. In these devices, longitudinal single mode operation with output levels exceeding 7.7, 5.6, and 2.8 mW was measured at 180, 200, and 240 K, respectively. This can be attributed to the limited gain bandwidth of QC lasers and the large mode spacing in these devices. By temperature control the emission wavelength can be tuned without mode jumps over 80 nm. The feasibility to pre-select the emission wavelength by a direct control of the Fabry-Perot mode was demonstrated by microlasers with 1 /spl mu/m cavity length difference.     

Singlemode InAs/InP quantum dash distributed feedback lasers emitting in 1.9 μm range

Laterally coupled, complex distributed feedback lasers based on InAs/ InGaAs/InAlGaAs/InP quantum dash-in-a-well layers emitting in the 1.9 mum wavelength range were fabricated. Total CW powers above 25 mW at room temperature and sidemode suppression ratios of more than 35 dB are demonstrated, which makes the devices promising for gas sensing applications.     

Micromirror device controlled tunable diode laser diode laser

An electronically controlled external cavity laser diode for fast wavelength tuning and multiple-colour lasing is presented. The spectral-tuning is accomplished by a digital micromirror device. Tuning of 47.4 nm with a tuning speed of 0.85 nm/ms was achieved. Simultaneous emission of up to 9 laser lines is demonstrated     

Room-temperature singlemode continuous-wave operation of distributed feedback GaInNAs laser diodes at 1.5 μm

Room-temperature continuous-wave operation of distributed feedback GalnNAs quantum well laser diodes on GaAs in the 1.5 mum wavelength range is demonstrated for the first time. Singlemode emission with a sidemode suppression ratio of more than 45 dB is obtained at 1486 nm with a threshold current of 44 mA and an external efficiency of 0.06 W/A.     

Respective role of the axial and appendicular systems in relation to the transition to limblessness

The soil nematode Caenorhabditis Elegans (C. elegans) is the most investigated of all multicellular organisms. Since the proposal to use it as a model organism, a series of research projects have been undertaken, investigating various aspects of this organism. As a result, the complete cell lineage, neural circuitry, and various genes and their functions have been identified. The complete C. elegans DNA sequencing and gene expression mapping for each cell at different times during embryogenesis will be identified in a few years. Given the abundance of collected data, we believe that the time is ripe to introduce synthetic models of C. elegans to further enhance our understanding of the underlying principles of its development and behavior. For this reason, we have started the Perfect C. elegans Project, which aims to produce ultimately a complete synthetic model of C. elegans' cellular structure and function. This article describes the goal, the approach, and the initial results of the project.     

Dynamic properties of 1.5 /spl mu/m quantum dash lasers on (100) InP

The static and dynamic properties of state-of-the-art InP -based QDash lasers around 1.55 mum are reported. Demonstrated are ridge waveguide lasers with a total output power of 37 mW and a total slope efficiency of 0.40 W/A that show a 3 dB modulation bandwidth of 8.0 GHz and a modulation efficiency of 0.76 GHz/y/mA in continuous-wave operation.     

GaAs/AlGaAs quantum cascade microlasers based on monolithic semiconductor-air Bragg mirrors

Edge emitting GaAs-based quantum cascade microlasers at a wavelength of 9 /spl mu/m were realised by monolithic integration of photonic bandgap mirrors based on deeply etched air-semiconductor Bragg gratings. The shortest operating device with Bragg mirrors on both sides has a cavity length of 180 /spl mu/m.     

Room temperature operation of ultra-short quantum cascade lasers with deeply etched Bragg mirrors

Mid-infrared GaAs based bound-to-continuum quantum cascade microlasers with ridge waveguide geometry are fabricated by the monolithic integration of deeply etched semiconductor-air Bragg mirrors. Devices with ultra-short cavities of 50 and 150 /spl mu/m can be operated near room temperature (260 K) or at room temperature (300 K), respectively. 50 /spl mu/m-long devices show singlemode emission up to relatively high drive currents due to the large mode spacing of about 30 cm/sup -1/ (340 nm).     

Mode switching and singlemode tuning in two-segment distributed feedback quantum cascade lasers

Two-segment distributed feedback (DFB) GaAs/AlGaAs bound-to-continuum quantum cascade lasers emitting at /spl sim/10.8 /spl mu/m were fabricated and investigated. Reversible switching between two different DFB modes by current injection control yielding sidemode suppression ratios up to >23 dB is reported. Two different devices were fabricated for which the distance between the different DFB modes is 1.5 and 2.5 cm/sup -1/, respectively, and quasi-continuous tuning over a range of >9 cm/sup -1/ (105 nm) between 120 and 250 K was observed.     

Monolithically Integrated Logic nor Gate Based on GaAs/AlGaAs Three-Terminal Junctions

Room-temperature operation of a logic NOR gate is demonstrated. The NOR gate is based on three three-terminal junctions (TTJs) monolithically integrated in a modulation-doped GaAs/AlGaAs heterostructure without any external load resistance. For the logic NOR gate, one of the TTJs serves as load transistor, whereas the other two are used as inputs. Each TTJ has a 90-nm-wide channel and shows clear transistor characteristics with drain currents up to 10 muA for a drain voltage of 1 V. Furthermore, voltage amplification is demonstrated for the logic NOR-gate function.