Matti Kaivola - Academia.edu (original) (raw)
Papers by Matti Kaivola
Optics Communications, 2010
We study the spatial coherence properties of a three-dimensional, primary, quasi-homogeneous, and... more We study the spatial coherence properties of a three-dimensional, primary, quasi-homogeneous, and isotropic source and the far field that it generates. We assess the spectrum, degree of polarization, electromagnetic degree of coherence, and effective degree of coherence of the source and of the far field. We also demonstrate the formalism for a spherical Gaussian Schell-model current source. The polarization properties of light are fully accounted for in the analysis, and it is found that certain results pertaining to scalar coherence theory are reproduced also within the electromagnetic treatment.
Optics Express, 2015
We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtain... more We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtained using a stroboscopic white-light interferometer. The data analysis makes use of the high resolution available in the measured interferometric phase data, enabling the characterization of the out-of-plane surface vibration fields in electrically excited microstructures with better than 100 pm amplitude resolution. The setup uses a supercontinuum light source with tailored spectral properties for obtaining the high amplitude resolution. The duration of the light pulses is less than 300 ps to allow the detection of high frequencies. These capabilities enabled a detailed measurement of the focusing of surface acoustic waves by an annular interdigital transducer structure operating at 74 MHz, featuring a maximum vibration amplitude of 3 nm.
Physical Review A, 1983
We report on a quantitative experimental investigation of velocity-changing collisions by means o... more We report on a quantitative experimental investigation of velocity-changing collisions by means of velocity-selective optical pumping (VSOP). We have calculated the VSOP line shape for an atom with hyperfine structure with the use of two phenomenological kernels for the collision effects: the Keilson-Storer kernel, and a two-term kernel consisting of a broad Keilson-Storer part and a narrower Gaussian component. Corrections were included to account for the finite absorption in the sample and the backward reflection of the pumping beam. The experiments were carried out in sodium vapor with neon as the perturber gas. The D~line of sodium was used for optical pumping, and the orientation of the ground state was detected. Free parameters of the theory were determined by fitting the predicted line shapes to experimental curves. The Keilson-Storer kernel proved unsatisfactory, but the two-term kernel reproduced well the observed line shapes over the entire collision profiles in the neon pressure range 0-57 mtorr. In an independent experiment using rapidly modulated VSOP we also measured directly the cross section of velocity-changing collisions: cr =(1.13+0.10)X 10 ' cm. The large weight obtained for the narrow Gaussian from the
Optics Communications, 1984
We report narrow structures observed in the population of the intermediate level of a two-photon ... more We report narrow structures observed in the population of the intermediate level of a two-photon transition in a fast beam of metastable 20Ne* atoms. Steady-state theory provides a description of two coherent processes leading to population trapping. Both processes proceed via the ordinary two-photon coherence. One is then completed with a reversed-time ordering of the last two interactions, leading to
Optical Materials Express, 2011
ABSTRACT We investigate into a new type of liquid crystal (LC) heterogeneous system that contains... more ABSTRACT We investigate into a new type of liquid crystal (LC) heterogeneous system that contains hydrogen-bonded polymer-azo-dye complexes at a low concentration. The suspension shows a unique selforienting property and a spontaneous anchoring transition from planar to homeotropic alignment on a rubbed polyimide surface. We suggest a simple polymer adsorption model to explain the universal homeotropic orienting property. The complex-doped LC suspension can be used as a new liquid crystalline material that does not require any additional alignment processing or treatment.
Frontiers in Optics, 2005
The degree of polarization in high-NA focused random optical fields is analyzed using the Richard... more The degree of polarization in high-NA focused random optical fields is analyzed using the Richards-Wolf method and 3D spectral coherence theory. Significant changes in the polarization degree are predicted. These results are explained by considering the focal-field spectral densities and electric-field correlations.
