Lasers current-injected

The efforts made from both experimental and theoretical standpoints will render organic semiconductors even more useful. One of the priorities with organic semiconductor research is to establish current-injected laser oscillation. This is because it is a definite yardstick for measuring the potential of semiconductor materials and devices. 

Kam Y. Lau and Amnon Yariv, High-Frequency Current Modulation of Semiconductor Injection Lasers... 

Other more exotic mechanisms include chemical reactions in gases, high-voltage electron beam pumping of gases, and direct current injection across the junction of a semiconductor laser. 

Kneissl, M., Teepe, M., Miyashita, N., Johnson, N.M., Chem, G.D., and Chang, R.K., 2004, Current-injection spiral-shaped microcavity disk laser diodes with unidirectional emission, Appl. Phys. Lett. 84(14) 2485-2487. 

The different pumping methods, such as the commonly used current injection or optical pumping electron beam pumping and avalanche breakdown have been studied in detail (for further refs, see and information has been obtained regarding the excitation probabilities of the different interband transitions. The very short laser pulses (less than 10 sec) obtained enable rapid processes and their time dependence to be studied. 

Fig. 5. A simple semiconductor laser. It is a p-n junction in a semiconductor crystal the end laces of which are flat and perfectly parallel, thus, the faces form a pair of sendreflecliag mirrors tliat bounce plioious back anJ forth llirough tlie active layer of thecrystal. Current injection causes photons to arise by spontaneous emission. Those photons traversing the semiconductor cause an avalanche of stimulated emission. Refleclious at the mirrors are self-rednforcing provided that the wavelength of the photon fits evenly into the length of the laser. See also Fig. 6...

Fig. 9. The energy diagram of the C3 laser illustrates its Lunability by current injection. As explained by Tsang, the current to one of the half-lasers elevates it above its lasing threshold. Thus, its resonant modes are fixed as indicated in...

C5.1 InGaN/GaN/AlGaN-based laser diodes C5.2 Optically pumped lasing and current injection lasing in GaN-based laser structures... 

Stimulated emission and lasing in GaN-based structures can be achieved by both optical pumping and current injection. We have presented some of the most recent results of optically pumped SE and laser action studies in GaN and related heterostructures. Current injection LD operation repotted in the literature has been presented in a table in chronological order. 

Much has been learned in the thirty-five years since the demonstration of the first GaAs injection lasers [1,2], The main lesson from that period is that defect-free material is needed, hi the 1970s MITI set up a successful five year crash programme to make zero-defect GaAs. The reason behind the zero defect goal for diode lasers is that defects cause emission line broadening, and the threshold current for an injection laser is directly proportional to the emission linewidth. Excitons in semiconductors are very fragile. They can be easily destroyed, or have their linewidth broadened by crystal lattice disruptions of any sort. 

Figure 3. Light output as a function of current of the injection laser operating at 1.51 pm (at 20 °C). Insert shows quantum-well parameters. (Adapted from Ref. 39.)...

The proton-implanted laser in Fig. 13b has a contact stripe which is created by implanting protons into the metalization layer, leaving only a small stripe which has not been implanted. The implanted regions become highly resistive to current injection, while the unimplanted region has a low resistivity, which serves as the electrical stripe contact. Using this method, it is possible to control the amount of current confinement by varying the depth of proton implantation. 

The direct modulation property of semiconductor injection lasers is one of their unique characteristics and this feature provides the potential for many scientific and commercial applications. Unlike other solid state and liquid lasers, modulating the injection current can directly control the optical output of the semiconductor laser. 

The modulation bandwidth of the semiconductor injection laser given by Eq. (15), is determined by the gain coefiicient, photon lifetime, and the steady-state photon density. These parameters are influenced by the structure of the laser, the operating temperature, and the laser diode material system. For a given laser, increasing the injection current, as shown in Fig. 16, can increase the bandwidth. However the maximum current is limited by the... 

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