A non-degenerate optical parametric oscillator as a high-flux source for quantum lithography

We investigate the use of a non-degenerate parametric oscillator (NDPO) as a source for quantum lithography, for which the light can have high-flux and strong non-classical features. This builds on the proposal of Boto, et al. [A. N. Boto, et al., PRL (85), 2733 (2000)], for etching simple patterns on multi-photon absorbing materials with sub-Rayleigh resolution, using special two-mode entangled states of light. An NDPO has two outgoing modes differentiated by polarization or direction of propagation, but sharing the same optical frequency. We derive analytical expressions for the multi-photon absorption rates when the NDPO is operated below, near, and above its threshold. The resulting interference patterns are characterized by an effective wavelength half that for the illuminating modes. We compare our results with those for the case of a high-gain optical amplifier source, and discuss the relative merit of the NDPO

Higher order antibunching is not a rare phenomenon

Since the introduction of higher order nonclassical effects, higher order squeezing has been reported in a number of different physical systems but higher order antibunching is predicted only in three particular cases. In the present work, we have shown that the higher order antibunching is not a rare phenomenon rather it can be seen in many simple optical processes. To establish our claim, we have shown it in six wave mixing process, four wave mixing process and in second harmonic generation process.Comment: 6 pages, no figure, Latex 2

Driving the atom by atomic fluorescence: analytic results for the power and noise spectra

We study how the spectral properties of resonance fluorescence propagate through a two-atom system. Within the weak-driving-field approximation we find that, as we go from one atom to the next, the power spectrum exhibits both sub-natural linewidth narrowing and large asymmetries while the spectrum of squeezing narrows but remains otherwise unchanged. Analytical results for the observed spectral features of the fluorescence are provided and their origin is thoroughly discussed.Comment: 13 pages, 5 figures; to be published in Phys. Rev. A Changed title and conten

Two-Level Atom in an Optical Parametric Oscillator: Spectra of Transmitted and Fluorescent Fields in the Weak Driving Field Limit

We consider the interaction of a two-level atom inside an optical parametric oscillator. In the weak driving field limit, we essentially have an atom-cavity system driven by the occasional pair of correlated photons, or weakly squeezed light. We find that we may have holes, or dips, in the spectrum of the fluorescent and transmitted light. This occurs even in the strong-coupling limit when we find holes in the vacuum-Rabi doublet. Also, spectra with a sub-natural linewidth may occur. These effects disappear for larger driving fields, unlike the spectral narrowing obtained in resonance fluorescence in a squeezed vacuum; here it is important that the squeezing parameter $N$ tends to zero so that the system interacts with only one correlated pair of photons at a time. We show that a previous explanation for spectral narrowing and spectral holes for incoherent scattering is not applicable in the present case, and propose a new explanation. We attribute these anomalous effects to quantum interference in the two-photon scattering of the system.Comment: 10 pages, 17 figures, submitted to Phys Rev

INDIACo m-2009 Co mputing For Nation Development

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CROP SUITABILITY ANALYSIS FOR CEREAL CROPS OF UTTAR PRADESH, INDIA

The crop suitability is the process of assessing the appropriateness or ability of a given type of land on the basis of growing conditions of a particular crop. The study focused on the crop suitability analysis of cereal crops for their production in Uttar Pradesh. Information about crop suitability is essential for proper management of agriculture in the study area. Remote sensing and GIS data provide a reliable information and technique to find suitable land for crops. The research was based on GIS based Multi-Criteria Decision Approach. The AMSR-2 (Advance Microwave Scanning Radiometer) soil moisture data, Carto-DEM, soil chemical and physical properties and climate data were used to identify the crop suitability in the study area. Weightage of different factors was arrived at based on input and feedback from experts. An Analytical Hierarchical Process (AHP) was used in ArcGIS environment to generate suitability map for the cereals crop. The suitability map has been categorised in the form of highly suitable, moderately suitable, low suitable and non-agricultural/ non-suitable region of the study area for Wheat, Rice, Sorghum, Maize and Pearl Millet/Bajra.The overall study indicates that the study area has a huge potential of cereal crop production. Therefore, improved levels of agricultural production can be achieved by cultivating crop in highly and moderately suitable areas; and practicing diversification of marginally suitable areas to crops other than that for which it is low suitable.</p

Securing recruitment and obtaining informed consent in minority ethnic groups in the UK

Background: Previous health research has often explicitly excluded individuals from minority ethnic backgrounds due to perceived cultural and communication difficulties, including studies where there might be language/literacy problems in obtaining informed consent. This study addressed these difficulties by developing audio-recorded methods of obtaining informed consent and recording data. This report outlines 1) our experiences with securing recruitment to a qualitative study investigating alternative methods of data collection, and 2) the development of a standardised process for obtaining informed consent from individuals from minority ethnic backgrounds whose main language does not have an agreed written form. Methods: Two researchers from South Asian backgrounds recruited adults with Type 2 diabetes whose main language was spoken and not written, to attend a series of focus groups. A screening tool was used at recruitment in order to assess literacy skills in potential participants. Informed consent was obtained using audio-recordings of the patient information and recording patients' verbal consent. Participants' perceptions of this method of obtaining consent were recorded. Results: Recruitment rates were improved by using telephone compared to face-to-face methods. The screening tool was found to be acceptable by all potential participants. Audio-recorded methods of obtaining informed consent were easy to implement and accepted by all participants. Attrition rates differed according to ethnic group. Snowballing techniques only partly improved participation rates. Conclusion: Audio-recorded methods of obtaining informed consent are an acceptable alternative to written consent in study populations where literacy skills are variable. Further exploration of issues relating to attrition is required, and a range of methods may be necessary in order to maximise response and participation

Resonance fluorescence spectrum in a weak squeezed field with an arbitrary bandwidth

We analyze the linewidth narrowing in the fluorescence spectrum of a two-level atom driven by a squeezed vacuum field of a finite bandwidth. It is found that the fluorescence spectrum in a low-intensity squeezed field can exhibit a (omega - omega(0))(-6) frequency dependence in the wings. We show that this fast fall-off behavior is intimately related to the properties of a narrow-bandwidth squeezed field and does not extend into the region of broadband excitation. We apply the Linear response model and find that the narrowing results from a convolution of the atom response with the spectrum of the incident field. On the experimental side, we emphasize that the linewidth narrowing is not sensitive to the solid angle of the squeezed modes coupled to the atom. We also compare the fluorescence spectrum with the quadrature-noise spectrum and find that the fluorescence spectrum for an off-resonance excitation does not reveal the noise spectrum. We show that this difference arises from the competing three-photon scattering processes. [S1050-2947(98)04308-X]