2010 IEEE International Ultrasonics Symposium, 2010
ABSTRACT We report laser probing results on a set of piezo electrically actuated square plate MEM... more ABSTRACT We report laser probing results on a set of piezo electrically actuated square plate MEMS resonators. The plate size of the resonators is systematically varied in order to study the frequency scaling of the main, square-extensional resonance mode in the range between 13-30 MHz. In electrical impedance measurements, an unexpected splitting of the main mode branch into two separate mode branches is observed at intermediate plate size dimensions. To get further insight of the origin of the splitting phenomenon, the two observed mode branches are directly measured by laser probing. The laser probe measurements confirmed that the vibration modes on both branches had a lateral vibration field characteristic for a square-extensional mode. Furthermore, the results indicate that the square-extensional mode may couple to other resonance modes occurring around 20-22 MHz, hence causing the splitting of the mode branch.
Optics Express, 2014
We present a picosecond supercontinuum light source designed for stroboscopic white-light interfe... more We present a picosecond supercontinuum light source designed for stroboscopic white-light interferometry. This source offers a potential for high-resolution characterization of vibrational fields in electromechanical components with frequencies up to the GHz range. The light source concept combines a gain-switched laser diode, the output of which is amplified in a two-stage fiber amplifier, with supercontinuum generation in a microstructured optical fiber. Implemented in our white-light interferometer setup, optical pulses with optimized spectral properties and below 310 ps duration are used for stroboscopic illumination at freely adjustable repetition rates. The performance of the source is demonstrated by characterizing the surface vibration field of a square-plate silicon MEMS resonator at 3.37 MHz. A minimum detectable vibration amplitude of less than 100 pm is reached.
19th Congress of the International Commission for Optics: Optics for the Quality of Life, 2003
ABSTRACT
2010 9th Euro-American Workshop on Information Optics, 2010
This work is focused on the design and fabrication of plasmonic nanostructures for spectroscopic ... more This work is focused on the design and fabrication of plasmonic nanostructures for spectroscopic applications. Our goal is to fabricate large-surface-area plasmonic nanostructures that provide local enhancement of electromagnetic fields for applications in fluorescence and Raman scattering spectroscopy. Periodic two-dimensional arrays of nanogrooves and nanopillars are obtained by holographic photolithography that makes use of surface relief gratings on azo-polymer films.
SPIE Proceedings, 2007
ABSTRACT We show that hydrogen bonding between azo molecules and polymer host enhances the photoi... more ABSTRACT We show that hydrogen bonding between azo molecules and polymer host enhances the photoinduced optical anisotropy in azo-containing polymers without sacrificing the ease of processing of conventional guest–host sys-tems. The primary mechanism behind the enhancement is the possibility to use high dye doping levels compared to conventional guest–host systems due to reduced aggregation tendency of the dyes. For Disperse Red 1, the saturated birefringence is enhanced by a factor of 8 due to hydrogen bonding at 30 wt % loading. Moreover, hydrogen bonding reduces the mobility of the guest molecules in the polymer host which improves the temporal stability of the induced birefringence to a level comparable to side-chain polymers.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
Photoinduced optical anisotropy of azobenzene-containing polymers has emerged as a source of exci... more Photoinduced optical anisotropy of azobenzene-containing polymers has emerged as a source of exciting optical phenomena with a range of potential applications. Here we show that the benefits of the guest-host and covalently-linked systems can be combined by exploiting specific non-covalent interactions between the dye molecules and the polymer host. More precisely, hydrogen bonding between the dye and the polymer host
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT Nonlinear effects have become an important issue in microacoustic component development ... more ABSTRACT Nonlinear effects have become an important issue in microacoustic component development to improve performance. In addition to the modeling, simulations and electrical characterization tools, a direct method for observing the nonlinear vibration fields in these components would be beneficial in the device design. We use laser probing for studying the nonlinear acoustic behavior in two square-extensional (SE) mode MEMS resonators, whose electrically measured SE-resonances compress above a certain, unexpectedly low, input drive power level. In the laser probe measurements, the vibration amplitude of the SE mode is observed to nearly saturate above this drive power level, and simultaneously another mode at a different frequency is excited. It is also observed that the nonlinearly excited modes are different in the two resonators, and each resonator has a distinct nonlinear behavior.
Optics Letters, 2010
We present a novel materials concept for optical inscription of stable birefringent optical eleme... more We present a novel materials concept for optical inscription of stable birefringent optical elements into guest-host type polymers by making use of chromophore aggregation. The method is based on photoalignment of azobenzene chromophores, the aggregation of which leads to significant enhancement and stabilization of the photoinduced birefringence. The obtained order parameter of the molecular alignment (0.3) in combination with the exceptional thermal stability of the anisotropy renders the material system unique among amorphous azobenzene-containing polymers and provides a route toward designing efficient photoresponsive optical elements through the guest-host type approach.
