R. Michalzik

Universität Ulm, Ulm, Baden-Württemberg, Germany

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Publications (230)192.16 Total impact


  • No preview · Article · Jan 2016 · Applied Physics Letters
  • M.R. Hofmann · T. Pusch · M. Lindemann · R. Michalzik · N.C. Gerhardt
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    ABSTRACT: Using the elasto-optic effect, increase of the frequency difference between the two orthogonally polarised modes, the so-called birefringence splitting, in standard single-mode oxide-confined AlGaAs-based vertical-cavity surface-emitting lasers is achieved to values beyond 250 GHz. A large birefringence is required for the generation of ultra-fast polarisation oscillations for potential future high-speed communication applications.
    No preview · Article · Sep 2015 · Electronics Letters
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    ABSTRACT: Spintronic lasers offer promising perspectives for new concepts superior to options of purely charge-based devices. Especially spin-polarized vertical-cavity surface-emitting lasers (spin-VCSELs) exhibit ultrafast spin and polarization dynamics. Using pulsed spin-injection, oscillations in the circular polarization degree can be generated, which have the potential to exceed frequencies of 100 GHz. The oscillations evolve due to coupling of the carrier-spin-photon system for linear modes via birefringence in the VCSEL's cavity. They are independent of the conventional relaxation oscillations and thus their usage can be the cornerstone for ultrafast directly modulated spin-VCSELs in the near future. After giving a short overview of the state of scientific and technical knowledge we will outline a method to control the polarization oscillations by multiple spin-injection pulses. It is possible to switch these oscillations on and off, depending on phase and amplitude conditions of two consecutive excitation pulses. Even half-cycles can be generated, which is the basis for short polarization pulses, only limited by the polarization oscillation resonance frequency. We investigate influences of the birefringence, which directly determines the oscillation frequency, by means of calculations with the spin-flip-model and experimental verification using 850 nm VCSELs. Furthermore we discuss experimental possibilities of increasing the birefringence and therefore the oscillation frequency, such that ultrashort pulses come into reach.
    No preview · Article · Jan 2015 · Proceedings of SPIE - The International Society for Optical Engineering
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    Niazul Islam Khan · Anna Bergmann · Rainer Michalzik
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    ABSTRACT: In recent years, optical manipulation has been emerging as a powerful technique in a wide range of applications, especially in the field of biological sciences. It is a mechanism to handle micrometer sized particles without mechanical or thermal damage or contamination. Lately, the use of VCSELs (vertical-cavity surface-emitting lasers) as light sources in optical manipulation has got significant attention because of their various advantages compared to conventional lasers. Particularly, their small dimensions with typical active diameters of less than ten micrometers, the possibility of simple and inexpensive formation of two-dimensional VCSEL arrays and their integration capability have made them convenient for optical manipulation applications. Another field of interest in biological research is microfluidics, which studies the manipulation and analysis of fluids in microscale. In this paper, we combine these three basic elements – VCSELs, optical manipulation, and microfluidics – to form VCSEL-based miniaturized optical trap array modules. In our previous work, the fabrication of VCSEL arrays and their characterization results were presented. In this paper, the integration of the VCSEL arrays into the module will be presented. Optical deflection experiments with microparticles will also be shown.
    Full-text · Conference Paper · Dec 2014
  • Markus Daubenschuez · Philipp Gerlach · Rainer Michalzik
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    ABSTRACT: We are implementing an electro–thermal simulation tool to optimize the characteristics of GaAs-based vertical- cavity surface-emitting lasers (VCSELs). For this purpose it turned out to be necessary to revisit basic material parameters. In this paper we elaborate on the composition, carrier density, and temperature dependencies of the electron mobility of AlxGa1−xAs semiconductors. We present the principles of the pragmatic quasi-three- dimensional (q3D) device model and show selected results.
    No preview · Conference Paper · May 2014
  • Marwan Bou Sanayeh · Anna Bergmann · Rainer Michalzik
