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A photo of the fabricated LTCC module: (a) bottom view, module without optional central bridge. The PTC resistor consists of the four black lines on the top part. The red arrows highlight the two small bridges that connect the cold zone (bottom) and the hot zone (top). In the yellow rectangle there are the wire-bonding pads. (b) Top), top view of the module, with optional central bridge. The heating silver serpentine covers the entire hot zone on the top. In the red rectangle there are SMD pads where it is possible to solder a resistor that will alter the current flow through the bottom part of the heated area.
Source publication
We present a compact frequency-stabilized laser system locked to the Rubidium absorption line of a micro-fabricated reference cell. A printed circuit board (PCB) is used to carry all the components and part of the electronics, and low-temperature co-fired ceramic (LTCC) modules are used to temperature-stabilize the laser diode and the miniature Rub...
Contexts in source publication
Context 1
... area is insulated from the external "cold" area, where the electrical connections are placed: both zones only communicate through two small bridges (Figs. 2 and 3) of dimensions 0.6 × 5 mm 2 . Another additional optional central bridge is present in the original configuration. This bridge can be cut away if low-loss configuration is desired (Fig. 3a), or kept, if a more robust module able to withstand heavier weight is preferred (Fig. 3b). When equipped with the intermediate bridge, a controlled temperature gradient is introduced into the system in the form of an additional conduction loss, which thermal simulations show to be approx. 20% with respect to the low-loss configuration ...
Context 2
... placed: both zones only communicate through two small bridges (Figs. 2 and 3) of dimensions 0.6 × 5 mm 2 . Another additional optional central bridge is present in the original configuration. This bridge can be cut away if low-loss configuration is desired (Fig. 3a), or kept, if a more robust module able to withstand heavier weight is preferred (Fig. 3b). When equipped with the intermediate bridge, a controlled temperature gradient is introduced into the system in the form of an additional conduction loss, which thermal simulations show to be approx. 20% with respect to the low-loss configuration [11]. Moreover, it is possible to further adjust the temperature gradient between two ...
Context 3
... with respect to the low-loss configuration [11]. Moreover, it is possible to further adjust the temperature gradient between two well-defined regions of the heated area using an SMD resistor, soldered on dedicated pads (Fig.3b), which changes the current flow in the bottom part of the heated area. ...
Context 4
... V, 9.6 mA). Moreover, in case the bottom part of the serpentine is disabled (short circuit on the dedicated solder pads), simulations show that the unheated zone is 10°C colder than the heated area, when the latter is kept at 70°C and in case the module is efficiently thermally insulated [11]. On the bottom layer, there are also wire-bonding pads (Fig. 3a), in case additional devices (e.g. external sensors) must be added and connected to the carrier ...
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Citations
... From Fig. 3, we calculate that this stability level should be explained by fluctuations at 1 day of laser power and laser frequency, such that ∆P = 7.6 µW (∆P/P = 10.6 %), and ∆ f = 177 MHz (∆ f / f = 5.2 × 10 −7 ), respectively. These values are high in comparison with those reported in the literature 3,29,33 . Variations ∆P µW of the microwave power of only 0.06 dB at 1 day might be more suspected 3,6,29 to justify the stability limitation. ...
The mid-term fractional frequency stability of miniaturized atomic clocks can be limited by light-shift effects. In this Letter, we demonstrate the implementation of a symmetric auto-balanced Ramsey (SABR) interrogation sequence in a microcell-based atomic clock based on coherent population trapping. Using this advanced protocol, the sensitivity of the clock frequency to laser power, microwave power, and laser frequency variations is reduced, at least by one order of magnitude, in comparison with continuous-wave or Ramsey interrogation schemes. Light-shift mitigation obtained with the SABR sequence benefits greatly to the clock Allan deviation for integration times between 10² and 10⁵ s. These results demonstrate that such interrogation techniques are of interest to enhance the timekeeping performance of chip-scale atomic clocks.
