A thermal lens approach for measuring two-photon absorption cross sections (2PACSs) in fluorescent liquid samples is described and demonstrated. The method takes advantage of the sensitivity of a Sagnac interferometer, and the accumulative photothermal effect, for the detection of the induced photothermal phase shift. This leads to absolute estimations of the 2PACS of the sample. Experimental results demonstrate that this approach is suitable for obtaining the nonlinear absorbance spectrum of fluorescent molecules frequently used in two-photon fluorescence microscopy with a sensitivity of λ/1500.

There is an increasing need for environmentally friendly holographic recording materials which can be produced in bulk with little risk to the health of workers in manufacturing. This is why the development of non-toxic photopolymer materials is crucial, and has attracted attention in recent years. The composition and preliminary characterization of a new non-toxic photopolymer material are presented. It operates well at a range of spatial frequencies, and achieves diffraction efficiencies and refractive index modulation comparable to those of the known acrylamide-based photopolymers.

We show that the Plebanski based approach to transformation optics overlooks some subtleties in the electrodynamics of moving dielectrics that restricts its applicability to a certain class of transformations. An alternative, completely covariant, approach is developed that is more generally applicable and provides a clearer picture of transformation optics.

A super-resolution imaging method for the deep sub-wavelength structure has been proposed, which is achieved by controlling the propagating direction of the evanescent components of the incident field through a one-dimensional metamaterial structure (ODMS) with an anisotropic dielectric permittivity. We provide the mechanism of this kind of super-resolution imaging method in detail and discuss some factors influencing image quality. A two-dimensional finite element method (FEM) has been used to verify the imaging mechanism. Furthermore, the same sub-diffraction limited image could be obtained at different incident wavelengths at the far side of the imaging structure with different working distances.

Light-initiated quasi-instant solidification of a liquid polymer is attractive for its ultra-precise spatial and temporal control of the photochemical reaction. In this paper we present microlenses structured by femtosecond laser-induced photopolymerization. Due to nonlinear phenomena the fabrication resolution is not restricted to the diffraction limit for the applied laser excitation wavelength but is determined by the intensity of a focused beam. Furthermore, pin-point structuring enables one to produce three-dimensional structures of any form from the photopolymer. The smallest structural elements of 200 nm lateral dimensions can be achieved reproducibly by using high numerical aperture oil immersion focusing optics (NA = 1.4). Axial resolution (which is fundamentally a few times worse than lateral resolution due to the distribution of light intensity in the focal region) can be controlled to a precision of a few hundred nanometers by decreasing the scanning step. In our work...

Nanoplasmonics has recently experienced explosive development with many novel ideas and dramatic achievements in both fundamentals and applications. The spaser has been predicted and observed experimentally as an active element—a generator of coherent local fields. Even greater progress will be achieved if the spaser can function as an ultrafast nanoamplifier—an optical counterpart of the MOSFET (metal–oxide–semiconductor field effect transistor). A formidable problem with this is that the spaser has inherent feedback, causing quantum generation of nanolocalized surface plasmons and saturation and consequent elimination of the net gain, making it unsuitable for amplification. We have overcome this inherent problem and shown that the spaser can perform functions of an ultrafast nanoamplifier in two modes: transient and bistable. On the basis of quantum density matrix (optical Bloch) equations we have shown that the spaser amplifies with gain

A self-consistent computational scheme is presented for one-dimensional (1D) and two-dimensional (2D) metamaterial systems with gain incorporated into the nanostructures. The gain is described by a generic four-level system. The loss compensation and the lasing behavior of the metamaterial system with gain are studied. A critical pumping rate exists for compensating the losses of the metamaterial. There exists a wide range of input signals where the composite system behaves linearly. Nonlinearities arise for stronger signals due to gain depletion. The retrieved effective parameters are presented for one layer of gain embedded in two layers of Lorentz dielectric rods and split ring resonators (SRR) with two different gain inclusions: (1) gain is embedded in the gaps only and (2) gain is surrounding the SRR. When the pumping rate increases, there is a critical pumping rate at which the metamaterial system starts lasing.

We have theoretically investigated two-dimensional photonic crystal (2D PC) nanocavities with low-refractive-index (low- n) material cladding using a 3D finite-difference time-domain method. When the refractive index of the cladding is increased from 1 to 1.535, corresponding to that of organic polymers, the Q factor markedly decreases ( Q<10 ³). We finely adjusted the positions of the holes at both edges of the 2D PC nanocavities. The Q factor can be increased by a factor of up to 21 ( Q>10 ⁴) by shifting the neighboring four pairs of holes inward by suitable amounts. In addition, we examined the real and wavevector space distributions of the resonant modes. We revealed significant design rules based on single and double Gaussian envelope functions, which can be used to effectively and flexibly develop and finely adjust the optical properties of 2D PC nanocavities with low- n material cladding.

We develop a perturbation analysis that describes the effect of third-order dispersion on the similariton pulse solution of the nonlinear Schrödinger equation in a fibre gain medium. The theoretical model predicts with sufficient accuracy the pulse structural changes induced, which are observed through direct numerical simulations.

The paper explores a partial unfolding of the canonical three-dimensional diffraction field associated with the optical catastrophe X ₉ with modulus K = −6. A practical realization would be the focal region of a thin lens created by setting a drop of water on a horizontal glass slide and constraining its perimeter to be square. The pattern of caustics formed around the focus is a twisted and ribbed double trumpet with 4-fold symmetry. Like all diffraction catastrophes the essential structure is based on a pattern of line singularities (wave dislocations or optical vortices) on which the amplitude is zero and the phase is indeterminate. The caustic is encircled on the outside, and in the focal plane, by a highly puckered and non-circular ring and a forest of other dislocations. Far from the axis these are organized by the planar group 3 m, despite the 4-fold symmetry. On the inside, the dislocation lines form a curved quasi-periodic lattice of small, ...