Peer Fischer

Publications (13)55.92 Total impact

• Article: Weak value amplified optical activity measurements.

  Marcel Pfeifer, Peer Fischer
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  ABSTRACT: We present a new form of optical activity measurement based on a modified weak value amplification scheme. It has recently been shown experimentally that the left- and right-circular polarization components refract with slightly different angles of refraction at a chiral interface causing a linearly polarized light beam to split into two. By introducing a polarization modulation that does not give rise to a change in the optical rotation it is possible to differentiate between the two circular polarization components even after post-selection with a linear polarizer. We show that such a modified weak value amplification measurement permits the sign of the splitting and thus the handedness of the optically active medium to be determined. Angular beam separations of Δθ ∼ 1 nanoradian, which corresponds to a circular birefringence of Δn ∼ 1 × 10(-9), could be measured with a relative error of less than 1%.
  Optics Express 08/2011; 19(17):16508-17. · 3.59 Impact Factor
• Article: Quantum-cascade laser-based vibrational circular dichroism.

  Steffen Lüdeke, Marcel Pfeifer, Peer Fischer
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  ABSTRACT: Vibrational circular dichroism (VCD) spectra were recorded with a tunable external-cavity quantum-cascade laser (QCL). In comparison with standard thermal light sources in the IR, QCLs provide orders of magnitude more power and are therefore promising for VCD studies in strongly absorbing solvents. The brightness of this novel light source is demonstrated with VCD and IR absorption measurements of a number of compounds, including proline in water.
  Journal of the American Chemical Society 03/2011; 133(15):5704-7. · 9.91 Impact Factor
• Article: Magnetically actuated propulsion at low Reynolds numbers: towards nanoscale control.

  Peer Fischer, Ambarish Ghosh
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  ABSTRACT: Significant progress has been made in the fabrication of micron and sub-micron structures whose motion can be controlled in liquids under ambient conditions. The aim of many of these engineering endeavors is to be able to build and propel an artificial micro-structure that rivals the versatility of biological swimmers of similar size, e.g. motile bacterial cells. Applications for such artificial "micro-bots" are envisioned to range from microrheology to targeted drug delivery and microsurgery, and require full motion-control under ambient conditions. In this Mini-Review we discuss the construction, actuation, and operation of several devices that have recently been reported, especially systems that can be controlled by and propelled with homogenous magnetic fields. We describe the fabrication and associated experimental challenges and discuss potential applications.
  Nanoscale 02/2011; 3(2):557-63. · 5.91 Impact Factor
• Article: Full phase and amplitude control in computer-generated holography.

  Markus Fratz, Peer Fischer, Dominik M Giel
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  ABSTRACT: We report what we believe to be the first realization of a computer-generated complex-valued hologram recorded in a single film of photoactive polymer. Complex-valued holograms give rise to a diffracted optical field with control over its amplitude and phase. The holograms are generated by a one-step direct laser writing process in which a spatial light modulator (SLM) is imaged onto a polymer film. Temporal modulation of the SLM during exposure controls both the strength of the induced birefringence and the orientation of the fast axis. We demonstrate that complex holograms can be used to impart arbitrary amplitude and phase profiles onto a beam and thereby open new possibilities in the control of optical beams.
  Optics Letters 12/2009; 34(23):3659-61. · 3.40 Impact Factor
• Source

  Available from: rowland.org

  Article: Controlled propulsion of artificial magnetic nanostructured propellers.

  Ambarish Ghosh, Peer Fischer
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  ABSTRACT: For biomedical applications, such as targeted drug delivery and microsurgery, it is essential to develop a system of swimmers that can be propelled wirelessly in fluidic environments with good control. Here, we report the construction and operation of chiral colloidal propellers that can be navigated in water with micrometer-level precision using homogeneous magnetic fields. The propellers are made via nanostructured surfaces and can be produced in large numbers. The nanopropellers can carry chemicals, push loads, and act as local probes in rheological measurements.
  Nano Letters 06/2009; 9(6):2243-5. · 13.20 Impact Factor
• Article: Digital polarization holograms with defined magnitude and orientation of each pixel's birefringence.

  Markus Fratz, Dominik M Giel, Peer Fischer
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  ABSTRACT: A new form of digital polarization holography is demonstrated that permits both the amplitude and the phase of a diffracted beam to be independently controlled. This permits two independent intensity images to be stored in the same hologram. To fabricate the holograms, a birefringence with defined retardance and orientation of the fast axis is recorded into a photopolymer film. The holograms are selectively read out by choosing the polarization state of the read beam. Polarization holograms of this kind increase the data density in holographic data storage and allow higher quality diffractive optical elements to be written.
  Optics Letters 05/2009; 34(8):1270-2. · 3.40 Impact Factor
• Source

  Available from: ArXiv

  Article: Janus particles with coupled electric and magnetic moments make a disordered magneto-electric medium

  Ambarish Ghosh, Nicholas K. Sheridon, Peer Fischer
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  ABSTRACT: We demonstrate that by combining permanent electric and magnetic moments in particles, it is possible to realize a new type of medium that allows for a cross-correlation between electric and magnetic properties of matter, known as magnetoelectric coupling. Magnetoelectric materials have so far been restricted to systems that exhibit long-range order in their electric and magnetic moments. Here, we show that a room-temperature, switchable magnetoelectric can be realized that is naturally disordered. The building blocks are Tellegen particles that orient in either an electric or a magnetic field.
  09/2007;
• Source

  Available from: rowland.org

  Article: Circular differential double diffraction in chiral media.