... The latter has been widely-used for laser frequency stabilization with glass-blown vapor cells [28][29][30][31][32][33]. The use of SDS for the development of microcell-based frequency-stabilized lasers was investigated initially in [34] with the demonstration of a micro-fabricated saturated absorption laser spectrometer and in further studies [35][36][37]. In [37], the frequency stabilization of a DBR laser onto a Rb microcell, using some light routing through an integrated silicon nitride waveguide and grating system to the cell, was demonstrated at the level of 10 −11 for time scales up to 10 4 s. ...
The combination of atomic spectroscopy, integrated photonics, and microelectromechanical systems leads the way to the demonstration of microcell-based optical atomic clocks. Here, we report the short-term stability budget of table-top Cs microcell-stabilized lasers based on dual-frequency sub-Doppler spectroscopy (DFSDS). The dependence of the sub-Doppler resonance properties on key experimental parameters is studied. The detection noise budget and absolute phase noise measurements are in good agreement with the measured short-term frequency stability of the laser beatnote, at the level of $1.1 \times {10^{- 12}} {\tau ^{- 1/2}}$ 1.1 × 10 − 12 τ − 1 / 2 until 100 s, currently limited by the intermodulation effect from a distributed-feedback laser setup. The fractional frequency stability of the laser beatnote at 1 s is about 100 times greater than that of commercial microwave chip-scale atomic clocks and validates interest in the DFSDS approach for the development of high-performance microcell-based optical standards.
... In this technology, multi-layer ceramic tapes can be structured in green state for fabricating high-density substrates and integrable circuits. Apart from gas-sensing applications, LTCC-based hotplates are used in variety of heating applications owing to their low thermal conductivity such as in flow sensors (Fournier et al., 2010), discharge lamps (Venkatraman et al., 2012), microfluidics (Belavic et al., 2012) and frequency stabilized lasers (Gruet et al., 2013). Also, LTCC meso-hotplates based differential scanning calorimetric system has been demonstrated by Missal et al. (2011). ...
Purpose
Low temperature co-fired ceramics (LTCC) technology-based micro-hotplates are of immense interest owing to their ruggedness, high temperature stability and reliability. The purpose of this paper is to study the role of thermal mass of LTCC-based micro-hotplates on the power consumption and temperature for gas-sensing applications.
Design/methodology/approach
The LTCC micro-hotplates with different thicknesses are designed and fabricated. The role of thermal mass on power consumption and temperature of these hotplates are simulated and experimentally studied. Also, a comparison study on the performance of LTCC and alumina-based hotplates of equivalent thickness is done. A thick film-sensing layer of tin oxide is coated on LTCC micro-hotplate and demonstrated for the sensing of commercial liquefied petroleum gas.
Findings
It is found from both simulation and experimental studies that the power consumption of LTCC hotplates was decreasing with the decrease in thermal mass to attain the same temperature. Also, the LTCC hotplates are less power-consuming than alumina-based one, owing to their superior thermal characteristics (low thermal conductivity, 3.3 W/ [m-K]).
Originality/value
This study will be beneficial for designing hotplates based on LTCC technology with low power consumption and better stability for gas-sensing applications.
... La spectroscopie par absorption saturée (SAS) a été investiguée de manière préliminaire dans une microcellule Rb dans [253], démontrant la détection de résonances sub-Doppler par le biais d'un dispositif expérimental très réduit. Dans [254], [255], des diodes laser VCSEL ont été stabilisées en fréquence sur des creux d'absorption élargis par effet Doppler en microcellule, démontrant des stabilités de fréquence de l'ordre de 10 −9 de 1 à 1000 s. Dans [256], la sortie d'un laser miniature à effet Brillouin stimulé a été stabilisé sur des atomes de Rb dans une microcellule, démontrant une stabilité relative de fréquence de 10 −11 jusque 1000 s. ...
