Discover the results of our students’ mini-projects!

Atom throw and catch (experiment)

Mathis Roussel (03/2024-08/2024): Mathis worked on the experimental setup to reproduce and go beyond an experiment demonstrated by the group of Prof. Jaewook Ahn (KAIST, Korea) on accelerating, throwing and recapturing atoms with moving optical tweezers. He succeeded! and by throwing atoms, we can now bring them at much closer distance to each other’s than previously with static tweezers. Thanks Mathis and now enjoy your master at ETH Zurich.

Atom throw and catch (theory)

Axel-Ugo Leriche (03/2024-08/2024): Axel worked on the theoretical aspect of throwing and catching atoms with optical tweezers, together with Mathis (see above post). He generated helpful simulations guiding us in the good choice of parameters, as well as illustrative animations of moving tweezers (and flying atoms) that everyone in the group (and visitors) enjoyed much. Congrats Axel-Ugo and best wishes for your master 2 in Paris.

Spectral shaping of picosecond laser pulses (Part II: tuning of CBG and pulse compression)

Sapna Hassanaly (04/2024-08/2024): Sapna took over the work of Arnab on characterizing the chirp of CBGs (chirped Bragg gratings). Going beyond our previous achievements, she upgraded the CBG system to control its temperature, and more precisely, the temperature gradient through its length. This allows to tune the chirp of the CBG which she could successfully observe with her measurement bench. Finally, she used two CBGs to chirp (with opposite signs) two laser pulses of 780 and 1250 nm and then, after sum-frequency-generation, she could generate a spectrally-compressed 480 nm pulse. In particular, she generated the most-compressed pulse ever generated in our group, obtained a bandwidth of 20 GHz (the record was 60 GHz so far). Congrats Sapna, and see you after the holidays for starting your PhD work with us again : ) Enjoy the Olympics !

Digital Micro-Mirror Devices for Holography

Characterization of Spatial Light Modulators (Part II: phase noise)

Isaline Duperon (05/2024-08/2024): Isaline continued the project of Bee on characterizing SLM (Spatial Light Modulators) based on liquid crystals. In particular, she tackled the question of the noise imprinted by the SLM on the laser beam, an important point when considering that the laser beam will be used for very precise manipulation of neutral atoms (trapping, excitation, …). She developed an optical test-bench for measuring the phase noise imprinted by the fluctuating liquid crystals and measured it for the first time in our laboratory (and we didn’t find other measurement in the open scientific literature!). She also compared the performance of two SLMs from different manufacturers. Finally, she pushed her project further and measured the intensity noise of a holographic tweezers array generated with the SLM. Thanks Isaline for your effort, the knowledge gained in this project helps us to understand more the possible errors caused by SLM. Have fun for your Master in Stockholm.   

Characterization of Spatial Light Modulators (Part I: diffraction efficiency and phase calibration)

Homebuilt Lasers for Coherent Rydberg Excitation

Spectral shaping of picosecond laser pulses (Part I: characterization of CBG)

Arnab Maity (07/2023-05/2024): Arnab focused his effort on characterizing and using a chirped Bragg grating (CBG), a highly dispersive optical component, for spectral shaping of our picosecond pulses. For our ultrafast Rydberg experiments, we require pulses with a duration of 10 – 100 picoseconds to perform excitation of a valence electron from its ground state to a giant Rydberg orbital. Our group is interested in using CBGs to imprint a large chirp on our pulses. His work was first to precisely characterize the CBG chirp, for which he developed 2 test benches resulting in a measurement precision 10 times better than the results of the CBG manufacturer! Followingly, he used the CBG and the chirped laser pulse to perform an advanced type of coherent excitation called Rapid Adiabatic Passage.  His efforts resulted in a good step forward for our group in the ultrafast manipulation of Rydberg states, and was later continued by Sapna. Thanks Arnab and best of luck for your PhD in France !

