Experimental Vacuum Squeezing in Rubidium Vapor via Self-Rotation

We report the generation of optical squeezed vacuum states by means of polarization self-rotation in rubidium vapor following a proposal by Matsko et al. [Phys. Rev. A 66, 043815 (2002)]. The experimental setup, involving in essence just a diode laser and a heated rubidium gas cell, is simple and easily scalable. A squeezing of 0.85+-0.05 dB was achieved

Management of late-preterm and term infants with hyperbilirubinaemia in resource-constrained settings.

Hyperbilirubinaemia is a ubiquitous transitional morbidity in the vast majority of newborns and a leading cause of hospitalisation in the first week of life worldwide. While timely and effective phototherapy and exchange transfusion are well proven treatments for severe neonatal hyperbilirubinaemia, inappropriate or ineffective treatment of hyperbilirubinaemia, at secondary and tertiary hospitals, still prevails in many poorly-resourced countries accounting for a disproportionately high burden of bilirubin-induced mortality and long-term morbidity. As part of the efforts to curtail the widely reported risks of frequent but avoidable bilirubin-induced neurologic dysfunction (acute bilirubin encephalopathy (ABE) and kernicterus) in low and middle-income countries (LMICs) with significant resource constraints, this article presents a practical framework for the management of late-preterm and term infants (≥ 35 weeks of gestation) with clinically significant hyperbilirubinaemia in these countries particularly where local practice guidelines are lacking. Standard and validated protocols were followed in adapting available evidence-based national guidelines on the management of hyperbilirubinaemia through a collaboration among clinicians and experts on newborn jaundice from different world regions. Tasks and resources required for the comprehensive management of infants with or at risk of severe hyperbilirubinaemia at all levels of healthcare delivery are proposed, covering primary prevention, early detection, diagnosis, monitoring, treatment, and follow-up. Additionally, actionable treatment or referral levels for phototherapy and exchange transfusion are proposed within the context of several confounding factors such as widespread exclusive breastfeeding, infections, blood group incompatibilities and G6PD deficiency, which place infants at high risk of severe hyperbilirubinaemia and bilirubin-induced neurologic dysfunction in LMICs, as well as the limited facilities for clinical investigations and inconsistent functionality of available phototherapy devices. The need to adjust these levels as appropriate depending on the available facilities in each clinical setting and the risk profile of the infant is emphasised with a view to avoiding over-treatment or under-treatment. These recommendations should serve as a valuable reference material for health workers, guide the development of contextually-relevant national guidelines in each LMIC, as well as facilitate effective advocacy and mobilisation of requisite resources for the optimal care of infants with hyperbilirubinaemia at all levels

Observation of polarization quantum noise of laser radiation in Rb vapor cell

We present experimental study of polarization quantum noise of laser radiation passed through optically think vapor of Rb87. We observe a step-like noise spectrum. We discuss various factor which may result in such noise spectrum and prevent observation of squeezing of quantum fluctuations predicted in Matsko et al. PRA 63, 043814 (2001).Comment: 4 pages, 5 figures. Translated from Russian by I. Novikov

Gap solitons in Bragg gratings with a harmonic superlattice

Solitons are studied in a model of a fiber Bragg grating (BG) whose local reflectivity is subjected to periodic modulation. The superlattice opens an infinite number of new bandgaps in the model's spectrum. Averaging and numerical continuation methods show that each gap gives rise to gap solitons (GSs), including asymmetric and double-humped ones, which are not present without the superlattice.Computation of stability eigenvalues and direct simulation reveal the existence of completely stable families of fundamental GSs filling the new gaps - also at negative frequencies, where the ordinary GSs are unstable. Moving stable GSs with positive and negative effective mass are found too.Comment: 7 pages, 3 figures, submitted to EP

Two-Photon Interferometry for High-Resolution Imaging

We discuss advantages of using non-classical states of light for two aspects of optical imaging: creating of miniature images on photosensitive substrates, which constitutes the foundation for optical lithography, and imaging of micro objects. In both cases, the classical resolution limit given by the Rayleigh criterion is approximately a half of the optical wavelength. It has been shown, however, that by using multi-photon quantum states of the light field, and multi-photon sensitive material or detector, this limit can be surpassed. We give a rigorous quantum mechanical treatment of this problem, address some particularly widespread misconceptions and discuss the requirements for turning the research on quantum imaging into a practical technology.Comment: Presented at PQE 2001. To appear in Special Issue of Journal of Modern Optic

Quantum correlations and fluctuations in the pulsed light produced by a synchronously pumped optical parametric oscillator below its oscillation threshold

We present a simple quantum theory for the pulsed light generated by a synchronously pumped optical parametric oscillator (SPOPO) in the degenerate case where the signal and idler trains of pulses coincide, below threshold and neglecting all dispersion effects. Our main goal is to precise in the obtained quantum effects, which ones are identical to the c.w. case and which ones are specific to the SPOPO. We demonstrate in particular that the temporal correlations have interesting peculiarities: the quantum fluctuations at different times within the same pulse turn out to be totally not correlated, whereas they are correlated between nearby pulses at times that are placed in the same position relative to the centre of the pulses. The number of significantly correlated pulses is of the order of cavity finesse. We show also that there is perfect squeezing at noise frequencies multiple of the pulse repetition frequency when one approaches the threshold from below on the signal field quadrature measured by a balanced homodyne detection with a local oscillator of very short duration compared to the SPOPO pulse length.Comment: 12 pages, 3 figure

Pediatric Critical Care in Resource-Limited Settings-Overview and Lessons Learned.

Pediatric critical care is an important component of reducing morbidity and mortality globally. Currently, pediatric critical care in low middle-income countries (LMICs) remains in its infancy in most hospitals. The majority of hospitals lack designated intensive care units, healthcare staff trained to care for critically ill children, adequate numbers of staff, and rapid access to necessary medications, supplies and equipment. In addition, most LMICs lack pediatric critical care training programs for healthcare providers or certification procedures to accredit healthcare providers working in their pediatric intensive care units (PICU) and high dependency areas. PICU can improve the quality of pediatric care in general and, if properly organized, can effectively treat the severe complications of high burden diseases, such as diarrhea, severe malaria, and respiratory distress using low-cost interventions. Setting up a PICU in a LMIC setting requires planning, specific resources, and most importantly investment in the nursing and permanent medical staff. A thoughtful approach to developing pediatric critical care services in LMICs starts with fundamental building blocks: training healthcare professionals in skills and knowledge, selecting resource appropriate effective equipment, and having supportive leadership to provide an enabling environment for appropriate care. If these fundamentals can be built on in a sustainable manner, an appropriate critical care service will be established with the potential to significantly decrease pediatric morbidity and mortality in the context of public health goals as we reach toward the sustainable development goals

Spatiotemporally localized solitons in resonantly absorbing Bragg reflectors

We predict the existence of spatiotemporal solitons (``light bullets'') in two-dimensional self-induced transparency media embedded in a Bragg grating. The "bullets" are found in an approximate analytical form, their stability being confirmed by direct simulations. These findings suggest new possibilities for signal transmission control and self-trapping of light.Comment: RevTex, 3 pages, 2 figures, to be published in PR

Spatiotemporally Localized Multidimensional Solitons in Self-Induced Transparency Media

"Light bullets" are multi-dimensional solitons which are localized in both space and time. We show that such solitons exist in two- and three-dimensional self-induced-transparency media and that they are fully stable. Our approximate analytical calculation, backed and verified by direct numerical simulations, yields the multi-dimensional generalization of the one-dimensional Sine-Gordon soliton.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let