Final Report Summary - MOLCHIP (A molecular laboratory on a chip)
The manipulation of atoms with magnetic fields above a chip is a mature field of research. Miniaturization of the magnetic field structures allows for the creation of large field gradients and steep potential wells above the chip. Moreover, present-day lithographic techniques enable the integration of complicated tools and devices on a compact surface area.
Atom chips have been employed for matter-wave interferometry and for gravitational field sensing and are sufficiently robust that they can be used, for instance, in free-fall experiments.
In this ERC project we have – in analogy to the atom chips – experimentally explored and developed the manipulation of polar molecules with electric fields above a chip, to create a gas-phase molecular physics laboratory on a chip. For molecules, the additional vibrational and rotational degrees of freedom prevent the use of the laser cooling techniques that have been essential for loading of atoms on chips. We therefore load polar molecules directly from a molecular beam onto the chip, where they can be trapped in minima of the electric field created above a microstructured array of electrodes. The additional vibrational and rotational degrees of freedom are actually advantageous as these allow the coupling of the molecules on the chip to photons over an enormous range of frequencies, from the microwave region to the UV, thereby opening up fascinating new experimental possibilities.
The molecule-chip consists of a microstructured array of 1254 electrodes (1848 in a newer version) on a flat glass substrate, and is shown in Figure 1. The electrodes are configured to generate an array of local minima of the electric field strength with a periodicity of 120 μm about 25 μm above the substrate. By applying sinusoidally varying potentials to the electrodes, these minima can be made to move smoothly over the array. Polar molecules in low-field seeking quantum states can be trapped in these traveling potential wells. We have experimentally demonstrated this by guiding metastable CO molecules at a constant velocity of around 300 m/s in the 15-35 mK deep potentials from one end of the chip to the other. We have also used this microstructured array to decelerate metastable CO molecules. For this, the frequency of the waveforms is chirped down while the molecules are above the chip. By chirping the frequency down to zero Hertz, the electric field traps containing the molecules are brought to a standstill. This can be done while the molecules travel a distance of only a few centimeters, corresponding to a deceleration of more than 10^5 g. After a certain holding time, the molecules are accelerated off the chip again for detection. This loading and detection methodology is very general, and applicable to a wide variety of polar molecules. Moreover, the position on the chip where the molecules are stopped is about where the eye of the observer looks through the chip (see Figure 1), and we thus have excellent optical access to the trapped molecules. This is of advantage for imaging the two-dimensional spatial distribution of the molecules on the chip and enables one to efficiently couple various sources of radiation to the molecules to excite them to different rotational or vibrational levels, as we have been able to show.
Atom chips have been employed for matter-wave interferometry and for gravitational field sensing and are sufficiently robust that they can be used, for instance, in free-fall experiments.
In this ERC project we have – in analogy to the atom chips – experimentally explored and developed the manipulation of polar molecules with electric fields above a chip, to create a gas-phase molecular physics laboratory on a chip. For molecules, the additional vibrational and rotational degrees of freedom prevent the use of the laser cooling techniques that have been essential for loading of atoms on chips. We therefore load polar molecules directly from a molecular beam onto the chip, where they can be trapped in minima of the electric field created above a microstructured array of electrodes. The additional vibrational and rotational degrees of freedom are actually advantageous as these allow the coupling of the molecules on the chip to photons over an enormous range of frequencies, from the microwave region to the UV, thereby opening up fascinating new experimental possibilities.
The molecule-chip consists of a microstructured array of 1254 electrodes (1848 in a newer version) on a flat glass substrate, and is shown in Figure 1. The electrodes are configured to generate an array of local minima of the electric field strength with a periodicity of 120 μm about 25 μm above the substrate. By applying sinusoidally varying potentials to the electrodes, these minima can be made to move smoothly over the array. Polar molecules in low-field seeking quantum states can be trapped in these traveling potential wells. We have experimentally demonstrated this by guiding metastable CO molecules at a constant velocity of around 300 m/s in the 15-35 mK deep potentials from one end of the chip to the other. We have also used this microstructured array to decelerate metastable CO molecules. For this, the frequency of the waveforms is chirped down while the molecules are above the chip. By chirping the frequency down to zero Hertz, the electric field traps containing the molecules are brought to a standstill. This can be done while the molecules travel a distance of only a few centimeters, corresponding to a deceleration of more than 10^5 g. After a certain holding time, the molecules are accelerated off the chip again for detection. This loading and detection methodology is very general, and applicable to a wide variety of polar molecules. Moreover, the position on the chip where the molecules are stopped is about where the eye of the observer looks through the chip (see Figure 1), and we thus have excellent optical access to the trapped molecules. This is of advantage for imaging the two-dimensional spatial distribution of the molecules on the chip and enables one to efficiently couple various sources of radiation to the molecules to excite them to different rotational or vibrational levels, as we have been able to show.