C. Peroz

Microfluidic dye laser intracavity absorption

The authors report absorption measurements on low concentration analytes using a microfluidic dye laser. The laser cavity is made of two gold mirrors coated on the end faces of two optical fibers inserted in a chip. Rhodamine 6G dye molecules dissolved in ethanol are used for laser amplification and absorption measurements are done with methylene blue dye solutions. When optically pumped with a frequency doubled Nd:YAG laser at 532nm wavelength, the device shows a laser output emission at 565nm and a high sensitivity of the lasing output to the losses in the cavity, in good agreement with the results of numerical calculations.

Compact dye laser on a chip fabricated by ultraviolet nanoimprint lithography

High aspect ratio and high resolution distributed feed back (DFB) gratings have been patterned on a fused silica plate by ultraviolet nanoimprint lithography and reactive ion etch techniques. Then, they were integrated into a microfluidic chip for optofluidic operations. The authors observed laser emission from organic dye solutions flowing through an optical resonator formed between two third order DFB gratings. Such a dye layer can operate with a picoliter dye solution. With rhodamine 6G dye molecules dissolved in ethanol and pumped by a frequency-doubled Nd:YAG pulsed laser, a laser emission of threshold of 12μJ∕mm2 has been found.

High critical current densities observed in PrBa2Cu3O7−δ∕YBa2Cu3O7−δ∕PrBa2Cu3O7−δ ultrathin film constrictions

An original process has been developed for fabricating 0.45×0.45μm2 constrictions with normal metal banks using stacked YBa2Cu3O7−δ and PrBa2Cu3O7−δ ultrathin films. High values of critical temperature Tc≈89K and critical current densities Jc≈2×107A∕cm2 at 77K were measured on 17nm thick YBa2Cu3O7−δ, after the complete fabrication on MgO substrate. The observed robust superconducting properties of the device under applied magnetic field are attributed to large edge barriers opposed to vortex entry inside the nanobridge section. As there is no apparent degradation of the superconducting properties after long time storage, the benefit of using ultrathin PrBa2Cu3O7−δ buffer and overlayer in YBa2Cu3O7−δ constrictions is confirmed. Such YBa2Cu3O7−δ nanowires are shown well adapted to phase-slip based devices and expected to fulfill the performances required in high frequency applications.

Fabrication of third order Bragg gratings by UV nanoimprint lithography for optofluidic lasers

Soft UV nanoimprint lithography has be used to fabricate third order Bragg gratings for visible light and microfluidic dye laser operation. Soft stamps has been made by casting a poly-dimethylsiloxane on a silicon mould and a bi-layer imprinting process has used to obtain resist patterns of high density and high aspect ration line-and-space features. After a lift-off of thin nickel film, reactive ion etching was applied to transfer the patterned features into a glass substrate with aspect ratios up to 12. The integration of the fabricated Bragg gratings into a microfluidic chip allowed us to observe laser emission from a dye molecule (Rhodamine 6G) solution of very small volumes (30 to 75 pL), thereby providing a new method of making functioning optofluidic devices

Microfluidic dye laser chip for intra-cavity absorption measurements

Among many others, absorbance measurement is one of the most useful techniques to determine sample concentration on a microfluidic chip. The main drawback of this technique comes from the limited optical path length that can be achieved on a chip. We propose here an original design of a microfluidic dye laser to perform intracavity absorption measurements. The effective optical path length and so the sensitivity are enhanced by a factor of about 15 in comparison with single pass measurement. In addition, the nanoliter active sample volume we used is six orders of magnitude less in comparison with common milliliter cuvette. Simple calculations that emphasize the potential utility of the method are also presented