Distributed feed-back lasers

For the continuous-wave semiconductor (AlGaAs) distributed feed back lasers (DFB) used in telecommunication technology today a nonlinear refractive index n2=S cm2/GW would be necessary for all-optical switching, which is presumably impossible to reach. Including an Erbium doped fiber amplifier (EDFA) the needed nonlinearity drops only by a factor of ten. 

Amplified spontaneous emission was recently observed by Bawendi, Klimov and coworkers for spherical colloidal CdSe QDs in close-packed films where pumping vhth an amplified femtosecond laser source was used to compete with fast non-radiative Auger decay processes [13, 88]. In further studies, films vhth CdSe nanocrystals were deposited on a distributed feed-back grating structure to yield optically pumped lasing that was tunable through the visible range by changing the nanocrystal size [89, 90]. 

The current passes from the back of the cathode wall from one element to the back of the anode wall of the subsequent element by a series of contact strips. Voltage losses are kept low by a laser-welded, direct connection between the outer contact strips and by vertical inner current-conducting plates and the electrodes (Fig. 5.35). Both brine and caustic enter the element through flexible hoses leading to horizontal inner distribution pipes. These provide uniform feed concentration profiles inside the compartments. Internal circulation is enhanced by two baffle plates located in the anode compartment The upper, inclined baffle plate provides a constant exposure of brine to the membrane, thereby avoiding gas-phase blistering of the membrane. In addition, the vertical... 

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