Deep UV Raman – The Other Side of the Spectrum
Oct/23/2009 15:00 Filed in: Seminars
Electro-Optics/Phsics Seminar
Friday, October 23, 2009
3:00pm College Park Center Room 580
All are invited
“Deep UV Raman – The Other Side of the Spectrum”
Robert V. Chimenti (UD Electro-Optics Master’s Graduate)
B&W Tek, Inc.
Friday, October 23, 2009
3:00pm College Park Center Room 580
All are invited
“Deep UV Raman – The Other Side of the Spectrum”
Robert V. Chimenti (UD Electro-Optics Master’s Graduate)
B&W Tek, Inc.
The Raman effect first discovered by Sir Chandrasekhara Venkata Raman is caused by inelastic scattering of a monochromatic light source, during which there is a photon – phonon coupling causing an energy transfer between the light source and the material. This energy transfer results in a frequency shift of the incident light know as a Stokes (red) or Anti-Stokes (blue) shift. By measuring and analyzing the spectrum of the shifted radiation it is possible deduce the identity of the material in question, and as a result Raman spectroscopy is quickly becoming the method of choice for material identification.
The major drawback of Raman spectroscopy is that the conversation efficiency into the first order Stokes shift is often significantly lower than that of the natural fluorescents of the material. In order to work around this issue the majority of Raman spectrometers utilize a 785nm laser sources so that the Stokes shift of the scattered radiation is pushed out to the near IR where the fluorescents is significantly less than in the visible (but not inconsequential), while still staying below the 1.1mm cut off of silicon based detectors.
Due to recent advancements in laser technology it is now possible to utilize Deep UV laser sources (< 250nm) where the Raman spectrum is completely separated from the fluorescents spectrum of most materials. In this talk I will shown how the development of compact HeAg and NeCu lasers has made it possible to produce a self contained deep UV Raman spectrometer. I will also show experimental data to illustrate not only the advantage of operated below fluorescents, but also how the high photon energy of the source can correlate into enhanced Raman efficiency via Rayleigh and resonance effects.
The major drawback of Raman spectroscopy is that the conversation efficiency into the first order Stokes shift is often significantly lower than that of the natural fluorescents of the material. In order to work around this issue the majority of Raman spectrometers utilize a 785nm laser sources so that the Stokes shift of the scattered radiation is pushed out to the near IR where the fluorescents is significantly less than in the visible (but not inconsequential), while still staying below the 1.1mm cut off of silicon based detectors.
Due to recent advancements in laser technology it is now possible to utilize Deep UV laser sources (< 250nm) where the Raman spectrum is completely separated from the fluorescents spectrum of most materials. In this talk I will shown how the development of compact HeAg and NeCu lasers has made it possible to produce a self contained deep UV Raman spectrometer. I will also show experimental data to illustrate not only the advantage of operated below fluorescents, but also how the high photon energy of the source can correlate into enhanced Raman efficiency via Rayleigh and resonance effects.