R. Michalzik

Universität Ulm, Ulm, Baden-Württemberg, Germany

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Publications (205)204.88 Total impact

  • 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.
    Proc SPIE, http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=1871483; 04/2014
  • Anna Bergmann, Alexander Hein, Rainer Michalzik
    The European Conference on Lasers and Electro-Optics; 05/2013
  • The European Conference on Lasers and Electro-Optics; 05/2013
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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.
    Optics Express 03/2013; 21(5):5781-5792. · 3.55 Impact Factor
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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.
    IEEE Journal of Quantum Electronics 03/2013; 49(3):301-308. · 2.11 Impact Factor
  • A. Kern, A. Al-Samaneh, D. Wahl, R. 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.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(4):6100313-6100313. · 4.08 Impact Factor
  • H. Roscher, R. 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.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(4):1700810-1700810. · 4.08 Impact Factor
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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.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(4):1701410-1701410. · 4.08 Impact Factor
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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.
    Applied Physics Letters 10/2012; 101(17). · 3.79 Impact Factor
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    ABSTRACT: A novel type of all-optical pressure sensor has been developed. In this context, a vertical-cavity surface-emitting laser (VCSEL) has been modified in its design to provide simultaneous light emission from both facets. One beam serves as measuring signal while the other establishes a reference; and both paths lie on the same optical axis. The VCSELs are based on active InGaAs quantum wells for laser output close to 960 nm wavelength where the GaAs substrate is transparent. From both top and bottom facet, single-polarization and single-mode beams are observed, having a power ratio of 1:2 to 1:4. In this paper we give insight into this new sensing application for VCSELs, describe the laser fabrication and the static operation characteristics as well as the noise properties which have paramount importance for high performance of the sensor. With regard to the sensor application in acoustics, the focus of the noise measurements is put on the low-frequency, i.e. kHz, regime. While laser diode noise performance is readily available for the MHz to GHz frequency range, only very limited data exists in the Hz to kHz domain. The relative intensity noise of both beams is measured and compared and the mutual correlation properties are investigated. The frequency noise is quantified.
    Proc SPIE 05/2012;
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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.
    Proc SPIE 05/2012;
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    ABSTRACT: In recent years, microfluidic devices have become important tools for cell analysis in biology and medicine. They enable fast and inexpensive analysis with reduced consumption of analytes. However, for optical detection involving FACS (fluorescence-activated cell sorting), sample preparation by attaching an antibody-labeled fluorochrome to the cell is required. Cell tagging by fluorochromes is a mature technology but might affect cell viability and function. In this paper we present a novel concept for marker-free detection and first realization steps. We show the integration of a microfluidic chip and an electrically pumped GaAs-based oxide-confined VECSEL (vertical-extended- cavity surface-emitting laser). Particles in the microchannel flow through the laser resonator and induce a change of the cavity resonance, thus allowing sensitive detection to trigger a subsequent sorting process.
    Biophotonics: Photonic Solutions for Better Health Care III, Proc. SPIE; 04/2012
  • Rainer Michalzik, Alexander Kern, Dietmar Wahl
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    ABSTRACT: We summarize the properties of 850nm wavelength AlGaAs/GaAs-based transceiver chips, monolithically integrating vertical-cavity surface-emitting lasers (VCSELs) and metal-semiconductor-metal (MSM) or PIN-type (p-doped-intrinsic-n-doped) photodiodes. Different chip designs enable half- and full-duplex bidirectional optical interconnection at multiple Gbit/s data rate over a single butt-coupled glass or polymer-clad optical fiber with core diameters ranging from 50 to 200 μm. The chips at both fiber ends are nominally identical and no external optics is required, which leads to lower cost in addition to volume and weight reduction. The commercial availability of such chips would directly enable applications in data communication and sensing networks in various environments such as automotive, home, industrial, in-building, or medical.
    Proc SPIE 02/2012;
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    ABSTRACT: The operation and optical crosstalk properties of low-cost AlGaAs-GaAs-based transceiver chips consisting of a VCSEL and a PIN photodetector are presented. Butt-coupled to a single 550 m long OM4-type standard multimode fiber, error-free bidirectional data transmission in full- and half-duplex mode is demonstrated at 10 Gbit/s.
