Dmitri L. Boiko
École Polytechnique Fédérale de Lausanne
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Featured researches published by Dmitri L. Boiko.
Optical Materials Express | 2011
Joo Yeon Kim; Nils Benedict Brauer; Vahid Fakhfouri; Dmitri L. Boiko; Edoardo Charbon; Gabi Grützner; Jürgen Brugger
Microlens arrays fabricated by a direct ink-jet printing of UV-curable hybrid polymer are reported. A periodic pattern of polymer drops was ink-jet printed on the surface-treated glass substrate and cured in the UV-light. Using this simple technique, we demonstrated periodic arrays of almost semi-spherical microlenses of 50 µm diameter size and a focal distance of 48µm. The optical characteristics of solitary µ-lenses and arrays comprising up to 64x64 microlenses are measured both in the near- and far-field zones. Large numerical aperture and short focal distance make the ink-jet printing of microlenses very attractive for applications in optical interconnects, large 2D VCSEL arrays and pixelated imagine sensors utilizing CCD or SPAD arrays, offering thus an efficient, simple and a cheap alternative to the conventionally used photolithography technique.
international conference on micro electro mechanical systems | 2008
V. Fakhfouri; N. Cantale; Grégory Mermoud; Joo Yeon Kim; Dmitri L. Boiko; Edoardo Charbon; Alcherio Martinoli; Jürgen Brugger
This paper describes a novel method to fabricate polymer MEMS based on the inkjet printing of SU-8, with a special emphasis on integrated micro-optical lens arrays. Inkjet control parameters are optimized in order to enable a stable and reproducible ejection of SU-8 drops in both continuous and drop-on-demand (DOD) modes. Arbitrary patterns of single and multiple polymer drops and arrays of convex microlenses are printed on different substrates. The influence of surface wetting properties on the size and the shape of the printed patterns is investigated. The optical properties of the microlenses are investigated in details. A model for inkjet printing of high-viscous functional materials for polymer MEMS has been used.
Applied Physics Letters | 2007
Lars D. A. Lundeberg; Gregory P. Lousberg; Dmitri L. Boiko; E. Kapon
The spatial coherence and the optical phase distribution across a two-dimensional (2D) photonic crystal implemented with coupled arrays of vertical cavity surface emitting lasers (VCSELs) are experimentally characterized. This is achieved by performing Young’s interference experiments between pairs of array elements using a spatial light modulator arrangement. In contrast to far-field measurements that provide information only on the global spatial coherence, this approach can yield full mapping of the complex degree of spatial coherence. Examples of such analysis are presented for nominally uniform one-dimensional and 2D arrays of coupled VCSELs and possible mechanisms of the observed coherence degradation are discussed.
Optics Express | 2012
Dmitri L. Boiko; P. P. Vasil’ev
We analyze theoretically the superradiant emission (SR) in semiconductor edge-emitting laser heterostructures using InGaN/GaN heterostructure quantum well (QW) as a model system. The generation of superradiant pulses as short as 500 fs at peak powers of over 200 W has been predicted for InGaN/GaN heterostructure QWs with the peak emission in the blue/violet wavelength range. Numerical simulations based on semiclassical traveling wave Maxwell-Bloch equations predict building up of macroscopic coherences in the ensemble of electrons and holes during SR pulse formation. We show that SR is covered by the Ginzburg-Landau equation for a phase transition to macroscopically coherent state of matter. The presented theory is applicable to other semiconductor materials.
Optics Letters | 2009
Marek Gersbach; Dmitri L. Boiko; C. Niclass; Carl C. H. Petersen; Edoardo Charbon
The fluorescence decay of high-affinity nonratiometric Ca2+ indicator Oregon Green BAPTA-1 (OGB-1) is analyzed with unprecedented temporal resolution in the two-photon excitation regime. A triple exponential decay is shown to best fit the fluorescence dynamics of OGB-1. We provide a model for accurate measurements of the free Ca2+ concentration and dissociation constants of nonratiometric calcium indicators.
IEEE Journal of Quantum Electronics | 2007
Vladislav Shteeman; Dmitri L. Boiko; E. Kapon; A. Hardy
Coupled-mode theory, developed for several parallel waveguides, is extended to the case of infinite 2-D photonic crystals. Periodic boundary conditions, applied to a system of coupled identical waveguides, are used to compute the photonic band structures. This approach is shown to be more efficient than the usual numerical methods when tested on finite, but large-sized, arrays. Photonic crystals made of single-mode and multimode waveguide arrays are examined
Optics Express | 2011
I. V. Smetanin; Peter P. Vasil’ev; Dmitri L. Boiko
Analytical theory of the high-power passively mode-locked laser with a slow absorber is developed. In distinguishing from previous treatment, our model is valid at pulse energies well exceeding the saturation energy of absorber. This is achieved by solving the mode-locking master equation in the pulse energy-domain representation. The performances of monolithic sub-picosecond blue-violet GaN mode-locked diode laser in the high-power operation regime are analyzed using the developed approach.
Applied Physics Letters | 2013
Peter P. Vasil'ev; A. B. Sergeev; I. V. Smetanin; Thomas Weig; Ulrich T. Schwarz; Luca Sulmoni; J. Dorsaz; J.-M. Lamy; J.-F. Carlin; N. Grandjean; X. Zeng; T. Stadelmann; S. Grossmann; A. C. Hoogerwerf; Dmitri L. Boiko
Passive mode-locked pulses with repetition frequencies in the range 40 to 90 GHz were observed in blue-violet GaN-based quantum-well lasers without external cavities. The lasers had two-section geometry with built-in saturable absorber section. The individual pulses had durations as short as 3–5 ps at peak powers of around 320 mW.
Applied Physics Letters | 2012
X. Zeng; Dmitri L. Boiko; Gatien Cosendey; Marlene Glauser; J.-F. Carlin; N. Grandjean
Optically pumped InGaN/GaN quantum well vertical-external-cavity surface-emitting laser emitting at 420 nm has been realized. Lasing at external cavity lengths of up to 50 mm is demonstrated, making integration of practical sized intracavity elements possible. Spectral and beam profile measurements indicate best operation conditions in a semiconfocal cavity configuration. Lasing threshold of 20.9 W is achieved for a 49 mm long cavity with output beam quality parameter M2 not exceeding 1.1.
Optics Express | 2004
Dmitri L. Boiko; Gilles Guerrero; E. Kapon
The vectorial model of two-dimensional photonic crystals based on coherently coupled arrays of Vertical Cavity Surface - Emitting Lasers (VCSELs) is proposed in non-Hermitian Hamiltonian eigenproblem formulation. The polarization modes of square-symmetry photonic lattices are investigated theoretically. Rich mode structure with complimentary patterns of intensity for orthogonal polarizations of electromagnetic Bloch wave is predicted. The predicted near-field patterns of the polarization modes are confirmed in measurements of InGaAs/AlGaAs VCSEL arrays emitting at 965nm wavelength.