research

Young's double slits experiment at the single photon level

What is the pattern of light illuminating two fine openings, two slits?
Classical particle, like ping-pong balls, would just go through one of the two openings and form two little bunches on the far screen (right in the figure). Classical waves would interfere and form a pattern with maxima and minima (left in the figure). 

wave-particle

The photons are quantum particles, with both the wave and particle nature, and arrive one by one, as particle would do but forming an interference pattern, as waves would do. This can be seen in the video, which is an actual experiment we have perform, "just to be sure" that quantum mechanics works.

When I was a student this was one of the most striking and illuminating experiment I have done, showing at once one of the most intriguing concepts of quantum mechanics, the wave-particle duality. Once more experiments can resonate and teach more than a thousand words!

Image recorded with a Princeton PRO EMccd, gain at 95, integration time per frame 10 ms, accumulation over 1000 frames (here shown in 3 sec).

The freelance postdoc experiment

We are all well aware of how difficult is to get a permanent position in academia. The employers are very cautious as the tenured position comes with a very strong contractual stability and in some country with immortality (as civil service status). The postdocs work longer and longer hours to face the increasing competition. Academia needs more and more advanced skills that can only be acquired with years of experience but it refrains from rewarding it with a permanent job. An interesting alternative is that of the academic freelancer as proposed by Katie Rose Guest Pryal here, as a mean to alleviate the intense and extenuating life of a postdoc or not-tenured academic.

We have already started such an experiment, as I have hired a recently graduate and unemployed colleague to perform some theoretical calculations that we need for our experiments. The difference with respect to a normal collaboration is that this time I am paying him by the hour and he is performing the work choosing his time and without being based in London, just coming for a meetings to discuss the results. All the other discussions are done by Skype, email and probably soon in Slack.

In this way we can reward skills and actual hours of work, and potentially we can resolve personal issues such as family relocation etc… Would this work also for experimental work? It is hard to tell, but I could imagine having a setup in my house and performing experiments on demand as a freelancer does. Shared facilities similar to maker and hacker space could also make lab space and equipment more accessible.

Sooner or later we will have to invent a new way to develop science, a research 2.0, and it may start by embracing new concept such as remote and freelance work.

Tuning random lasing in photonic glasses

We have just published a new theoretical model including frequency interaction and mode competition in random lasing which allows to predict resonance-driven tuning of random lasing.   As it builds on solid previous models, we believe that it could be of practical use to predict the behavior of your random lasing system. If you are interested in the code just contact us.

Tuning random lasing in photonic glasses, Michele Gaio, Matilda Peruzzo and Riccardo Sapienza, Optics Letters 2015.
Abstract

Tuning random lasing in photonic glasses

We present a detailed numerical investigation of the tunability of a diffusive random laser when Mie resonances are excited. We solve a multimode diffusion model and calculate multiple light scattering in presence of optical gain which includes dispersion in both scattering and gain, without any assumptions about the β parameter. This allows us to investigate a realistic photonic glass made of latex spheres and rhodamine and to quantify both the lasing wavelength tunability range and the lasing threshold. Beyond what is expected by diffusive monochromatic models, the highest threshold is found when the competition between the lasing modes is strongest and not when the lasing wavelength is furthest from the maximum of the gain curve.

PDF available here: Tuning random lasing in photonic glasses