CN116888427A

CN116888427A - Lambdade ion frequency reference instrument and methods of making and using same

Info

Publication number: CN116888427A
Application number: CN202280016765.7A
Authority: CN
Inventors: 特拉维斯·奥特里; 伊恩·康茨; 詹尼弗·埃利斯; 丹尼·金; 克里斯托弗·罗珀
Original assignee: HRL Laboratories LLC
Current assignee: HRL Laboratories LLC
Priority date: 2021-03-10
Filing date: 2022-01-15
Publication date: 2023-10-13

Abstract

In some variations, an interferometric frequency reference comprises: an atomic source configured to supply neutral atoms to be ionized; an ionizer configured to excite the neutral atoms to form ionized atoms; an ion collimator configured to form a collimated beam of the ionized atoms; a probe laser; and a Doppler laser configured to determine a ground state population of the ionized atoms, wherein the atomic source, the ionizer, and the ion collimator are disposed within a vacuum chamber. Other variations provide a method of generating a stable frequency reference, the method comprising: forming ionized atoms from the atomic vapor; forming a collimated beam of ionized atoms; irradiating ionized atoms with first and second probe lasers; adjusting the frequency of the first and second probe lasers to an s→d transition of ionized atoms using a lamb Ji Guangpu method; and determining the ground state population of the ionized atoms with another laser.

Description

Lambdade ion frequency reference instrument and methods of making and using same

Priority data

The international patent application claims priority from U.S. provisional patent application No. 63/159,167 filed on day 3, month 10 of 2021 and U.S. patent application No. 17/576,897 filed on day 1, month 14 of 2022, each of which is hereby incorporated by reference.

Technical Field

The present invention relates generally to an optical frequency reference (frequency reference).

Background

The frequency standard is a device for generating or detecting a frequency. The optical frequency standard refers to a stable optical frequency and is generated by an optical atomic clock and an optical cavity. Frequency standards may be used for fiber optic communications, timing, radio Frequency (RF) photonics, and inertial sensing, among other techniques. Applications for ultra-precise optical frequency standards include high-precision laser spectroscopy, small atomic instruments (e.g., atomic clocks and gyroscopes), global positioning systems, precision laser sensing (e.g., remote nuclear explosion detection), and ultra-stable oscillators for high-speed analog-to-digital converters and radar systems.

The active optical frequency standard is a laser source (e.g., a stable HeNe laser) that emits light with a well-defined and known optical frequency. A passive optical frequency standard is a passive device with a well-defined frequency response that can be used to construct an active standard. Important examples are high quality factor reference cavities and devices such as multi-channel gas cells for detecting certain optical transitions.

The optical frequency standard is typically based on some optically detected electronic transitions (typically dipole forbidden but quadrupole allowed transitions), with atoms (e.g., ca, rb, sr, yb, mg or H), ions (e.g., hg ⁺ 、Sr ⁺ 、Yb ⁺ 、Ba ⁺ 、In ⁺ Or Al ⁺ ) Or molecules (e.g. CH ₄ Or I ₂ ) Is a narrow frequency bandwidth of (a). The electron transition is used to stabilize the frequency of the single frequency laser to the electron transition frequency of an atom, ion, or molecule. To reduce non-uniform broadening caused by thermal motion and collisions, the particles may be retained in a trap within the vacuum chamber as the laser cools. This conventional arrangement allows accurate spectral measurements of clock transitions.