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    ABSTRACT: Optical trapping for isolation and sorting of cells and particles inside microfluidic channels is an efficient non-destructive manipulation technique in the field of biophotonics. In recent years, vertical-cavity surface-emitting lasers (VCSELs) have been proven to be excellent light sources for particle manipulation inside microfluidic channels, where the small dimension and low power consumption of these devices enable direct integration with the channels. With such integration, however, the simultaneous manipulation or trapping of multiple particles require the usage of densely packed VCSEL arrays with very small device pitch, which makes the fabrication process more expensive and more complicated. We present an innovative technique for simultaneous optical multi-particle manipulation using one rectangular-shaped top-emitting AlGaAsGaAs VCSEL resonator having an active aperture area of around 100  14 µm2. The VCSEL emission wavelength is about 850 nm, which is suitable for usage in biophotonics, as biological materials present very little absorption in the near-infrared spectral range. Furthermore, this oblong VCSEL can potentially be integrated with polydimethylsiloxane (PDMS) microfluidic channels to form miniaturized optofluidic chips for ultra-compact particle handling and manipulation. We show efficient single as well as multiple polystyrene particle trapping and sorting inside PDMS microfluidic channels.
    No preview · Conference Paper · Apr 2014
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    Niazul Islam Khan · Anna Bergmann · Rainer Michalzik
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    ABSTRACT: Recently, optical manipulation combined with microfluidics has gained increasing interest in the field of biological sciences. This combination enables fast and inexpensive sample analysis and manipulation with reduced consumption of analytes. Another important factor in biology and medicine is the contamination-free handling of micrometer sized biological cells that makes the combination an attractive tool for the researchers. In recent years, the use of VCSELs (vertical-cavity surface-emitting lasers) as light sources in optical manipulation has got significant attention for their various advantages like the possibility of two-dimensional VCSEL array formation and their integration capability that enable parallel particle manipulation and miniaturization, respectively. In this paper, we present the fabrication of the integration-capable VCSEL arrays to form a VCSEL-based miniaturized optical trap module. To enhance the suitability of the VCSELs for optical trapping, we fabricate AlGaAs-GaAs-based surface-relief VCSEL arrays with a very small device pitch.
    Full-text · Conference Paper · Dec 2013
  • Hendrik Roscher · Rainer Michalzik
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    ABSTRACT: We present a novel approach to flip-chip-bondable vertical-cavity surface-emitting lasers and 2-D arrays emitting at 850 nm, the standard for multimode fiber optical interconnects. A unique sequence of wet-etching steps renders laser fabrication particularly efficient and allows the incorporation of near-cavity heat spreaders. Record-low thermal resistances of substrate-removed devices are achieved without compromising the dynamic properties.
    No preview · Article · Jul 2013 · IEEE Journal of Selected Topics in Quantum Electronics
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    ABSTRACT: Vertical-cavity surface-emitting lasers (VCSELs) with single-mode, single-polarization emission at a wavelength of 894.6 nm have been fabricated for Cs-based atomic clock applications. For polarization control, monolithically integrated surface gratings are employed. Simulated and experimental results show that the longitudinal position of the surface grating has a significant influence on the threshold current. With a grating in the topmost in-phase layer, the threshold currents are reduced to 40% compared to earlier atomic clock grating VCSELs with inverted structure. The output polarization is parallel to the grating lines with a peak-to-peak difference between the dominant and the suppressed polarization modes of 25 dB even at substrate temperatures up to 80 °C. Small-signal modulation characteristics of grating VCSELs are presented. The modulation bandwidth exceeds the required 5 GHz at a bias current of only 0.9 mA above threshold at room temperature. A revised chip design with smaller mesa size and thinner passivation layer has been implemented. The VCSELs show similar electrical parasitic bandwidths but require fewer fabrication steps and hence have reduced processing complexity. K-factors of less than 0.4 ns corresponding to a maximum 3-dB bandwidth exceeding 25 GHz are obtained at 80 °C ambient temperature.
    Full-text · Article · Jul 2013 · IEEE Journal of Selected Topics in Quantum Electronics
  • Alexander Kern · Ahmed Al-Samaneh · Dietmar Wahl · Rainer Michalzik
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    ABSTRACT: We present the monolithic integration, properties, and operation of 850-nm wavelength AlGaAs/GaAs-based vertical-cavity surface-emitting lasers (VCSELs) and PIN (p-doped-intrinsic-n-doped) photodetectors. The stacked layer structure requires sophisticated fabrication methods, but enables the use as, e.g., low-cost transceiver (TRx) devices. The TRx chips reported here are especially designed for bidirectional short-reach optical data links using a single butt-coupled standard multimode fiber (MMF). Photodiodes (PDs) with three different epitaxial layer structures are investigated. Devices with a 3-μm-thick intrinsic region show a responsivity of >0.6 A/W and have the lowest dark currents and highest 3-dB bandwidths of around 8 GHz. The maximum small-signal bandwidth of the VCSEL is 12.5 GHz. The parasitics of both devices are extracted by modeling the reflection spectra from S-parameter measurements. Investigations regarding the mutual influence between the closely integrated devices in full-duplex operation are carried out. The optical crosstalk is below -11 dB and the maximum electrical crosstalk between VCSEL and PIN PD of around -50 dB is nearly negligible. The butt-coupled MMF with a core diameter of 50 μm allows maximum fiber alignment tolerances in the range of 14-26 μm. Data transmission in the 10-Gb/s range is demonstrated in half-duplex and full-duplex mode.
