Experimental demonstration of single-mode large mode area multi-trench fiber for UV-VIS light transmission

Step-index optical fibers are widely used waveguides for light transmission. However, non-linear effects are always a severe challenge for optical fibers with increasing power level. This challenge is more severe at shorter wavelengths, where core size has to be much smaller in order to maintain a single mode operation. For an example, for 0.005 core refractive index with respect to cladding, a 10µm core diameter can ensure single mode operation at 1550nm. On other hand, core diameter has to be ~4µm and ~2µm at lambda=632nm and 300nm respectively for single mode operation. At these shorter wavelengths, photonic crystal fiber (PCF) and hollow core photonic bandgap fiber (HC-PBGF) have been proposed to address non-linear effects by offering large core diameter and air-core respectively [1-2]. However, such fibers are relatively difficult to fabricate. Moreover, presence of air-holes causes considerable difficulties in cleaving and splicing.Recently, we proposed an all-solid fiber design known as multi-trench fiber (MTF) as shown in Fig. 1(a) [3]. In this paper, we demonstrated their mode area scaling capability for UV-VIS wavelengths. Numerical simulations show the potential of achieving an effective single mode for 10µm and 20µm core diameter MTF by ensuring high loss to the higher order modes (HOMs) at ~300nm and ~632nm respectively. Fig. 1(b) shows numerically computed bending loss of a 20µm core MTF with trench thickness (t)=1.34µm, refractive index difference between core and cladding (Delta.n)=0.005, and resonant ring thickness (d)=6µm at 632nm. It is important to note that MTF ensures similar level of loss (as shown in Fig. 1(b)) to the HOMs even in an unbent case thanks to the resonant coupling between modes of core and resonant ring, which ensures suitability for beam delivery applications. Fig. 1(c) shows the RIP and microscope image of a 20µm core MTF fabricated by MCVD process in conjunction with rod-in-tube technique. Fig. 1(d) shows the measured bending loss of fiber. The loss remains lower than 0.2dB/m and 0.5dB/m at ~30cm and ~15cm bend radius respectively at ~632nm. This loss can even be reduced down with further refinement in fabrication process. We investigated the output profile of a 2m long MTF using the experimental set-up shown in Fig. 1(e) with respect to the multi-mode input beam as shown in Fig. 1(g). Fig. 1(f) shows the output for different offset launching, while fiber is coiled at ~20cm bend radius. On the other hand, Fig. 1(h) shows the output at different coil radii for optimum launching. In this paper, for the first time, to the best of our knowledge, an effective-single-mode behaviour of an all-solid and cylindrical symmetrical fiber of a large core (~20µm) fiber at ~632nm has been demonstrated. All-solid design and cylindrical symmetry ensure suitability for mass-scale production and easy cleaving and splicing. Further, with these advantages, a large core (~10µm) MTF at ~300nm as confirmed by our simulations can also be achieved and details will be presented at conference

Recent progress in the development of few mode fiber amplifier

We review the performances of both core and cladding pumped few-mode erbium doped fiber amplifiers supporting 6 spatial modes (4 mode groups) which incidentally the highest mode count demonstrated to date

Nonstationary Stochastic Resonance in a Single Neuron-Like System

Stochastic resonance holds much promise for the detection of weak signals in the presence of relatively loud noise. Following the discovery of nondynamical and of aperiodic stochastic resonance, it was recently shown that the phenomenon can manifest itself even in the presence of nonstationary signals. This was found in a composite system of differentiated trigger mechanisms mounted in parallel, which suggests that it could be realized in some elementary neural networks or nonlinear electronic circuits. Here, we find that even an individual trigger system may be able to detect weak nonstationary signals using stochastic resonance. The very simple modification to the trigger mechanism that makes this possible is reminiscent of some aspects of actual neuron physics. Stochastic resonance may thus become relevant to more types of biological or electronic systems injected with an ever broader class of realistic signals.Comment: Plain Latex, 7 figure

Numerical Test of Disk Trial Wave function for Half-Filled Landau Level

The analyticity of the lowest Landau level wave functions and the relation between filling factor and the total angular momentum severely limits the possible forms of trial wave functions of a disk of electrons subject to a strong perpendicular magnetic field. For N, the number of electrons, up to 12 we have tested these disk trial wave functions for the half filled Landau level using Monte Carlo and exact diagonalization methods. The agreement between the results for the occupation numbers and ground state energies obtained from these two methods is excellent. We have also compared the profile of the occupation number near the edge with that obtained from a field-theoretical method. The results give qualitatively identical edge profiles. Experimental consequences are briefly discussed.Comment: To be published in Phys. Rev. B. 9 pages, 6 figure

