Light-induced Atomic Desorption Research Articles

Optical control of coherent magneto-optical resonances in potassium

The influence of Light Induced Atomic Desorption (LIAD) on the potassium D2 line magneto-optical resonances in uncoated buffer-gas optical cell is investigated. LIAD effect reduces the drawbacks of conventional heating for achieving high atomic density that is essential for many spectroscopy-based applications. Another feature of LIAD is the impact on the dwelling time of the atoms when colliding with the surface of the cell. In this work we investigate LIAD from point of view to distinguish the influence of LIAD on the atomic density from the dwelling time as well as to control and improve the parameters of magneto-optical resonances in potassium vapor. The results are interesting for development of new precise optical sensors and devices for various applications.

Fast loaded dual species magneto optical trap of cold sodium and potassium atoms with light-assisted inter-species interaction

We present the design, implementation, and detailed experimental characterization and comparison with numerical simulations of two-dimensional magneto-optical traps (MOTs) of bosonic 23Na and 39K atoms for loading the cold atomic mixture in a dual-species 3DMOT with a large number of atoms. We report our various measurements pertaining to the characterization of two 2D+MOTs via the capture rate in the 3DMOT and also present the optimized parameters for the best performance of the system of the cold atomic mixture. Under the optimized condition, we capture more than 3 × 101039K atoms and 5.8 × 10823Na atoms in the 3DMOT simultaneously from individual 2D+MOTs with a capture rate of 5 × 1010 and 3.5 × 108 atoms/sec for 39K and 23Na, respectively. We also demonstrate improvements of more than a factor of 5 in the capture rate in the 3DMOT from the cold atomic sources when a relatively high-power ultraviolet light is used to cause light-induced atomic desorption in the 2D+MOT glass cells. A detailed study of the light assisted interspecies cold collisions between the co-trapped atoms is presented, and interspecies loss coefficients have been determined to be βNaK ∼ 2 × 10−12 cm3/sec. The cold atomic mixture would be useful for further experiments on quantum simulation with ultra-cold quantum mixtures in optical potentials.

Transient Density-Induced Dipolar Interactions in a Thin Vapor Cell.

We exploit the effect of light-induced atomic desorption to produce high atomic densities (n≫k^{3}) in a rubidium vapor cell. An intense off-resonant laser is pulsed for roughly one nanosecond on a micrometer-sized sapphire-coated cell, which results in the desorption of atomic clouds from both internal surfaces. We probe the transient atomic density evolution by time-resolved absorption spectroscopy. With a temporal resolution of ≈ 1 ns, we measure the broadening and line shift of the atomic resonances. Both broadening and line shift are attributed to dipole-dipole interactions. This fast switching of the atomic density and dipolar interactions could be the basis for future quantum devices based on the excitation blockade.

Light-Induced Atomic Desorption in Microfabricated Vapor Cells for Demonstrating Quantum Optical Applications

In the quest to employ miniaturized atomic vapor cells for quantum applications, unfortunately such a short optical path is insufficient to obtain a decent signal that can be used to lock a laser. Heating up the cell would work, but at the price of undesired currents and linewidth broadening. Instead, the authors use light-induced atomic desorption (LIAD) to increase the atomic (and optical) density. Using LIAD yields a much larger contrast than does conventional spectroscopy---even at room temperature. Furthermore, eliminating the need for heating allow remote operation, without the need to provide electrical contacts to the device, which can be an important advantage in applications.

Optical control of high-density alkali atom vapor in antirelaxation coated cells

In this work, we report on our investigations on LIAD (Light Induced Atomic Desorption) aimed at achieving high density of alkali atoms vapor in a coated cell at room temperature. The experimental results show the possibility to reach a density up to the limit when the medium becomes optically thick by applying highly efficient homogeneous illumination. The photon reabsorption mechanism prevents the precise evaluation of the density by measuring the absorption of a probe laser beam, but there is clear evidence that densities can be achieved higher by two orders of magnitude than the thermodynamic equilibrium value.

Photothermal Effect in Light-Induced Atomic Desorption

Photothermal Effect in Light-Induced Atomic Desorption

Light-induced atomic desorption of lithium.

