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- ItemWedged Nd:YVO4 crystal for wavelength tuning of monolithic passively Q-switched picosecond microchip lasers(Washington, DC : Soc., 2021) Marianovich, André; Spiekermann, Stefan; Brendel, Moritz; Wessels, Peter; Neumann, Jörg; Weyers, Markus; Kracht, DietmarWe present a monolithic integrated passively Q-switched sub-150 ps microchip laser at 1064 nm with a wedged Nd:YVO4 crystal operating up to a repetition rate of 1 MHz. The wedge enables to change the cavity length by a small amount to fine tune the spectral cavity mode position over the full gain bandwidth of Nd:YVO4 and hence to optimize the output power. This additional degree of freedom may be a suitable approach to increase the wafer scale mass production yield or also to simplify frequency tuning of CW single-frequency microchip lasers.
- ItemHigh-temperature electromechanical loss in piezoelectric langasite and catangasite crystals(Melville, NY : American Inst. of Physics, 2021) Suhak, Yuriy; Fritze, Holger; Sotnikov, Andrei; Schmidt, Hagen; Johnson, Ward L.Temperature-dependent acoustic loss Q−1 is studied in partially disordered langasite (LGS, La3Ga5SiO14) and ordered catangasite (CTGS, Ca3TaGa3Si2O14) crystals and compared with previously reported CTGS and langatate (LGT, La3Ga5.5Ta0.5O14) data. Two independent techniques, a contactless tone-burst excitation technique and contacting resonant piezoelectric spectroscopy, are used in this study. Contributions to the measured Q−1(T) are determined through fitting to physics-based functions, and the extracted fit parameters, including the activation energies of the processes, are discussed. It is shown that losses in LGS and CTGS are caused by a superposition of several mechanisms, including intrinsic phonon–phonon loss, point-defect relaxations, and conductivity-related relaxations.
- ItemEngineering the semiconductor/oxide interaction for stacking twin suppression in single crystalline epitaxial silicon(111)/insulator/Si(111) heterostructures(College Park, MD : Institute of Physics Publishing, 2008) Schroetter, T.; Zaumseil, P.; Seifarth, O.; Giussani, A.; Müssig, H.-J.; Storck, P.; Geiger, D.; Lichte, H.; Dabrowski, J.The integration of alternative semiconductor layers on the Si material platform via oxide heterostructures is of interest to increase the performance and/or functionality of future Si-based integrated circuits. The single crystalline quality of epitaxial (epi) semiconductor-insulator-Si heterostructures is however limited by too high defect densities, mainly due to a lack of knowledge about the fundamental physics of the heteroepitaxy mechanisms at work. To shed light on the physics of stacking twin formation as one of the major defect mechanisms in (111)-oriented fcc-related heterostructures on Si(111), we report a detailed experimental and theoretical study on the structure and defect properties of epi-Si(111)/Y2O 3/Pr2O3/Si(111) heterostructures. Synchrotron radiation-grazing incidence x-ray diffraction (SR-GIXRD) proves that the engineered Y2O3/Pr2O3 buffer dielectric heterostructure on Si(111) allows control of the stacking sequence of the overgrowing single crystalline epi-Si(111) layers. The epitaxy relationship of the epi-Si(111)/insulator/Si(111) heterostructure is characterized by a type A/B/A stacking configuration. Theoretical ab initio calculations show that this stacking sequence control of the heterostructure is mainly achieved by electrostatic interaction effects across the ionic oxide/covalent Si interface (IF). Transmission electron microscopy (TEM) studies detect only a small population of misaligned type B epi-Si(111) stacking twins whose location is limited to the oxide/epiSi IF region. Engineering the oxide/semiconductor IF physics by using tailored oxide systems opens thus a promising approach to grow heterostructures with well-controlled properties. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
- ItemA novel engineered oxide buffer approach for fully lattice-matched SOI heterostructures(College Park, MD : Institute of Physics Publishing, 2010) Giussani, A.; Zaumseil, P.; Seifarth, O.; Storck, P.; Schroeder, T.Epitaxial (epi) oxides on silicon can be used to integrate novel device concepts on the canonical Si platform, including functional oxides, e.g. multiferroics, as well as alternative semiconductor approaches. For all these applications, the quality of the oxide heterostructure is a key figure of merit. In this paper, it is shown that, by co-evaporating Y2O3 and Pr2O3 powder materials, perfectly lattice-matched PrYO3(111) epilayers with bixbyite structure can be grown on Si(111) substrates. A high-resolution x-ray diffraction analysis demonstrates that the mixed oxide epi-films are single crystalline and type B oriented. Si epitaxial overgrowth of the PrYO3(111)/Si(111) support system results in flat, continuous and fully lattice-matched epi-Si(111)/PrYO3(111)/Si(111) silicon-on-insulator heterostructures. Raman spectroscopy proves the strain-free nature of the epi-Si films. A Williamson-Hall analysis of the mixed oxide layer highlights the existence of structural defects in the buffer, which can be explained by the thermal expansion coefficients of Si and PrYO3. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
- ItemDiode-pumped sub-50-fs Kerr-lens mode-locked Yb:GdYCOB laser(Washington, DC : Soc., 2021) Zeng, Huangjun; Lin, Haifeng; Lin, Zhanglang; Zhang, Lizhen; Lin, Zhoubin; Zhang, Ge; Petrov, Valentin; Loiko, Pavel; Mateos, Xavier; Wang, Li; Chen, WeidongWe present a sub-50-fs diode-pumped Kerr-lens mode-locked laser employing a novel “mixed” monoclinic Yb:Ca4(Gd,Y)O(BO3)3 (Yb:GdYCOB) crystal as a gain medium. Nearly Fourier-limited pulses as short as 43 fs at 1036.7 nm are generated with an average power of 84 mW corresponding to a pulse repetition rate of ∼70.8 MHz. A higher average power of 300 mW was achieved at the expense of the pulse duration (113 fs) corresponding to an optical-to-optical efficiency of 35.8% representing a record-high value for any Yb-doped borate crystal. Non-phase-matched self-frequency doubling is observed in the mode-locked regime with pronounced strong spectral fringes which originate from two delayed green replicas of the fundamental femtosecond pulses in the time domain.