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Room temperature electron-beam pumped (U ¼ 15-26 keV) green lasers and laser arrays based on multiple quantum well II-VI structures with an extended up to 2 mm waveguide have been studied. The maximum achieved output pulse power is as high as 31 and 630 W per facet from a single 0.24-mm-wide laser element at the cavity length of 0.4 mm and a laser array consisting of 26 elements, respectively. 1 Introduction Electron-beam pumped (EBP) green semiconductor lasers based on undoped II-VI-based structures can be used for numerous applications, such as projection television, optical navigation, location systems, medicine, etc. Sufficient progress in the development of EBP lasers has been achieved using semiconductor heterostructures as the laser active elements instead of bulk materials [1]. The minimum value of the room temperature (RT) threshold current density in electron beam, achieved in a transverse pumping geometry for ZnSe-based separate confinement heterostructure lasers with the active region based on single CdSe quantum dot (QD) sheets, has been recently reported to be as low as 0.4-0.5 A/cm 2 at the electron energy of 8-9 keV [2]. Multiple quantum well (MQW) laser structures with the similar design of each active layers demonstrated the quantum efficiency up to 8.5% and the peak output pulsed power of 12 W per facet at RT [3]. To increase the peak output power one can use both the larger laser active region, e.g. an extended MQW waveguide, and the multielement laser array. This paper reports on design and studies of MQW ZnSe-based lasers and laser arrays pumped by a pulsed electron beam. We have used a homemade electron gun with the maximum total current of an electron beam as high as 600 mA at the electron energy below 26 keV. In contrast to our previous studies [1,2], this gun enables one to pump the laser array of several

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Electron beam pumped (EBP) laser heterostructures with graded index waveguide (GIW) have been grown by molecular beam epitaxy and studied in detail. The maximum achieved output pulse power per facet is as high as 8.5 W at an electron beam energy of 16 kV. No saturation of output power with the increase of electron beam current as well as no suitable degradation of GIW EBP laser structures have been observed. The ways for further optimizations of GIW heterostructures are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electron-beam-pumped (EBP) green semiconductor lasers can be used for projection television, optical communications via plastic fibers, medicine etc. The application of such lasers is strongly restricted by both a relatively high threshold current density at room-temperature (RT) and a high energy of the electron beam needed for laser generation. Sufficient progress in the development of EBP lasers has been achieved using semiconductor heterostructures as the laser active elements. The lasing with microgun excitation has been demonstrated [1], although at low temperatures. Recently we have reported on fabrication of EBP blue-green RT lasers based on alternatelystrained superlattice (SL) waveguide and CdSe/ZnSe quantum dot (QD) active region with the value of threshold current density as low as 0.8 A/cm 2 at electron beam energy 16 keV [2,3]. In the present paper we report on the results of studies of EBP lasers based on the CdSe/ZnSe QD structures with an ultra thin upper cladding layer. Usage of thin top claddings allows to obtain lasing at electron beam energy as low as 3.7 keV. The CdSe/ZnSe/ZnMgSSe laser structures were grown by molecular beam epitaxy (MBE) pseudomorphically on GaAs (001) substrates via a GaAs MBE buffer. The structures consist of a bottom Zn 0.92 Mg 0.08 S 0.15 Se 0.85 cladding layer followed by a ZnS 0.14 Se 0.86 /ZnSe SL waveguide lattice-matched to GaAs as a whole. The structures are capped with a Zn 0.92 Mg 0.08 S 0.15 Se 0.85 cladding layer followed by a ZnSe cap. The width of the top cladding layer for different structures varies from 20 to 50 nm. One 20-nm-thick ZnSe quantum well centered with the CdSe QD sheet of a nominal thickness 2.8 monolayer was placed inside the ZnSSe/ZnSe SL waveguide. A pulse electron beam with the energy up to 12 keV was used as a pumping source. The pulse duration was equal to 0.2 µs at the repetition rate up to 10 Hz. We used transverse excitation geometry. All experiments were performed at RT.Laser generation was observed for electron beam energies exceeding 3.7 keV. With increasing the electron beam energy, the value of threshold current density J th decreases gradually, reaching a minimum value for electron beam energy about 8-9 keV, and then grows up. The minimum value of J th = 0.4-0.5 A/cm 2 was measured for a laser chip with the cavity length of 0.92 mm. J th increases with decreasing the cavity length and raises dramatically with increasing the width of the upper cladding layer from 20 to 50 nm. Maximum output pulse power of 2W was obtained. The temporary behavior of the electron beam current and the output light intensity are practically coincident. The lasing wavelength of 535 nm was measured, the width of spectral line being 2-3 nm.Experimental dependence of the threshold current density on the electron beam energy agrees well with the calculated ones. The theoretical model takes into account the inhomogeneous spatial distribution of pumping energy, the diffusion of the carriers and nonradiative transitions in different layers of the semiconduct...