We demonstrate loading of a Li magneto-optical trap using light-induced atomic desorption. The magnetooptical trap confines up to approximately 4 × 104 7Li atoms with loading rates up to approximately 4 × 103 atoms per second. We study the Li desorption rate as a function of the desorption wavelength and power. The extracted wavelength threshold for desorption of Li from fused silica is approximately 470 nm. In addition to desorption of lithium, we observe light-induced desorption of background gas molecules. The vacuum pressure increase due to the desorbed background molecules is ≲ 50 % and the vacuum pressure decreases back to its base value with characteristic timescales on the order of seconds when we extinguish the desorption light. By examining both the loading and decay curves of the magneto-optical trap, we are able to disentangle the trap decay rates due to background gases and desorbed lithium. Our results show that light-induced atomic desorption can be a viable Li vapor source for compact devices and sensors.

Optical characterization of antirelaxation coatings

Antirelaxation coatings (ARC) are used in optical cells containing alkali metal vapor to reduce the depolarization of alkali atoms after collisions with the cell walls. The long-lived ground state polarization is a basis for development of atomic clocks, magnetometers, quantum memory, slow light experiments, precision measurements of fundamental symmetries etc. In this work, a simple method for measuring the number of collisions of the alkali atoms with the cell walls without atomic spin randomization (Nasyrov et al., Proc. SPIE (2015)) was applied to characterize the AR properties of two PDMS coatings prepared from different solutions in ether (PDMS 2% and PDMS 5%). We observed influence of the light-induced atomic desorption (LIAD) on the AR properties of coatings.

Solid-State Electrochemical Bidirectional Alkali Vapor Source for Cold Atom Microsystems

Cold atom microsystems have the potential to bring the precision measurement capabilities of cold atom clocks, gyroscopes, and accelerometers to portable systems and platforms (1). Trapping cold atoms in a vapor cell requires controlling alkali vapor pressure, which is a function of temperature. Using temperature control to control alkali vapor pressure is common in the lab, but requires too much power for portable microsystems. Techniques such as light-induced atomic desorption, pulsed alkali dispensers, and double MOT chambers have also been used to control alkali vapor density in the lab, but none is rapid, bidirectional, low-power, and miniaturizable as needed for portable cold atom microsystems. Solid ion conductors have been used with widely spaced Pt electrodes as alkali sources, but operate at high voltages (≥50V) and elevated temperatures (≥120°C) (2), thus requiring more power that allowable for portable microsystems applications. We present a low-power bidirectional alkali vapor source based on solid-state electrochemistry. The device comprises a solid electrolyte, beta”-alumina, in between two electrodes. One electrode contacts the alkali vapor inside the vapor cell and consists of a uniform 10nm glassy carbon layer covered with widely spaced Pt lines. The other electrode, which serves as a solid-state alkali reservoir, consists of widely space Pt lines and graphite particles. The thin glassy carbon layer getters rubidium until it becomes saturated. When a positive voltage is applied across the device electrodes, alkali atoms in the glassy carbon layer are oxidized and alkali ions transport into the solid electrolyte. This reduces the rubidium concentration in the glassy carbon and, rubidium vapor gettering resumes, causes rubidium vapor pressure reduction. Alkali ions are reduced at the other electrode and alkali atoms are intercalated in the graphite in the solid state alkali reservoir to maintain ion balance in the solid electrolyte. When a negative voltage is applied the process reverses. Alkali ions are reduced at the glassy carbon electrode, thus quickly saturating the glassy carbon with alkali atoms to stop rubidium gettering and further providing additional rubidium to evaporate and increase the rubidium vapor pressure in the vapor cell. Reversible actuation with this device has been demonstrated with voltages as low as 5 V and peak power as low as 3.4 mW. Furthermore, we will present the use of this device in a feedback loop to control Rb vapor density. The ability to electrically control alkali vapor pressure at low power is an enabling advance for cold atom microsystems. This material is based upon work supported by the Defense Advanced Research Projects Agency (DARPA) and Space and Naval Warfare Systems Center Pacific (SSC Pacific) under Contract No. N66001-15-C-4027. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of DARPA or SSC Pacific. 1. J. Kitching, S. Knappe and E. A. Donley, IEEE Sensors J, 11, 1749 (2011). 2. J. J. Bernstein, A. Whale, J. Brown, C. Johnson, E. Cook, L. Calvez, X. Zhang and S. W. Martin, in Solid-State Sensors, Actuators and Microsystems Workshop, p. 180, Hilton Head Island, South Carolina (2016).