Optics Letters, 2004
The normalized intensity fluctuations of arbitrary electromagnetic wave fields obeying Gaussian s... more The normalized intensity fluctuations of arbitrary electromagnetic wave fields obeying Gaussian statistics are expressed in terms of the three-dimensional degree of polarization. This general formulation implies an important physical result concerning the polarization of planar fields and the dimensionality of the formalism. The results are expected to be particularly useful in intensity interferometry.
Optics Express, 2013
We present an approach for numerically solving the multimode generalized nonlinear Schrödinger eq... more We present an approach for numerically solving the multimode generalized nonlinear Schrödinger equation (MM-GNLSE). We propose to transform the MM-GNLSE to a system of first-order ordinary differential equations (ODEs) that can then be solved using readily available ODE solvers, thus making modeling of pulse propagation in multimode fibers easier. The solver is verified for the simplest multimode case in which only the two orthogonal polarization states in a non-birefringent microstructured optical fiber are involved. Also, the nonlinear dynamics of the degree and state of spectral polarization are presented for this case.
Optics Express, 2013
Nanoscale plasmonic structures allow for control of the emission of single emitters, such as fluo... more Nanoscale plasmonic structures allow for control of the emission of single emitters, such as fluorescent molecules and quantum dots, enabling phenomena such as lifetime reduction, emission redirection and color sorting of photons. We present single emitter emission tailored with arrays of holes of heterogeneous size, perforated in a gold film. With spatial control of the local amplitude and phase of the electromagnetic field radiated by the emitter, a desired near-or far-field distribution of the electromagnetic waves can be obtained. This control is established by varying the aspect ratio of the individual holes and the periodicity of the array surrounding the emitter. As an example showing the versatility of the technique, we present the strong focusing of the radiation of a highly divergent dipole source, for both p-and s-polarized waves.
Optics Communications, 2010
We study the spatial coherence properties of a three-dimensional, primary, quasi-homogeneous, and... more We study the spatial coherence properties of a three-dimensional, primary, quasi-homogeneous, and isotropic source and the far field that it generates. We assess the spectrum, degree of polarization, electromagnetic degree of coherence, and effective degree of coherence of the source and of the far field. We also demonstrate the formalism for a spherical Gaussian Schell-model current source. The polarization properties of light are fully accounted for in the analysis, and it is found that certain results pertaining to scalar coherence theory are reproduced also within the electromagnetic treatment.
Optics Express, 2015
We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtain... more We present phase-sensitive absolute amplitude measurements of surface acoustic wave fields obtained using a stroboscopic white-light interferometer. The data analysis makes use of the high resolution available in the measured interferometric phase data, enabling the characterization of the out-of-plane surface vibration fields in electrically excited microstructures with better than 100 pm amplitude resolution. The setup uses a supercontinuum light source with tailored spectral properties for obtaining the high amplitude resolution. The duration of the light pulses is less than 300 ps to allow the detection of high frequencies. These capabilities enabled a detailed measurement of the focusing of surface acoustic waves by an annular interdigital transducer structure operating at 74 MHz, featuring a maximum vibration amplitude of 3 nm.