    No preview · Article · Jul 2013 · IEEE Journal of Selected Topics in Quantum Electronics
  • Anna Bergmann · Alexander Hein · Rainer Michalzik
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    ABSTRACT: Vertical-cavity surface-emitting lasers (VCSELs) can be readily arranged in two-dimensional arrays for diverse applications such as parallel fiber-optic data transmission or high-power generation for illumination, but also optical trapping in microfluidic channels. Optical trapping is a phenomenon where a focused laser beam attracts particles to the beam center [1]. These forces, which arise from momentum transfer, enable the contamination-free handling of micrometer-sized particles in various applications. So-called optical lattices are two-dimensional arrangements of optical traps and are an attractive tool for automated particle handling, e.g., deflection or sorting. Typical methods for the formation of the beam patterns such as interferometry [2] or holography [3] require the use of bulky external optics which need accurate alignment. By directly integrating VCSEL arrays with microfluidic channels, it is possible to minimize the distance between the lasers and the particles. External optics can thus be eliminated. Owing to the small beam divergence, optical manipulation is then performed without any focusing lenses.
    No preview · Conference Paper · May 2013
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    Md. Jarez Miah · Ahmed Al-Samaneh · Dietmar Wahl · Rainer Michalzik
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    ABSTRACT: The work has fabricated flip-chip-bondable VCSELs for hybrid integration with atomic clock microsystems. A shallow surface relief in combination with a surface grating are etched in an extra topmost GaAs quarter-wave antiphase layer in the VCSEL structure, which establishes an inverted grating relief
    Full-text · Conference Paper · May 2013
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    ABSTRACT: We report on the characterization and validation of custom-designed 894.6 nm vertical-cavity surface-emitting lasers (VCSELs), for use in miniature Cs atomic clocks based on coherent population trapping (CPT). The laser relative intensity noise (RIN) is measured to be 1 × 10<sup>-11</sup> Hz<sup>-1</sup> at 10 Hz Fourier frequency, for a laser power of 700 μW. The VCSEL frequency noise is 10<sup>13</sup> · f<sup>-1</sup> Hz<sup>2</sup>/Hz in the 10 Hz < f < 10<sup>5</sup> Hz range, which is in good agreement with the VCSEL's measured fractional frequency instability (Allan deviation) of ≈ 1 × 10<sup>-8</sup> at 1 s, and also is consistent with the VCSEL's typical optical linewidth of 20-25 MHz. The VCSEL bias current can be directly modulated at 4.596 GHz with a microwave power of -6 to +6 dBm to generate optical sidebands for CPT excitation. With such a VCSEL, a 1.04 kHz linewidth CPT clock resonance signal is detected in a microfabricated Cs cell filled with Ne buffer gas. These results are compatible with state-of-the-art CPT-based miniature atomic clocks exhibiting a short-term frequency instability of 2-3×10<sup>-11</sup> at τ = 1 s and few 10<sup>-12</sup> at τ = 10<sup>4</sup> s integration time.
    No preview · Article · Mar 2013 · Optics Express
  • Pierluigi Debernardi · Wolfgang Schwarz · Rainer Michalzik
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    ABSTRACT: Recently, we reported the first successful fabrication of a marker-free microparticle detector with a unique working principle: when a particle is introduced into the cavity of an electrically pumped vertical-external-cavity surface-emitting laser, both the change of electrical operation as well as optical output parameters can be directly monitored, which enables phenotyping of properties, such as particle volume and refractive index. In the present contribution, we investigate this mechanism by numerical modeling of the wave-optical characteristics of the sensor.
    No preview · Article · Mar 2013 · IEEE Journal of Quantum Electronics
  • J.M. Ostermann · R. Michalzik
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    ABSTRACT: In most types of VCSELs, the light output polarization is inherently unstable. While, in case of single-mode oscillation, the emitted light is mainly linearly polarized, its orientation is not well defined. This is because both the resonator and the gain medium are quasi isotropic in the plane of the active layers. Since a stable polarization is required for almost all sensing and some datacom applications, extensive and in-depth investigations have been undertaken during the last twenty years in order to stabilize the polarization of VCSELs without affecting their favorable operation parameters. Polarization control of VCSELs can be achieved by introducing a polarization-dependent gain, an asymmetric resonator, or mirrors with a polarization-dependent reflectivity. It has turned out that the last approach is most promising. It can be realized by incorporating a shallow surface grating in the upper mirror of a top-emitting VCSEL. Several million grating VCSELs are in reliable operation meanwhile, mainly in optical computer mice.
    No preview · Article · Jan 2013 · Springer Series in Optical Sciences
  • Rainer Michalzik
