Supercontinuum generation in large mode-area microstructured fibers.

Supercontinuum generation in large mode-area microstructured fibers is demonstrated by launching into the fiber ns pulses from a passively Q-switched Nd:YAG laser. The special properties of these fibers open the way to compact, single-mode, high-power supercontinuum sources with a low divergence of the output beam. The nonlinear phenomena leading to the formation of the broad spectrum are also described.

Supercontinuum and gas cell in a single microstructured fiber.

We exploit both the high nonlinearity and the holey structure of microstructured fibers to combine a broad-band light source and a gas cell in a single microstructured fiber. A broadband supercontinuum is formed by launching nanosecond pulses from a compact, Q-switched Nd:YAG laser into a microstructured fiber filled with acetylene. This continuum is self-referenced to the acetylene lines in the 1500 nm region. The performance of different index-guiding narrow-core microstructured fibers as nonlinear and host media is evaluated. The concept offers many possibilities and can be applied to various gases absorbing at different wavelengths.

Gas sensing using air-guiding photonic bandgap fibers.

We demonstrate the high sensitivity of gas sensing using a novel air-guiding photonic bandgap fiber. The bandgap fiber is spliced to a standard single-mode fiber at the input end for easy coupling and filled with gas through the other end placed in a vacuum chamber. The technique is applied to characterize absorption lines of acetylene and hydrogen cyanide employing a tunable laser as light source. Measurements with a LED are also performed for comparison. Detection of weakly absorbing gases such as methane and ammonia is explored.