The paper describing the frequency reference includes McFerran et al, "Fractional frequency instability in the 10 ^-14 range with a thermal beam optical frequency reference [ at 10 with thermal beam optical frequency reference ] ^-14 Fractional frequency instability in a range]", J.Opt.Soc.Am.B [ journal of the American society of optics B ]]27,277-285 (2010); norcia et al, "Frequency Measurements of Superradiance from the Strontium Clock Transition [ frequency measurement of superirradiation from strontium Zhong Yue migration ]]", phys.Rev.X [ physical comment X ]]8,021036 (2018); davila-Rodriguez et al, "Compact, thermal-noise-limited reference cavity for ultra-low-noise microwave generation [ Compact thermal noise limiting reference cavity for ultra-low noise microwave generation ]]", opt.lett. [ optical flash report ] ]42,1277-1280 (2017); matei et al, "1.5 mu m Lasers with Sub-10mHz Linewidth [ 1.5 mu m laser with Linewidth below 10mHz ]]", phys. Rev. Lett. [ physical comment flash report ]]118,263202 (2017); kessler et al, "A sub-40-mHz-linewidth laser based on a silicon single-crystal optical cavity [ laser with linewidth lower than 40mHz based on silicon single crystal optical cavity ]]", nature Photonics [ Nature Photonics ]]6,687-692 (2012); cook et al, "Laser-Frequency Stabilization Based on Steady-State spectra-Hole Burning in Eu ³⁺ :Y ₂ SiO ₅ Eu-based ³⁺ :Y ₂ SiO ₅ Laser-frequency stabilization of mid-steady state spectral hole burning]", phys. Rev. Lett. [ physical comment flash report ]]114,253902 (2015); olson et al, "Ramsey-Boodne Water-Wave Interferometry for Laser Frequency Stabilization at 10 ^-16 Frequency Instability and Below [ lambda-Bode substance wave interferometry for use at 10 ^-16 Laser frequency stabilization for frequency and lower instabilities]", phys. Rev. Lett. [ physical comment flash report ]]123,073202 (2019), each of which is hereby incorporated by reference.

High precision optical frequency references play an important role in many applications. For example, an optical frequency reference with better performance than commercially available standards is desired to enable high-precision spectroscopy at multiple locations. In general, known frequency references are extremely accurate at the expense of large size, weight, and power, or they sacrifice performance for reduced size, weight, and power. Large frequency references based on optical cavities are currently the standard method of generating optical frequency references at short integration/averaging times. At longer average times, an optical atomic clock is used.

There remains a long felt need for a compact, ultra-stable, atomic-based frequency reference that operates on a short (e.g., <1 second) time scale and shows a high degree of stability on a long time scale.

Summary of The Invention

The foregoing needs in the art are addressed by the present invention, as will now be summarized and then described in detail further below.

In some variations, an interferometric frequency reference (interferometric frequency-reference apparatus) includes:

a vacuum chamber;

an atomic source configured to supply neutral atoms to be ionized;

an ionizer configured to excite neutral atoms to form ionized atoms (such as but not limited to Ca ⁺ Or Sr ⁺ )；

An ion collimator configured to form a collimated beam of ionized atoms;

one or more probe lasers with frequencies near Zhong Yueqian (e.g., quadrupole transitions); and

a readout laser configured to determine the ground state population of ionized atoms, typically by measuring the cyclic transitions of the atoms (such as the S-P transition in sr+),

wherein the atomic source, the ionizer, and the ion collimator are disposed within a vacuum chamber.

In some embodiments, the atomic source is a solid state electrochemical atomic source.

In some embodiments, the ionizer is disposed inside the ion collimator. In these embodiments, ionized atoms are formed within the ion collimator. In other embodiments, the ionizer is disposed outside the ion collimator. In these embodiments, ionized atoms are formed and then implanted into an ion collimator. The ionizer may be one or more ionization lasers, electron beam emitters, or the like.

In some embodiments, the ion collimator is a linear collimator. For example, the linear collimator may be selected from the group consisting of a linear quadrupole trap, a penning trap, a surface ion trap, and a mass filter. In other embodiments, the ion collimator is a non-linear collimator. The non-linear collimator may be in a recirculating configuration, such as a racetrack configuration, a loop, or a curved loop.

The ion collimator may be configured such that the collimated beam of ionized atoms has a beam waist selected from about 10 nanometers to about 10 meters. Preferably, the beam waist is selected from about 50 nanometers to about 500 nanometers. The ion collimator may be configured such that the collimated beam of ionized atoms has a beam velocity selected from about 1 μm/s to about 0.99c, where c is the speed of light in vacuum. Preferably, the beam speed is selected from about 1m/s to about 20m/s.

