1. ProgressTowardTrapping Ions
Jackie Liu, Liz Donoghue, Patrick Becker, and Steven Olmschenk
Denison University, Department of Physics and Astronomy, Granville, Ohio 43023
Abstract
Acknowledgments
This research is supported by the Army Research Office, Research Corporation for Science
Advancement, and Denison University. Additionally, L.D. acknowledges support from the Hodgson,
and J.L. acknowledges support from the Anderson Endowment.
References
[1] “A 750-mW, continuous-wave, solid-state laser source at 313 nm for cooling and
manipulating trapped 9Be+ ions,” A.C. Wilson, C. Ospelkaus, A.P. VanDevender, J.A.
Mlynek, K.R. Brown, D. Leibfried, D.J. Wineland, Applied Physics B. 105, 741 (2011)
[2] Adam V. Steele, Barium Ion Cavity QED and triply ionized Thorium ion trapping,
Georgia Institute of Technology, 2008.
Second Harmonic Generation
of 490nm Light
Second-Harmonic Generation (SHG) is an optical phenomenon in which a light beam of
frequency ω passes through a non-linear crystal and is converted into a beam with a frequency of
2ω. Molecules within the non-linear crystal may absorb two photons of the same energy and
consequently emit a single photon with twice the energy of each incident photon, effectively
doubling the frequency of the input light.[1]
The maximum power of our laser diode (~300mW) is too low for any noticeable amount of
frequency doubling, and so we constructed a resonating cavity to amplify the effective input IR
power.
• Barium ions can be laser cooled with 490nm light because they absorb light at this
wavelength.
• Continuous wave 490nm (blue) laser diodes are very expensive, unreliable, and almost
nonexistent. 980nm (Infrared) laser diodes are much cheaper and more stable.
• It is cheaper and more practical to frequency double IR light to get 490nm light.
Dimensions:
M1 to M4=172mm;
M2 to M3=129mm;
M3 to crystal=29mm;
crystal to M4= 23mm;
M4 to M1=127mm;
M1
M4 Radius=5cm
M2
M3
Radius=5cm490nm
output
980nm
input24°
BiBO
Power
Supply
Piezo
𝑆𝐻𝐺 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 ∝ 𝐼𝑛𝑡𝑒𝑛𝑠𝑖𝑡𝑦 ∝
1
𝐵𝑒𝑎𝑚 𝑊𝑎𝑖𝑠𝑡
We achieved 74.43µW of 490nm light with 72mW of 980nm input
This group plans to trap and laser cool Lanthanum and Barium ions for use in Quantum
Information. To this effect, we present work towards creating a stable laser light source at 490nm
using Second Harmonic Generation to laser cool Barium ions, modelling the quadrupole ion trap
for containing the ions, and modelling and designing the imaging system to be used to extract
information from the trapped and cooled ions. Future goals involve utilizing these three
components as well as an ultra-high vacuum chamber to establish an isolated system of quantum
bits for investigations into quantum information and communication.
Cavity off resonance: very little SHG Cavity on resonance: significant SHG
• Out of the four longer rods, two of the rods have AC voltages and the other two
have DC voltages (labeled with different colors).
• In order to stabilize ions in the trap, we need to find the voltages that are stable
for the ions that we wish to trap and unstable for ions that we wish to eject.
• Computer simulations can be used to determine the appropriate voltages that
are stable for certain ions based on mass selection.
• The a and q factors are proportional to DC and AC voltages respectively.
• The relationship among β, a and q is:
• The boundaries for the stabilized region are created when β is equal to 0 and 1.
Within the equation, a geometric factor α determined by orientation of the trap
can be added.
• By fitting the boundaries with the experiment done by previous researchers, the
geometric factor is approximately 0.42. Based on this value, a graph is
generated to show the stabilization regions for both La2+ and La+.
• The shaded area is where the voltages are stable for La2+ and unstable for La+
since La2+ is what we want to trap. Approximately, the maximum DC voltage is
at 50V and the maximum AC voltage is 380V to trap La2+ while ejecting La+.
IonTrap Simulation
*Ion trap image generated by
CPO software
Imaging System
The imaging system allows us to ascertain if trapping and cooling have been successful.
Photons from the trapped ion are collected and mapped onto the pixels of an InGaAs camera
through a series of lenses.
• Photons are given off in all directions, so a lens needs to be close to the atom
• Need diffraction limited image
• The system must be able to resolve multiple ions
• Use multiple lenses to correct for aberrations in any individual lens
• Use OSLO to model potential lenses and see if these criteria are met
An Airy Pattern (left) forms from a
circular aperture. When more than
85% of the light is in the central
bright spot, or Airy disk, the image is
said to be diffraction limited. The
surface plot of intensity (right)
illustrates the same concept, with the
central peak corresponding to the
central bright spot.
The ray-trace diagram generated by OSLO, showing how rays of light pass
through the various lenses in the system.
Figures retrieved from URL http://en.wikipedia.org/wiki/Airy_disk