On some notions of good reduction for endomorphisms of the projective line

Let $\Phi$ be an endomorphism of \SR(\bar{\Q}), the projective line over the algebraic closure of \Q, of degree $\geq2$ defined over a number field $K$. Let $v$ be a non-archimedean valuation of $K$. We say that $\Phi$ has critically good reduction at $v$ if any pair of distinct ramification points of $\Phi$ do not collide under reduction modulo $v$ and the same holds for any pair of branch points. We say that $\Phi$ has simple good reduction at $v$ if the map $\Phi_v$, the reduction of $\Phi$ modulo $v$, has the same degree of $\Phi$. We prove that if $\Phi$ has critically good reduction at $v$ and the reduction map $\Phi_v$ is separable, then $\Phi$ has simple good reduction at $v$.Comment: 15 page

Modal gain control in a multimode erbium doped fiber amplifier incorporating ring doping

We theoretically demonstrate the performance of a step index multimode (two mode-group) erbium-doped fiber amplifier with a localized erbium doped ring distribution for Space Division Multiplexed (SDM) transmission

Experimental investigation of inter-modal cross-gain modulation and transient effects in a two mode group erbium doped fiber amplifier

We report what we believe to be the first experimental study of inter-modal cross-gain modulation and associated transient effects as different spatial modes and wavelength channels are added and dropped within a two-mode amplifier for SDM transmission

Where Are You From? A Validation of the Foreigner Objectification Scale and the Psychological Correlates of Foreigner Objectification Among Asian Americans and Latinos

Many ethnic minorities in the United States consider themselves to be just as American as their European American counterparts. However, there is a persistent cultural stereotype of ethnic minorities as foreigners (i.e., the perpetual foreigner stereotype) that may be expressed during interpersonal interactions (i.e., foreigner objectification). The goal of the present study was to validate the Foreigner Objectification Scale, a brief self-report measure of perceived foreigner objectification, and to examine the psychological correlates of perceived foreigner objectification. Results indicated that the Foreigner Objectification Scale is structurally (i.e., factor structure) and metrically (i.e., factor loadings) invariant across foreign-born and U.S.-born Asian Americans and Latinos. Scalar (i.e., latent item intercepts) invariance was demonstrated for the two foreign-born groups and the two U.S.-born groups, but not across foreign-born and U.S.-born individuals. Multiple-group structural equation models indicated that, among U.S.-born individuals, perceived foreigner objectification was associated with less life satisfaction and more depressive symptoms, and was indirectly associated with lower self-esteem via identity denial, operationalized as the perception that one is not viewed by others as American. Among foreign-born individuals, perceived foreigner objectification was not significantly associated directly with self-esteem, life satisfaction, or depressive symptoms. However, perceived foreigner objectification was positively associated with identity denial, and identity denial was negatively associated with life satisfaction. This study illustrates the relevance of perceived foreigner objectification to the psychological well-being of U.S.-born Asian Americans and Latinos

Experimental characterization of a graded-index ring-core fiber supporting 7 LP mode groups

We design and characterize a graded-index-ring-core fiber supporting 7 LP modegroups (13 spatial modes) for mode multiplexed transmission with low MIMO processing complexity. Spatial and temporal modal properties are analyzed using an SLM-based mode multiplexer/demultiplexer

DNA methylation loss promotes immune evasion of tumours with high mutation and copy number load

Mitotic cell division increases tumour mutation burden and copy number load, predictive markers of the clinical benefit of immunotherapy. Cell division correlates also with genomic demethylation involving methylation loss in late-replicating partial methylation domains. Here we find that immunomodulatory pathway genes are concentrated in these domains and transcriptionally repressed in demethylated tumours with CpG island promoter hypermethylation. Global methylation loss correlated with immune evasion signatures independently of mutation burden and aneuploidy. Methylome data of our cohort (n = 60) and a published cohort (n = 81) in lung cancer and a melanoma cohort (n = 40) consistently demonstrated that genomic methylation alterations counteract the contribution of high mutation burden and increase immunotherapeutic resistance. Higher predictive power was observed for methylation loss than mutation burden. We also found that genomic hypomethylation correlates with the immune escape signatures of aneuploid tumours. Hence, DNA methylation alterations implicate epigenetic modulation in precision immunotherapy