| 1. |
- Agarwal, Girish, et al.
(författare)
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Light, the universe and everything-12 Herculean tasks for quantum cowboys and black diamond skiers
- 2018
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 65:11, s. 1261-1308
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Tidskriftsartikel (refereegranskat)abstract
- The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mind-boggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world's leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited - such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centres in diamond? (8) What is the future of quantum coherence, squeezing and entanglement for enhanced super-resolution and sensing? (9) How can we solve (some of) humanity's biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free-electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics?
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| 2. |
- Basiev, T. T., et al.
(författare)
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Pre-selection of optical transitions in rare-earth ions in crystals perspective for quantum information processing
- 2012
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 59:2, s. 166-178
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Tidskriftsartikel (refereegranskat)abstract
- A systematic analysis of decoherence rates due to electron-phonon interactions for optical transitions of rare-earth dopant ions in crystals is presented in the frame of the point charge model. For this model, the large value of any one of the matrix elements of the unit tensor operator U((k)) of rank k for transitions within the 4f-electronic configuration, viz. U2, U4 or U6, is enough to ensure the strong optical transition between different levels, while the Stark-Stark transitions within the multiplet can be characterized by the matrix element U2 alone, the influence of elements U4, U6 being of much smaller order of magnitude and neglected. The circumstance that exactly such Stark-Stark transitions within the multiplet define the efficiency of electron-phonon interaction and, consequently, the decoherence rate (except for the case of lowest, less than approximately 2-4 K, temperatures), enables selection of optical transitions which are strong enough and at the same time are characterized by relatively small decoherence rates. Correspondingly, these optical transitions, provided that they lie in an appropriate spectral range and the gap to the nearest neighboring energy level is large enough (>500 cm(-1)) to prevent eventual fast phonon-assisted relaxation, should be considered as prospective for subsequent use in quantum informatics processing and communication. The list of such pre-selected transitions is given; the applicability area and limitations of our approach are discussed.
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| 3. |
- Berrah, Nora, et al.
(författare)
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Femtosecond x-ray induced fragmentation of fullerenes
- 2016
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 63:4, s. 390-401
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Tidskriftsartikel (refereegranskat)abstract
- A new class of femtosecond, intense, short – wavelength lasers – the free-electron laser – has opened up new opportunities to investigate the structure and dynamics in many scientific areas. These new lasers, whose performance keeps increasing, enable the understanding of physical and chemical changes at an atomic spatial scale and on the time scale of atomic motion which is essential for a broad range of scientific fields. We describe here the interaction of fullerenes in the multiphoton regime with the Linac Coherent Light Source (LCLS) X-ray free-electron laser at SLAC National Laboratory. In particular, we report on new data regarding the ionization of Ho3N@C80 molecules and compare the results with our prior C60 investigation of radiation damage induced by the LCLS pulses. We also discuss briefly the potential impact of newly available instrumentation to physical and chemical sciences when they are coupled with FELs as well as theoretical calculations and modeling.
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| 4. |
- Bourennane, Mohamed, et al.
(författare)
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Experimental long wavelength quantum cryptography: from single-photon transmission to key extraction protocols
- 2000
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 47, s. 563-579
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Tidskriftsartikel (refereegranskat)abstract
- We present experiments on long wavelength (λ = 1.55 μm) 'plug and play' quantum cryptography systems. We discuss the performance of single-photon detectors at λ = 1.55 μm. Furthermore, we address the full implementation of the quantum cryptography protocol, discussing in detail the implementation of protocols for error correction and privacy amplification needed to get a secure key. We illustrate the theory with examples from a full software simulation to show the performance of the complete protocol in terms of final secure key creation rate
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| 5. |
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| 6. |
- Brüning, E, et al.
(författare)
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Parametrizations of density matrices
- 2012
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 59:1, s. 1-20
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Forskningsöversikt (refereegranskat)abstract
- This article gives a brief overview of some recent progress in the characterization and parametrization of density matrices of finite dimensional systems. We discuss in some detail the Bloch-vector and Jarlskog parametrizations and mention briefly the coset parametrization. As applications of the Bloch parametrization we discuss the trace invariants for the case of time dependent Hamiltonians and in some detail the dynamics of three-level systems. Furthermore, the Bloch vector of two-qubit systems as well as the use of the polarization operator basis is indicated. As the main application of the Jarlskog parametrization we construct density matrices for composite systems. In addition, some recent related articles are mentioned without further discussion.