In some embodiments, the one or more probe lasers are configured to perform a lambda (Ramsey) or a Rabi (Ramsey) spectroscopy on the ionized atoms. In a preferred embodiment, all probe lasers present are configured to perform the lamb Ji Guangpu method on ionized atoms. The number of probe lasers may vary, but is preferably two or more, such as four probe lasers (see, e.g., fig. 4).

In some embodiments, the one or more probe lasers are configured to detect quadrupole transitions or both dipole and quadrupole transitions of ionized atoms. Configuration includes selecting the appropriate wavelength and ensuring a sufficiently narrow linewidth.

In some embodiments, a readout laser may be used for quantum transition measurement. Quantum transition measurements can be made after a lambda probe using a readout laser via fluorescence from the S→P cycling transition.

In some embodiments, the interferometric frequency reference further comprises a cooled laser. The cool laser is configured to cool ionized atoms in preparation for the lamb Ji Guangpu method. In some embodiments, the readout laser itself is configured for cooling, and there is not necessarily a physically distinct cooling laser.

The interferometric frequency reference may further comprise injection electrodes. The injection electrode is different from the ionizer. In embodiments in which atoms are ionized outside of the ion collimator, the injection electrode may generate a potential field that directs ionized atoms into the ion collimator. In a preferred embodiment, atoms are ionized within an ion collimator; thus, injection electrodes are not necessary.

The interferometric frequency reference may further comprise an ion sink configured to collect ionized atoms exiting the ion collimator. The ion sink is preferably arranged within the vacuum chamber.

The interferometric frequency reference preferably further comprises an imaging system configured to focus fluorescence from the ionized atoms.

In some embodiments, an interferometric frequency reference provides an optical frequency reference. In some embodiments, an interferometric frequency reference provides a microwave frequency reference.

Other variations of the invention provide a method of generating a stable frequency reference, the method comprising:

(a) Generating atomic vapor;

(b) Ionizing at least some of the atoms in the atomic vapor to form ionized atoms;

(c) Collimating the ionized atoms in an ion collimator to form a collimated beam of ionized atoms;

(d) Optionally, irradiating some of the ionized atoms with a cooled laser;

(e) Irradiating at least some of the ionized atoms with a first probe laser at a first probe laser frequency;

(f) Irradiating at least some of the ionized atoms with a second probe laser at a second probe laser frequency;

(g) Adjusting the first probe laser frequency and the second probe laser frequency to an s→d transition of at least some of the ionized atoms using a lamb Ji Guangpu method; and

(h) At least some of the ionized atoms are irradiated with a readout laser to determine the ground state population of the ionized atoms.

In some methods, the atomic vapor and/or ionized atoms are obtained from a solid state electrochemical atomic source. In some embodiments, the ionized atoms may be Ca ⁺ And/or Sr ⁺ 。

The ionized atoms provided in step (b) may be formed within the ion collimator provided in step (c). Alternatively, or in addition, ionized atoms provided in step (b) are formed and then injected into the ion collimator. Steps (b) and (c) may be integrated such that at least some of the ionization occurs inside the ion collimator. In some preferred embodiments, steps (b) and (c) may be integrated such that all ionization occurs inside the ion collimator.

In some methods, step (d) is performed to cool the ionized atoms in preparation for the lamb Ji Guangpu method. The cooling may be the same laser as the read-out laser (in this case also the cooling laser) or the cooling may be a physically different laser.

In some methods, the ion collimator is a linear collimator. For example, the ion collimator may be a linear collimator selected from the group consisting of a linear quadrupole trap, a penning trap, a surface ion trap, and a mass filter. In other methods, the ion collimator is a non-linear collimator. For example, the ion collimator may be a non-linear collimator selected from the group consisting of a racetrack configuration, a ring, a curved loop, or other recirculating configuration.

The collimated beam of ionized atoms may have a beam waist selected from about 10 nanometers to about 10 meters, such as from about 50 nanometers to about 500 nanometers. The collimated beam of ionized atoms may have a beam velocity selected from about 1 μm/s to about 0.99c, such as from about 1m/s to about 20m/s, where c is the speed of light in vacuum.

