298 research outputs found

    Nano-jet Related to Bessel Beams and to Super-Resolutions in Micro-sphere Optical Experiments

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    The appearance of a Nano-jet in the micro-sphere optical experiments is analyzed by relating this effect to non-diffracting Bessel beams. By inserting a circular aperture with a radius which is in the order of subwavelength in the EM waist, and sending the transmitted light into a confocal microscope, EM fluctuations by the different Bessel beams are avoided. On this constant EM field evanescent waves are superposed. While this effect improves the optical-depth of the imaging process, the object fine-structures are obtained, from the modulation of the EM fields by the evanescent waves. The use of a combination of the micro-sphere optical system with an interferometer for phase contrast measurements is described.Comment: 14 pages , 2 figure

    Raman and quantitative-phase microscope with counter-propagating beams demonstrated on HeLa cells

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    Raman spectroscopy probes the chemical composition of biological samples with sub-micron resolution, rendering it a powerful tool in the diagnosis of several diseases and the study unstained biological samples. However, the weak Raman signal leads to long acquisition times, unsuited to study dynamical processes or large samples. Quantitative phase microscopy can speed up the diagnosis, provide complementary data, and potentially link the Raman fingerprint of the sample with corresponding refractive indices. Here we demonstrate a 4Pi microscope that records both the Raman and quantitative phase information from the same sample spot

    Conventional and differential scanning optical microscopy using higher-order Gaussian-Hermite beam patterns

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    This thesis addresses the problem of contrast in scanning optical microscopy by resorting to differential imaging. The use of a unique, two-wavelength laser as the coherent source in a scanning format is investigated. In particular, it is shown that the TEM10 mode of this laser provides a novel method for performing simultaneous conventional and differential microscopy. Results are presented on the use of the laser for performing differential imaging. In addition, the technique is extended to encompass a second, tunable, laser. Rather than performing electronic differentiation, the TEMi0 mode of this, second, laser provides an in-situ, optical differential microscope. Two different optical configurations are implemented, one system relies on electronic differentiation, while the second differentiates optically. These techniques could have special applications in general microscopy, and precision metrology

    Electro-optic routing of photons from single quantum dots in photonic integrated circuits

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    Recent breakthroughs in solid-state photonic quantum technologies enable generating and detecting single photons with near-unity efficiency as required for a range of photonic quantum technologies. The lack of methods to simultaneously generate and control photons within the same chip, however, has formed a main obstacle to achieving efficient multi-qubit gates and to harness the advantages of chip-scale quantum photonics. Here we propose and demonstrate an integrated voltage-controlled phase shifter based on the electro-optic effect in suspended photonic waveguides with embedded quantum emitters. The phase control allows building a compact Mach-Zehnder interferometer with two orthogonal arms, taking advantage of the anisotropic electro-optic response in gallium arsenide. Photons emitted by single self-assembled quantum dots can be actively routed into the two outputs of the interferometer. These results, together with the observed sub-microsecond response time, constitute a significant step towards chip-scale single-photon-source de-multiplexing, fiber-loop boson sampling, and linear optical quantum computing.Comment: 7 pages, 4 figues + supplementary informatio

    Design and Development of an Optical Chip Interferometer For High Precision On-Line Surface Measurement

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    Advances in manufacturing and with the demand of achieving faster throughput at a lower cost in any industrial setting have put forward the need for embedded metrology. Embedded metrology is the provision of metrology on the manufacturing platform, enabling measurement without the removal of the workpiece. Providing closer integration of metrology upon the manufacturing platform will improve material processing and reliability of manufacture for high added value products in ultra-high-precision engineering. Currently, almost all available metrology instrumentation is either too bulky, slow, destructive in terms of damaging the surfaces with a contacting stylus or is carried out off-line. One technology that holds promise for improving the current state-of-the-art in the online measurement of surfaces is hybrid photonic integration. This technique provides for the integration of individual optoelectronic components onto silicon daughter boards which are then incorporated on a silica motherboard containing waveguides to produce a complete photonic circuit. This thesis presents first of its kind a novel chip interferometer sensor based on hybrid integration technology for online surface and dimensional metrology applications. The complete metrology sensor system is structured into two parts; hybrid photonic chip and optical probe. The hybrid photonic chip interferometer is based on a silica-on-silicon etched integrated-optic motherboard containing waveguide structures and evanescent couplers. Upon the motherboard, electro-optic components such as photodiodes and a semiconductor gain block are mounted and bonded to provide the required functionality. Optical probe is a separate entity attached to the integrated optic module which serves as optical stylus for surface scanning in two measurement modes a) A single-point for measuring distance and thus form/surface topography through movement of the device or workpiece, b) Profiling (lateral scanning where assessment of 2D surface parameters may be determined in a single shot. Wavelength scanning and phase shifting inteferometry implemented for the retrival of phase information eventually providing the surface height measurement. The signal analysis methodology for the two measurement modes is described as well as a theoretical and experimental appraisal of the metrology capabilities in terms of range and resolution. The incremetal development of various hybrid photonic modules such as wavelength encoder unit, signal detection unit etc. of the chip interferometer are presented. Initial measurement results from various componets of metrology sensor and the surface measurement results in two measurement modes validate the applicability of the described sensor system as a potential metrology tool for online surface measurement applications

    Examining the relationship of variables related to litigation regarding students with significant cognitive disabilities