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| 7. |
- Caleman, Carl, et al.
(författare)
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Simulations of radiation damage in biomolecular nanocrystals induced by femtosecond X-ray pulses
- 2011
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 58:16, s. 1486-1497
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Tidskriftsartikel (refereegranskat)abstract
- The Linac Coherent Light Source (LCLS) is the first X-ray free electron laser to achieve lasing at subnanometer wavelengths (6 angstrom). LCLS is poised to reach even shorter wavelengths (1.5 angstrom) and thus holds the promise of single molecular imaging at atomic resolution. The initial operation at a photon energy of 2 keV provides the possibility to perform the first experiments on damage to biological particles, and to assess the limitations to coherent imaging of biological samples, which are directly relevant at atomic resolution. In this paper we theoretically investigate the damage formation and detection possibilities for a biological crystal, by employing and comparing two different damage models with complementary strengths. Molecular dynamics provides a discrete approach which investigates structural details at the atomic level by tracking all atoms in the real space. Our continuum model is based on a non-local thermodynamics equilibrium code with atomic kinetics and radiation transfer and can treat hydrodynamic expansion of the entire system. The latter approach captures the essential features of atomic displacements, without taking into account structural information and intrinsic atomic movements. This proves to be a powerful computational tool for many samples, including biological crystals, which will be studied with X-ray free electron lasers.
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| 8. |
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| 9. |
- Chang, Lin, et al.
(författare)
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Multi-surface phase-shifting algorithm using the window function fitted by the nonlinear least squares method
- 2022
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Ingår i: Journal of Modern Optics. - : TAYLOR & FRANCIS LTD. - 0950-0340 .- 1362-3044. ; 69:3, s. 160-171
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Tidskriftsartikel (refereegranskat)abstract
- A multi-surface phase demodulation algorithm is proposed to measure surfaces of the transparent plate simultaneously. A non-linear least-squares method based on the trust region is utilized to fit the window function derived from the characteristic polynomials. The fitted window function requires fewer parameters and has a flexible form, which means the window length can be stretched freely and used flexibly. Then, a multi-surface phase demodulation technique combining the discrete Fourier principle and the fitted window function is investigated, allowing simultaneous reconstruction of the measured front surface, rear surface, and thickness variation. During the implementation of our algorithm, the processing time for the interferograms with 850x850 pixels is around 5.1s. Measurement errors caused by several factors are analyzed, including wavelength-tuning error, frequency order error, cavity length error, and average thickness error. The experimental result on a rectangular transparent plate further verifies the effectiveness of our algorithm.
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| 10. |
- Ekert, Artur, et al.
(författare)
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Geometric quantum computation
- 2000
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. ; 47:14-15, s. 2501-2513
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Tidskriftsartikel (refereegranskat)abstract
- We describe in detail a general strategy for implementing a conditional geometric phase between two spins. Combined with single-spin operations, this simple operation is a universal gate for quantum computation, in that any unitary transformation can be implemented with arbitrary precision using only single-spin operations and conditional phase shifts. Thus quantum geometrical phases can form the basis of any quantum computation. Moreover, as the induced conditional phase depends only on the geometry of the paths executed by the spins it is resilient to certain types of errors and offers the potential of a naturally fault-tolerant way of performing quantum computation.
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| 11. |
- Hallstig, E., et al.
(författare)
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Fringing fields in a liquid crystal spatial light modulator for beam steering
- 2004
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 51:8, s. 1233-1247
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Tidskriftsartikel (refereegranskat)abstract
- Phase modulating spatial light modulators (SLMs) can be used to alter the shape of a laser wavefront to achieve a deflection or change in the shape of a laser beam. This paper reports the results of characterization, simulation and optimization of a one-dimensional liquid crystal (LC) SLM. The device has a large ratio between LC layer thickness and pixel pitch that results in a fringing field between pixels. In effect, the applied phase patterns will be low-pass filtered and the loss of high frequency components limits, for instance, the usable steering range. A method is presented where intensity measurements in the far field are used to determine how the phase modulation at the SLM is distorted. The inhomogeneous optical anisotropy of the device was determined by modelling the liquid crystal director distribution within the electrode-pixel structure. Finite-difference time-domain (FDTD) simulations were used to calculate the light propagation through the LC. The simulated phase distortion was compared with the experimental results. A voltage compensation scheme to improve the diffraction efficiency was developed utilizing the measured and simulated results. It is demonstrated that a modification of the voltage patterns can give a better realization of high frequency components in the phase distribution and an increase in maximum steering angle by a factor two.
