arXiv subjects

Yann Kersalé

Publications and source records attributed to Yann Kersalé.

At least 19 recordsLinked to original sources

arXiv2025

Sub-kelvin measurement of silicon thermal expansion with a Fabry-Pérot cavity stabilized laser

In this letter, we report the measurement of the coefficient of thermal expansion (CTE) of single-crystal silicon from 655 mK to 16 K using an ultra-stable laser based on a single-crystal silicon Fabry-Perot cavity. Below 1 K temperatures, the CTE is in the $10^{-13}$ K$^{-1}$ range with a lowest point at $\boldsymbol{α(}655$ mK$ \boldsymbol{)=} 3.5 \pm 0.4 \times 10^{-13}$ K$^{-1}$. We produce a theoretical model based on Debye and Einstein models to effectively approximate the CTE measured in this temperature range. This is the lowest-temperature CTE measurement of silicon to date, as well as the lowest operating temperature for an ultra-stable Fabry-Perot cavity for laser frequency stabilization.

physics.optics↗

arXiv2025

Development of a laser stabilized on an ultra-stable silicon cryogenic Fabry-Perot cavity for dark matter detection

Astrophysical observations suggest the existence of an unknown kind of matter in the Universe, in the frame of the $Λ$CDM model. The research field of dark matter covers an energy scale going from massive objects to ultra-light scalar fields, which are the focus of the present work. It is supposed that ultra-light scalar fields affect the length of objects, whereas the speed of light stays unchanged. It follows that Fabry-Perot cavities are ideal tools for ultra-light dark matter detection since the fluctuations in the length of a cavity can be detected on the frequency of the laser stabilized to it. At FEMTO-ST, we have set up an ultra-stable silicon cavity suitable for a test of detection of ultra-light dark matter in an energy range close to 10$^{-10}$ eV. Our 14 cm cavity is composed of two mirrors optically bonded to an ultra-rigid spacer, with each element made in single-crystal of silicon, and cooled at 17 K in order to cancel the first order thermal expansion coefficient of the silicon spacer. The projected fractional frequency stability of the laser is $3 \times 10^{-17}$, mainly limited by the thermal noise of the amorphous dielectric reflective coatings. To reach this remarkable stability, several effects have to be reduced below the thermal noise limit. While the contribution of the residual amplitude modulation is now acceptable, we are currently implementing a laser power lock with residual fluctuations lower than 3~nW and a piezoelectric-based servo loop to actively reduce the vibration noise that has to be inferior to $-110 \textrm{~dB(m s}^{-2})^2/\textrm{Hz}$ at 1 Hz. Here, we present both the status of the development of our ultra-stable laser and the mechanical response of the cavity in the presence of ultra-light dark matter.

astro-ph.IM↗

arXiv2025

Guidelines for designs for ultrastable laser with $\mathbf{10^{-17}}$ fractional frequency instability

Lasers with long coherence time and narrow linewidth are an essential tool for quantum sensors and clocks. Ultrastable cavities and laser systems are now commercially available with fractional frequency instabilities in the mid $10^{-16}$ range. This document aims to provide technical guidance for researchers starting in the field of ultrastable lasers and to give an outlook toward the next generation of improved ultrastable lasers. These guidelines have arisen from the scope of the EMPIR project ``Next generation ultrastable lasers'' ( https://www.ptb.de/empir2021/nextlasers ) with contributions from the European project partners.

physics.optics↗

arXiv2025

Offset sideband locking to iodine for laser cooling on the $\mathrm{{}^1 S_0}\rightarrow \mathrm{{}^3 P_1}$ transition of ${}^{171}\mathrm{Yb}$

We present absolute frequency measurements of a laser stabilized using an offset sideband locking technique on the P(49)24-1 rovibrational transition of $^{127}\mathrm{I}_2$ near 556 nm. The P(49)24-1 transition is offset by 4.8 GHz from the intercombination transition of ${}^{171}\mathrm{Yb}$. A dual-tone electro-optical modulator is employed to bridge this frequency gap, enabling frequency stabilization of the 556 nm laser near the Yb transition, achieving a fractional frequency stability of $1.2 \times 10^{-11}$ at one second. We thoroughly characterize the frequency shifts associated with this locking scheme, with typical systematic effects fractional uncertainties of $9 \times 10^{-12}$.

