Mother and Son, by F Odun Balogen, A Brief Analysis Through the Lens of New Historicism

This article employs New Historicism to analyze F. Odun Balogun\u27s short story Mother and Son, exploring its reflection of social, political, and cultural dynamics. By examining the story through a New Historicism lens, this analysis sheds light on the complexities of navigating a rapidly changing society while acknowledging the enduring racial barriers faced by the narrator. The essay was created in response to an assignment prompt that asked students to choose a literary theory and apply it to a story in order to argue for the story\u27s meaning

Properties of bright squeezed vacuum at increasing brightness

A bright squeezed vacuum (BSV) is a nonclassical macroscopic state of light, which is generated through high-gain parametric down-conversion or four-wave mixing. Although the BSV is an important tool in quantum optics and has a lot of applications, its theoretical description is still not complete. In particular, the existing description in terms of Schmidt modes with gain-independent shapes fails to explain the spectral broadening observed in the experiment as the mean number of photons increases. Meanwhile, the semiclassical description accounting for the broadening does not allow us to decouple the intermodal photon-number correlations. In this work, we present a new generalized theoretical approach to describe the spatial properties of a multimode BSV. In the multimode case, one has to take into account the complicated interplay between all involved modes: each plane-wave mode interacts with all other modes, which complicates the problem significantly. The developed approach is based on exchanging the (k, t ) and (ω, z) representations and solving a system of integrodifferential equations. Our approach predicts correctly the dynamics of the Schmidt modes and the broadening of the angular distribution with the increase in the BSV mean photon number due to a stronger pumping. Moreover, the model correctly describes various properties of a widely used experimental configuration with two crystals and an air gap between them, namely, an SU(1,1) interferometer. In particular, it predicts the narrowing of the intensity distribution, the reduction and shift of the side lobes, and the decline in the interference visibility as the mean photon number increases due to stronger pumping. The presented experimental results confirm the validity of the new approach. The model can be easily extended to the case of the frequency spectrum, frequency Schmidt modes, and other experimental configurations

Optical modelling of a Si-based DBR laser source using a nanocrystal Si-sensitized Er-doped silica rib waveguide in the C-band

The availability of reliable silicon-based laser sources is at the basis of the integration of photonic and microelectronic devices on a single chip with consequent development of wavelength division multiplexing telecommunication systems. A high efficiency Si-based laser source with good stability at room temperature would encourage and push the large scale of integration of electronic and photonic devices within a single chip. Several techniques have been proposed for generating light with an internal quantum efficiency some order of magnitude greater than that typical of silicon (10-6) by using either electrical or optical pumping. Among them we mention the improvement of some fabrication process steps, reduction of the channels of non-radiative recombination, quantum confinement, the use of silicon nanocrystals (Si-ncs) incorporated in a silica matrix. This last technique is used in combination with Er3+ doping to generate light emission around 1500 nm in silicon, since Er-doped Si-ncs behave as electron-hole pairs trap, and the presence of Er shifts the emission peak to around 1500 nm. In this paper we have pointed out the optical model of a Si-based DBR laser including a Si-ncs Er-doped SiO2 rib waveguide, working at a wavelength in C-band. In particular, after a brief description of the structural and optical properties of the silicon crystals, we report on the model and design of the Er:Si-nc/SiO2 rib waveguide, of the optical cavity and of the Bragg mirrors. Numerical results are in good agreement with the literature

