1,721,026 research outputs found
Smoke rings of light
No full textThe ability to create complex three-dimensional structures of light has reached new heights with the experimental observation of two distinct kinds of toroidal pulses, the optical analogue of smoke rings
Longitudinal fields and transverse rotations
No full textElectromagnetic fields in light waves are mainly transverse to propagation direction but actually also have longitudinal components, which may give rise to unexpected optical phenomena involving the angular momentum of light, such as transverse spin and optical torques
Determinants and relevance of internalisation of environmental management systems
Full text linkThe internalisation of Environmental Management Systems (EMS) is raising interest among scholars. Authors have identified it as the reason of controversial results in literature about the relation between EMS and environmental performance. Often, certified companies without an internalised system are labelled to have symbolic behaviour in environmental management. However, the literature lacks of studies aimed to identify other justifications that could influence the performance of certified companies, also in absence of an internalised EMS. This study wants to analyse the role of the environmental manager satisfaction in the internalisation of EMS and in achieving environmental performance. The paper uses data from a survey of 438 EMAS registered organisations. The results show that the managers' satisfaction positively influence the environmental reputation and competitiveness also without considering the mediating role of internalisation. The paper opens new research avenues on the understanding of the real importance of EMS internalisation and on the need to further investigate the relation between EMS and performance
Large-scale free-space photonic circuits in two dimensions
Full text linkPhotonic circuits, engineered to couple optical modes according to a specific map, serve as processors for classical and quantum light. The number of components typically scales with that of processed modes, thus correlating system size, circuit complexity, and optical losses. We present a photonic-circuit technology implementing large-scale unitary maps in free space, coupling a single input to hundreds of output modes in a two-dimensional compact layout. The map corresponds to a quantum walk of structured photons, realized through light propagation in three liquid-crystal metasurfaces, having their optic axes artificially patterned. Theoretically, the walk length and the number of connected modes can be arbitrary while keeping losses constant. The patterns can be designed to replicate multiple unitary maps. We also discuss limited reconfigurability by adjusting the overall birefringence and the relative displacement of the optical elements. These results lay the basis for the design of low-loss nonintegrated photonic circuits, primarily for manipulating multiphoton states in quantum regimes
Terahertz Hyper-Raman Time-Domain Spectroscopy
No full textA new spectroscopic method has been demonstrated on the benchmark crystal α-SiO2. The new technique makes use of femtosecond optical pulses and intense, sub-ps, broadband terahertz (THz) pulses to generate a THz-optical four wave mixing in the investigated material. The spectrum of the generated signal is resolved in wavelength and displays two pronounced frequency sidebands close to the optical second harmonic central frequency 2ωL, where ωL is the optical central frequency of the fundamental beam. The two sidebands develop around the central frequency at the
(anti-) Stokes side of ωs;a = 2ωL ∓ ωT, where ωT is the THz central frequency, thus resembling the spectrum of standard hyper-Raman scattering, and hence, we named this effect “THz Hyper-Raman” - THYR. Due to the large laser and THz bandwidths, it is not possible to resolve the THYR signal in the frequency domain. Nonetheless, by taking advantage of the same principle at work in THz time-domain spectroscopy, it is possible to follow the evolution of the THYR signal in time and access the frequency domain again by Fourier Transform. In this way we were able to observe pronounced oscillations in time of the THYR signal whose frequencies correspond to a large variety of material excitations including Γ-point phonons, polaritons, and phonons out of the Γ-point, which are usually observed only by neutron scattering techniques. To complement the richness of these observations, we will show that the selection rules of the THYR process allow the simultaneous observation of both IR- and Raman-active material modes, thus highlighting the potential of this innovative experimental method
Tunable Two-Photon Quantum Interference of Structured Light
No full textStructured photons are nowadays an important resource in classical and quantum optics due to the richness of properties they show under propagation, focusing, and in their interaction with matter. Vectorial modes of light in particular, a class of modes where the polarization varies across the beam profile, have already been used in several areas ranging from microscopy to quantum information. One of the key ingredients needed to exploit the full potential of complex light in the quantum domain is the control of quantum interference, a crucial resource in fields like quantum communication, sensing, and metrology. Here we report a tunable Hong-Ou-Mandel interference between vectorial modes of light. We demonstrate how a properly designed spin-orbit device can be used to control quantum interference between vectorial modes of light by simply adjusting the device parameters and no need of interferometric setups. We believe our result can find applications in fundamental research and quantum technologies based on structured light by providing a new tool to control quantum interference in a compact, efficient, and robust way
Reconfigurable homodyne detector for vortex beams
No full textWe review the general properties of balanced optical homodyne detectors (BHD) that provide a physical implementation of the quantum field quadrature observable. Then, we discuss the particular case of a BHD designed to span a prescribed sub-space of vortex optical modes carrying orbital angular momentum. By properly tailoring the geometrical features of the local oscillator, mode matching with the signal to be detected is achieved guaranteeing a visibility around 97%. This performance has recently allowed the detection of continuous-variable entanglement between structured modes. Homodyning structured light may pave the way to its use in optical coherent communication and quantum communication protocols
Continuous variable entanglement over different degree of freedom for entanglement multiplexing
No full textContinuous variable entanglement is usually set between pairs of optical modes sharing the same geometrical property where distinguishability is demanded to polarization and/or frequency. Thus, the inherent non-local correlation shows-up in quantum quadratures relative to two distinct e.m. modes. In this contribution we will show how the polarization d.o.f. of a pair of entangled modes is coupled to the optical orbital angular momentum giving, at the end, a pair of entangled modes that have orthogonal OAM and polarization. We also show how this experimental scheme can be extended to give more than a pair of entangled modes paving the way to CV entanglement multiplexing
Continuous-variable entangled states of light carrying orbital angular momentum
Full text linkThe orbital angular momentum of light, unlike spin, is an infinite-dimensional discrete variable and may hence offer enhanced performances for encoding, transmitting, and processing quantum information. Hitherto, this degree of freedom of light has been studied mainly in the context of quantum states with definite number of photons. On the other hand, field-quadrature continuous-variable quantum states of light allow implementing many important quantum protocols not accessible with photon-number states. Here, we realize a scheme based on a q-plate device for endowing a bipartite continuous-variable Gaussian entangled state with nonzero orbital angular momentum. We then apply a reconfigurable homodyne detector working directly with such nonzero orbital angular momentum modes in order to retrieve experimentally their entire quantum-state covariance matrix, thus providing a full characterization of their quantum fluctuation properties. Our work is a step towards generating multipartite continuous-variable entanglement in a single optical beam
- …