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| 12. |
- Jaroszewicz, Z., et al.
(författare)
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Programmable axicon for variable inclination of the focal segment
- 2004
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 51:14, s. 2185-2190
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Tidskriftsartikel (refereegranskat)abstract
- An axicon creates a long and narrow focal segment along its optical axis and therefore it is widely recognized as a cornerstone element in metrology and alignment techniques. In oblique incidence the shape of the axicon can be designed such that its sharp focal line is retained. However, when an elliptical or circular axicon is illuminated at an angle different from the nominal angle, the focal segment suffers from astigmatism and broadens significantly. The use of a spatial light modulator is proposed for real-time compensation of the ensuing aberration. The result is a diffractive axicon with its degree of ellipticity adjusted to the inclination angle of the incident light, thus producing a diffraction-limited Bessel beam for a wide range of illumination angles.
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| 13. |
- Johnsson, Per, et al.
(författare)
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Trains of attosecond electron wave packets
- 2006
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 53:1-2, s. 233-245
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Tidskriftsartikel (refereegranskat)abstract
- We study temporally localized electron wave packets, generated using a train of extreme ultraviolet (XUV) attosecond pulses to ionize the target atoms. Both the electron wave packets and the attosecond pulse train ( APT) are characterized using the same technique, based on interference of two-photon transitions in the continuum. We study, in particular, the energy transfer from a moderately strong infrared (IR) field to the electron wave packets as a function of time delay between the XUV and the IR fields. The use of an APT to generate the electron wave packets enables the generation at times not accessible through tunneling ionization. We find that a significant amount of energy is transferred from the IR field to the electron wave packets, when they are generated at a zero-crossing of the IR laser field. This energy transfer results in a dramatically enhanced above-threshold ionization even at IR intensities that alone are not strong enough to induce any significant ionization.
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| 14. |
- Kallioniemi, I., et al.
(författare)
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Characterization of random rough surfaces from scattered intensities by neural networks
- 2001
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 48:9, s. 1447-1453
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Tidskriftsartikel (refereegranskat)abstract
- Optical scatterometry, a non-invasive characterization method, is used to infer the statistical properties of random rough surfaces. The Gaussian model with rms-roughness sigma and correlation length Lambda is considered in this paper but the employed technique is applicable to any representation of random rough surfaces. Surfaces with wide ranges of Lambda and sigma, up to 5 wavelengths (lambda), are characterized with neural networks. Two models are used: self-organizing map (SOM) for rough classification and multi-layer perceptron (MLP) for quantitative estimation with nonlinear regression. Models infer Lambda and sigma from scattering, thus involving the inverse problem. The intensities are calculated with the exact electromagnetic theory, which enables a wide range of parameters. The most widely known neural network model in practise is SOM, which we use to organize samples into discrete classes with resolution Delta Lambda = Delta sigma = 0.5 lambda. The more advanced MLP model is trained for optimal behaviour by providing it with known parts of input (scattering) and output (surface parameters). We show that a small amount of data is sufficient for an excellent accuracy on the order of 0.3 lambda and 0.15 lambda for estimating Lambda and sigma, respectively.
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| 15. |
- Khrennikov, Andrei
(författare)
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Born's rule from measurements of classical signals by threshold detectors which are properly calibrated
- 2012
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 59:7, s. 667-678
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Tidskriftsartikel (refereegranskat)abstract
- The very old problem of the statistical content of quantum mechanics (QM) is studied in a novel framework. The Born's rule (one of the basic postulates of QM) is derived from theory of classical random signals. We present a measurement scheme which transforms continuous signals into discrete clicks and reproduces the Born's rule. This is the scheme of threshold type detection. Calibration of detectors plays a crucial role. Creation of such a detection model provides a possibility to represent the basic quantum phenomena as classical field phenomena completed by measurements with threshold type and properly calibrated detectors. Finally, the wave-particle duality has been resolved in favor of the purely wave description. It is well known that coincidence probability plays an important role in the debate on the possibility to reduce quantum theory (especially quantum optics) to classical field theory. Our model matches well the predictions of quantum theory and experiment. It violates the prediction of the classical field model which does not take into account the presence of threshold type detectors with proper calibration.
