Electron Beam Pumped Semiconductor Lasers
Electron Beam Pumped Lasers of Visible and Ultra-Violet Ranges Based on Quantum-Size Semiconductor Heterostructures
Tech Area / Field
- PHY-OPL/Optics and Lasers/Physics
8 Project completed
Senior Project Manager
Malakhov Yu I
Moscow State Technical University of Radioengineering, Electronics and Automation, Russia, Moscow
- Russian Academy of Sciences / Physical Technical Institute, Russia, St Petersburg\nVNIIEF, Russia, N. Novgorod reg., Sarov
- CNRS / Equipe Nanophysique et Semiconducteurs, France, Grenoble\nTechnische Universitat Braunschweig / Institut für Halbleitertechnik, Germany, Braunschweig\nCNRS / Institut Neel, France, Grenoble
Project summaryThe main target of the project is a development of prototypes of room-temperature quasi-cw electron beam pumped semiconductor lasers of visible and ultra-violet ranges with an average output power of 0.1-1 W.
The state of the art in the field of the research. The progress in physics and technology of semiconductor heteroctructures determines the possibility of commercial production of injection lasers in near-IR, red and blue-violet ranges of the spectra. However, the commercial production of semiconductor injection lasers emitting in both green part of visible spectrum and UV range of wavelength is currently impracticable due to the set of unresolved problems of fabrication of such lasers. Among these is the achievement of relatively high p-type doping with the simultaneous maintenance of degradation stability of laser structures based on wide-gap II-VI compounds.
Electron beam pumped semiconductor lasers allows one to obtain emission in wide spectral range, virtually at any wavelength from UV to IR. There are two most-used and well-studied types of electron beam pumped semiconductor lasers: pulsed lasers and quasi-cw (scanning) lasers with a longitudinal pumping by fine-focused electron beam. The pulsed multi-elements electron beam pumped lasers have demonstrated the output power as high as 20 MW at the energy of light pulse of 250 mJ. The maximum average power of ~ 1 W in pulse-periodic mode has been recorded at electron beam energy of ~ 300 keV. The average power of ~ 40 W in quasi-cw (scanning) mode of scanning lasers with longitudinal pumping has been achieved at cryogenic temperatures and electron beam current density of dozens A/cm2, but at room temperature the average power is only a few watts. In this case the energy of electron beam was as high as 60÷70 keV.
The high values of electron beam energy used for pumping of such lasers provide inconvenience for practical use of the lasers. The noticeable reduce of the threshold of laser generation at a moderate values of electron beam energy should be expected when utilizing heterostructures in lasers with transverse excitation geometry. As an example, recently has been suggested to use structures with active layer based on CdSe/ZnSe quantum dots (QDs), that resulted in a decrease of threshold current density in electron beam down to ~ 1 A/cm2 at RT, which is considered as a record value up to now. Noticeable part of the project proposed is devoted to the further development of this approach with the aim to decrease the threshold current at a low accelerating voltage of electron beam.
Interest in CdSe/ZnSe QDs is aroused mainly by the possibility to obtain coherent emission in green and blue-green spectral ranges, which is important for a large number of commercial applications such as projection television, studying of the fluorescence of biological cells, medicine et al.
Stimulated emission in 360÷390 nm range is expected to obtain using of Zn(Mg)O heterostructures. Due to the ZnO bandgap at RT is of ~ 3.34 eV, this material can be considered as a promising candidate for the UV low-threshold lasers provided that the effective pumping of inverted population is realized. One-dimensional flat ZnO micro-resonators confined with a Bragg reflector are of a prime interest. The extremely low threshold (~ 3 kW/cm2 at 300 K under optical pumping) of laser generation has been suggested in such structures due to a boson condensation of exciton-polaritons.
Besides the studies of MBE growth and optimization of parameters of heterostructures, emitting in green and UV spectral ranges, noticeable part of this research is devoted to the development of experimental techniques for the effective excitation of semiconductor crystals as well as to the optimization of their laser parameters.
A number of publications on design of electron beam pumped semiconductor lasers with a quantum-size layers were reported in the last few years. It is shown that such devices could be relatively small in sizes. Recently, electron beam pumped blue semiconductor laser with an average output power up to 30 mW, in which the source of electrons, focusing system and laser active element placed in vacuum volume have an overall length as small as 15 mm, has been realized. However, in these works, unlike current project, the cryogenic cooling of the samples was used.
Summarizing, it is suggested that light sources emitting in blue-green and UV spectral ranges with an average output power of 0.1-1 W at RT will be realized for a numerous technical and commercial applications, employing the excitation of heterostructures by a scanning electron beam with energy of ~ 10 keV. In this case we can utilize advantages of electron beam pumped lasers, such as possibility to vary parameters of laser radiation, including the variation of the wavelength by means of modulation and scanning of electron beam.
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