Cette thèse reporte une horloge atomique à cellule de césium de haute-performance basée sur le phénomène de piégeage cohérent de population (CPT). Cette horloge associe une diode laser DFB (à 895 nm, raie D1 du Cs), un modulateur électro-optique fibré, un modulateur acousto-optique, un système Michelson, une électronique bas bruit contrôlée par une carte FPGA et une cellule à vapeur de césium contenant un mélange de gaz tampon azote-argon. L’horloge exploite un schéma de pompage CPT optimisé nommé push-pull optical pumping (PPOP) permettant la détection de résonances CPT à fort contraste.L’horloge repose sur l’exploitation d’un nouveau protocole d’interrogation pulsé nommé Auto-Balanced Ramsey (ABR). Ce dernier repose sur l’utilisation de deux séquences Ramsey avec des temps noirs de durées différentes. Ce dernier repose sur l’utilisation de deux séquences Ramsey avec des temps noirs de durées différentes. La mise en place de ce protocole ABR-CPT, amélioré par la suite avec symétrisation (SABR-CPT), conduit à une réduction drastique des effets de déplacement lumineux, avec en particulier une diminution de la sensibilité de la fréquence d’horloge aux variations de puissance laser par un facteur 80 comparativement à une interrogation Ramsey-CPT conventionnelle. Cette horloge CPT démontre à ce jour une stabilité relative de fréquence de 2 10-13 τ -1/2, atteignant le niveau record (pour ce type d’horloge) de 2,5 10-15 à 10 000 s. Des travaux annexes de spectroscopie laser en microcellules à vapeur de césium sont aussi reportés dans ce manuscrit. On notera en particulier la démonstration d’un laser stabilisé par spectroscopie sub-Doppler bi-fréquence dans une microcellule Cs avec une stabilité de fréquence préliminaire meilleure que 2 10-12 à 1 s. Ces performances sont 10 fois meilleures que celles de micro-horloges atomiques micro-ondes CPT.
... Such microfabricated cells are a critical component of chip-scale atomic clocks operating at microwave frequencies [33], but their properties for Doppler-free saturated absorption spectroscopy in the optical domain have only been explored in preliminary studies [34]. Vertical cavity surface-emitting lasers have been locked to Dopplerbroadened lines in microfabricated vapor cells and long-term instabilities in the optical frequency in the range of 10 -9 have been achieved [35]. Here we demonstrate the frequency locking of a 6-mm diameter microresonator SBS laser operating at 1560 nm (linewidth = 820 Hz) to the D2 transition of the Rb cell at 780 nm, which improves the SBS laser drift from the level of a few megahertz to ~5 kHz at the 1000 s time scale. ...
We frequency stabilize the output of a miniature stimulated Brillouin scattering (SBS) laser to rubidium atoms in a microfabricated cell to realize a laser system with frequency stability at the 10⁻¹¹ level over seven decades in averaging time. In addition, our system has the advantages of robustness, low cost and the potential for integration that would lead to still further miniaturization. The SBS laser operating at 1560 nm exhibits a spectral linewidth of 820 Hz, but its frequency drifts over a few MHz on the 1 hour timescale. By locking the second harmonic of the SBS laser to the Rb reference, we reduce this drift by a factor of 10³ to the level of a few kHz over the course of an hour. For our combined SBS and Rb laser system, we measure a frequency noise of 4 × 10⁴ Hz²/Hz at 10 Hz offset frequency which rapidly rolls off to a level of 0.2 Hz²/Hz at 100 kHz offset. The corresponding Allan deviation is ≤2 × 10⁻¹¹ for averaging times spanning 10⁻⁴ to 10³ s. By optically dividing the signal of the laser down to microwave frequencies, we generate an RF signal at 2 GHz with phase noise at the level of −76 dBc/Hz and −140 dBc/Hz at offset frequencies of 10 Hz and 10 kHz, respectively.
... Heating devices range from millimeters to several centimeters, so-called meso-hotplates, have been widely studied and utilized for many applications: gas and flow sensors [1,2], micro power generators [3][4][5], frequency-stabilized lasers [6], discharge lamps for atomic clocks and magnetometers [7] and microfluidics [3,8,9], just to name a few. Such meso-hotplates typically contain metallic or resistive heaters fabricated on a thermomechanically decoupled area of a dielectric substrate. ...
... W m −1 K −1 [48], k LTCC = ∼3 W m −1 K −1 , and k Pt = ∼72 W m −1 K −1 [48]. Given that all "resistors" are in parallel at the LTCC bridges, the R bridge then can be obtained according to Eqs. (5) and (6). As the LTCC hotplate stays at T op = 560-570 • C, the estimated R bridge corresponds to ∼680 K W −1 . ...