physics.ins-det↗

arXiv2024

Preliminary characterization of a surface electrode Paul trap for frequency metrology

We are developing a single-ion optical clock based on a surface-electrode (SE) trap that we will operate with $^{171}$Yb$^+$ ions on the electric quadrupole transition at 435.5 nm. We present heating rate measurements performed with a prototype SE trap. We also introduce a new, micro-fabricated SE trapping chip using silicon on insulator technology. Electric tests were performed under ultra-high vacuum using a testing chip, including breakdown voltages measurements and flashover detection. We present suitable trapping parameters for this chip, as well as a road-map for improving its design.

physics.atom-ph↗

arXiv2024

Towards a sub-kelvin cryogenic Fabry-Perot silicon cavity

We report on the development of a sub-kelvin, single-crystal silicon Fabry-Perot cavity. Operating such a cavity below 1~K should reduce the thermal noise limit of the cavity, and by this way address the current limitations of ultrastable lasers. To further decrease mechanical losses, mirrors with silicon substrates and crystalline coatings are optically contacted to the spacer, resulting in a room-temperature finesse of 220,000. To operate our cavity at sub-kelvin temperatures, we use a dilution refrigerator able to reach temperatures down to 10 mK. We have designed a mechanical mount to house our cavity in such a cryostat, with optimized heat transfer that will decrease the cooldown time for temperatures below 1~K. The estimated thermal noise is projected to be $\sim 7{\times}10^{-19}$ at 100~mK. However, silicon cavities with crystalline mirror coatings at cryogenic temperatures have shown birefringence correlated frequency fluctuations as well as unknown additional noise mechanisms \cite{yu2023, kedar2023}. We have measured a room-temperature TEM$_{00}$ birefringent mode splitting of about 250 kHz. Understanding and measuring these noise mechanisms will be a key to attaining fractional frequency stabilities beyond state-of-the-art.

physics.ins-det↗

arXiv2022

Heating rate measurement and characterization of a prototype surface-electrode trap for optical frequency metrology

We present the characterization of a prototype surface-electrode (SE) trap as a first step towards the realization of a compact, single-ion optical clock based on Yb$^+$. The use of a SE trap will be a key factor to benefit from clean-room fabrication techniques and technological advances made in the field of quantum information processing. We succesfully demonstrated trapping at a 500 $μ$m electrodes distance and characterized our trap in terms of lifetime and heating rate. This is to our knowledge the highest distance achieved for heating rates measurements in SE traps. This simple 5-wire design realized with simple materials yields a heating rate of $\mathbf{8\times 10^3}$ phonons/s. We provide an analysis of the performances of this prototype trap for optical frequency metrology.

quant-ph↗

arXiv2022

Residual amplitude modulation at the $10^{-7}$ level for ultra-stable lasers

The stabilization of lasers on ultra-stable optical cavities by the Pound-Drever-Hall (PDH) technique is a widely used method. The PDH method relies on the phase-modulation of the laser, which is usually performed by an electro-optic modulator (EOM). When approaching the $10^{-16}$ level, this technology requires an active control of the residual amplitude modulation (RAM) generated by the EOM in order to bring the frequency stability of the laser down to the thermal noise limit of the ultra-stable cavity. In this article, we report on the development of an active system of RAM reduction based on a free space EOM, which is used to perform PDH-stabilization of a laser on a cryogenic silicon cavity. A RAM stability of $1.4 \times 10^{-7}$ is obtained by employing a digital servo that stabilizes the EOM DC electric field, the crystal temperature and the laser power. Considering an ultra-stable cavity with a finesse of $2.5\times 10^5$, this RAM level would contribute to the fractional frequency instability at the level of about $5\times 10^{-19}$, well below the state of the art thermal noise limit of a few $ 10^{-17}$.

physics.optics↗

arXiv2021

Digital Doppler-cancellation servo for ultra-stable optical frequency dissemination over fiber