Optimizing AODs for Atom Rearrangement in Optical Tweezers

Developing Broadband Microwave Drives for Rydberg Atom Manipulation

Optical Ruler for Ultra-Precise Atomic Positioning (Part II)

Sota Kitade (04/2022 – 03/2024): Kitade-kun developed an optical ruler to (ultra-)precisely measure the position of atoms in our vacuum chambers. Indeed, we create an array of atoms held in holographic tweezers, and we were wondering if the tweezers (and thus the atoms) are located precisely where we want them to sit. We just developed a technique, that we call “optical ruler”, to measure the atom position by interfering two laser beams that then form a standing wave (the ruler). The lasers are chosen resonant with an atomic transition, and the measurement of the scattering rate of the atom in this standing wave tell us what is the atom position. With this technique, Kitade-kun has shown that there was 130 nm of uncertainty of position. Even more, based on this information, he corrected the hologram and could decrease this uncertainty to 70 nm. This study is an important part of our publication “ultra-precise holographic optical tweezers” (arXiv:2407.20699). Thanks and congrats Kitade-kun !

Titanium-Sapphire Laser for Large-Scale Atomic Array

Masato Tsugaoka (04/2022 – 12/2023): Tsugaoka-kun was in charge of installing a new laser system for trapping atoms. He characterized the beam profile of the laser and worked on improving it to obtain a good coupling of the laser beam into an optical fiber for delivery to the experimental setup. After several efforts with the laser company to debug problems in the manufacturing of the laser, he could finally obtained a successful coupling and we are now routinely using his laser system to trap atoms in our tweezers experiment. O-tsukare-sama Tsugaoka-kun !

Motional Squeezed States in Optical Tweezers

Romain Martin (03/2023-08/2023): Our laboratory can routinely produce atoms cooled at the very bottom of optical tweezers. Despite removing all thermal fluctuations, quantum physics dictates that the position of the atom is not yet known with absolute accuracy but instead is limited by quantum fluctuation. In our experiments with two closely interacting atoms, this is problem and we thus asked Romain to beat the standard quantum limit by producing squeezed state of motions displaying a reduction of quantum uncertainty of position (at the acceptable cost of an increase in velocity uncertainty). Romain simulated the experimental protocol to generate such states and quantified the effect of experimental imperfections, for example the inhomogeneity of shapes (see Martin project below), or the inherence anharmonicity of optical tweezers. He finally performed experiments generating and observing these squeezed state of motions. Soon, we will be able to combine them together with interaction between two closeby atoms. Thanks Romain for your efforts, and enjoy your next games with atoms during your Master and PhD in France. 

Ultra-Precise Holographic Optical Tweezers

Martin Poitrinal (03/2023-08/2023): Arbitrary 2d, and even 3d, arrays of tweezers can be generated by holograms displayed on spatial light modulators. While this is now a well-established technique, small inhomogeneities of the tweezers can be observed when generated this way. For example, the intensity, shape (see Romain project) and position (see Jorge and Kitade project) of each tweezer vary slightly by a few percent. Based on some preliminary tests, we asked Martin to develop a feedback routine based on precisely measuring the intensity and shape of the tweezers with the atoms and use this information to fine tune the hologram. After learning how to perform such measurements and push their precision, Martin coded a program that automatically perform all these tasks and generate a well-optimized array of tweezers. His work is now a great part of our publication “ultra-precise holographic optical tweezers” (arXiv:2407.20699). Thanks Martin and best wishes for your Master studies in ETH Zurich.  

