Laser-induced transient magnons in SrIrO throughout the Brillouin zone.

Although ultrafast manipulation of magnetism holds great promise for new physical phenomena and applications, targeting specific states is held back by our limited understanding of how magnetic correlations evolve on ultrafast timescales. Using ultrafast resonant inelastic X-ray scattering we demonstrate that femtosecond laser pulses can excite transient magnons at large wavevectors in gapped antiferromagnets and that they persist for several picoseconds, which is opposite to what is observed in nearly gapless magnets. Our work suggests that materials with isotropic magnetic interactions are preferred to achieve rapid manipulation of magnetism.

Measuring non-equilibrium dynamics in complex solids with ultrashort X-ray pulses.

Strong interactions between electrons give rise to the complexity of quantum materials, which exhibit exotic functional properties and extreme susceptibility to external perturbations. A growing research trend involves the study of these materials away from equilibrium, especially in cases in which the stimulation with optical pulses can coherently enhance cooperative orders. Time-resolved X-ray probes are integral to this type of research, as they can be used to track atomic and electronic structures as they evolve on ultrafast timescales.

Non-equilibrium control of complex solids by nonlinear phononics.

We review some recent advances in the use of optical fields at terahertz frequencies to drive the lattice of complex materials. We will focus on the control of low energy collective properties of solids, which emerge on average when a high frequency vibration is driven and a new crystal structure induced. We first discuss the fundamentals of these lattice rearrangements, based on how anharmonic mode coupling transforms an oscillatory motion into a quasi-static deformation of the crystal structure.

Pulse shaping in the mid-infrared by a deformable mirror.

We present a pulse-shaping scheme operating in the mid-infrared (MIR) wavelength range up to 20 μm. The spectral phase is controlled by a specially designed large stroke 32-actuator deformable mirror in a grating-based 4f configuration. We demonstrate the shaper capability of compressing the MIR pulses, imparting parabolic and third-order spectral phases and splitting the spectral content to create two independent pulses.

Single-shot detection and direct control of carrier phase drift of midinfrared pulses.

We introduce a scheme for single-shot detection and correction of the carrier-envelope phase (CEP) drift of femtosecond pulses at mid-IR wavelengths. Difference frequency mixing between the mid-IR field and a near-IR gate pulse generates a near-IR frequency-shifted pulse, which is then spectrally interfered with a replica of the gate pulse. The spectral interference pattern contains shot-to-shot information of the CEP of the mid-IR field, and it can be used for simultaneous correction of its slow drifts.

Molecular host-guest energy-transfer system with an ultralow amplified spontaneous emission threshold employing an ambipolar semiconducting host matrix.

We report on the characteristics of a host-guest lasing system obtained by coevaporation of an oligo(9,9-diarylfluorene) derivative named T3 with the red-emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (DCM). We demonstrate that the ambipolar semiconductor T3 can be implemented as an active matrix in the realization of a host-guest system in which an efficient energy transfer takes place from the T3 matrix to the lasing DCM molecules. We performed a detailed spectroscopic study on the system by systematically varying the DCM concentration in the T3 matrix.

Pilot study: optical coherence tomography as a non-invasive diagnostic perspective for real time visualisation of onychomycosis.

The objective of this study was to compare optical coherence tomography (OCT) with conventional techniques such as KOH-preparation, culture and histology in the identification of the fungal elements in the nail. A total of 18 patients were examined; 10 with clinically evident onychomycosis in toe nails, two with psoriatic nail lesions, one with nail affection caused by lichen planus and five healthy controls. Serial in vivo OCT analyses of onychomycosis was performed prior to KOH-preparation, culture and punch biopsy of the nail plate for consecutive histology.

High-resolution simultaneous dual-band spectral domain optical coherence tomography.

A fiber-based spectral domain optical coherence tomography (OCT) system is described, imaging simultaneously at 740 and 1300 nm central wavelengths. Real-time imaging is demonstrated with axial resolutions <3 and <5 microm, respectively. This technique allows for in vivo high-resolution functional OCT imaging with outstanding spectroscopic contrast.

Circular grating resonators as small mode-volume microcavities for switching.