In some embodiments, the method further comprises irradiating at least some of the ionized atoms with a third probe laser. In certain embodiments, the method further comprises irradiating at least some of the ionized atoms with a fourth probe laser after irradiating at least some of the ionized atoms with the third probe laser.

In a preferred embodiment, the method is continuous, utilizing a continuously moving atomic beam (rather than a fixed, trapped atom) and a continuous wave laser array with continuous interrogation. Continuous referencing of atoms as the atom beam passes through a series of laser beams allows for direct rapid locking of the atom transitions. The use of optical transitions produces a higher resonant quality factor than RF transitions. The result of the continuous method is a continuous fast readout of the optical transitions, which is a significant benefit for next generation timing solutions.

In some methods, the stable frequency reference is an optical frequency reference. In some methods, the stable frequency reference is a microwave frequency reference.

Some methods utilize an interferometric frequency reference that includes the following: a vacuum chamber; an atomic source configured to supply neutral atoms to be ionized; an ionizer configured to excite neutral atoms to form ionized atoms; an ion collimator configured to form a collimated beam of ionized atoms; one or more probe lasers; and a readout laser configured to determine a ground state population of ionized atoms, wherein the atomic source, the ionizer, and the ion collimator are disposed within the vacuum chamber.

Drawings

Fig. 1A is a schematic cross-sectional view of a linear quadrupole trap configured with rods.

Fig. 1B is a schematic cross-sectional view of a linear quadrupole trap configured with vanes.

Fig. 2 is a top view of a linear ion collimator in some embodiments.

Fig. 3 is a top view of a non-linear ion collimator in some embodiments.

Fig. 4 is a schematic diagram of an interferometric frequency reference in some variations.

Fig. 5 is a method flow diagram in some embodiments.

Detailed Description

The apparatus, method and system of the present invention will be described in detail with reference to various non-limiting embodiments.

The description will enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention. These and other embodiments, features, and advantages of the present invention will become more readily apparent to those of ordinary skill in the art when taken in conjunction with the following detailed description of the invention.

As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Unless otherwise indicated, all numbers expressing conditions, concentrations, dimensions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon at least the particular analytical technique.

The term "comprising" synonymous with "including", "containing", or "characterized by" is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. "comprising" is a term of art used in claim language that means that the specified claim elements are necessary, but other claim elements may be added and still constitute concepts within the scope of the claims.

As used herein, the phrase "consisting of … …" does not include any elements, steps or components not specified in the claims. When the phrase "consisting of … …" (or variants thereof) appears in the clauses of the claim body, rather than immediately following the preamble, the phrase merely limits the elements set forth in that clause; other elements are not excluded from the claims as a whole. As used herein, the phrase "consisting essentially of … …" limits the scope of the claims to the specified elements or method steps, plus those that do not materially affect the basis and one or more novel characteristics of the claimed subject matter.

With respect to the terms "comprising," "consisting of … …," and "consisting essentially of … …," when one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms. Thus, in some embodiments not explicitly recited otherwise, any instance of "comprising" may be replaced by "consisting of … …" or alternatively "consisting essentially of … …".

In some variations, the present invention provides an ion-based frequency reference that provides an optical frequency standard with extremely high level stability and fast, continuous readout in a compact package. The present invention is based, at least in part, on a lambda-bird (Ramsey-bordete) interferometer. A lambda-bode interferometer involves a linear flow of atoms detected by a well-defined sequence of oscillating fields. In the present invention, instead of using thermally neutral atoms, a cooled collimated stream of guided ions is employed. Ions may be directed by a specially designed Radio Frequency (RF) penny trap or a mass filter designed precisely for this purpose. By employing a cooled, controlled ion flow, a combination of features not available to any other frequency reference can be achieved: (i) very low fractional frequency instability, (ii) fast, continuous readout, (iii) compact size due to reduced atomic velocity, and/or (iv) reduced vacuum requirement due to deep well depth.

