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42 UEC Int’l Mini-Conference No.53

53rd UEC International Mini-conference
STRUCTURED LIGHT MEETS ULTRA-COLD ATOMS
Urgunoon SALEEM *, Haruka TANJI-SUZUKI & Yoko MIYAMOTO
a,b
c
a,b
a
Department of Engineering Science, the University of Electro-Communications
Institute for Advanced Science, the University of Electro-Communications
b
c
Institute for Laser Science, the University of Electro-Communications
1-5-1, Chofugaoka, Chofu, Tokyo, 182-8585, Japan.
Keywords: Orbital Angular Momentum (OAM) Light, Vortex Beams, Magneto-Optical Trap (MOT), Ultra-Cold Atoms
Brief Overview
 Structured light can carry orbital angular momentum (OAM), which is encoded in the beam’s helical phase structure.
OAM light offers significant advantages in applications such as optical tweezers, quantum communication, and
astrophysical measurements.
 Ultra-cold atoms are neutral atoms that have been slowed down to temperatures around or below the millikelvin
(mK) range . Since the thermal motion of the atoms is significantly lowered, effects of OAM light can be observed more
clearly.

How do we get OAM Light?
An effective way to convert Gaussian modes into a structured beam (e.g., Lagurre-
Guassian modes) is to use computer generated holograms. In recent years, these
holograms have been realized using a device called a spatial light modulator (SLM).
(a) (b)

+

Figure (1): A beam whose
irradiance profile matches Figure (2): (a) This computer generated hologram diffracts
that of a Gaussian beams with plane wavefronts into a beam with helical
distribution is called a wavefronts. This image is from ref [1] (b) The SLM was
Gaussian beam. connected to the computer in order to produce the hologram. [2] Figure (3): Wavefronts, phase profile, and intensity profiles
of OAM beams. (a) ℓ = 0 represents a donutshaped Gaussian
In OAM beams the azimuthal winding number ℓ determines the number of phase beam with no twist/OAM in the wave front; (b) ℓ = 1, which
twists in the beam. A higher ℓ-value means more twists per wavelength, resulting in defines one twist; (c) ℓ = 2, which defines two twists; (d) ℓ =
helical wavefronts and a vortex-shaped intensity profile. 3, which defines three twists per wavelength. Reprinted from
Ref. [3]
How do we COOL Atoms? Combining OAM light and atoms
LASER COOLING + ZEEMAN SPLITTING  EIT based phenomena like Spatially Structured
transparency [6]
(a) (b)  Studying how cold atoms’ spatial distribution
responds to light carrying OAM [7]
Future Work

 Read more literature reporting experimental findings
based on Laser cooling
℃ K  Read more literature reporting experimental findings
for OAM light generation
(c) (d) (e)  Design and perform experiments for OAM light
generation and creating ultra-cold atoms.
Anti-
Hemholtz References
coils
Magnetic
field YOU [1] Padgett, M., & Allen, L. (1999). Optical and quantum electronics. Optical
Strength and Quantum Electronics, 31, 1–12.
ARE [2] Simpson, N. B., Padgett, M., & Allen, L. (1996). Journal of Modern Optics,
Rb-87 atomic cloud MOT Laser cooling Apparatus HERE!! 43, 2485–2491.
[3] Willner, A. E., Song, H., Zou, K., Zhou, H., & Su, X. (2023). Orbital angular
Figure (4): (a) Due to the Doppler effect, atoms that are moving see slightly different momentum beams for high-capacity communications. Journal of Lightwave

Technology, 41, 1918–1933.
wavelengths than those at rest. Figure from [5]. (b) If we set up a magnetic field that has [4] King-Smith, D. (2014). Creating Laguerre-Gaussian modes using a spatial light
gradients (different values at different points in space) the atom’s energy will depend upon its modulator (Undergraduate thesis). The College of Wooster, Wooster, Ohio, USA

[6] Radwell, N., Clark, T. W., Piccirillo, B., Barnett, S. M., & Franke-Arnold, S.
spatial location Figure from [5]. (c) The 3D Magneto-Optical Trap (MOT) allows atoms to reach (2015). Spatially dependent electromagnetically induced transparency.
Physical Review Letters, 114 ( 12), 123603.
(e.g. Rubidium) temperatures around millikelvin. Figure from [5]. (d) Rb-87 atomic cloud and [7] Baio, G., Robb, G. R. M., Yao, A. M., & Oppo, G.-L. (2020).
(e) MOT LASER cooling apparatus at Tanji-Lab, ILS, UEC Tokyo. Optomechanical transport of cold atoms induced by structured light. Physical
Review Research, 2(2), 023126.
Quantum Effects Become But why ‘COOL’ Precision: Website
[5] University of Alberta. (n.d.). Laser cooling background. Retrieved from
Prominent: Energy levels, Position https://sites.ualberta.ca/~ljleblan/background/laser-cooling.html
Superposition states, Entanglement atoms?