  Ambarish Ghosh, Furqan M Fazal, Peer Fischer
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  ABSTRACT: In an optically active liquid the diffraction angle depends on the circular polarization state of the incident light beam. We report the observation of circular differential diffraction in an isotropic chiral medium, and we demonstrate that double diffraction is an alternate means to determine the handedness (enantiomeric excess) of a solution.
  Optics Letters 08/2007; 32(13):1836-8. · 3.40 Impact Factor
• Source

  Available from: arxiv.org

  Article: Observation of the Faraday effect via beam deflection in a longitudinal magnetic field

  Ambarish Ghosh, Peer Fischer
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  ABSTRACT: We report the observation of the magnetic field induced circular differential deflection of light at the interface of a Faraday medium. The difference in the angles of refraction or reflection between the two circular polarization components is a function of the magnetic field strength and the Verdet constant. The reported phenomena permit the observation of the Faraday effect not via polarization rotation in transmission, but via changes in the propagation direction in refraction or in reflection. An unpolarized light beam is predicted to split into its two circular polarization components. The light deflection arises within a few wavelengths at the interface and is therefore independent of pathlength.
  02/2007;
• Source

  Available from: arxiv.org

  Article: Chiral molecules split light: Reflection and refraction in a chiral liquid.

  Ambarish Ghosh, Peer Fischer
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  ABSTRACT: A light beam changes direction as it enters a liquid at an angle from another medium, such as air. Should the liquid contain molecules that lack mirror symmetry, then it has been predicted by Fresnel that the light beam will not only change direction, but will actually split into two separate beams with a small difference in the respective angles of refraction. Here we report the observation of this phenomenon. We also demonstrate that the angle of reflection does not equal the angle of incidence in a chiral medium. Unlike conventional optical rotation, which depends on the path-length through the sample, the reported reflection and refraction phenomena arise within a few wavelengths at the interface and thereby suggest a new approach to polarimetry that can be used in microfluidic volumes.
  Physical Review Letters 11/2006; 97(17):173002. · 7.37 Impact Factor
• Source

  Available from: Frank Vollmer

  Article: Ring-resonator-based frequency-domain optical activity measurements of a chiral liquid.

  Frank Vollmer, Peer Fischer
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  ABSTRACT: Chiral liquids rotate the plane of polarization of linearly polarized light and are therefore optically active. Here we show that optical rotation can be observed in the frequency domain. A chiral liquid introduced in a fiber-loop ring resonator that supports left and right circularly polarized modes gives rise to relative frequency shifts that are a direct measure of the liquid's circular birefringence and hence of its optical activity. The effect is in principle not diminished if the circumference of the ring is reduced. The technique is similarly applicable to refractive index and linear birefringence measurements.
  Optics Letters 03/2006; 31(4):453-5. · 3.40 Impact Factor
• Source

  Available from: François Hache

  Article: Nonlinear optical spectroscopy of chiral molecules.

  Peer Fischer, François Hache
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  ABSTRACT: We review nonlinear optical processes that are specific to chiral molecules in solution and on surfaces. In contrast to conventional natural optical activity phenomena, which depend linearly on the electric field strength of the optical field, we discuss how optical processes that are nonlinear (quadratic, cubic, and quartic) functions of the electromagnetic field strength may probe optically active centers and chiral vibrations. We show that nonlinear techniques open entirely new ways of exploring chirality in chemical and biological systems: The cubic processes give rise to nonlinear circular dichroism and nonlinear optical rotation and make it possible to observe dynamic chiral processes at ultrafast time scales. The quadratic second-harmonic and sum-frequency-generation phenomena and the quartic processes may arise entirely in the electric-dipole approximation and do not require the use of circularly polarized light to detect chirality. They provide surface selectivity and their observables can be relatively much larger than in linear optical activity. These processes also give rise to the generation of light at a new color, and in liquids this frequency conversion only occurs if the solution is optically active. We survey recent chiral nonlinear optical experiments and give examples of their application to problems of biophysical interest.
  Chirality 11/2005; 17(8):421-37. · 2.35 Impact Factor
• Source

  Available from: Frank Vollmer

  Article: Frequency-domain displacement sensing with a fiber ring-resonator containing a variable gap

  Frank Vollmer, Peer Fischer
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  ABSTRACT: Ring-resonators are in general not amenable to strain-free (non-contact) displacement measurements. We show that this limitation may be overcome if the ring-resonator, here a fiber-loop, is designed to contain a gap, such that the light traverses a free-space part between two aligned waveguide ends. Displacements are determined with nanometer sensitivity by measuring the associated changes in the resonance frequencies. Miniaturization should increase the sensitivity of the ring-resonator interferometer. Ring geometries that contain an optical circulator can be used to profile reflective samples.
  Sensors and Actuators A: Physical.