Dynamics of the light-induced atomic desorption at homogeneous illumination

An experimental investigation of Light-Induced Atomic Desorption (LIAD) at homogeneous illumination in uncoated Rb glass cell is reported. The dynamics parameters of LIAD and their dependences on the illumination intensity in uncoated cell are measured and compared with these in paraffin-coated cell and the theoretical dependences for coated cell at homogeneous illumination. The homogeneous illumination not only increases the yield of LIAD, but increases the rates of desorption and adsorption. The results are interesting for the better understanding of the process of LIAD and the atom-surface interaction, for the development of new LIAD-loaded atomic devices, all-optical control of light, optical sensors miniaturization, and new methods for surface and coating diagnostics and nanostructuring.

Ultrahigh and persistent optical depths of cesium in Kagomé-type hollow-core photonic crystal fibers

Alkali-filled hollow-core fibers are a promising medium for investigating light-matter interactions, especially at the single-photon level, due to the tight confinement of light and high optical depths achievable by light-induced atomic desorption (LIAD). However, until now these large optical depths could only be generated for seconds, at most once per day, severely limiting the practicality of the technology. Here we report the generation of the highest observed transient (>10(5) for up to a minute) and highest observed persistent (>2000 for hours) optical depths of alkali vapors in a light-guiding geometry to date, using a cesium-filled Kagomé-type hollow-core photonic crystal fiber (HC-PCF). Our results pave the way to light-matter interaction experiments in confined geometries requiring long operation times and large atomic number densities, such as generation of single-photon-level nonlinearities and development of single photon quantum memories.

Light-induced atomic desorption in a compact system for ultracold atoms

In recent years, light-induced atomic desorption (LIAD) of alkali atoms from the inner surface of a vacuum chamber has been employed in cold atom experiments for the purpose of modulating the alkali background vapour. This is beneficial because larger trapped atom samples can be loaded from vapour at higher pressure, after which the pressure is reduced to increase the lifetime of the sample. We present an analysis, based on the case of rubidium atoms adsorbed on pyrex, of various aspects of LIAD that are useful for this application. Firstly, we study the intensity dependence of LIAD by fitting the experimental data with a rate-equation model, from which we extract a correct prediction for the increase in trapped atom number. Following this, we quantify a figure of merit for the utility of LIAD in cold atom experiments and we show how it can be optimised for realistic experimental parameters.

Light-induced atomic desorption in cells with different PDMS coatings

Light-induced atomic desorption (LIAD) is a non-thermal process in which atoms adsorbed at a surface are released under illumination. It is applied mostly to implementing optical dispensers in the cases when high atomic density at low temperature is needed – for example, for loading atomic devices as atomic magnetometers, atomic clocks, magneto-optical traps and their miniaturization. However, as the desorption depends on the atom-surface interaction, it can also be used for optical characterization and manipulation of alkali metal nanoparticles. The paper describes an experimental investigation of the shape of the transmission spectra and their dependence on the illuminating blue-light power in PDMS coated cells prepared with two different concentrations of PDMS in ether. A comparison is conducted with the LIAD effect in SC-77 coated and in uncoated cells. All measurements are performed on the Rb D2 line in vacuum. The potential is discussed for application of these dependences to analyzing the quality of the coating surface and its optimization.