Progress made in optical references, including ultra-stable Fabry-Perot cavities, optical frequency combs and optical atomic clocks, have driven the need for ultra-stable optical fiber networks. Telecom-wavelength ultra-pure optical signal transport has been demonstrated on distances ranging from the laboratory scale to the continental scale. In this manuscript, we present a Doppler-cancellation setup based on a digital phase-locked loop for ultra-stable optical signal dissemination over fiber. The optical phase stabilization setup is based on a usual heterodyne Michelson-interferometer setup, while the Software Defined Radio (SDR) implementation of the phase-locked loop is based on a compact commercial board embedding a field programmable gate array, analog-to-digital and digital-to-analog converters. Using three different configurations including an undersampling method, we demonstrate a 20 m long fiber link with residual fractional frequency instability as low as $10^{-18}$ at 1000 s, and an optical phase noise of $-70$ dBc/Hz at 1 Hz with a telecom frequency carrier.

physics.ins-det↗

arXiv2019

Ultra-compact reference ULE cavity

We present a first experimental characterization of our ultra-compact, ultra-stable laser. The heart of the apparatus is an original Fabry-Perot cavity with a 25 mm length and a pyramidal geometry, equipped with highly-reflective crystalline coatings. The cavity, along with its vacuum chamber and optical setup, fits inside a 30 L volume. We have measured the cavity thermal and vibration sensitivities, and present a first estimation of the cavity fractional frequency instability at $σ_y(1\rm{s})=7.5{\times}10^{-15}$.

physics.ins-det↗

arXiv2019

Absolute frequency measurements of the ${}^1{\rm S}_0 \rightarrow {}^1{\rm P}_1$ transition in ytterbium

The ytterbium atom is widely used in the fields of atomic physics, cavity quantum electrodynamics, quantum information processing and optical frequency standards. There is however a strong dispersion among the reported values of the ${}^1{\rm S}_0 \rightarrow {}^1{\rm P}_1$ transition frequency. In this article, we present two independent measurements of the absolute frequency of this transition performed with two different wavemeters using atomic fluorescence spectroscopy. The cancellation of Doppler shifts is obtained by fine tuning the angle between the probe laser and the atomic beam. The resulting $^{174}\mathrm{Yb}$ isotope transition frequency is estimated to be $\,751\,526\,537\pm27$ MHz.

physics.atom-ph↗

arXiv2018

Photonic Generation of High Power, Ultrastable Microwave Signals by Vernier Effect in a Femtosecond Laser Frequency Comb

Optical frequency division of an ultrastable laser to the microwave frequency range by an optical frequency comb has allowed the generation of microwave signals with unprecedently high spectral purity and stability. However, the generated microwave signal will suffer from a very low power level if no external optical frequency comb repetition rate multiplication device is used. This paper reports theoretical and experimental studies on the beneficial use of the Vernier effect together with the spectral selective filtering in a double directional coupler add-drop optical fibre ring resonator to increase the comb repetition rate and generate high power microwaves. The studies are focused on two selective filtering aspects: the high rejection of undesirable optical modes of the frequency comb and the transmission of the desirable modes with the lowest possible loss. Moreover, the conservation of the frequency comb stability and linewidth at the resonator output is particularly considered. Accordingly, a fibre ring resonator is designed, fabricated, and characterized, and a technique to stabilize the resonator's resonance comb is proposed. A significant power gain is achieved for the photonically generated beat note at 10 GHz. Routes to highly improve the performances of such proof-of-concept device are also discussed.

physics.ins-det↗

arXiv2017

Residual Phase Noise Measurement of Optical Second Harmonic Generation in PPLN Waveguides