Physical Review A, 1983
We report on a quantitative experimental investigation of velocity-changing collisions by means o... more We report on a quantitative experimental investigation of velocity-changing collisions by means of velocity-selective optical pumping (VSOP). We have calculated the VSOP line shape for an atom with hyperfine structure with the use of two phenomenological kernels for the collision effects: the Keilson-Storer kernel, and a two-term kernel consisting of a broad Keilson-Storer part and a narrower Gaussian component. Corrections were included to account for the finite absorption in the sample and the backward reflection of the pumping beam. The experiments were carried out in sodium vapor with neon as the perturber gas. The D~line of sodium was used for optical pumping, and the orientation of the ground state was detected. Free parameters of the theory were determined by fitting the predicted line shapes to experimental curves. The Keilson-Storer kernel proved unsatisfactory, but the two-term kernel reproduced well the observed line shapes over the entire collision profiles in the neon pressure range 0-57 mtorr. In an independent experiment using rapidly modulated VSOP we also measured directly the cross section of velocity-changing collisions: cr =(1.13+0.10)X 10 ' cm. The large weight obtained for the narrow Gaussian from the
Optics Communications, 1984
We report narrow structures observed in the population of the intermediate level of a two-photon ... more We report narrow structures observed in the population of the intermediate level of a two-photon transition in a fast beam of metastable 20Ne* atoms. Steady-state theory provides a description of two coherent processes leading to population trapping. Both processes proceed via the ordinary two-photon coherence. One is then completed with a reversed-time ordering of the last two interactions, leading to
Optical Materials Express, 2011
ABSTRACT We investigate into a new type of liquid crystal (LC) heterogeneous system that contains... more ABSTRACT We investigate into a new type of liquid crystal (LC) heterogeneous system that contains hydrogen-bonded polymer-azo-dye complexes at a low concentration. The suspension shows a unique selforienting property and a spontaneous anchoring transition from planar to homeotropic alignment on a rubbed polyimide surface. We suggest a simple polymer adsorption model to explain the universal homeotropic orienting property. The complex-doped LC suspension can be used as a new liquid crystalline material that does not require any additional alignment processing or treatment.
Frontiers in Optics, 2005
The degree of polarization in high-NA focused random optical fields is analyzed using the Richard... more The degree of polarization in high-NA focused random optical fields is analyzed using the Richards-Wolf method and 3D spectral coherence theory. Significant changes in the polarization degree are predicted. These results are explained by considering the focal-field spectral densities and electric-field correlations.
2010 IEEE International Ultrasonics Symposium, 2010
ABSTRACT We report laser probing results on a set of piezo electrically actuated square plate MEM... more ABSTRACT We report laser probing results on a set of piezo electrically actuated square plate MEMS resonators. The plate size of the resonators is systematically varied in order to study the frequency scaling of the main, square-extensional resonance mode in the range between 13-30 MHz. In electrical impedance measurements, an unexpected splitting of the main mode branch into two separate mode branches is observed at intermediate plate size dimensions. To get further insight of the origin of the splitting phenomenon, the two observed mode branches are directly measured by laser probing. The laser probe measurements confirmed that the vibration modes on both branches had a lateral vibration field characteristic for a square-extensional mode. Furthermore, the results indicate that the square-extensional mode may couple to other resonance modes occurring around 20-22 MHz, hence causing the splitting of the mode branch.
Optics Express, 2014
We present a picosecond supercontinuum light source designed for stroboscopic white-light interfe... more We present a picosecond supercontinuum light source designed for stroboscopic white-light interferometry. This source offers a potential for high-resolution characterization of vibrational fields in electromechanical components with frequencies up to the GHz range. The light source concept combines a gain-switched laser diode, the output of which is amplified in a two-stage fiber amplifier, with supercontinuum generation in a microstructured optical fiber. Implemented in our white-light interferometer setup, optical pulses with optimized spectral properties and below 310 ps duration are used for stroboscopic illumination at freely adjustable repetition rates. The performance of the source is demonstrated by characterizing the surface vibration field of a square-plate silicon MEMS resonator at 3.37 MHz. A minimum detectable vibration amplitude of less than 100 pm is reached.
19th Congress of the International Commission for Optics: Optics for the Quality of Life, 2003
ABSTRACT
2010 9th Euro-American Workshop on Information Optics, 2010
This work is focused on the design and fabrication of plasmonic nanostructures for spectroscopic ... more This work is focused on the design and fabrication of plasmonic nanostructures for spectroscopic applications. Our goal is to fabricate large-surface-area plasmonic nanostructures that provide local enhancement of electromagnetic fields for applications in fluorescence and Raman scattering spectroscopy. Periodic two-dimensional arrays of nanogrooves and nanopillars are obtained by holographic photolithography that makes use of surface relief gratings on azo-polymer films.