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    ABSTRACT: This chapter attempts to briefly review the research history of vertical-cavity surface-emitting lasers (VCSELs). Based on the contents of previous monographs on VCSELs written in English, we motivate the selection of topics in the present book and give an introduction to the individual chapters. Moreover, we mention some other research that is not covered in a dedicated chapter in order to provide the readers with even deeper insights into VCSEL research. Future directions and opportunities are also indicated.
    No preview · Article · Jan 2013 · Springer Series in Optical Sciences
  • Rainer Michalzik
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    ABSTRACT: In this chapter we outline major principles of vertical-cavity surface-emitting laser (VCSEL) design and operation. Basic device properties and generally applicable cavity design rules are introduced. Characteristic parameters like threshold gain and current, differential quantum efficiency and power conversion efficiency, as well as thermal resistance are discussed. We describe the design of Bragg reflectors and explain the transfer matrix method as a convenient tool to compute VCSEL resonator properties in a one-dimensional approximation. Experimental results illustrate the emission characteristics of high-efficiency VCSELs that apply selective oxidation for current and photon confinement. Both the 850 and 980 nm wavelength regions are considered. The basic treatment of laser dynamics and noise behavior is presented in terms of the small-signal modulation response as well as the relative intensity noise. Finally we give some examples of VCSEL applications in fiber-based optical interconnects, i.e., optical data transmission over short distances.
    No preview · Article · Jan 2013 · Springer Series in Optical Sciences
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    ABSTRACT: Vertical-cavity surface-emitting lasers (VCSELs) with single-mode, single-polarization emission at a wavelength of 894.6 nm have become attractive light sources for miniaturized Cs-based atomic clocks. So far, VCSELs used for these applications are single-mode because of small active diameters which has the drawbacks of increased ohmic resistance and reduced lifetime. By employing surface grating reliefs, enhanced fundamental-mode emission as well as polarization-stable laser oscillation are achieved. VCSELs with 5 μm active diameter show side-mode suppression ratios of 20 dB even at currents close to thermal roll-over with orthogonal polarization suppression ratios better than 20 dB at elevated ambient temperatures up to 100 °C.
    No preview · Article · Oct 2012 · Applied Physics Letters
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    Krassimir Panajotov · Rainer Michalzik · Kent D. Choquette
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    ABSTRACT: It was our great pleasure and honor to work for the success of this special issue. We thank the contributors for their careful writing and report on significantly new results. Many thanks go to all referees for their hard and prompt work. As a result, this special issue provides a relevant snapshot of the most recent advances to the field, and we hope that it will motivate further work on the basis of these findings, concepts, and applications. We thank the editorial staff of Advances in Optical Technologies for their kind attention and their efforts in making this special issue possible.
    Full-text · Article · Sep 2012 · Advances in Optical Technologies
  • Source
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    ABSTRACT: In recent years, optical manipulation has gained increasing interest, especially in combination with microfluidics. This combination offers promising tools for a fast and cost-effective sample analysis and manipulation. The contamination-free handling of micrometer-sized particles without any mechanical contact is an attractive tool for biology and medicine. VCSELs (vertical-cavity surface-emitting lasers) are an excellent choice for the trapping lasers, offering the opportunity of parallel particle manipulation by using two-dimensional VCSEL arrays, and of miniaturization by means of integration. In this paper, we present two novel concepts for the realization of the so-called integrated optical trap, resembling a strongly miniaturized version of the typically bulky setup of an optical trap. For this purpose, AlGaAs-GaAs-based VCSEL arrays with a very small device pitch were fabricated. We show the realization of integration-ready particle manipulation devices, both with top-emitting and with bottom-emitting densely packed VCSEL arrays. The smallest pitch of 18 μm is achieved with bottom-emitting VCSEL arrays, having mesa diameters of only 16 μm.
    Full-text · Article · May 2012 · Proceedings of SPIE - The International Society for Optical Engineering

Publication Stats

3k Citations
192.16 Total Impact Points

Institutions

  • 1992-2015
    • Universität Ulm
      • Institute of Optoelectronics
      Ulm, Baden-Württemberg, Germany
  • 2007
    • Kharkiv National University of Radio Electronics
      Charkow, Kharkiv, Ukraine
  • 2005-2006
    • Free University of Brussels
      • Applied Physics and Photonics (TONA)
      Brussels, BRU, Belgium
  • 2004
    • Minia University
      • Department of Physics
      Minyat an Naşr, Muhafazat ad Daqahliyah, Egypt
  • 2001
    • Infineon Technologies
      München, Bavaria, Germany
  • 1998
    • ETH Zurich
      Zürich, Zurich, Switzerland