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We demonstrate experimentally a very thin THz spatial phase modulator based on planar metamaterials hybridysed with a liquid-crystal (LC) cell. It consists of two layers of THz planar metamaterials separated by a 12 µm thick LC layer. Besides enhancing optical anisotropy of the LC layer, the metamaterials also act as spatially addressable electrodes, which transform the resulting structure into an array of sub-wavelength pixels with independently controlled electromagnetic phase. Our approach brings about a new family of LC-enabled but optically thin THz devices for efficient control and manipulation of THz wavefronts

Metamaterials (MMs) in optics represent a large class of nano-structured artificial media with optical characteristics not found, or superior, to those exhibited by natural materials. They have rapidly advanced over the past decade and are now expected to have major impact across the entire range of photonic technologies. The current effort in the field is focused on implementing the idea of active and tunable MMs, a generation of artificial photonic media with dynamically controlled optical properties.

We explore the limits of the photosensitive response of thin, 15 to 35 nm, films of complex azobenzene dyes. They show high refractive index, reaching 1.8, and significant photo-induced birefringence. We have successfully recorded strong, birefringent phase gratings with visible light and used the diffraction efficiency measurements to monitor their temporal evolution. The photo-induced gratings in such thin films were found not to be associated with any periodic surface relief, a typical feature in thicker azobenzene layers., Optical Materials Express, 8 (2), ISSN:2159-3930

Photoaligning azobenzene-based PAAD materials can show strong photoresponse without a surface relief pattern. We report an experimental investigation of PAADs optical properties, such as complex refractive indices and optically induced birefringence. Formation of photoinduced phase gratings in 20-50 nm, thin PAAD layers is demonstrated, with a strong dependence of diffraction on the probe beam polarization. The light induced diffraction in liquid crystal systems coupled with PAAD films is also studied. We demonstrate a stable and strong diffraction grating, which can be rewritten by illumination or switched off by reorienting the liquid crystals with a bias voltage.

We present a prototype of compact device for all-optical measurements of the elastic and dynamic properties of nematic liquid crystals. The device is based on a standard cross-polarized optical set-up and by using a three-step measurement protocol and a corresponding fitting procedure, it simultaneously determines the following LC parameters: the splay and bend elastic constants, K1 and K3, the rotational viscosity γ1, and the combination of Leslie viscosity coefficients α4+ α5. Moreover, by taking sampled measurements across the area of a LC cell, the map profile of the LC layer thickness and average pre-tilt on the surfaces can be determined.

Stiction is one of the major reliability issues limiting practical application of nano-electro-mechanical systems (NEMS), an emerging device technology that exploits mechanical movements on the scale of an integrated electronic circuit. We report on a discovery that stiction can be eliminated by infiltrating NEMS with nematic liquid crystals. We demonstrate this experimentally using a NEMS-based tunable photonic metamaterial, where reliable switching of optical response was achieved for the entire range of nanoscopic structural displacements admitted by the metamaterial design. Being a more straightforward and easy-to-implement alternative to the existing antistiction solutions, our approach also introduces an active mechanism of stiction control, which enables toggling between stiction-free and the usual (stiction-limited) regimes of NEMS operation. It is expected to greatly expand the functionality of electro-mechanical devices and enable the development of adaptive and smart nanosystems.

Optical micro-electromechanical systems (MEMS) based on suspended optical waveguides offer a range of interesting applications, e.g. in optical communications and sensing. In particular, if the waveguide dimensions are sufficiently small and thus the evanescent field of propagating light extends beyond the guiding material into air, two closely spaced parallel waveguides become optically coupled with a coupling strength that is strongly dependent on the waveguide separation. This effect can be exploited for mechanically actuated optical switching, tuning of micro-resonators, or even for changing the speed of light. &more...

The realisation of efficient ion-photon quantum interfaces is an essential step towards developing operational quantum information networks. Individual trapped ions have been shown as promising candidates for quantum information processing nodes, while effective ion manipulation and photonic links between nodes can be realised by deterministic coupling of ions to optical cavities. However, integrating optical cavities into ion traps remains a challenge as the trapping potential is affected by the presence of any dielectric or conductor.

We present the design and fabrication of a dual air-bridge waveguide structure integrated with MEMS functionality. The structure is designed to function as a tunable optical buffer for telecommunication application. The optical buffer structure is based on two parallel waveguides made of high refractive index material with subwavelength dimensions. They are suspended in air, and are separated by a sub-micron air gap. Due to the fact that the size of the waveguides is much smaller than the wavelength of light that propagates in the structure, a significant fraction of the optical mode is in the air gap between the waveguides. By changing the size of the air gap using MEMS techniques, we can vary this fraction and hence the effective refractive index of the waveguide structure, thus generating tunable optical delay.The optical buffer structure was grown on an InP substrate by molecular beam epitaxy, and the device layer was made of InGaP. An InGaAs layer was sandwiched between the device layer and the substrate to serve as a sacrificial layer. The sub-micron waveguides, their supports in the form of side pillars with tapered shapes in order to minimize optical losses, and the MEMS structures were patterned using electron beam lithography and plasma etching. Electrodes were integrated into the structure to provide electrostatic actuation. After the sample patterning, the waveguide structure was released using HF etch. Our simulations predict that by varying the waveguide separation from 50 nm to 500 nm, we could achieve a change in propagation delay by a factor of two.

In this paper we design a high-resolution line imaging device allowing for broadband operation at near-infrared wavelengths ranging from 1 µm to 2 µm utilizing the advantage of subwavelength light confinement in plasmonic waveguides. The device consists of an array of air-guided plasmonic waveguides in gold with fanned-out geometry. In the main part of the device the separation between waveguides increases gradually from the input towards the output. High resolution is achieved on the input side by tapering down the periodicity between channels to 150 nm, while simultaneously maintaining propagation losses of a few dB. The proposed design also minimizes optical cross-coupling between waveguides; each channel thus transmits optical fields independently allowing for high signal-to-noise ratio imaging. At the low-resolution side properly tailored output couplers are designed to enhance optical coupling to free space. This is also shown to be an effective method to reduce back reflection, thus minimizing Fabry-Perot effects in the waveguides and allowing for broadband operation.