Banca de DEFESA: PATRICK ALYSON GOUVEIA TORRES

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : PATRICK ALYSON GOUVEIA TORRES
DATE: 17/01/2023
TIME: 09:30
LOCAL: Através de Videoconferência:
TITLE:

Analysis of the transverse spatial image of beams transmitted and generated through a non-linear
process in rubidium vapor

KEY WORDS:

four-wave mixing, spatial correlation, spatial image, rubidium vapor,
non-linear process

PAGES: 70
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

In this work we describe an experimental investigation on the spatial intensity
distribution of the two transmitted beams and the two beams generated in a four-wave
mixing (FWM) process, using rubidium vapor as a nonlinear medium. The two FWM
signals are detected in the 2𝑘#⃗! −𝑘#⃗" and 2𝑘#⃗" −𝑘#⃗! directions, where 𝑘#⃗! and 𝑘#⃗" are the
incident beam directions. A diode laser, responsible by the two fields that driven the FWM
process, is tuned to the 5S1/2(F = 3) → 5P3/2 of the 85Rb. The images of the four beams are
obtained using a CMOS camera for a fixed atomic density and a fixed frequency of the
input beams. From each image we can determine the spatial distribution of the intensity of
the respective beam. We analyzed the spatial intensity distribution of the signals, as well
as the spatial intensity fluctuation. The spatial intensity distribution of the transmitted
beams shows a decrease of the beam waist for intensities close to the saturation intensity,
while for high intensities the spatial profile is almost constant. This behavior indicates an
autofocusing effect, related to the variation of the refractive index of the medium. The
spatial distribution of the intensity fluctuation is obtained considering an average surface
for each image, and is used to calculate the autocorrelation of the transmitted beams and
the two generated FWM beams. Working with the intensity fluctuation, we can define a
transverse spatial correlation length, which is used to compare the behavior of the four
beams with that of a free beam. In this sense, the autocorrelations of intensity fluctuations
of the transmitted beams show a decrease in the correlation length in the same region of
intensities where we observe the self-focusing effect, and as we increase the intensity, the
correlation length approaches the value obtained for the free beam. On the other hand, the
correlation length for the autocorrelations of the signals generated by FWM increases as
the intensity of the incident beams increases.

COMMITTEE MEMBERS:
Externo à Instituição - SEBASTIÃO JOSÉ NASCIMENTO DE PÁDUA - UFMG
Interno - 1295016 - ANDERSON MONTEIRO AMARAL
Presidente - 1132318 - SANDRA SAMPAIO VIANNA