Post-transient relaxation in graphene after an intense laser pulse

High intensity laser pulses were recently shown to induce a population inverted transient state in graphene [T. Li et al. Phys. Rev. Lett. 108, 167401 (2012)]. Using a combination of hydrodynamic arguments and a kinetic theory we determine the post-transient state relaxation of hot, dense, population inverted electrons towards equilibrium. The cooling rate and charge-imbalance relaxation rate are determined from the Boltzmann-equation including electron-phonon scattering. We show that the relaxation of the population inversion, driven by inter-band scattering processes, is much slower than the relaxation of the electron temperature, which is determined by intra-band scattering processes. This insight may be of relevance for the application of graphene as an optical gain medium.Comment: 10 pages, 4 figures, submitted as contribution of the IMPACT Special Topics series of the EP

Changes on Mitochondrial DNA Content in Non-small Cell Lung Cancer

Background and objective It has been proven that the mitochondrial DNA (mtDNA) mutations and content change were associated with increasing risk of tumorigenesis. MtDNA content is significantly reduced in most substantive tumors. The aim of this study is to demonstrate whether mtDNA content is positively associated with non-small cell lung cancer (NSCLC) risk. Methods MtDNA content in 37 matched lung carcinoma and histologically adjacent normal lung tissue samples from patients were analyzed by fluorogenic 5-nuclease real-time PCR techniques. Results The mean copy number of mtDNA in lung carcinoma tissue samples was statistically lower than that in adjacent histologically normal lung tissue samples (P < 0.001). Conclusion The change of mtDNA content may play an important role in NSCLC

Photoinduced femtosecond relaxation of antiferromagnetic orders in the iron pnictides revealed by ultrafast laser ellipsometry

We report ultrafast softening of the antiferromagnetic order, ~150fs after the electron thermalization, which follows a two-step recovery pathway to reveal a distinct interplay of magnetism and the nematic order in iron pnictides

Paired-angle-rotation scanning optical coherence tomography forward-imaging probe

We report a novel forward-imaging optical coherence tomography (OCT), needle-probe paired-angle-rotation scanning OCT (PARS-OCT) probe. The probe uses two rotating angled gradient-index lenses to scan the output OCT probe beam over a wide angular arc (∼19° half-angle) of the region forward of the probe. Among other advantages, this probe design is readily amenable to miniaturization and is capable of a variety of scan modes, including volumetric scans. To demonstrate the advantages of the probe design, we have constructed a prototype probe with an outer diameter of 1.65 mm and employed it to acquire four OCT images, with a 45° angle between adjacent images, of the gill structure of a Xenopus laevis tadpole. The system sensitivity was measured to be 93 dB by using the prototype probe with an illumination power of 450 μW on the sample. Moreover, the axial and the lateral resolutions of the probe are 9.3 and 10.3-12.5 μm, respectively

Wide field-of-view microscope based on holographic focus grid illumination

We have developed a new microscopy design that can achieve wide field-of-view (FOV) imaging and yet possesses resolution that is comparable to a conventional microscope. In our design, the sample is illuminated by a holographically projected light-spot grid. We acquire images by translating the sample across the grid and detecting the transmissions. We have built a prototype system with an FOV of 6mm×5mm and acquisition time of 2.5s. The resolution is fundamentally limited by the spot size—our demonstrated average FWHM spot diameter was 0.74μm. We demonstrate the prototype by imaging a U.S. Air Force target and a lily anther. This technology is scalable and represents a cost-effective way to implement wide FOV microscopy system

Lightwave Terahertz Quantum Manipulation of Non-equilibrium Superconductor Phases and their Collective Modes

We present a gauge-invariant density matrix description of non-equilibrium superconductor (SC) states with spatial and temporal correlations driven by intense terahertz (THz) lightwaves. We derive superconductor Bloch--Maxwell equations of motion that extend Anderson pseudo-spin models to include the Cooper pair center-of-mass motion and electromagnetic propagation effects. We thus describe quantum control of dynamical phases, collective modes, quasi-particle coherence, and high nonlinearities during cycles of carrier wave oscillations, which relate to our recent experiments. Coherent photogeneration of a nonlinear supercurrent with dc component via condensate acceleration by an effective lightwave field dynamically breaks the equilibrium inversion symmetry. Experimental signatures include high harmonic light emission at equilibrium-symmetry-forbidden frequencies, Rabi--Higgs collective modes and quasi-particle coherence, and non-equilibrium moving condensate states tuned by few-cycle THz fields. We use such lightwaves as an oscillating accelerating force that drives strong nonlinearities and anisotropic quasi-particle populations to control and amplify different classes of collective modes, e.g., damped oscillations, persistent oscillations, and overdamped dynamics via Rabi flopping. Recent phase-coherent nonlinear spectroscopy experiments can be modeled by solving the full nonlinear quantum dynamics including self-consistent light--matter coupling.Comment: 19 pages, 11 figure