The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Quantum readout of physical unclonable functions (PUFs) is a recently introduced method for remote authentication of objects. We present an extension of the protocol to enable the authentication of data: A verifier can check if received classical data were sent by the PUF holder. We call this modification QR-d or, in the case of the optical-PUF implementation, QSA-d. We discuss how QSA-d can be operated...
It is well known that a thick scattering medium (e.g. a slab of paint) is opaque since incident waves are thoroughly scrambled [1, 2]. In the diffusive transport regime, the scattered light has an (ensemble-averaged) energy density that linearly increases with depth from the front surface to about one mean free path 1, and then decreases linearly with depth to the back surface. Two main questions...
Photonic crystals are tailored periodic dielectric media that allow for an unprecedented control in the manipulation of light-matter interactions. One of their outstanding features is the realization of a complete photonic band gap that drastically inhibits light propagation in all directions and for all polarizations. A band gap is associated with a complete vanishing of the density of optical states...
Light propagates inside an ideal and infinite photonic crystal when the Bloch condition is satisfied and any allowed light wave is decomposed in a basis of propagating Bloch waves [1]. In real photonic crystals, light propagation is modified due to unavoidable fabrication-induced structural imperfections in size, positions, and permittivity of the building blocks, as well as the finite size of the...
Communication between a sender and receiver can be made secure by encrypting the message using public or private shared keys. Quantum key distribution utilizes the unclonability of a quantum state to securely generate a key between the two parties [1]. However, without some way of authentication of either the sender or the receiver, a man-in-the-middle attack with an eavesdropper mimicking the receiver...
Photonic crystal nanocavities have been intensively investigated due to their unique combination of high quality factors and small mode-volumes [1, 2]. When such cavities are optically coupled new phenomena and applications arise such as slow light [3]. To achieve complete tunability of coupled cavity systems one should be able to individually tune resonance frequencies of resonators as well as the...
We study numerically the effects of optical absorption on highly transmitting channels in strongly scattering media. We observe that they are robust against weak absorption. Surprisingly, in case of strong absorption diffusive transport becomes ballistic-like.
The control of light scattering is essential in many quantum optical experiments. Wavefront shaping is a technique used for ultimate control over wave propagation through multiple-scattering media by adaptive manipulation of incident waves. We control the propagation of single-photon Fock states through opaque scattering media by spatial phase modulation of the incident wavefront. We enhance the probability...
Light incident on a scattering medium is redistributed over transport channels that either transmit through or reflect from the medium. We perform experiments aiming at finding individual transport channels of extremely strongly scattering materials. A small number of transport channels in a scattering sample are open with transmission coefficient close to 1; field transmission mainly takes place...
Semiconductor microcavities have proven to be essential to strongly confine light [1], thereby enhancing the interaction between light and matter to the point of manipulating quantum states of matter. To achieve dynamic control of these processes, one must approach their characteristic time scales in the picosecond range, corresponding to THz modulation rates [2,3]. While all-optical switching is...
Non-invasive imaging requires the ability to form sharp pictures even when an opaque material act as a screen between the object and the detector. Light scattering scrambles the spatial information of the object, thereby blurring the picture and making imaging impossible. Gated imaging methods [1,2] such as optical coherence tomography [3] can separate the small amount of ballistic light that did...
It is well known that the propagation of light is scrambled while passing through a complex nanophotonic material with spatial inhomogeneities in the refractive index such as white paint, paper or biological tissue. Therefore, it is impossible to focus light through such media using conventional optics. Recently, it has been shown that light can be focused through a turbid medium using wavefront shaping,...
We present ultrafast reflectivity measurements on the dynamics of optically excited free carriers in semiconductor microcavities. We observe that the relaxation dynamics of the switched cavity is strongly frequency dependent, which points towards multiple carrier populations. The interest in ultrafast all-optical switching of nano-photonic structures has rapidly increased due to the inherent speed...
The ability to spatially control the phase and amplitude of light allows for many exciting applications. In adaptive optics, light fields are modulated to correct for aberrations in the atmosphere. It has recently been shown that by spatially modulating light it is possible to focus and image through and inside opaque materials [1-5].
There is a strong worldwide drive to efficient general lighting using white light emitting diodes (LEDs) [1,2]. White LEDs often consist of a semiconductor diode [3,4,5] combined with luminescent phosphors [5] to convert part of the blue light to green yellow, and red. In state-of-the art white-light LEDs one exploits multiple scattering of light [1,2]. The transport of light then becomes diffusive,...
Random scattering of light that one can observe in paper, paint and biological tissue is an obstacle to imaging and focusing of light and thus hampers many applications. At the same time scattering is a phenomenon of basic physical interest as it allows the study of interference effects such as Anderson localization [1-3], open transport channels [2,4], and speckle correlations [5].
We show that nanophotonic manipulation of biological fluorophores can alter the spectral characteristics of visible fluorescent proteins (VFP), and that the changed spectral properties quantitatively reflect the sub surface quality of photonic crystals. Nanophotonic manipulation of VFP fluorescence lifetimes gives access to the quantum efficiency of emitting states without biasing from dark states,...
Materials such as white paint, paper, milk, tissue appear opaque because they strongly scatter the incident light. It is impossible to focus light through such turbid media using conventional optics. However, it has been shown that it is possible to focus light through or inside such materials using a feedback based algorithm that spatially modifies the phase of the wavefront. When the incident wavefront...
Scattering of light is usually seen as a nuisance in microscopy. Scattering limits the penetration depth and strongly deteriorates the achievable resolution. However, by gaining active spatial control over the optical wave front it is possible to manipulate the propagation of scattered light even far in the multiple scattering regime.[1–3] It was recently shown that in this way scattered light can...
We numerically observe that open eigenmodes enhance the energy stored inside disordered media and prove that eigenmodes contribute to a single-channel optimizing mode, which is realized in recent experiments, in proportion to their eigenvalues.
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.