To the best of the inventors' knowledge, the lambda-bird interferometry on cooling ion streams has not been achieved to date. As described herein, a cooling ion stream is subjected to a lambda-bird interferometry with a high signal-to-noise ratio by utilizing an ion collimator (such as a modified RF-verve trap/mass filter) that collimates the cooling ions and confines them in a one-dimensional stream. In this disclosure, "trap/filter" is synonymous with "ion collimator". The trap/filter is configured to optimize fractional frequency instability and size, weight and power of the device. The trap/filter controls the ion propagation velocity, thereby significantly reducing the size requirements, doppler error and transit time error. The trap/filter also provides a deep trapping potential to relax the vacuum requirements.

In this disclosure, "frequency reference" is synonymous with "interferometric frequency reference" or similar terms.

The stability and ultimate size of conventional lambda-bode interferometers are limited by doppler contributions to errors (first and second order) and the broadening of the atomic species with respect to the transit time of the laser beam. Historically, lambda-bird spectroscopy used an array of four lasers with neutral atomic beam transitions. According to the present invention, neutral atom beams used in historical implementations are replaced with collimated ion beams. The applied electric field of the trap/filter allows for precise speed control, as well as controlled ion density and spacing. The novel ion beam use can significantly reduce the Doppler broadening and the lambda-bird transit time broadening suffered by conventional neutral atom methods. The controlled ion beam velocity may also be such that long lambda-bird transit times are achieved without sacrificing size and power requirements.

To date, atomic-based frequency references (both RF and optical) employ trapped atoms whose transitions are detected via low duty cycle (on the order of Hz), long integration time spectroscopy. Each pulse sequence can only necessarily make one reference to an atom, resulting in very slow feedback of atoms, on the order of seconds. In contrast, the present invention preferably utilizes a continuously moving atomic beam (rather than a fixed, trapped atom) and a continuous wave laser array with continuous interrogation. Continuous referencing of atoms as the atom beam passes through a series of laser beams allows for direct rapid locking of the atom transitions. The use of optical transitions produces a higher resonant quality factor than RF transitions. The result of the continuous method is a continuous fast readout of the optical transitions, which is a significant benefit for next generation timing solutions.

The frequency references disclosed herein are achieved by generating ultra-narrow linewidth lasers. A frequency reference may be used to lock the laser source for precision sensing/timing applications. The frequency reference may be used as an ultra-stable optical frequency reference to which an external laser may be locked via a standard beat-lock (beat-lock) for use by other optical, quantum, metrology, or communication instruments.

In some variations, the present invention provides a field-compatible (e.g., about 10cm long) interferometric frequency reference that has competitive stability with conventional atomic clocks, can operate at shorter average times, and has a drift impedance that is greater than the cryogenic optical cavities of the prior art.

The disclosed device (interferometric frequency reference) can fill the gap of a conventional stable oscillator, while having other applications realized by realizing an ultra-stable laser. One application is precision sensing. An example of precision sensing is legal seismology using submarine fiber-optic cables for remote explosion detection, where conventional seismometers are not available or practical.

In some variations, the present invention provides a compact frequency reference with low fractional frequency instability (low alembic) and fast continuous readout. The alembic variance is the most common statistical function used to characterize and classify frequency fluctuations of frequency references. See alan, statistics of Atomic Frequency Standards [ statistics of atomic frequency standards ], PROCEEDINGS OF THE IEEE [ institute of electrical and electronics engineers ] volume 54, phase 2, 1966, which is incorporated by reference. The alembic bias ("ADEV") is the square root of the alembic variance. ADEV is used to characterize random deviations related to noise in frequency. While there are other ways to define the fractional frequency instability, including a modified alembic bias, in this disclosure, "fractional frequency instability" means the above-defined unit-free alembic bias, ADEV.

In various embodiments, the present invention provides a number of benefits over prior art optical frequency references. Unlike a cavity that is a passive optical resonator, the frequency reference is substantially limited only by atomic characteristics and thus can be averaged over a long period of time. Thus, the limit of fractional frequency stability is about 10 as dictated by quantum physics ^-18 Basic stability limit of (ADEV).

