Optical fiber probes are generating a large interest for portable Raman spectrometers. However, the use of conventional fibers is severely limited by the high luminescence background generated in the silica, which complicates the signal processing and/or the probe implementation.
We solve this issue in a recent article published in Optics Letters by using a new type of hollow core photonic crystal fiber probe for Raman spectroscopy and endoscopy. Thanks to a design based on a large pitch Kagome lattice, the transmission range spans over 150nm, enabling both the excitation and Raman beams to be counter-propagating through the same fiber.
Compared to earlier work, our approach combines several novel key features: (i) the very simple optical configuration, (ii) the two orders of magnitude reduction in silica background noise, and (iii) the large spectral bandwidth for Raman shifts.
Petru and Jerome made the show during Marseille's science festival 2012. About 400 people could discover several optics experiments:
- seeing stress in plastics
- origin of the blue color of butterfly wings
- the schweppes luminescence
- high rate internet with lasers and fibers
Check our work recently published online at the Advanded Materials website. For the first time, we investigate experimentally the luminescence enhancement of a single quantum dot deterministically coupled to a plasmonic gap antenna. We also provide the full information hidden behind this luminescence enhancement by quantifying independently the excitation enhancement and quenching effects.
Our approach combines two technological breakthroughs: (i) the custom-synthesis of colloidal QD with controlled multiply excited states, and (ii) the deterministic QD-antenna coupling via double step e-beam lithography. A remarkable feature is that excitation enhancement can still be investigated even in the presence of strong quenching losses affecting the emission. This study provides new routes to experimentally investigate the physics of optical antennas, and optimize the excitation and emission processes independently for the future development of bright single-photon sources and biochemical sensors.
This research is done in close collaboration with the groups of Dan Oron at Weizmann Institute of Science and Romain Quidant at ICFO, and is conducted in the scope of the NaBi associated European laboratory.