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Magneto-Optical Trap

Magneto-optical traps (MOTs) use a combination of lasers and magnetic fields to localize and cool neutral atoms to temperatures in the micro Kelvin regime. MOTs are essential for ultra-cold atoms research and have enabled extensive studies of Bose Einstein Condensates and Degenerate Fermi Gases.

To operate a MOT, two lasers need to be frequency locked such that they are slightly detuned to the red of the atomic transitions and stabilized to less than the 5 MHz natural transition linewidth. Locking offset from the actual transitions is easily achieved with the Thorlabs DAVS stabilized tunable laser. See the Stabilized Laser tab for more information. For more information about components featured in the MOT, see the System Components tab.

The image on the right shows the fluorescence of Rb atoms in the MOT cell, as detected by a CCD camera.

Figure 1 shows six beams of which three are right circularly polarized (σ+) and three are left circularly polarized (σ-). These six beams are necessary to provide confinement and cooling in three dimensions. For successful operation, two lasers have to be stabilized close to the Rubidium D2 transitions. One laser, often referred to as the "trap laser" and represented by (a) and (b) in the energy level diagram (Figure 2), provides the trapping forces. The second laser, known as the "re-pump laser" and represented by (c), (d), and (e) in Figure 2, ensures that the Rubidium atoms do not accumulate in the F=2 ground state, which cannot be accessed by the trap laser.

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The Magneto-Optical Trap is under development and will be available soon. For more information, contact Tobias Paprotta.



MOT SchematicLine Diagram
Figure 1: Schematic diagram of working principle of MOTFigure 2: Energy level diagram


  • Laser Stabilized to Rubidium Transitions for Atom Cooling and Atomic Physics Applications
  • 40 mW Output Power
  • Instantaneous Linewidth <100 kHz, Long Term Stability <2 MHz
  • ~500 MHz Wide Capture Range

Thorlabs' frequency-stabilized laser kit extends our line of tunable diode lasers by providing an option for stabilizing the laser output to an atomic transition frequency.

This light source is suitable for cooling and trapping of Rubidium atoms, as well as other atomic physics applications. The kit employs Dichroic Atomic Vapor Spectroscopy (DAVS) to stabilize the frequency of a Thorlabs tunable diode laser to less than 2 MHz RMS long term.

The DAVS technique allows for a large capture range of ~500 MHz, making the system resilient to external perturbations. Furthermore, the laser can be locked so that it is detuned from the line center frequency.


DAVS Signal

Dichroic Atomic Vapor Spectroscopy

The Rubidium vapor cell is placed in a weak longitudinal magnetic field, followed by a retarder and a polarizing beamsplitter (Wollaston prism). The absorption profiles of the two circular components (σ+ and σ-) that comprise the linearly polarized input beam are shifted to higher and lower frequencies, respectively. The dispersion-like DAVS curve (as seen above) is generated from the difference between the two signals, which provides an error signal for the lock.
DAVS Schematic

Components Featured in the Magneto Optical Trap

The items listed here are featured components in the MOT. For more information on any of these items, click on the links below.

Integral Feedback Controller

IdestaQE's integral feedback controller features a proportional (P) and integral (I) gain stage. The proportional -3 dB bandwidth extends to 10 MHz, while the low-frequency gain is more than 80 dB. The group delay through the device is less than 50 ns up to a frequency of 12 MHz. Gain settings can be changed completely independent of corner frequencies. Our purely analog device is designed for ultra-low internal noise.

Contact: Jens Schumacher
Coming Soon

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 Integral Feedback Controller from IdestaQE

Tunable Laser Kit 

Tunable Laser Kits

The Tunable Laser Kits are external cavity lasers designed for superior cavity construction flexibility and high-stability performance. Kits are offered with center wavelengths at 770, 1050, 1310, 1550, 1900, and 1950 nm. Additionally, customer-furnished AR-coated laser diodes can be easily incorporated into the cavity for lasing at non-standard wavelengths.

Contact: Lars Sandstrom
Available Now

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