We study the creation and erasure of the linear electrooptical effect in silicate fibers by optical poling. Carriers are released by exposure to green light and displaced with simultaneous application of an internal dc field. The second order nonlinear coefficient induced grows with poling bias. The field recorded (~108 V/m) is comparable to that obtained through classical thermal poling of fibers. In the regime studied here, the second-order nonlinearity induced (~0.06 pm/V) is limited by the field applied during poling (1.2 × 108 V/m). Optical erasure with high-power green light alone is very efficient. The dynamics of the writing and erasing process is discussed, and the two dimensional (2D) field distribution across the fiber is simulated.
A micro-structured fiber-based system for identification and collection of fluorescent particles is demonstrated. An optical fiber probe with longitudinal holes in the cladding is used to retrieve fluorescent particles by exerting microfluidics forces. Laser induced fluorescent (LIF) is carried out by the fiber probe and an optical setup. When a particle with a previously chosen fluorescence wavelength is identified, a vacuum pump is activated collecting the particle into a hole. Green and red fluorescent polystyrene particles were detected and selectively retrieved.
Optofluidic dye lasers may play a significant role in future laser applications in numerous areas, combining wavelength flexibility with integration and ease of operation. Nevertheless, no all-fiber integrated dye lasers have been demonstrated so far. In this paper, we report on a series of optofluidic all-fiber Rhodamine optical sources operating at a repetition rate as high as 1 kHz. Dye bleaching is avoided by circulating the Rhodamine dye during optical excitation. The laser radiation is extracted via conventional fibers that are spliced to the dye-filled capillary active medium. A tuneable amplified spontaneous emission source, a multimode laser, and a few transverse-mode laser are demonstrated by adjusting the setup. Threshold pump energies as low as similar to 1 mu J and slope efficiencies of up to mu 9% were obtained, indicating the potential for realworld applications in areas such as spectroscopy and biomedicine.
The visibility of graphene is greatly increased by illuminating samples deposited on transparent dielectrics at the substrates' Brewster angle. Using a commercial ellipsometer, the reflectivity of monolayers of chemical vapour deposition (CVD) graphene is found to be up to 33 times higher than that of the substrate, i.e., an optical contrast as high as 3200% is obtained, more than 380 times higher than with standard optical microscopy.
Also, with a simpler, homemade, experimental setup, a 1400% optical contrast was measured for a monolayer of CVD graphene and linear features as small as ~20 μm were visible in a monolayer, while ~6 × 17 μm2trilayers could still be imaged in exfoliated samples.
It is also shown that the reflectance/transmittance ratio increases quadratically with the number of graphene layers, which may allow for counting layer numbers and identifying wrinkles and folds in transferred samples.
Hollow silica capillaries are examined as optical waveguides evaluating the antiresonant reflecting optical waveguide (ARROW) effect by sequentially reducing the wall thickness through etching and measuring the optical transmission. It is found that the periodicity of the transmission bands is proportional to the wall thickness and that the propagation loss is of the order of a few dB/m.