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Surface‐initiated atom transfer radical polymerization (SI‐ATRP) was used to graft poly(N‐isopropylacrylamide) (PNIPAM) brush layers with a controllable thickness in the 10‐nm range from silicon substrates. The rate of polymerization of N‐isopropylacrylamide was tuned by the [Cu(II)]0/[Cu(I)]0 ratio between the deactivating and activating species. The polymer layer thickness was characterized by atomic...
Quantum optics experiments require ultimate control over the propagation of light in linear optical networks to realize programmable photon correlations [1]. Integrated optics provides a robust and low-loss platform for implementing such linear optical networks. However, to achieve ultimate control on the quantum state of light, it is necessary to program the network [2]. Tuning the network for controlled...
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...
Authentication of people or objects using physical keys is insecure against secret duplication. Physical unclonable functions (PUF) are special physical keys that are assumed to be unclonable due to the large number of degrees of freedom in their manufacturing [1]. Opaque scattering media, such as white paint and teeth, comprise of millions of nanoparticles in a random arrangement. Under coherent...
The energy-efficient generation of white light has recently become an important societal issue. The technology of white-light emitting diodes (LEDs) is one of the most promising solutions to efficiently generate white light for home, office, and street locations, and even for remote locations without electric power grid [1]. One of the outstanding in the development of LED technology are understanding...
We investigate theoretically and numerically the transport of light in a three-dimensional (3D) crystal of cavities inside a 3D inverse woodpile photonic crystal. This class of crystals consists of two perpendicular arrays of pores and has a very broad 3D photonic band gap. An individual point defect is formed by reducing the radius of two intersecting pores. An earlier study revealed that an isolated...
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...
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...
Light transport in opaque scattering media mixes the light across the large number of modes in the system. The mixing results in the scrambling of information encoded on the incident light, which is generally detrimental. However, the multimodal transport hints at the possibility of utilizing them as complex optical networks if the transport could be controlled. In recent years, wavefront shaping...
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.
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,...
Impressive progress has been achieved in controlling the spontaneous emission rate for emitters in Nanophotonic structures[1,2], such as microcavities[1,3], photonic crystals[4] and nano-antennas[5]. In all cases, however, the modification of the emission is stationary in time. Thus, the emission rate is time-independent and the distribution of photon emission times are stochastic and follow an exponential...
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,...
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