The frequency references disclosed herein do not require cryogenic operation or any cryogenic components.

Unlike conventional optical clocks, the frequency reference has a fast readout without the need for system calibration.

In the case of cooling atoms, the propagation length of the atomic beam may be reduced proportionally when the beam size is set by the velocity of the atoms relative to the intrinsic atomic quadrupole linewidth.

By using trapped ions instead of neutral atoms, a higher degree of control over the atomic velocity distribution can be achieved. Exemplary ion trap/filter geometries include linear filter and racetrack trap geometries. The linear filter is conceptually simpler, while the racetrack trap geometry can eliminate residual doppler broadening and can be used to shut off the atomic source for recycling ions.

The conventional frequency reference with the lowest fractional frequency instability to date is an optical atomic clock. They maintain fractional frequency instability at 10 ^-18 World records on the order of magnitude. However, the extreme complexity and huge size/weight/power requirements disqualify an optical atomic clock for practical deployment.Furthermore, optical atomic clocks require that their lasers be locked to large (about 40cm long) or cryogenic optical cavities. The laser lock narrows the laser linewidth and provides an electromagnetic source (laser) as a stable optical oscillator. However, the optical cavity is large, operates at its fundamental limit, and cannot achieve long-term stability sufficient to achieve independent operation without an optical atomic clock. There have been some demonstrations of atomic-based frequency references, but they are physically large because their size is set by atomic velocity distribution and/or cryogenic operation. Any attempt to miniaturize laboratory-scale optical atomic clocks must address the requirements of optical frequency references for operation.

Most field-enabled frequency references are high-quality-factor radio frequency cavities-e.g., an oven-controlled crystal oscillator (OCXO) -that interface with standard electronics. While attractive in terms of size/weight/power requirements, such frequency references are based on materials such as quartz that experience long-term drift and cannot be stabilized in the need for long-term stability (adev≡10) ^-10 -10 ^-13 ) Is used in the case of (2).

For applications requiring timing and long term stability over OCXOs while maintaining deployability (e.g., global positioning system applications), a warm radio frequency atomic clock is used. However, these clocks are still complex, requiring their own separate precision oscillators to read them, which is limited to very long time scales. Subsequently, chip-scale atomic clocks are almost always paired with their own highly stable frequency references. However, their performance on a short time scale is still at adev≡10 ^-13 And is improved only on a long time scale such as over 100 seconds.

In a preferred embodiment, a significant difference between the disclosed frequency references compared to prior art lambda-bird interferometers or atomic clocks is that thermally neutral atoms in the interferometer or cold trapped atoms in the clock are replaced by a continuously moving ion beam.

Another significant difference from conventional techniques is that in the preferred embodiment, the disclosed frequency reference replaces the pulsed laser (in a clock) with a series of spatially separated continuous wave lasers. By implementing a lambda-bird interferometer in a guided ion (collimation) system, a continuous beam of atoms is used for fast readout while avoiding the problem of velocity distribution of neutral atoms.

Another difference from conventional techniques is that in the preferred embodiment, the disclosed frequency references greatly relax the requirements for complex cooling procedures. The frequency reference is preferably cooled with a minimum of laser light and then ions are trapped/guided in a deep Radio Frequency (RF) potential field. The RF-paul trap can be used to fabricate deeper traps than the typical magnetic field traps required for neutral atoms. Furthermore, the deep RF-vero trap allows to control the propagation speed. The preferred method uses only radio frequency and direct current fields and therefore requires fewer lasers. The disclosed frequency references are compatible with integrated solid state paths and are easier to miniaturize.

a vacuum chamber;

an atomic source configured to supply neutral atoms to be ionized;

An ion collimator configured to form a collimated beam of ionized atoms;

one or more probe lasers; and

a readout laser configured to determine a ground state population of ionized atoms,

In some embodiments, the atomic source is a solid state electrochemical atomic source. Integration with a solid state electrochemical atomic beam source can reduce size, weight, and power because the frequency reference is smaller, more power efficient, and provides a collimated beam (when compared to conventional atomic furnaces).