Spin randomization of light-induced desorbed Rb atoms

We present the first experimental observation of atomic spin randomization of Rb atoms released by light-induced atomic desorption (LIAD). A natural mixture of Rb atoms contained in paraffin and PDMS coated glass cells is irradiated by a free-running diode laser light tuned to the Rb D2 resonance line. The transmission spectrum of the Rb vapor is thus modified and shows a strong enhancement of the hyperfine optical pumping as the light intensity is increased and the laser-frequency scanning rate is decreased. The D2 line spectra are compared for two cases: without and with illumination of the walls of the cell by a UV lamp centered around the wavelength of 404 nm. A simple theoretical model based on the solution of the rate balance equations is introduced in order to analyze the experimental results.

Light-induced atomic desorption under different types of illumination

We studied the light-induced atomic desorption (LIAD) at different geometries and homogeneities of cell illumination. An original system for homogeneous illumination of the cells was developed and the Rb D2 line absorption spectra in several uncoated and coated cells were compared without illumination, with single-side illumination and with homogeneous illumination. The transmission as a function of the illumination intensity and the tuning direction was measured. The absorption coefficients with and without illumination of the stem were compared. The system developed for homogeneous illumination increases the efficiency of the LIAD, enables the investigation of LIAD without lateral diffusion, prevents cluster formation and reduces the influence of the stem. A good knowledge of the factors influencing the alkali atom spectra will be useful not only for the development of new LIAD-loaded atomic devices and their miniaturization, but also for the study of atom-dielectric surface interactions and the development of new all-optical methods for surface and coating diagnostics.

Light-induced changes in an alkali metal atomic vapor cell coating studied by X-ray photoelectron spectroscopy

The light-induced desorption of Rb atoms from a paraffin coating is studied with depth-profiling X-ray photoelectron spectroscopy (XPS) using tunable synchrotron radiation. Following Rb exposure, shifts of the C1s signal to higher binding energies, as well as the appearance of lower binding energy components in the O1s region, were observed. These effects were diminished after irradiation with desorbing light. Additionally, following desorbing-light irradiation, changes in the depth-dependent concentration of carbon were observed. These observations offer an insight into the microscopic changes that occur during light-induced atomic desorption and demonstrate the utility of XPS in understanding atom-coating interactions.

Publisher’s Note: Comment on “Light-induced atomic desorption and diffusion of Rb from porous alumina” [Phys. Rev. A82, 056901 (2010)

Publisher’s Note: Comment on “Light-induced atomic desorption and diffusion of Rb from porous alumina” [Phys. Rev. A<b>82</b>, 056901 (2010)

Comment on “Light-induced atomic desorption and diffusion of Rb from porous alumina”

In a recent article [Phys. Rev. A 81, 032901 (2010)] a theory of light-induced atomic desorption for Rb in porous alumina is proposed. We point out that both the main assumption of this theory (the diffusion inside the pores treated as a random walk with the adsorption to the inner surface of the pores at any step) and several further hypotheses supporting the theoretical model require a revision.

Reply to Comment on Light-induced atomic desorption and diffusion of Rb from porous alumina

We argue that the model used in our paper [Phys. Rev. A 81, 032901 (2010)] for the analysis of the experimental study of light-induced atomic desorption in porous alumina is the simplest consistent approach to a previously unexplored physical system.

Investigation of antirelaxation coatings for alkali-metal vapor cells using surface science techniques

Many technologies based on cells containing alkali-metal atomic vapor benefit from the use of antirelaxation surface coatings in order to preserve atomic spin polarization. In particular, paraffin has been used for this purpose for several decades and has been demonstrated to allow an atom to experience up to 10 000 collisions with the walls of its container without depolarizing, but the details of its operation remain poorly understood. We apply modern surface and bulk techniques to the study of paraffin coatings in order to characterize the properties that enable the effective preservation of alkali spin polarization. These methods include Fourier transform infrared spectroscopy, differential scanning calorimetry, atomic force microscopy, near-edge x-ray absorption fine structure spectroscopy, and x-ray photoelectron spectroscopy. We also compare the light-induced atomic desorption yields of several different paraffin materials. Experimental results include the determination that crystallinity of the coating material is unnecessary, and the detection of C[Double Bond]C double bonds present within a particular class of effective paraffin coatings. Further study should lead to the development of more robust paraffin antirelaxation coatings, as well as the design and synthesis of new classes of coating materials.