Incoherent and coherent beam combination for master oscillator/power amplifier system with stimulated Brillouin scattering mirror

In this paper, we studied incoherent and coherent beam combining for the master oscillator/power amplifier （MOPA） system with stimulated Brillouin scattering （SBS） mirror. Optic field intensity distributions in the near and far field are numerically calculated for the two kinds of system. The results show that good beam quality in the far field could be obtained. It provides a theoretical basis for experimental research in the future.

Long-wave infrared emission properties of strain-balanced InAs/In_(x)Ga_(1-x)As_(y)Sb_(1-y)type-Ⅱsuperlattice on different substrates

High-performance type-Ⅱsuperlattices ofⅢ-Ⅴsemiconductor materials play an important role in the development and application of infrared optoelectronic devices.Improving the quality of epitaxial materials and clarifying the luminescent mechanism are of great significance for practic al applic ations.In this work,strain-balanced and high-quality In As/In_(x)Ga_(1-x)As_(y)Sb_(1-y)superlattices without lattice mismatch were achieved on InAs and GaSb substrates successfully.Superlattices grown on In As substrate could exhibit higher crystal quality and surface flatness based on high-resolution X-ray diffraction(HRXRD)and atomic force microscopy(AFM)measurements'results.Moreover,the strain distribution phenomenon from geometric phase analysis indicates that fluctuations of alloy compositions in superlattices on GaSb substrate are more obvious.In addition,the optical properties of superlattices grown on different substrates are discussed systematically.Because of the difference in fluctuations of element composition and interface roughness of superlattices on different substrates,the superlattices grown on In As substrate would have higher integral intensity and narrower full-width at half maximum of long-wave infrared emission.Finally,the thermal quenching of emission intensity indicates that the superlattices grown on the In As substrate have better recombination ability,which is beneficial for increasing the operating temperature of infrared optoelectronic devices based on this type of superlattices.

InAs/InAsSb type-Ⅱ superlattice with near room-temperature long-wave emission through interface engineering

Ga-free InAs/InAsSb type-Ⅱ superlattices(T2SL) have extensive application prospective in infrared photodetectors. Achieving higher operation temperature is critical to its commercial applications. Here, a fractional monolayer alloy method was used to grow InAsSb alloy with better controlled alloy composition. The as-grown T2SL gave eleven satellite peaks and a first satellite peak with a narrow full-width-half-maximum (FWHM) of 20.5arcsec (1 arcsec=0.01592°). Strain mapping results indicated limited Sb diffusion through the As-Sb exchange process at the interface. Moreover, unlike interface states caused by the As-Sb exchange effect, this relatively clear interface was distinctive with localized states with higher activation energies of the non-radiative recombination process ((18±1) meV and (84±12) meV at different temperature ranges), which means that this interface state introduced by fractional monolayer alloy growth method can effectively suppress Auger recombination process in T2SL. Through this interface engineering of InAs/InAsSb Type-Ⅱ superlattice, it achieved detective photoluminescence (PL) signal with the center wavelength of 9μm at 250K.

Nondiffracting Beams With Finite Beam Width

Since Durnin reported the first experiment of Bessel beams, the related researchwork has developed extensively because of their 'nondiffracting' property andinteresting potential applications. It was shown that nearly nondiffracting Besselbeams can be realized experimentally by using various methods, such as an annularslit system, holographic amplification, an F-P interferometer, axicon and refractingsystem. This note presents the investigation results of the authors on nondiffractingBessel beams with finite beam width, i.e. beams limited by an aperture. Experimentshave been performed to illustrate the advantages of generating Bessel beams with anaxicon. A detailed study of the axial intensity and maximum nondiffracting range ofBessel beams vs. aperture size, and the conversion efficiency of the axicon as a Besselbeam convertor has been given. Within the experimental errors the result are ingood agreement with the theory.