SPIE Proceedings, 2007
ABSTRACT We show that hydrogen bonding between azo molecules and polymer host enhances the photoi... more ABSTRACT We show that hydrogen bonding between azo molecules and polymer host enhances the photoinduced optical anisotropy in azo-containing polymers without sacrificing the ease of processing of conventional guest–host sys-tems. The primary mechanism behind the enhancement is the possibility to use high dye doping levels compared to conventional guest–host systems due to reduced aggregation tendency of the dyes. For Disperse Red 1, the saturated birefringence is enhanced by a factor of 8 due to hydrogen bonding at 30 wt % loading. Moreover, hydrogen bonding reduces the mobility of the guest molecules in the polymer host which improves the temporal stability of the induced birefringence to a level comparable to side-chain polymers.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
Photoinduced optical anisotropy of azobenzene-containing polymers has emerged as a source of exci... more Photoinduced optical anisotropy of azobenzene-containing polymers has emerged as a source of exciting optical phenomena with a range of potential applications. Here we show that the benefits of the guest-host and covalently-linked systems can be combined by exploiting specific non-covalent interactions between the dye molecules and the polymer host. More precisely, hydrogen bonding between the dye and the polymer host
2012 IEEE International Ultrasonics Symposium, 2012
ABSTRACT Nonlinear effects have become an important issue in microacoustic component development ... more ABSTRACT Nonlinear effects have become an important issue in microacoustic component development to improve performance. In addition to the modeling, simulations and electrical characterization tools, a direct method for observing the nonlinear vibration fields in these components would be beneficial in the device design. We use laser probing for studying the nonlinear acoustic behavior in two square-extensional (SE) mode MEMS resonators, whose electrically measured SE-resonances compress above a certain, unexpectedly low, input drive power level. In the laser probe measurements, the vibration amplitude of the SE mode is observed to nearly saturate above this drive power level, and simultaneously another mode at a different frequency is excited. It is also observed that the nonlinearly excited modes are different in the two resonators, and each resonator has a distinct nonlinear behavior.
Optics Letters, 2010
We present a novel materials concept for optical inscription of stable birefringent optical eleme... more We present a novel materials concept for optical inscription of stable birefringent optical elements into guest-host type polymers by making use of chromophore aggregation. The method is based on photoalignment of azobenzene chromophores, the aggregation of which leads to significant enhancement and stabilization of the photoinduced birefringence. The obtained order parameter of the molecular alignment (0.3) in combination with the exceptional thermal stability of the anisotropy renders the material system unique among amorphous azobenzene-containing polymers and provides a route toward designing efficient photoresponsive optical elements through the guest-host type approach.
Optics Letters, 2004
The normalized intensity fluctuations of arbitrary electromagnetic wave fields obeying Gaussian s... more The normalized intensity fluctuations of arbitrary electromagnetic wave fields obeying Gaussian statistics are expressed in terms of the three-dimensional degree of polarization. This general formulation implies an important physical result concerning the polarization of planar fields and the dimensionality of the formalism. The results are expected to be particularly useful in intensity interferometry.
Optics Express, 2013
We present an approach for numerically solving the multimode generalized nonlinear Schrödinger eq... more We present an approach for numerically solving the multimode generalized nonlinear Schrödinger equation (MM-GNLSE). We propose to transform the MM-GNLSE to a system of first-order ordinary differential equations (ODEs) that can then be solved using readily available ODE solvers, thus making modeling of pulse propagation in multimode fibers easier. The solver is verified for the simplest multimode case in which only the two orthogonal polarization states in a non-birefringent microstructured optical fiber are involved. Also, the nonlinear dynamics of the degree and state of spectral polarization are presented for this case.
Optics Express, 2013
Nanoscale plasmonic structures allow for control of the emission of single emitters, such as fluo... more Nanoscale plasmonic structures allow for control of the emission of single emitters, such as fluorescent molecules and quantum dots, enabling phenomena such as lifetime reduction, emission redirection and color sorting of photons. We present single emitter emission tailored with arrays of holes of heterogeneous size, perforated in a gold film. With spatial control of the local amplitude and phase of the electromagnetic field radiated by the emitter, a desired near-or far-field distribution of the electromagnetic waves can be obtained. This control is established by varying the aspect ratio of the individual holes and the periodicity of the array surrounding the emitter. As an example showing the versatility of the technique, we present the strong focusing of the radiation of a highly divergent dipole source, for both p-and s-polarized waves.