V. Rangelov

Universität Kassel, Kassel, Hesse, Germany

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Publications (9)4.86 Total impact

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    ABSTRACT: Optical filters capable of single control parameter-based wide tuning are implemented and studied. The surface micromachined Fabry-Perot filter consists of two InP-air-gap distributed Bragg reflectors and shows a wavelength tuning of more than 140 nm using only a single voltage of up to 3.2 V at currents below 0.2 mA. The membrane-based filter is designed to block all wavelengths in the whole range of 1250-1800 nm apart from its transmission wavelength.
    IEEE Photonics Technology Letters 04/2003; · 2.04 Impact Factor
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    ABSTRACT: Continuously tunable Fabry-Pérot filters manufactured using multiple air-gap MOEMS technology are studied and presented. The InP/air-gap filters optimized for optical telecommunication systems using the third optical telecommunication window (1550nm) exhibit a wide tuning range of 142nm and an extremely wide stop-band of 550nm (1250nm-1800nm). The tuning is continuously adjustable requiring ultra-low actuation voltages between 0V (1599nm) and 3.2V (1457nm). The filters are based on a relatively simple vertical structure which is fabricated by few surface micro machining steps. No mirror alignment or subsequent micro mounting are necessary facilitating a compact batch process production.
    03/2003;
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    ABSTRACT: A novel low cost technology for fabrication of micro-opto-electro-mechanical devices based on plasma enhanced chemical vapor deposition (PECVD) of dielectric materials is presented. Applying surface micromachining, we produce suspended dielectric membranes and cantilevers by involving a common photo resist as sacrificial layer. The intrinsic stress in the layers is adjusted using an interlacing of high (13.56MHz) and low (130kHz) plasma excitation frequencies in the PECVD. A diffraction image method and microstructures are used for the homogeneous stress evaluation. The stress of silicon nitride can be varied in a wide range between +850MPa compressive and −300MPa tensile and no dependence of the frequency on silicon dioxide intrinsic stress is noticed. Depending on lateral design and gradient stress variation, Fabry-Perot filter membranes with radius of curvature (ROC) between −1.7mm and 51mm as well as cavity lengths between 2.3μm and 13.5μm are implemented. Thus, convex, concave and plane membranes are produced. Furthermore, a thermally tuned air-gap Fabry-Perot filter with 8nm FWHM and a tunability of 15nm/mA is fabricated. Strategies of combining these filters with organic laser materials are developed. For this purpose, molecular glasses capable of amplified spontaneous emission (ASE) are chosen, e.g. the molecular glass 4-Spiro which shows an amplified spontaneous emission line at a low threshold of 3.2μJ/cm2 pump laser power density.
    Photonics Fabrication Europe; 03/2003
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    ABSTRACT: We present ultra-widely tunable micro-cavity devices realized by micro-opto-electro-mechanical system (MOEMS) technology. We modeled, fabricated and characterized 1.55μm micromachined optical filter and VCSEL devices capable of wide, monotonic and kink-free tuning by a single control parameter. Our vertical cavity devices comprise single or multiple horizontal air-gaps in the dielectric and InP-based material system. Distributed Bragg mirrors with multiple air-gaps are implemented. Due to the high refractive index contrast between air (n=1) and InP (n=3.17) only 3 periods are sufficient to guarantee a reflectivity exceeding 99.8% and offer an enormous stop-band width exceeding 500nm. Unlike InGaAsP/InP or dielectric mirrors they ensure short penetration depth of the optical intensity field in the mirrors and low absorption values. Stress control of the suspended membrane layers is of outmost importance for the fabrication of MOEMS devices. By controlling the stress we are able to fabricate InP membranes which are extremely thin (357nm thickness) and at the same time flat (radius of curvature above 5mm). Micromechanical single parametric actuation is achieved by both, thermal and electrostatic actuation. Filter devices with a record tuning over 127nm with 7.3V are presented.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
    11/2002;
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    ABSTRACT: Continuously tunable Fabry-Perot filters based on multiple InP/air-gap MOEMS technology are presented. Record wavelength tuning >112 nm with an actuation voltage of only 5 V is demonstrated. The FWHM remains constant over the entire tuning range. The stopband covers both the second and third optical telecommunication window (1250-1800 nm).
    Electronics Letters 11/2002; · 1.04 Impact Factor