In some embodiments, the ionizer is disposed inside the ion collimator. In these embodiments, ionized atoms are formed within the ion collimator. In other embodiments, the ionizer is disposed outside the ion collimator. In these embodiments, ionized atoms are formed and then implanted into an ion collimator.

In some embodiments, the ion collimator is a linear collimator. For example, the linear collimator may be selected from the group consisting of a linear quadrupole trap, a penning trap, a surface ion trap, and a mass filter. Fig. 1A is a schematic cross-sectional view of a linear quadrupole trap configured with rods. Fig. 1B is a schematic cross-sectional view of a linear quadrupole trap configured with vanes. Fig. 2 is a top view of a linear ion collimator in some embodiments.

In other embodiments, the ion collimator is a non-linear collimator. The non-linear collimator may be in a recirculating configuration, such as a racetrack configuration (see, e.g., fig. 3), a loop, or a curved loop. Fig. 3 is a top view of a non-linear ion collimator in some embodiments.

In some embodiments, the one or more probe lasers are configured to perform a lamb Ji Guangpu method on ionized atoms. In a preferred embodiment, all probe lasers present are configured to perform the lamb Ji Guangpu method on ionized atoms. The number of probe lasers may vary, but is preferably two or more, such as four probe lasers (see, e.g., fig. 4).

In some embodiments, the readout laser is a doppler laser configured to make quantum transition measurements via fluorescence from the s→p cycle transition after a lambda probe to determine the ground state population.

The interferometric frequency reference may further comprise an ion sink configured to collect ionized atoms exiting the ion collimator. The ion sink (if present) is preferably arranged within the vacuum chamber.

The interferometric frequency reference preferably further comprises an imaging system configured to focus fluorescence from the ionized atoms. The imaging system may include an optical lens or a system of lenses, a camera, a photomultiplier tube, and/or a photon bucket detector.

Fig. 4 is a schematic diagram of an interferometric frequency reference in some variations. The frequency references shown in fig. 4 include vacuum chambers, atomic sources, ionizers, ion collimators, injection electrodes, ion clusters, four probe lasers, doppler lasers (typically readout lasers), and imaging systems. The injection electrode and imaging system are optional components.

In certain embodiments, an interferometric frequency reference precursor instrument is provided that has no vacuum chamber. At a later time, the precursor instrument is placed in a vacuum chamber. Prior to being disposed within the vacuum chamber, the interferometric frequency reference precursor instrument comprises:

an atomic source configured to supply neutral atoms to be ionized;

An ion collimator configured to form a collimated beam of ionized atoms; one or more probe lasers; and

a readout laser configured to determine a ground state population of ionized atoms.

(a) Generating atomic vapor;

(d) Optionally, irradiating some of the ionized atoms with a cooled laser;

Fig. 5 depicts a method flow diagram in some embodiments. The steps of irradiating the ions with a cooling laser, irradiating the ions with a third probe laser, and irradiating the ions with a fourth probe laser are optional. The readout laser may be a doppler laser. The step of irradiating ions with a doppler laser (or other read-out laser) may be performed before or after the step of adjusting the frequency of the probe laser using the lamb Ji Guangpu method.

In some methods, atomic vapors and/or ionized atoms are obtained from the solidA source of electrochemical atoms in a state. In some embodiments, the ionized atoms may be Ca ⁺ And/or Sr ⁺ . The solid state electrochemical atomic source is described in more detail later in this detailed description.

Some variants will now be further described in more detail, it being understood that this description is non-limiting and that the invention is not limited by any assumptions or theories.

An interferometric frequency reference is a device that lambda-interrogates a collimated ion beam to directly and rapidly feedback lock onto an ultra-stable laser. Referring to fig. 4, components and optional components are shown.

