Orbital Angular Momentum Reversal due to Extreme Doppler Shifts - Graham Gibson

Hello everyone!

Continuing the Optics Group's turn at hosting seminars will be Graham Gibson. The talk, titled Orbital Angular Momentum Reversal due to Extreme Doppler Shifts, will take place on Thursday 25th October at 16:00 in Room 257. The abstract is as follows:

The linear Doppler shift is familiar to everyone as the change in the observed frequency of an ambulance siren as it passes by. A less well known form is the rotational Doppler shift which is proportional to the relative rotation rate between source and observer, multiplied by the angular momentum carried by the beam. Using an acoustic source of orbital angular momentum we can demonstrate an extreme Doppler shift that is larger than the rest-frame frequency, resulting in the observed frequency becoming negative in the case of a red shift. The emergence of negative frequencies in physical systems is often accompanied by intriguing consequences. For the linear case this is associated with a time reversal of the received signal. For the rotational case it is associated with a handedness reversal of the detected orbital angular momentum.

Snacks will be provided in the common room after the seminar and once again Curler's Rest has been nominated as a pub where discussion can continue after work.

Kyle

The applications of single-pixel imaging - Steven Johnson & Yiwei Zhang

Hello everyone!

This weeks Seminar will be given by Steven Johnson & Yiwei Zhang on The applications of single-pixel imaging. The talk will take place on Thursday 11th October at 16:00 in Room 257. The abstract is as follows:

Single-pixel imaging enables the photography of phenomena that would be impossible with a traditional camera. Most images are captured with pixelated-arrays such as a CCD or CMOS sensors; whereas single-element detectors can be manufactured to be sensitive to unusual wavelengths, outside the visible spectrum, or have very fast response times. By using a detector with high temporal resolution, events occurring on the order of nanoseconds can be imaged. Using a digital micro-mirror device and a pulsed laser we have applied single-pixel imaging methods to many applications, these include: 3D videos of a scene, imaging the light-in-flight, fluorescence lifetime imaging and duel-band astronomy.

Snacks will be provided in the common room after the seminar and once again Curler's Rest has been nominated as a pub where discussion can continue after work. Turnout was great two weeks ago so I look forward to seeing people there again!

Kyle.