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    Non-null interferometry offers a viable alternative to traditional interferometric testing of aspheric micro-lenses since computer generated holograms or null optics whose fabrication and testing are very expensive, are not required. However, due to the violation of the Nyquist sampling theorem these non-null tests provide limited dynamic range. The dynamic range of these non-null tests can be extended by implementing an index liquid which allows the measurement of micro-lenses with several microns of departure from a sphere. The first objective of this dissertation was to test important micro-lens properties such as the sag, radius of curvature and form errors for a micro-lens by using an index liquid. The results compared favorably to measurements taken on a Twyman-Green interferometer, a contact profilometer and an optical non-contact profilometer. Also, retrace errors, which are aberrations caused by altered ray paths of the test beam through a micro-lens were investigated. Reverse ray-trace and reverse optimization techniques are typically used to calibrate retrace errors, but in depth knowledge of the interferometer optics is assumed, and hence cannot be used for systems containing commercial optics. In this dissertation, re-trace errors are quantified and a novel calibration procedure derived to experimentally compensate for these errors. This retrace error calibration led to agreement of within 1% for the sag values between the index liquid technique and a profilometer. The second objective of this dissertation was to enable measurements of arbitrary geometries and to reduce testing time compared to profilometry. The index liquid technique was applied to faceted microstructured optical products which are becoming more widespread due to advances in manufacturing. Many of these structures contain faceted surfaces with steep slopes. Adequate metrology for such surfaces is lacking. The use of the index liquid technique achieved high quality, high speed measurements of such faceted microstructures. Refraction is accounted for at the interfaces, rather than consider only optical path length changes due to the index liquid, and this significantly improves the facet angle measurement. The technique is demonstrated with the measurement of an array of micro-pyramids and show that our results are in good agreement with measurements taken on a contact profilometer. The index liquid measurements took approximately five seconds to complete compared to a measurement time of six hours for the contact profilometer. The technique was also extended to measure opaque micro-corner cubes by implementing an intermediate replication step. This allowed a measurement of the angle between facets of a nickel micro-corner cube hexagonal array, a combination not previously demonstrated in the literature. A first order uncertainty analysis was carried out on the index liquid technique to determine any limiting factors that need to be taken into account when assessing such parameters as the sag and facet angle. The uncertainties in the sag and facet angle were found to be well below 1%. Lastly secondary factors such interferometer bias, refraction, masking effects and pixel calibration were investigated to understand the possible implications on the sag and facet angle calculation

    A new method of temporal phase shifting using principle of stroboscopy for characterizing microstructures

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    Temporal Phase Shifting Interferometry is the most common method for characterization of surface, profile and displacement properties of micro devices. Common methods of phase shifting require PZT based devices that have inherent errors due to non-linearity. To avoid these errors during phase shifting, a new phase shifting technique is presented in this work. A detailed analysis of the temporal phase shifting technique was performed and an optimized methodology for phase shifting was also established. This technique utilizes the advantage of stroboscopic interferometry to create phase shifted images without requiring any component for phase shifting. The feasibility of the proposed method of phase shifting was demonstrated using the developed Acoustic-Optic Modulated Stroboscopic Interferometer (AOMSI) on simple 1D and 2D micro structures designed specifically for this purpose. The proposed method was used for surface profiling and static characterization of the microstructures. Experiments were performed on microcantilevers in order to extract the curvature of the device due to residual stress on it. The same device was tested under a commercial surface profiler with 1Å resolution and the results were found to be in good agreement with the results from the proposed technique. Static characterization was performed to identify the tip deflection and profile variation of the microcantilever in response to various DC voltages. A capacitor-based cantilever was tested under varied electrostatic loads and the deflection of the cantilever was extracted using the proposed method. The deflection of the cantilever was predicted using a theoretical model based on energy method. Static characterization results from the proposed technique were found to be in good agreement with the predicted results. To extend the applicability of this technique without affecting the spatial resolution for micro devices larger than the field of view of the interferometer, stitching method was proposed and three different stitching configurations were also presented. The same device was tested in full-field of view under the commercial profiler. Good agreement between the result of presented stitching methods and commercial profiler demonstrates the reliability of the presented methods for stitching large structures

    A novel heterodyne interferometer for scanning optical microscopy

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    A phase sensitive scanning optical microscope is described which can measure surface height changes of about 1 Å. The system is based on a heterodyne version of the Michelson interferometer, and has been designed to reject phase noise caused by vibration in the optics and the sample. A specially constructed objective lens is used to direct two laser beams onto the object surface. The first beam forms a tightly focused spot to probe the sample structure and the second remains collimated, acting as a large area on sample reference beam. In the simplest implementation, the objective may be fabricated by drilling a hole in a lens singlet. The configuration allows the relative areas illuminated by the two beams to be varied both arbitrarily and independently, thus guaranteeing an accurate absolute phase measurement. This is an important advantage over existing techniques, in which the range of suitable samples is restricted by the limited size of the on sample reference beam. The two beams reflected from the sample are interfered with a third frequency shifted beam, so forming two heterodyne Michelson interferometers in parallel. The light from each interferometer is detected separately, resulting in two AC signals. The phase of these signals are then compared to provide the object surface phase structure. Path length fluctuations due to microphonics are common to both interferometers and are cancelled by this comparison. Results from a bench top version of the system are presented which demonstrate the principle of the technique and a detailed study is made of the factors limiting the sensitivity of the phase measurement. The conclusions of this study have been applied to the design of a prototype microscope and this has been used to record micrographs of a number of representative samples. In addition the particular imaging characteristics of the system are discussed using a combination of geometrical optics and a transfer function approach

    Surface Plasmon Fluorescence Microscopy: Characteristics and Application to Bioimaging

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    Ph.DDOCTOR OF PHILOSOPH
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