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| 16. |
- Khrennikov, Andrei
(författare)
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Quantum-like model for classical random electromagnetic field
- 2008
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 55:14, s. 2257-2267
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Tidskriftsartikel (refereegranskat)abstract
- Semiclassical models can be used, see e.g. Scully and Zubairy [Quantum Optics; Cambridge University Press: Cambridge, 1997], to simulate some distinguishing features of quantum optics. In this paper we show that one can also proceed successfully in the opposite direction. A quantum-like model for the classical random electromagnetic field is proposed. Averages with respect to classical random fields can be approximated by quantum-like averages given by the von Neumann trace-formula: . The operators ρ and can be easily determined as classical quantities. Here ρ is obtained by normalization of the covariance operator of the random field. It has all the features of the von Neumann density operator. Additionally an analogue of the quantum observable is given by the second derivative of a functional (‘classical variable’) f (E, B) of the classical electromagnetic field ψ = (E, B).
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| 17. |
- Lakshminarayanan, Vasudevan, et al.
(författare)
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Vision Science and Ophthalmic Optics
- 2011
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 58:19-20, s. 1679-1680
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Larson, Jonas, et al.
(författare)
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Adiabatic state preparation in a cavity
- 2003
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 50:11, s. 1663-1678
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Tidskriftsartikel (refereegranskat)abstract
- The paper discusses the single-mode Jaynes-Cummings model with time-dependent parameters. Solvable models for two-level systems are utilized to consider the changes in the photon distribution effected by the passage of atoms through the cavity. It is suggested that such systems may be used as filters to modify the photon distribution. The effect can be enhanced by repeatedly sending new atoms through the cavity. We show that such filters can cut out either small or large photon numbers. It is also shown that the method can be used to narrow down photon distributions and in this way achieve highly non-classical sub-Poissonian states. Some limitations and applications of the method are presented.
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| 19. |
- Larson, Jonas, et al.
(författare)
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Cavity field ensembles from non-selective measurements
- 2004
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 51:1, s. 129-138
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Tidskriftsartikel (refereegranskat)abstract
- We continue our investigations of cavity QED with time-dependent parameters. In this paper we discuss the situation where the state of the atoms leaving the cavity is reduced but the outcome is not recorded. In this case our knowledge is limited to an ensemble description of the results only. By applying the Demkov - Kunike level-crossing model, we show that even in this case, the filtering action of the interaction allows us to prepare a preassigned Fock state with good accuracy. The possibilities and limitations of the method are discussed and some relations to earlier work are presented.
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| 20. |
- Larson, Jonas, et al.
(författare)
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Dynamics of a Raman coupled model: entanglement and quantum computation
- 2004
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 51:11, s. 1691-1704
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Tidskriftsartikel (refereegranskat)abstract
- The evolution of a Raman coupled three-level Lambda atom with two quantized cavity modes is studied in the large detuning case; i.e. when the upper atomic level can be adiabatically eliminated. Particularly the situation when the two modes are prepared in initial coherent or squeezed states, with a large average number of photons, is investigated. It is found that the atom, after specific interaction times, disentangles from the two modes, leaving them, in certain cases, in entangled Schrodinger cat states. These disentanglement times can be controlled by adjusting the ratio between average numbers of photons in the two modes. It is also shown how this effective model may be used for implementing quantum information processing. Especially it is demonstrated how to generate various entangled states, such as EPR and GHZ states, and quantum logic operations, such as the control-not and the phase gate.
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| 21. |
- Larson, Jonas, et al.
(författare)
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Photon filters in a microwave cavity
- 2003
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Ingår i: Journal of Modern Optics. - 0950-0340 .- 1362-3044. ; 50:18, s. 2705-2715
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Tidskriftsartikel (refereegranskat)abstract
- In an earlier paper we concluded that time-dependent parameters in the atom-mode interaction can be utilized to modify the quantum field in a cavity. When an atom shoots through the cavity field, it is expected to experience a trigonometric time dependence of its coupling constant. We investigate the possibilities this offers to modify the field. As a point of comparison we use the solvable Rosen-Zener model, which has parameter dependences roughly similar to the ones expected in a real cavity. We do confirm that by repeatedly sending atoms through the cavity, we can obtain filters on the photon states. Highly non-classical states can be obtained. We find that the Rosen-Zener model is more sensitive to the detuning than the case of a trigonometric coupling.