    Optical Communications (ECOC), 2012 38th European Conference and Exhibition on; 01/2012
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    ABSTRACT: This paper reports the characterization of compact Cs CPT clocks based on a single buffer gas Cs-Ne microcell. Two different experimental set-ups are tested. The first set-up uses an externally-modulated 895 nm Distributed Feedback (DFB) laser source while the second one uses a directly-modulated custom-designed 895 nm Vertical Cavity Surface Emitting Laser (VCSEL) source. Using the DFB set-up, through reduction of the temperature-dependent collisional frequency shift and an active light shift suppression technique, a clock frequency stability of 3.8 × 10-11 at 1 s and greatly better than 10-11 at 60000 s is demonstrated. This proves the potential of single buffer gas Cs-Ne microfabricated cells for the development of miniature atomic clocks. Preliminar characterization of CPT resonances are reported with the VCSEL-based setup. It is expected that similar clock stability performances are achievable in this case.
    European Frequency and Time Forum (EFTF), 2012; 01/2012
  • Advances in Optical Technologies 01/2012; 2012.
  • Source
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    ABSTRACT: We report the integration of an electrically pumped GaAs-based oxide-confined vertical-extended-cavity surface-emitting laser and a microfluidic chip. Particles in the microchannels flow through the laser resonator and induce a change of the cavity resonance, thus allowing sensitive detection to trigger a subsequent sorting process.
    4th EOS Topical Meeting on Optical Microsystems; 09/2011
  • Source
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    ABSTRACT: We report the monolithic integration, fabrication, and electrooptical properties of AlGaAs-GaAs-based transceiver (TRx) chips for 850nm wavelength optical links with data rates of multiple Gbit/s. Using a single butt-coupled multimode fiber (MMF), low-cost bidirectional communication in half- and even full-duplex mode is demonstrated. Two design concepts are presented, based on a vertical-cavity surface-emitting laser (VCSEL) and a monolithically integrated p-doped-intrinsic-n-doped (PIN) or metal-semiconductor-metal (MSM) photodetector. Whereas the VCSEL-PIN photodiode (PD) chips are used for high-speed bidirectional data transmission over 62.5 and 50 μm core diameter MMFs, MSM TRx chips are employed for 100 or 200 μm large-area fibers. Such a monolithic transceiver design based on a well-established material system and avoiding the use of external fiber coupling optics is well suited for inexpensive and compact optical interconnects over distances of a few hundred meters. Standard MMF networks can thus be upgraded using high-speed VCSEL-PIN transceiver chips which are capable to handle data rates of up to 10Gbit/s.
    Advances in Optical Technologies 09/2011; Volume 2012.
  • Source
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    ABSTRACT: We present the monolithic design, fabrication, and properties of 850-nm wavelength AlGaAs-GaAs-based transceiver chips for low-cost bidirectional optical data transmission over a butt-coupled standard multimode fiber of a few hundred meter length. The chips with a stacked layer structure of a vertical-cavity surface-emitting laser (VCSEL) and a PIN (p-doped-intrinsic-n-doped) photodetector can well handle data rates of 9 Gb/s in back-to-back mode and 7 Gb/s over a 500-m-long 50-μm core diameter fiber.
    IEEE Photonics Technology Letters 09/2011; · 2.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We report the polarization stability and small-signal characteristics of single-polarization single-mode vertical-cavity surface-emitting lasers (VCSELs) emitting at 894.6-nm wavelength for Cs-based miniature atomic clock applications. Polarization control is achieved by integration of a semiconducting surface grating in the top Bragg mirror. The VCSELs are polarized orthogonal to the grating lines with a peak-to-peak difference between the dominant and the suppressed polarization modes reaching 29 dB even at substrate temperatures up to 65°C . A modulation bandwidth of more than 5 GHz is reached at only 0.5-mA bias. Modulation current efficiency factors larger than 12 GHz/√(mA) are achieved. Moreover, the intrinsic modulation characteristics of the VCSELs are investigated. A K -factor of less than 0.30 ns and a maximum 3-dB bandwidth exceeding 30 GHz are obtained.
    IEEE Photonics Technology Letters 09/2011; · 2.04 Impact Factor

Publication Stats

1k Citations
204.88 Total Impact Points


  • 1992–2013
    • Universität Ulm
      • Institute of Optoelectronics
      Ulm, Baden-Württemberg, Germany
  • 2008
    • Institute of Optoelectronics
      Essen, North Rhine-Westphalia, Germany
  • 2007
    • Kharkiv National University of Radio Electronics
      Charkow, Kharkivs’ka Oblast’, Ukraine
  • 2005–2007
    • Politecnico di Torino
      Torino, Piedmont, Italy
  • 2003–2006
    • 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
    • Ecole Normale Supérieure de Paris
      Lutetia Parisorum, Île-de-France, France
    • Infineon Technologies
      München, Bavaria, Germany