Monday at the Laser World of Photonics

So the Bavarian adventure continues! The evening had a Bavarian evening hosted by OSA, which was great German beer, traditional food and some song and dance.

Today was a fun and very tiring day again at the conference. 

So what did I attend:

  1. Optofluidics in Energy Applications by Demetri Psaltsis, EPFL Lausanne.

This was a brilliant talk giving an overview and idea of the research topics in this fascinating area. The focus was on applications for energy and that was my interest. He explained different how solar energy is used in solar fuel (convert one fuel/chemicals to another); solar thermal (use solar light to heat up liquids)… The thing I found fascinating was his explanation of why photosynthesis in plants/leaves is very inefficient! Apparently the efficiency is as low as 1-2%. The key thing is that water contents in leaves etc is heated and escapes as vapour, creating a negative pressure, because of which water moves up to the leaves from the roots, trunk etc. All this because plants too have an optimal temperature (about 20degrees Centigrade) and need to cool down. So essentially photosynthesis as a process only providing part of the energy needs of the plants, while the heating of the fluids is moving huge amounts of water and expending lots of energy! This is also a reason that bio-mimetic PV should not look at photosynthetic processed as an inspiration. Some papers from this group mentioned in the talk include: Optics Express, Vol. 21, no S3, pp A460, 2013; Nature Photonics Vol. 4, pp. 583, 2011.

2. Mode instabilities in LMA fibers: the speaker gave a great over view of this barrier to power scaling of high power fiber lasers. The basic idea is that apart from effects like SBS, SRS, damage threshold of materials, and heating of fibers, there exists another issue. This issue is that for most fibers after power increases above a threshold, the mode changes and seems to oscillate between higher order and fundamental modes.  This generates an interference pattern which affects the mode inversion of the fiber laser, leading in turn to an inhomogeneous temperature profile and due to the thermal properties of the material this creates a refractive index grating. As the pump power is not absorbed homogenously the power scaling gets limited. Some papers from this group mentioned in the talk include: Optics Express, Vol. 19, pp 13218, 2011; Optics Letters, Vol. 35, pp. 94, 2010; Optics Express Vol. 20, pp 11407, 2012.

3. Quantum Coherence at the level of a individual light harvesting complexes.   In this fantastic talk from the group of Nick van Hulst, were presented results for light harvesting by a bacterial complex. So essentially bacterial photosynthesis. The transport of the excitation energy was found to be almost 95%! The possibility of quantum coherence leading to such high efficiency was discussed. They cited Brinks, Hildner et al. Optics Express, 2011. This talk has given me a reason to go back to the Quantum Mechanics textbooks and undertand quantum coherence.

I also saw part of the exhibition and got lost! It was HUGE! There are about 1000 exhibitors so you can imagine. In trying to see the entire exhibition in 1 day (mistake and could not manage it anyway) I ended up missing the poster session. Bummer!

I hope to make it to the posters tomorrow. Till then!


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