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| 22. |
- Larson, Jonas
(författare)
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Scheme for generating entangled states of two field modes in a cavity
- 2006
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 53:13, s. 1867-1877
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Tidskriftsartikel (refereegranskat)abstract
- This paper considers a two-level atom interacting with two cavity modes with equal frequencies. Applying a unitary transformation, the system reduces to the analytically solvable Jaynes-Cummings model. For some particular field states, coherent and squeezed states, the transformation between the two bare bases, related by the unitary transformation, becomes particularly simple. It is shown how to generate (the highly non-classical) entangled coherent states of the two modes, both in the zero and large detuning cases. An advantage of the zero detuning case is that the preparation is deterministic and no atomic measurement is needed. For the large detuning situation, a measurement is required, leaving the field in either of two orthogonal entangled coherent states.
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| 23. |
- Lepine, F., et al.
(författare)
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Short XUV pulses to characterize field-free molecular alignment
- 2007
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 54:7, s. 953-966
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Tidskriftsartikel (refereegranskat)abstract
- We present experiments on field-free molecular alignment of N-2 and CO2 probed with short XUV pulses that are obtained via high-harmonic generation. The XUV pulses induce a dissociative ionization or a Coulomb explosion of the molecule, where the fragment ion recoil (measured using the velocity map imaging technique) provides information on the alignment of the parent molecule at the time of ionization. We discuss how photoelectron detection may in future allow the determination of molecular-frame photoelectron angular distributions and molecular structure.
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| 24. |
- Lundström, Linda, et al.
(författare)
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Symmetries in peripheral ocular aberrations
- 2011
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 58:19-20, s. 1690-1695
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Tidskriftsartikel (refereegranskat)abstract
- A mirror symmetry in the aberrations between the left and right eyes has previously been found foveally, but while a similar symmetry for the peripheral visual field is likely, it has not been investigated. Nevertheless, the peripheral optical quality is often evaluated in only one eye, because it is more time efficient than analyzing the whole visual field of both eyes. This study investigates the correctness of such an approach by measuring the peripheral wavefront aberrations in both eyes of 22 subjects out to +/- 40 degrees horizontally. The largest aberrations (defocus, astigmatism, and coma) were found to be significantly correlated between the left and right eyes when comparing the same temporal or nasal angle. The slope of the regression line was close to +/- 1 (within 0.05) for these aberrations, with a negative slope for the horizontally odd aberrations, i.e. the left and right eyes are mirror symmetric. These findings justify that the average result, sampled in one of the two eyes of many subjects, can be generalized to the other eye as well.
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| 25. |
- Miranda, Miguel, et al.
(författare)
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Spatiotemporal characterization of ultrashort optical vortex pulses
- 2017
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 64:sup4, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- We use a spiral phase plate to generate few-cycle optical vortices from an ultrafast titanium:sapphire oscillator and characterize them in the spatiotemporal domain with a recently introduced technique based on spatially resolved Fourier transform spectrometry. The performance of this simple approach to the generation of optical vortices is analysed from a wavelength-dependent perspective as well as in the spatiotemporal domain, allowing us to characterize ultrashort vortex pulses in space, frequency and time.
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| 26. |
- Pedrini, Giancarlo, et al.
(författare)
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Spatial filtering in digital holographic microscopy
- 2000
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 47:8, s. 1447-1454
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Tidskriftsartikel (refereegranskat)abstract
- An optical system based on digital holography suitable for microscopic investigations is described. A lensless digital hologram of the object under test is recorded on a CCD faceplate. The reference point source and the object are equidistant from the CCD. The point source for the illumination of the transparent microscopic object is located in another plane some millimetres behind the object. For digital reconstruction of the wavefronts the Sommerfeld propagation relation is used. The particular recording arrangement allows one to perform spatial filtering. Examples of amplitude filtering are presented.
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| 27. |
- Pettersson, Anna Lindskoog, et al.