Real-Time Generation of Waveforms for Moving Tweezers

Jean-Samuel Tettekpoe (03/2023-08/2023): We trap single atoms in optical tweezers (focused beam of light). It is possible to create an array of moving tweezers by diffracting a single laser beam with an acousto-optic deflector driven by a multi-tone radio-frequency signal. More specifically, this signal consists of a sum of sinusoids with instantaneous frequencies ranging typically from 50 to 150 MHz. We gave the mission to Jean-Samuel of generating such signal in “real-time”, i.e., as fast as it is played to the deflector and with as little delay as possible. As tools, we gave him an arbitrary waveform generator which can generate the signal at a rate of one sample every nanosecond, and a graphic processing unit to do the calculation. Jean-Samuel brilliantly accomplished the mission, by finding a number of subtle computing tricks to minimize the calculation time. In addition, he also prepared algorithms to re-arrange an initially disorded atomic arrays with a set of parallel moving tweezers. Looking forward to implementing this! Thanks Jean-Samuel for these accomplishments, and hope that you will enjoy your next challenge with superconducting qubits.  

Intelligent Laser System for Cold-Atom Experiment

Sub-Microsecond Laser Phase Noise Eater (Part III)

Sub-Microsecond Laser Phase Noise Eater (Part II)

Tom Denecker (02/2023-08/2023). As Tom enjoyed playing with laser phase noise so much in his 1^st internship, he joined back the group for a second one! He upgraded the electronic system for the detection and feedforward cancellation of laser phase noise and obtained even more impressive results than last time. Have fun for the Master in Palaiseau and see you in one year for starting the PhD work ; )

Optical Ruler for Ultra-Precise Atomic Positioning (Part I)

Jorge Mauricio (12/2023-03/2023): Jorge joined for a spring-break internship during his bachelor studies at the University of Kyoto. Together with Tomita-sensei, he developed an optical breadboard for creating and interfering two laser beams to form a standing wave. It serves as an “optical ruler” to precisely measure the position of atoms in our vacuum chamber. Jorge succesfully completed the system and obtained a first experimental signature from the atom. After going back to Kyoto University to complete his bachelor, Kitade-kun took over the project (see Part II), which is now part of one of our scientific publication (“ultra-precise holographic optical tweezers”, arXiv:2407.20699). Thanks for joining and happy to have you back in the team for the Master/PhD program of Sokendai from 2024.

Sub-Microsecond Laser Phase Noise Eater (Part I)

Tom Denecker (04/2022-08/2022). After much patience for the Japanese border to re-open following the global health crisis, Tom could finally join the group for an internship. Following on a side project of Sylvain on measuring and correcting the fast phase noise of lasers, Tom took the project to the next step. While the initial setup was based on free-space optics, Tom upgraded it to a fiberized system and could successfully reproduce and improve the experiment. His project was continued by … himself … see Part II.

Generation of Sub-Nanosecond Pulses (Part III)

Joa Molar-Al-Yahya (03/2022-08/2022): Together with Robin, Joa updated the project started with Matsubara-kun. While we first used a free-space electro-optic crystal to switch on and off the laser beam in slightly less than 10 nanosecond with Matsubara-kun, we moved here to a waveguide electro-optic modulator allowing switching speed as fast as 30 picoseconds. They are designed in two versions: phase and intensity modulators, with the later one consisting in a Mach-Zender interferometer acting as a phase-to-intensity convertor. They are however limited in extinction ratio (typically only a factor of 100), which motivated us to ask Joa to build the Mach-Zender interferometer herself, with fibers, and challenge her in obtaining the maximum extinction ratio. She completed the mission and could obtain an extinction as high as a few 1000s. Combined with the project of Robin (below), they improve upon the results of Matsubara-kun and got clearer and faster Rabi oscillations. Thanks for your effort Joa, and have fun with your Master 2 and PhD back in France.

Generation of sub-nanosecond pulses from a cw-laser (Part II: semiconductor optical amplifier)

Robin Kocik (05/2022-08/2022): We continued the project started with Matsubara-kun by replacing the awful electro-optic Pockel cell (slow, hard to drive, …) by two faster and fancier devices: a 100 picosecond-scale electro-optic switch (see Part III) and a nanosecond-scale semiconductor optical amplifier.

Generation of sub-nanosecond pulses from a cw-laser (Part I)