This paper presents a meso-scale low-temperature co-fired ceramic (LTCC) hotplate system. Using embedded thick-film platinum heaters, the hotplate has been able to operate at about 600 °C in a reliable manner, while its operating temperature can be regulated using an automation setup. The capability of structuring in LTCC materials made it possible to create an efficient thermal decoupling to have two temperature zones in the device, an active heating area and a cold-zone (<100 °C), which becomes greatly beneficial to the integration of standard fluidic and electrical interconnections. A heat dissipation model has been developed for understanding thermal characteristics of the LTCC hotplate system, while the reliability tests have shown robust mechanical structure of the device as well as durable performance of the thick-film heaters after 70 thermal cycles up to 600 °C. Moreover, potential applications in the use of the LTCC hotplate have been demonstrated, including a high-temperature microreactor for a highly efficient hydrogen production and a miniaturized thermal transpiration gas pump.
... Screen-printed thick-film sensors, as previously developed [36][37][38], provide an ideal platform for realizing such an SPE. Hence, the aims of the present work, originated in a preliminary conference paper [39], are to present the steps of the fabrication process and the quality parameters of the obtained sensors. ...
Simple, low-cost and acid-resistant carbon-based screen-printed electrodes (SPEs) addressed to detection of hexavalent chromium species, Cr(VI), in sulfuric acid at pH about 1, were prepared and characterized. Working and counter electrodes were prepared jointly on the same substrate in a single strip (working-counter electrodes pair). The batch printing process allowed obtaining many working-counter electrode pairs in a unique step. The developed working electrodes are comprised of several layers deposited on an alumina substrate: (1) bottom silver conductor, (2) dense organic–graphite composite conductor, (3) active layer consisting of a porous organic–graphite composite which contains a Cr(III) ionophore for testing Cr(III) obtained after reducing Cr(VI), and (4) an insulating and protective dielectric. All materials except the bottom Ag conductor were made on an organic matrix based on a thermoplastic polymer, polyvinylbutyral (PVB). The amperometric determination of Cr(VI) species at pH 1 was performed over a wide concentration range (dynamic range 3 μM–40 mM). The range for linear amperometric response is 3 μM–10 mM, with sensitivity about 0.08 mA mM−1. The sensitivity is improved in comparison with previously developed sensors, while keeping a low limit of detection (LOD about 1 μM). The response of the sensors are not interfered by the presence of Cr(III) in the solution, although the sensor can detect local formation of Cr(III) at the electrode surface after the reduction of Cr(VI) when diethylenetriamine-pentaacetic acid (DTPA), a complexing agent for Cr(III) is incorporated into the pastes.
... A VCSEL temperature of 48°C, a cell temperature of 104°C and a light power through the cell of 40 µW are identified as best operation parameters for optimized frequency stability. With this configuration, a stability of 1.3×10 -10 at 1 second and ≤ 8×10 -10 up to one day for 85 Rb is obtained by our stabilized laser [253]. This result is up to a factor of four better, depending on the timescale, than previously reported results obtained with a significantly larger setup [252]. ...
... The total volume of the assembled device is ca. 0.14 L[253], a photo of which is shown inFigure 6. 2 and can be compared with the block diagram inFigure 6. 1. ...
The mid-term fractional frequency stability of miniaturized atomic clocks can be limited by light-shift effects. In this Letter, we demonstrate the implementation of a symmetric Auto-Balanced Ramsey (SABR) interrogation sequence in a microcell-based atomic clock based on coherent population trapping (CPT). Using this advanced protocol, the sensitivity of the clock frequency to laser power, microwave power and laser frequency variations is reduced, at least by one order of magnitude, in comparison with continuous-wave (CW) or Ramsey interrogation schemes. Light-shift mitigation obtained with the SABR sequence benefits greatly to the clock Allan deviation for integration times between 10$^2$ and 10$^5$ s. These results demonstrate that such interrogation techniques are of interest to enhance timekeeping performances of chip-scale atomic clocks.