(författare)
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Accommodation in young adults wearing aspheric multifocal soft contact lenses
- 2011
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 58:19-20, s. 1804-1808
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present project was to investigate accommodative behavior in young adults and adolescents fitted with an aspheric multifocal (center distance) contact lens with focus on evaluating whether these lenses can be an alternative treatment for subjects in which a reduced level of blur and thereby accommodation in near vision is aimed at. Twenty normal subjects aged between 21 and 35 years participated in the study. Aberrometry was perfomed using a Zywave (TM) aberrometer, first on the uncorrected eyes of all subjects, and again while the subjects wore a multifocal contact lens with a +1.00 add. A Shin-Nippon N Vision-K 5001 Autoref-Keratometer was used to measure accommodative response with two different refractive corrections: (1) habitual spectacle correction only, and (2) habitual correction and a aspheric multifocal (center distance) contact lens. Four hours of adaptation to the lens was allowed. The lag when wearing only the habitual spectacles was compared with the lag while wearing both the habitual spectacles and the aspheric multifocal contact lens. The mean lag of accommodation for the subject group was 0.85 D (+/-0.57 SD) and 0.75 D (+/-0.52 SD) without and with the multifocal lens, respectively. Statistical analyses showed no difference in lag (t = 0.8479, p = 0.407) with and without the lens. In conclusion, young normal subjects do not relax accommodation when fitted with aspheric multifocal center distance lenses when the addition is +1.00. It is therefore unlikely that subjects with accommodative ability, in whom the treatment purpose is to reduce blur and thereby accommodation, can be effectively treated with such lenses.
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| 28. |
- Praxmeyer, Ludmila, et al.
(författare)
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The information of ambiguity
- 2009
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 56:10, s. 1205-1219
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Tidskriftsartikel (refereegranskat)abstract
- The phase space characteristics of a quantum state are best captured by the Wigner distribution. This displays transparently the diagonality information of the density matrix. The complementary function offering transparently the off-diagonal elements is captured by a function called the S-function, or the ambiguity. In carrying the maximal information about the quantum coherences it represents the uncertainties or ambiguity of the diagonal information. Mathematically this is manifested in its role as the phase space moment generating function. Formally it complements the information in the Wigner function. These formal relations provide the starting point for the present investigations. As a measure of quantum uncertainties, ambiguity may be used to define a probability measure on the off-diagonality. The mathematical and physical consistency of this view is presented in this paper. For a pure state, we find the extraordinary result that such distributions are their own Fourier transforms. The physical interpretation of this distribution as a carrier of classical signal fuzziness suggests the introduction of heuristic approximations to the observational uncertainties. We illustrate the properties and interpretation of the ambiguity function by some specific examples. We find that for smooth, 'Gaussian-like' distributions, the heuristic considerations provide good approximations. On the other hand, representing quantum interferences, the ambiguity serves as the most positive probe for the ultimate quantum structures which have been called sub-Planckian. They are interesting because it has been argued that such structures are physically observable.
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| 29. |
- Rosén, Robert, et al.
(författare)
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Adaptive optics for peripheral vision
- 2012
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 59:12, s. 1064-1070
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Tidskriftsartikel (refereegranskat)abstract
- Understanding peripheral optical errors and their impact on vision is important for various applications, e.g. research on myopia development and optical correction of patients with central visual field loss. In this study, we investigated whether correction of higher order aberrations with adaptive optics (AO) improve resolution beyond what is achieved with best peripheral refractive correction. A laboratory AO system was constructed for correcting peripheral aberrations. The peripheral low contrast grating resolution acuity in the 20 nasal visual field of the right eye was evaluated for 12 subjects using three types of correction: refractive correction of sphere and cylinder, static closed loop AO correction and continuous closed loop AO correction. Running AO in continuous closed loop improved acuity compared to refractive correction for most subjects (maximum benefit 0.15logMAR). The visual improvement from aberration correction was highly correlated with the subject's initial amount of higher order aberrations (p=0.001, R 2=0.72). There was, however, no acuity improvement from static AO correction. In conclusion, correction of peripheral higher order aberrations can improve low contrast resolution, provided refractive errors are corrected and the system runs in continuous closed loop.
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| 30. |
- Schwenke, Jörg, et al.
