We demonstrated a method to construct high efficiency saturable absorbers based on the evanescent light field interaction of CVD monolayer graphene deposited on side-polished D-shaped optical fiber. A set of samples was fabricated with two different core-graphene distances (0 and 1 μm), covered with graphene ranging between 10 and 25 mm length. The mode-locking was achieved and the best pulse duration was 256 fs, the shortest pulse reported in the literature with CVD monolayer graphene in EDFL. As result, we find a criterion between the polarization relative extinction ratio in the samples and the pulse duration, which relates the better mode-locking performance with the higher polarization extinction ratio of the samples. This criterion also provides a better understanding of the graphene distributed saturable absorbers and their reproducible performance as optoelectronic devices for optical applications.
Signaling individuals must effectively capture and hold the attention of intended conspecific receivers while limiting eavesdropping by potential predators. A possible mechanism for achieving this balance is for individuals to modulate the physical properties of their signals or to alter the proportion of time spent signaling, depending upon local levels of predation pressure. We test the hypothesis that prey can alter their visual signaling behavior to decrease conspicuousness and potentially limit predation risk via modulation of signal properties or display rate. To do so, we conducted a manipulative experiment in nature to evaluate the possible effect of predation pressure on the physical properties of movementbased signals and on the proportion of time spent signaling by using a well-understood predator-prey system in the Bahamas, the semiarboreal lizard Anolis sagrei, and one of its main predators, the curly-tailed lizard Leiocephalus carinatus. We find that on islands onto which the predator was introduced, male anoles reduce the maximum amplitude of head-bob displays but not the proportion of time spent signaling, in comparison with control islands lacking the predator. This reduction of amplitude also decreases signal active space, which might alter the reproductive success of signaling individuals. We suggest that future studies of predatorprey interactions consider the risk effects generated by changes in signals or signaling behavior to fully determine the influence of predation pressure on the dynamics of prey populations.T he process of communication is central to many aspects of social interaction, from attracting mates to establishing territories. The major prerequisite for communication is that an individual or its signal must effectively capture and hold the attention of intended receivers (1, 2). However, communication rarely occurs in a context free from the risk of predation, and thus the presence of predators is an important selective pressure on the physical designs of signals and the behaviors associated with their display (e.g., refs. 3-9). In fact, predation pressure typically results in signals with reduced conspicuousness (i.e., the likelihood of being seen by a predator) at one or both of two timescales: (i) across generations (i.e., via evolutionary mechanisms) or (ii) within the lifetime of an individual (i.e., via behavioral mechanisms). The evolution of less conspicuous signal properties in response to predation pressure has been demonstrated across signaling modalities, including acoustic, electrical, visual, and ultrasonic signals (e.g., refs. 9, 10). Predation pressure also shapes the evolution of the behaviors associated with the production of signals, often resulting in a shift in the amount of time spent signaling throughout the day or in the use of less vulnerable display sites (11-16).Behavioral changes favoring a reduction in the likelihood of communication-associated predation typically precede evolutionary changes (12). This process most likely is driven by the plastic...
For the first time, we demonstrated the fabrication of mechanically exfoliated molybdenum disulfide (MoS2) samples deposited onto a D-shaped optical fiber. The MoS2 exfoliated flakes were deposited onto a stacked of 1.2 µm PVA (polyvinyl alcohol) and 300 nm PMMA (polymethyl methacrylate) layers and then transferred directly onto a side polished surface of D-shaped optical fiber with polishing length of 17 mm and no distance from the fiber core. The sample exhibited a high polarization performance as a polarizer with relative polarization extinction ratio of 97.5%. By incorporating the sample as a saturable absorber in the Erbium-doped fiber laser (EDFL), bandwidth of 20.5 nm and pulse duration of 200 fs were generated, which corresponded to the best mode-locking results obtained for all-fiber MoS2 saturable absorber at 1.5 µm wavelength.
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