We demonstrate the suitability of microcavities based on circular grating resonators (CGRs) as fast switches. This type of optical resonator is characterized by a high quality factor and very small mode volume. The waveguide-coupled CGRs are fabricated with silicon-on-insulator technology compatible with standard complementary metal-oxide semiconductor (CMOS) processing.

Dual femtosecond laser multiheterodyne optical coherence tomography.

A time domain optical coherence tomography (OCT) system without moving parts is described, which is based on multiheterodyning utilizing two mode-locked femtosecond lasers. By synchronizing the two lasers to slightly different repetition rates and coupling to an interferometric OCT setup, we obtain amplitude-modulated beat signals representing the structure of the specimen under investigation. Our system is suitable for biological imaging as well as technical applications.

25ps all-optical switching in oxygen implanted silicon-on-insulator microring resonator.

We present all-optical switching in oxygen ion implanted silicon microring resonators. Time-dependent signal modulation is achieved by shifting resonance wavelengths of microrings through the plasma dispersion effect via femtosecond photogeneration of electron-hole pairs and subsequent trapping at implantation induced defect states. We observe a switching time of 25 ps at extinction ratio of 9 dB and free carrier lifetime of 15 ps for an implantation dose of 7 x 10(12) cm(-2).

Visualization of the basement membrane zone of the bladder by optical coherence tomography: feasibility of noninvasive evaluation of tumor invasion.

Objectives: Imaging techniques with high resolution are evolving rapidly for medical applications and may substitute invasive diagnostic techniques. The use of ultrahigh resolution optical coherence tomography (UHR-OCT) to image healthy and morphologically altered bladder tissue with virtual histology is evaluated ex vivo to define parameters necessary for future, diagnostically relevant in vivo systems. Here, special focus is on the visualization of the basement membrane zone.

Analysis of hydrofluoric acid penetration and decontamination of the eye by means of time-resolved optical coherence tomography.

So far the study of chemical burns has lacked techniques to define penetration kinetics and the effects of decontamination within biological structures. In this study, we aim to demonstrate that high-resolution optical coherence tomography (HR-OCT) can close this gap. Rabbit corneas were exposed ex vivo to 2.

Dynamic analysis of chemical eye burns using high-resolution optical coherence tomography.

The use of high-resolution optical coherence tomography (OCT) to visualize penetration kinetics during the initial phase of chemical eye burns is evaluated. The changes in scattering properties and thickness of rabbit cornea ex vivo were monitored after topical application of different corrosives by time-resolved OCT imaging. Eye burn causes changes in the corneal microstructure due to chemical interaction or change in the hydration state as a result of osmotic imbalance.

Simultaneous dual-band ultra-high resolution optical coherence tomography.

Ultra-high resolution optical coherence tomography (OCT) imaging is demonstrated simultaneously at 840 nm and 1230 nm central wavelength using an off-the-shelf turn-key supercontinuum light source. Spectral filtering of the light source emission results in a double peak spectrum with average powers exceeding 100 mW and bandwidths exceeding 200 nm for each wavelength band. A free-space OCT setup optimized to support both wavelengths in parallel is introduced.

High-speed all-optical switching in ion-implanted silicon-on-insulator microring resonators.

We demonstrate high-speed all-optical switching via vertical excitation of an electron-hole plasma in an oxygen-ion implanted silicon-on-insulator microring resonator. Based on the plasma dispersion effect the spectral response of the device is rapidly modulated by photoinjection and subsequent recombination of charge carriers at artificially introduced fast recombination centers. At an implantation dose of 1 x 10(12) cm(-2) the carrier lifetime is reduced to 55 ps, which facilitates optical switching of signal light in the 1.

Simulation-based comparison of cell design concepts for phase change random access memory.

The RESET operation of different design concepts for phase change random access memory (PCRAM) cell is studied and compared using a three dimensional simulation model. This numerical algorithm comprises four interacting sub-models, which describe the electrical, thermal, phase change, and percolation dynamics in the PCRAM devices during the switching operation. The so-called vertical, confined, and lateral cell geometries are evaluated in terms of their current requirements for RESET operations, which is one of the most critical issues for an achievement of high integration densities.