(författare)
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Single-shot holography using high-order harmonics
- 2008
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 55:16, s. 2723-2730
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Tidskriftsartikel (refereegranskat)abstract
- This work demonstrates single-shot holography with ultrashort XUV pulses. The pulses are generated by high-harmonic generation in an Ar gas cell and focused to produce a strongly divergent reference beam suitable for in-line holography of micrometer size objects. The achieved intensity of the high-order harmonics in the XUV regime is sufficient for single-shot holography with good signal-to-noise ratio. A numerical algorithm is applied to reconstruct real images from the recorded holograms, which also includes an iterative process to reduce the twin-image blurring. Holograms and reconstructed images of microscope tips are presented and a description of the algorithm is given.
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| 31. |
- Shen, Jian Qi
(författare)
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Negatively refracting atomic vapour
- 2006
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 53:15, s. 2195-2205
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Tidskriftsartikel (refereegranskat)abstract
- A new mechanism for realizing negative refractive index with a four-level atomic system is suggested. The explicit expressions for the electric permittivity and magnetic permeability at probe frequency are presented. It is shown that there is a frequency band in which the four-level photonic-resonant atomic vapour may exhibit simultaneously negative permittivity and permeability, and that such an atomic vapour may become a left-handed material ( negatively refracting medium). Compared with the previous schemes to realize negative refraction within the framework of classical electromagnetic theory, the most remarkable features of the present scenario are as follows: ( i) isotropic material with microscopic structure units at atomic-scale level, ( ii) negative refraction in visible and infrared frequency bands, ( iii) controllable manipulation by external fields and ( iv) based on quantum coherence in a multilevel atomic system.
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| 32. |
- Stenholm, Stig, et al.
(författare)
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Open systems and time reversal
- 2004
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 51:6-7, s. 841-850
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we address the question of the direction of physical time. In particular we consider the meaning of time reversal for irreversible evolution. The work is based on the theory of Markovian generators in open quantum systems. The motivation and appearance of such evolution is reviewed and its implications for the direction of time are presented. A monotonically changing function, a Lyapunov functional, is demonstrated and the concept of time reversal invariance is introduced. Finally the evolution is shown to follow from an action principle. The method, however, does not single out any forward direction of time, information about the initial state is lost equally in both directions within the formalism.
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| 33. |
- Thaning, Anna, 1976-, et al.
(författare)
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Transverse variation of partially coherent axicon lines
- 2002
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 49:11, s. 1933-1941
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Tidskriftsartikel (refereegranskat)abstract
- Diffractive axicons operating in spatially partially coherent light can be designed non-iteratively, on the basis of asymptotic wave theory, to produce focal lines with prescribed on-axis intensity profiles. In this paper we analyse the transverse intensity variation of these axicon lines, concentrating on relatively coherent beams. By Taylor expansion, a way is found to approximate the transverse intensity profile, without the demanding numerical integration otherwise needed. From this expression, also the width of the focal line as a function of position on the optical axis can be easily found. As now both this width profile and the on-axis intensity profile can be determined, the two most important features of the partially coherent axicon focal line have been characterized.
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| 34. |
- Vargas, William E., et al.
(författare)
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Effective backscattering and absorption coefficients of light diffusing materials retrieved from reflectance and transmittance spectra of diffuse radiation
- 2021
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 68:12, s. 605-623
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Tidskriftsartikel (refereegranskat)abstract
- Solutions of the differential equations for the diffuse components of the four-flux model are obtained, including explicit expressions for the collimated-diffuse and diffuse-diffuse reflectance and transmittance for an optical three-layer system. We establish a method to invert collimated-diffuse reflectance and transmittance in order to obtain the spectral variation of all average pathlength parameters and forward scattering ratios, by applying a spectral simulated annealing method. The inversion procedure was tested with synthetic collimated-diffuse reflectance and transmittance spectra and showed very good convergence. Subsequently, the method was applied to measured spectra of a light scattering and absorbing medium containing TiO2 particles in a low-absorbing matrix, which was enclosed between two glass slides. Hence the present paper, together with our previous one, wherein we inverted collimated-collimated reflectance and transmittance spectra to obtain scattering and absorption coefficients, establishes a reliable inversion method for obtaining all parameters in the most general version of the four-flux theory from experimental data.
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| 35. |
- Vargas, William E., et al.