We report on the characterization, including residual phase noise and fractional frequency instability, of fiber-coupled PPLN non-linear crystals. These components are devoted to frequency doubling 871 nm light from an extended-cavity diode laser to produce a 435.5 nm beam, corresponding to the ytterbium ion electric quadrupole clock transition. We measure doubling efficiencies of up to 117.5 %/W. Using a Mach-Zehnder interferometer and an original noise rejection technique, the residual phase noise of the doublers is estimated to be lower than ${\rm -35\, dBrad^2/Hz}$ at 1 Hz, making these modules compatible with up-to-date optical clocks and ultra-stable cavities. The influence of external parameters such as pump laser frequency and intensity is investigated, showing that they do not limit the stability of the frequency-doubled signal. Our results demonstrate that such compact, fiber-coupled modules are suitable for use in ultra-low phase noise metrological experiments, including transportable optical atomic clocks.

physics.ins-det↗

arXiv2016

Compact Yb$^+$ optical atomic clock project: design principle and current status

We present the design of a compact optical clock based on the $^2S_{1/2} \rightarrow ^2D_{3/2}$ 435.5 nm transition in $^{171}$Yb$^+$. The ion trap will be based on a micro-fabricated circuit, with surface electrodes generating a trapping potential to localize a single Yb ion a few hundred $μ$m from the electrodes. We present our trap design as well as simulations of the resulting trapping pseudo-potential. We also present a compact, multi-channel wavelength meter that will permit the frequency stabilization of the cooling, repumping and clear-out lasers at 369.5 nm, 935.2 nm and 638.6 nm needed to cool the ion. We use this wavelength meter to characterize and stabilize the frequency of extended cavity diode lasers at 369.5 nm and 638.6 nm.

physics.atom-ph↗

arXiv2015

Frequency stability of a wavelength meter and applications to laser frequency stabilization

Interferometric wavelength meters have attained frequency resolutions down to the MHz range. In particular, Fizeau interferometers, which have no moving parts, are becoming a popular tool for laser characterization and stabilization. In this article, we characterize such a wavelength meter using an ultra-stable laser in terms of relative frequency instability $σ_y(τ)$ and demonstrate that it can achieve a short-term instability $σ_y(1 s) \approx 2{\times}10^{-10}$ and a frequency drift of order $10$ MHz/day. We use this apparatus to demonstrate frequency control of a near-infrared laser, where a frequency instability below $3{\times}10^{-10}$ from 1 s to 2000 s is achieved. Such performance is for example adequate for ions trapping and atoms cooling experiments.

physics.optics↗

arXiv2015

Characterization of the individual short-term frequency stability of Cryogenic Sapphire Oscillators at the 1e-16 level

We present the characterisation of three Cryogenic Sapphire Oscillators using the three-corner-hat method. Easily implemented with commercial components and instruments, this method reveals itself very useful to analyse the frequency stability limitations of these state-of-the-art ultra-stable oscillators. The best unit presents a fractional frequency stability better than 5e-16 at 1 s and below 2e-16 for integration times less than 5,000s.

physics.ins-det↗

arXiv2014

Influence of the ESR saturation on the power sensitivity of cryogenic sapphire resonators

Here, we study the paramagnetic ions behavior in presence of a strong microwave electromagnetic field sustained inside a cryogenic sapphire whispering gallery mode resonator. The high frequency measurement resolution that can be now achieved by comparing two CSOs permit for the first time to observe clearly the non-linearity of the resonator power sensitivity. These observations that in turn allow us to optimize the CSO operation, are well explained by the Electron Spin Resonance (ESR) saturation of the paramagnetic impurities contained in the sapphire crystal.

physics.ins-det↗

arXiv2012

Controlling the Frequency-Temperature Sensitivity of a Cryogenic Sapphire Maser Frequency Standard by Manipulating Fe3+ Spins in the Sapphire Lattice

To create a stable signal from a cryogenic sapphire maser frequency standard, the frequency-temperature dependence of the supporting Whispering Gallery mode must be annulled. We report the ability to control this dependence by manipulating the paramagnetic susceptibility of Fe3+ ions in the sapphire lattice. We show that the maser signal depends on other Whispering Gallery modes tuned to the pump signal near 31 GHz, and the annulment point can be controlled to exist between 5 to 10 K depending on the Fe3+ ion concentration and the frequency of the pump. This level of control has not been achieved previously, and will allow improvements in the stability of such devices.

physics.ins-det↗