Exploiting a particular wave property for a particular application necessitates components capable of discriminating in the basis of that property. While spectral or polarisation decomposition can be ...straightforward, spatial decomposition is inherently more difficult and few options exist regardless of wave type. Fourier decomposition by a lens is a rare simple example of a spatial decomposition of great practical importance and practical simplicity; a two-dimensional decomposition of a beam into its linear momentum components. Yet this is often not the most appropriate spatial basis. Previously, no device existed capable of a two-dimensional decomposition into orbital angular momentum components, or indeed any discrete basis, despite it being a fundamental property in many wave phenomena. We demonstrate an optical device capable of decomposing a beam into a Cartesian grid of identical Gaussian spots each containing a single Laguerre-Gaussian component, using just a spatial light modulator and mirror.
Control of the spatial and temporal properties of light propagating in disordered media have been demonstrated over the last decade using spatial light modulators. Most of the previous studies ...demonstrated spatial focusing to the speckle grain size, and manipulation of the temporal properties of the achieved focus. In this work, we demonstrate an approach to control the total temporal impulse response, not only at a single speckle grain but over all spatial degrees of freedom (spatial and polarization modes) at any arbitrary delay time through a multimode fiber. Global enhancement or suppression of the total light intensity exiting a multimode fibre is shown for arbitrary delays and polarization states. This work could benefit to applications that require pulse delivery in disordered media.
If there is one question that haunts Indian Christians, it is this: "What does it mean to be Indian and Christian?" This matter of identity presents a unique challenge, especially today, in the face ...of a Hindu nationalist challenge insisting that to be truly Indian, one must be Hindu. Christianity Remade, however, offers a unique path forward by studying the rise and character of Indian-initiated churches (IICs), Christian movements founded by Indians to address Indian issues, needs, and opportunities. IIC is not a common term in Indian church life or theology today. Only a few scholars have focused on Christian movements arising in India. Based on firsthand experience from research conducted through the Mylapore Institute for Indigenous Studies, Paul Joshua's groundbreaking work presents a truly striking discovery: IICs represent a pivotal, re-formative phase in the nearly twenty-century history of Indian Christianity. They result from critiques of the inherited structures and outlook of mission-founded Christianity. They respond to the deep needs of people on the lower rungs of Indian society, and they fashion their spiritual answers and modes of being from deeply Indian religious materials. Thus, they engage in a creative combination of Indian popular piety and the gospel of Jesus Christ as found in an Indian reading of the Bible. Joshua engages specific IIC movements to draw out singular contextual ingredients: the rise of Indian nationalism, the generative power of Christian revivalism, the movement for national independence, the bhakti tradition of popular Hindu devotional practice, the challenge of Hindu spiritual power, and the dynamism of contemporary urban culture. From these ingredients, and drawing on insights from postcolonial studies, Joshua reveals how a "subaltern" sensibility and vision from the margins of Indian society challenged both the colonial overlords and the mission-church hierarchs to create a Christianity made in India.
The largest complete mode transfer matrix of a fiber is measured consisting of 110 spatial and polarization modes. This matrix is then inverted and the pattern required to produce a desired output at ...the receiver are launched at the transmitter.
Lossless linear wave propagation is symmetric in time, a principle which can be used to create time reversed waves. Such waves are special "pre-scattered" spatiotemporal fields, which propagate ...through a complex medium as if observing a scattering process in reverse, entering the medium as a complicated spatiotemporal field and arriving after propagation as a desired target field, such as a spatiotemporal focus. Time reversed waves have previously been demonstrated for relatively low frequency phenomena such as acoustics, water waves and microwaves. Many attempts have been made to extend these techniques into optics. However, the much higher frequencies of optics make for very different requirements. A fully time reversed wave is a volumetric field with arbitrary amplitude, phase and polarisation at every point in space and time. The creation of such fields has not previously been possible in optics. We demonstrate time reversed optical waves with a device capable of independently controlling all of light's classical degrees of freedom simultaneously. Such a class of ultrafast wavefront shaper is capable of generating a sequence of arbitrary 2D spatial/polarisation wavefronts at a bandwidth limited rate of 4.4 THz. This ability to manipulate the full field of an optical beam could be used to control both linear and nonlinear optical phenomena.
Structured light, with spatially varying phase or polarization distributions, has given rise to many novel applications in fields ranging from optical communication to laser-based material ...processing. However the efficient and flexible generation of such beams from a compact laser source at practical output powers still remains a great challenge. Here we describe an approach capable of addressing this need based on the coherent combination of multiple tailored Gaussian beams emitted from a multicore fibre (MCF) amplifier. We report a proof-of-concept structured light generation experiment, using a cladding-pumped 7-core MCF amplifier as an integrated parallel amplifier array and a spatial light modulator (SLM) to actively control the amplitude, polarization and phase of the signal light input to each fibre core. We report the successful generation of various structured light beams including high-order linearly polarized spatial fibre modes, cylindrical vector (CV) beams and helical phase front optical vortex (OV) beams.
This review essay discusses the status of “World Christianity” as a field of study, then highlights the features of the book at hand. It is an exercise in world history more than church history, ...focusing on how Christianity in various parts of the world responded to the twentieth century’s greatest challenges. The book addresses the rise of millenarianism and fundamentalism, neo-orthodoxy, liberation theology, Pentecostalism, and ecumenism. But its more intent focus is on how Christianity addressed the century’s world wars, colonialism, nationalism, secularism, rise of radical Islam, human rights, migration, and the growing power of the state.
Abstract
Measuring polarisation, spectrum, temporal dynamics, and spatial complex amplitude of optical beams is essential to studying phenomena in laser dynamics, telecommunications and nonlinear ...optics. Current characterisation techniques apply in limited contexts. Non-interferometric methods struggle to distinguish spatial phase, while phase-sensitive approaches necessitate either an auxiliary reference source or a self-reference, neither of which is universally available. Deciphering complex wavefronts of multiple co-propagating incoherent fields remains particularly challenging. We harness principles of spatial state tomography to circumvent these limitations and measure a complete description of an unknown beam as a set of spectrally, temporally, and polarisation resolved spatial state density matrices. Each density matrix slice resolves the spatial complex amplitude of multiple mutually incoherent fields, which over several slices reveals the spectral or temporal evolution of these fields even when fields spectrally or temporally overlap. We demonstrate these features by characterising the spatiotemporal and spatiospectral output of a vertical-cavity surface-emitting laser.
Christian higher education is expanding rapidly in Africa, following the growth of Christian populations on the continent. Although dynamic, these universities face the same problems of resources, ...standards, and other that confront African universities generally. (HoF/text adopted).
PDF