(författare)
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Scattering and absorption cross sections of light diffusing materials retrieved from reflectance and transmittance spectra of collimated radiation
- 2020
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Ingår i: Journal of Modern Optics. - : Taylor & Francis Group. - 0950-0340 .- 1362-3044. ; 67:11, s. 974-991
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Tidskriftsartikel (refereegranskat)abstract
- Four-flux radiative transfer models have been extensively used to describe reflectance and transmittance (R&T) spectra of light scattering and absorbing (S&A) media. Solutions to the differential equations corresponding to the collimated fluxes are obtained by subsequent application of boundary conditions. Explicit expressions for the collimated R&T of light are reported, when considering a light S&A medium contained between two glass slides, an experimental arrangement which is appropriate for liquid suspensions and viscous matrices containing solid particles. A spectral simulated annealing method is applied to retrieve, from measured R&T spectra of collimated light under normal incident radiation, the scattering and absorption coefficients of the composite medium. First, the accuracy of the method is established by applying it to synthetic collimated R&T data. Secondly, we apply the method to experimental data and use it to determine the S&A coefficients of a layer of TiO2 particles dispersed in a PVP/water matrix.
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| 36. |
- Varju, Katalin, et al.
(författare)
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Frequency chirp of harmonic and attosecond pulses
- 2005
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 52:2-3, s. 379-394
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Tidskriftsartikel (refereegranskat)abstract
- We study the phase of the atomic polarization in the process of high-order harmonic generation. Its dependence on the laser intensity and the harmonic order induce a frequency variation in time (chirp) respectively of the harmonic pulses and attosecond pulses. We review the recent experimental results on the temporal characterization of the harmonic emission and show that measurements performed using very different techniques (like XFROG and RABITT), probing the phase in different parameter spaces, can be connected through the mixed phase derivatives, demonstrating the common underlying physics
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| 37. |
- Wahlberg, M., et al.
(författare)
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Clinical importance of spherical and chromatic aberration on the accommodative response in contact lens wear
- 2011
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Ingår i: Journal of Modern Optics. - : Informa UK Limited. - 0950-0340 .- 1362-3044. ; 58:19-20, s. 1696-1702
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to evaluate the accommodation response under both mono-and polychromatic light while varying the amount of spherical aberration. It is thought that chromatic and spherical aberrations are directional cues for the accommodative system and could affect response time, velocity or lag. Spherical aberration is often eliminated in modern contact lenses in order to enhance image quality in the unaccommodated eye. This study was divided into two parts. The first part was done to evaluate the amount of spherical and other Zernike aberrations in the unaccommodated eye when uncorrected and with two types of correction (trial lens and spherical-aberration controlled contact lens) and the second part evaluated the dynamic accommodation responses obtained when wearing each of the corrections under polychromatic and monochromatic conditions. Measurements of accommodation showed no significant differences in time, velocity and lag of accommodation after decreasing the spherical aberration with a contact lens, neither in monochromatic nor polychromatic light. It is unlikely that small to normal changes of spherical aberration in white light or monochromatic mid-spectral light affect directional cues for the accommodative system, not in white light or mid-spectral monochromatic light, since the accommodative response did not show any change.
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| 38. |
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| 39. |
- Barbieri, C., et al.
(författare)
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Astronomical applications of quantum optics for extremely large telescopes
- 2007
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Ingår i: Journal of Modern Optics. - 0950-0340. ; 54:2-3, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- A programme has been started to investigate photon properties that are not currently exploited in astronomical instruments, namely second- and higher-order coherence functions encoded in their arrival time, and the orbital angular momentum. This paper expounds the first results achieved in the study of a novel astronomical photometer capable of pushing time tagging towards the picosecond region. This conceptual device has been developed as a possible focal plane instrument for the future OverWhelmingly Large Telescope (OWL) of the European Southern Observatory. This instrument has been named QuantEYE, that is, the Quantum Eye of OWL.
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| 40. |
- Brugger, K, et al.
(författare)
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Nanofabricated atom optics: atom chips
- 2000
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Ingår i: JOURNAL OF MODERN OPTICS. - : TAYLOR & FRANCIS LTD. - 0950-0340. ; 47:14-15, s. 2789-2809
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Tidskriftsartikel (refereegranskat)abstract
- Small tight trapping and guiding potentials can be created for neutral atoms moving microns above surfaces patterned with nanofabricated charged and current-carrying structures. Surfaces holding such structures form atom chips which, for coherent matter w
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| 41. |
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| 42. |
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