Nonlinear interferometry with high-gain parametric down-conversion

Interferometers have become essential devices within research and industry because they can measure phase shifts, often very small ones. Increasing the number of probing photons enhances the accuracy of this measurement, but with a bounded scaling called the shot-noise limit. The field of nonlinear interferometry studies how to surpass this limit using nonclassical properties produced with nonlinear effects. The advantage offered -- often referred to as super-sensitivity -- becomes relevant when the precision cannot be pushed further, for instance, by an arbitrary increase of the number of photons. Therefore, this field pioneers the technological advance of interferometers and, in the last decades, it had a substantial impact on applications in quantum information, metrology and imaging. This thesis aims to demonstrate robust and versatile nonlinear interferometers that encompass the process of parametric down-conversion in nonlinear crystals as the source of nonclassical radiation. The squeezed vacuum state produced in this process can yield a macroscopic number of photons per mode in the strongly-pumped regime while still possessing quantum features. This state is injected together with a laser in a classical interferometer for the first experiment of this work. The super-sensitivity to a scalar phase shift results from the reduced noise in one electric field quadrature, a nonclassical feature. However, the output state can be fragile if the detection is lossy or inefficient; this work proves that noiseless optical amplification before detection leads to robustness and that a stronger amplification pre-compensates for a higher loss or inefficiency. This proof-of-principle scheme is suitable for many applications employing squeezed states, especially in those challenging wavelength ranges for detection like mid-infrared. The noiseless amplification is obtained here with the external stimulation of the down-conversion process in similar nonlinear crystals to the ones used to produce the squeezed vacuum. The measurement of a scalar phase shift does not fully exploit the potential of the squeezed vacuum and the amplification process: the broad multimode spatial structure would enable two-dimensional phase super-sensitivity. However, since the amplification in nonlinear crystals is not necessarily noiseless, as a preliminary step, this thesis addresses the unexplored conditions on the input signal to achieve this regime for the spatially-multimode case. The examples given here for the spatial degree are extensible also to the temporal domain, which is of great interest for quantum spectroscopy. This thesis proposes another scheme, usually referred to as the SU(1,1) interferometer, to pave the way towards two-dimensional super-sensitivity. In this scheme, the beam splitter, which is a passive building block of interferometers, is substituted with the nonlinear crystal, a pumped active element, and no other source than the squeezed vacuum may be required. Previous experiments achieved super-sensitive detection of scalar phase shifts, but the novel configuration presented here works with multiple spatial modes and in two dimensions. The operation in the quantum regime is ensured by the measured reduction in the quadrature noise for the plane-wave modes of the state that probes the phase shift. As the phase changes, this configuration is also stable in the output spatial mode content, both in the radial and azimuthal degree of freedom. The full mode structure for this interferometer is not analytically known; this thesis proposes a method to experimentally reconstruct the modes with the acquisition of only intensity distributions. The knowledge of this structure is fundamental for applications in remote sensing and sub-shot-noise imaging because it helps developing schemes that preserve the nonclassical properties, nontrivial for multiple modes

Ultra-Thin Plasma-Polymerized Functional Coatings for Biosensing: Polyacrylic Acid, Polystyrene and Their Co-Polymer

Recently, many efforts have been done to chemically functionalize sensors surface to achieve selectivity towards diagnostics targets, such as DNA, RNA fragments and protein tumoural biomarkers, through the surface immobilization of the related specific receptor. Especially, some kind of sensors such as microcantilevers (gravimetric sensors) and one-dimensional photonics crystals (optical sensors) able to couple Bloch surface waves are very sensitive. Thus, any kind of surface modifications devoted to functionalize them has to be finely controlled in terms of mass and optical characteristics, such as refractive index, to minimize the perturbation, on the transduced signal, that can affect the response sensitivity towards the detected target species

Overcoming detection loss and noise in squeezing-based optical sensing

Among the known resources of quantum metrology, one of the most practical and efficient is squeezing. Squeezed states of atoms and light improve the sensing of the phase, magnetic field, polarization, mechanical displacement. They promise to considerably increase signal-to-noise ratio in imaging and spectroscopy, and are already used in real-life gravitational-wave detectors. But despite being more robust than other states, they are still very fragile, which narrows the scope of their application. In particular, squeezed states are useless in measurements where the detection is inefficient or the noise is high. Here, we experimentally demonstrate a remedy against loss and noise: strong noiseless amplification before detection. This way, we achieve loss-tolerant operation of an interferometer fed with squeezed and coherent light. With only 50% detection efficiency and with noise exceeding the level of squeezed light more than 50 times, we overcome the shot-noise limit by 6 dB. Sub-shot-noise phase sensitivity survives up to 87% loss. Application of this technique to other types of optical sensing and imaging promises a full use of quantum resources in these fields

3D Cell Culture: Recent Development in Materials with Tunable Stiffness

It is widely accepted that three-dimensional cell culture systems simulate physiological conditions better than traditional 2D systems. Although extracellular matrix components strongly modulate cell behavior, several studies underlined the importance of mechanosensing in the control of different cell functions such as growth, proliferation, differentiation, and migration. Human tissues are characterized by different degrees of stiffness, and various pathologies (e.g., tumor or fibrosis) cause changes in the mechanical properties through the alteration of the extracellular matrix structure. Additionally, these modifications have an impact on disease progression and on therapy response. Hence, the development of platforms whose stiffness could be modulated may improve our knowledge of cell behavior under different mechanical stress stimuli. In this review, we have analyzed the mechanical diversity of healthy and diseased tissues, and we have summarized recently developed materials with a wide range of stiffness