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    ABSTRACT: Tailored scaling represents a principle of success that, both in nature and in technology, allows the effectiveness of physical effects to be enhanced. Mutation and selection in nature are imitated in technology, e.g. by model calculation and design. Proper scaling of dimensions in natural photonic crystals and our fabricated artificial 1D photonic crystals (DBRs, distributed Bragg reflectors) enable efficient diffractive interaction in a specific spectral range. For our optical microsystems we illustrate that tailored miniaturization may also increase the mechanical stability and the effectiveness of spectral tuning by thermal and electrostatic actuation, since the relative significance of the fundamental physical forces involved considerably changes with scaling. These basic physical principles are rigorously applied in micromachined 1.55-μm vertical-resonator-based devices. We modeled, implemented and characterized 1.55-μm micromachined optical filters and vertical-cavity surface-emitting laser devices capable of wide, monotonic and kink-free tuning by a single control parameter. Tuning is achieved by mechanical actuation of one or several air-gaps that are part of the vertical resonator including two ultra-highly reflective DBR mirrors of strong refractive index contrast: (i) Δn=2.17 for InP/air-gap DBRs (3.5 periods) using GaInAs sacrificial layers and (ii) Δn=0.5 for Si3N4/SiO2 DBRs (12 periods) with a polymer sacrificial layer to implement the air-cavity. In semiconductor multiple air-gap filters, a continuous tuning of >8% of the absolute wavelength is obtained. Varying the reverse voltage (U=0–5V) between the membranes (electrostatic actuation), a tuning range of >110nm was obtained for a large number of devices. The correlation of the wavelength and the applied voltage is accurately reproducible without any hysteresis. In two filters, tuning of 127 and 130nm was observed for about ΔU=7V. The extremely wide tuning range and the very small voltage required are record values to the best of our knowledge. For thermally actuated dielectric filters based on polymer sacrificial layers, Δλ/ΔU=-7nm/V is found.
    Applied Physics B 06/2002; 75(1):3-13. · 1.78 Impact Factor
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    ABSTRACT: We study 1.55micrometers filter and VCSEL devices capable of wide and continuous tuning based on a single control parameter. Ultra-high reflective DBR mirrors are realized with a low number of DBR periods using high refractive index contrast: (I) (Delta) n=2.17 for InP/airgap DBR's (3.5 periods) and (II) (Delta) n=0.5 for Si3N4/SiO2 DBR's (12 periods) with a polymer sacrificial layer to implement the air-cavity. Corresponding fabrication technologies are presented in detail. In both cases spectral tuning (>100nm, theoretically) is obtained by micomachined actuation of the included air-cavity. Large stopband widths and very large tuning efficiencies are obtained by model calculations. For VCSEL's a trade-off between lasing efficiency and tuning efficiency is obtained. Experimental results show very good optical properties: high mirror reflectance and clear single-line filter transmission. The first tunable dielectric filter based on polymer sacrificial layers is presented: (Delta) (lambda) /(Delta) U= -7nm/V at 1mA. The potential of the airgap concept: the filter transmission or the laser emission wavelength can be continuously tuned over more than 100nm, thus, the whole spectral gain profile can be addressed by a single control parameter.
    Proc SPIE 06/2002;
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    ABSTRACT: Dense wavelength division multiplex (DWDM) systems is a promising technology for long-haul networks using the established fiber networks. Tunable devices such as optical filters, highly selective photodetectors, as well as lasers are considered to be key components for dynamic WDM systems. A novel low-cost tunable dielectric filter consisting of an air-gap cavity embedded by two DBRs is presented. A FWHM of 8 nm and a tunability of 15 nm/mA at 2 kΩ heating resistance is obtained.
    Optical MEMs, 2002. Conference Digest. 2002 IEEE/LEOS International Conference on; 02/2002
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    ABSTRACT: Demonstrated micromechanically tunable Fabry-Perot filters with record electromechanical and optical performance. Wavelength tuning of 127nm applying only 7.3V is achieved. The stop-band of these filters is extremely wide (1250nm - 1800nm). These results open new application fields for micromechanically tunable filters, such as spectrometry for environmental and process analysis, medical diagnostics and colorimetry.
    Optical MEMs, 2002. Conference Digest. 2002 IEEE/LEOS International Conference on; 02/2002

Publication Stats

62 Citations
4.86 Total Impact Points

Institutions

  • 2002–2003
    • Universität Kassel
      • • Center for Interdisciplinary Nanostructure Science and Technology (CINSaT)
      • • Institute of Nanostructure Technologies and Analytics (INA)
      Kassel, Hesse, Germany