[seminar] Podsjetnik na nastupno predavanje dr. sc. Hrvoje Skenderović u UTORAK 16.05.2023. u 11:00h

[Damir Dominko]

**utorak, 16. svibnja 2023., u 11:00 sati**

*Holography and coherent optics*
**Dr.  sc. ***Hrvoje Skenderović*
*Institute of Physics***

The topic of the talk is research in the field of Digital Holography and 
connected themes. Especially, implementation of holographic measurements 
with scanning single photon avalanche detector (SPAD), as well as 
time-averaged digital holography (TADH) is presented. In TADH 
measurements, holograms of a vibrating object are recorded, usually in 
such a way that the exposure period of the camera recording the hologram 
is many times greater than the period of vibrations. We examined the 
error in the reconstruction if the exposure time is only a few times 
greater than the oscillation period and if it is a non-integer ratio of 
the two times. In the following, we have shown that it is possible to 
obtain an accurate hologram even when the exposure is only half the 
oscillation period with a known phase. Finally, we have given a 
procedure for determining the unknown oscillation period and phase with 
several short exposures. All these numerical calculations were confirmed 
by experimental measurements with real objects.

We also investigated the differences in sampling and nonlinearities in 
holography using a SPAD detector and a camera. We have shown how it is 
possible to determine the optimal sampling using a scanning detector. 
Also, the standard camera mainly works with an 8-bit image, that is, it 
has 256 gray levels, which easily leads to saturation in the recording, 
or to the appearance of non-linear members in the reconstruction of the 
hologram. In contrast, SPAD as a detector has an infinite dynamic range.

An experiment dealing with application of quantum light in holography is 
also discussed. The objective is to use individual photons in a classic 
holographic setup and see if they can be used to obtain a hologram and 
if visibility improves compared to classic source of the same (very low) 
intensity. Since holography is based on the interference of two light 
beams, and in the case of individual photons we a photon can not be 
split at the beam splitter, the possibility of interference is not clear 
a priori. Also, there is a problem with the phase, which is 
indeterminate for individual photons. It is shown that a hologram can be 
recorded, amplitude and phase reconstruction can be obtained, and the 
SNR is better compared to classical light of the same intensity.



Nastupno predavanje će se održati u predavaonici u 1. krilu Instituta.

Predavanje ćete moći pratiti i putem Zoom-a:

https://us06web.zoom.us/j/89856158536?pwd=b2l4bG5reDQ5Tk1wMU1MTG1MeExBdz09

Meeting ID: 898 5615 8536

Passcode: 332504


Predsjednik Znanstvenog vijeća Instituta za fiziku
dr. sc. Damir Starešinić
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