The vacuum chamber houses an atomic source, an ion sink, an ionizer, and an ion collimator, such as a modified RF ion paul filter/trap. Since the ions are collimated, rather than being trapped themselves, the requirement for ultra-high vacuum (to reduce background collisions) is relaxed compared to conventional ion trapping. The vacuum level may be medium, such as at about 10 ^-5 To about 10 ^-8 A chamber pressure in the range of the torr. The laser array and imaging system can be placed inside or outside the vacuum chamber, depending on whether these components are compact. The vacuum chamber may be a standard off-the-shelf (e.g., stainless steel) chamber, or may be a vacuum chamber customized, for example, from stainless steel, aluminum, borosilicate glass, aluminosilicate glass, sapphire, or a combination thereof.

The atomic source supplies a stream of neutral atoms to be ionized. The neutral atom stream is in a gas phase containing atoms. The atomic source may be positioned at or near the entrance of the ion collimator. For example, the atomic source may be a separate chamber with a conduction confinement whose pore size is close to the ionizer, a SAES distributor, a pill distributor (pill distributor), an alpha source distributor (alfasource dispenser), a liquid or solid phase of atoms (possibly mixed with other species), a LIAD (light induced atomic desorption) source, a graphite (or other) intercalation compound of atoms, or an electrochemical solid state source. For examples of electrochemical Solid state atomic sources that may be used in the frequency references herein, see section of this specification later entitled Solid-State Electrochemical Atom Sources Solid state electrochemical atomic sources. The neutral atoms to be ionized may be selected from the group consisting of Ca, sr, yb, li, na, K, rb, cs, hg and combinations thereof, for example. In some embodiments, the atoms are Ca and/or Sr, as single electron ionization of calcium or strontium produces hydrogen ions with broad cyclic dipole transitions and narrow quadrupole transitions (both of which are easily addressed by commercial lasers). The atomic species may be isotopically enriched with respect to its natural isotopic abundance.

The ionizer excites neutral atoms, facilitating the passage of valence electrons from atoms to the continuum and leaving behind ions, such as hydrogen ions. The ionizer may employ photoionization, i.e., ionization produced by the action of electromagnetic radiation (e.g., optical radiation). Some embodiments employ two-photon optical ionization, where ECDL (external cavity diode laser) is tuned to the electric dipole transition of a neutral atom (s→p), exciting a valence electron from the S ground state to the P excited state. From there, the second ECDL promotes P-state electrons to the continuum. The two laser beams are preferably focused near the entrance of the ion collimator. Optical ionization allows isotope selection: the first ECDL can be frequency tuned to selectively ionize one of a plurality of naturally occurring isotopes in an atomic sample (typical isotope displacements are large, on the order of ghz—easily addressed by MHz wide lasers). Frequency tuning can be accomplished by locking a loose, easily retrofitted DAVLL (dichroic atom vapor laser lock) to a vapor cell filled with neutral atoms. The second ECDL does not need to be frequency stabilized at all. The disadvantage of this approach is that a dedicated ionization laser (the first s→p laser) is required. Second, a p→continuum laser can be used simultaneously as the readout laser.

Alternatively, or in addition, the ionizer may employ electrodeionization. In the case of electrodeionization, small current-carrying filaments can be placed near the neutral atom beam exiting the atom source to excite the valence electrons directly into the continuum. While this technique eliminates the need for a dedicated ionization laser, it is not selective for certain isotopes. Thus, if the desired frequency reference utilizes isotopically enriched atoms, an isotopically enriched atomic source would be required. Electrodeionization is often the preferred ionization technique when size, weight, and power requirements are prioritized.

An ion collimator (trap) is used to collimate ionized atoms into a one-dimensional, velocity-controlled beam. The collimated beam travels along the length of the well, passing through a series of spatially separated lasers for cooling, lamb Ji Tanxun and readout. The ion collimator may be a modified RF ion filter. In some embodiments, the ion collimator contains an ionizer within the ion collimator. In other embodiments, the ion collimator receives ions that are individually generated by an ionizer that is physically disposed outside the ion collimator.

Many geometries of ion collimators may be used. The linear collimator may be a modified RF ion filter with four parallel (e.g., tungsten) rods (fig. 1A) or vanes (fig. 1B). Two of these rods/blades support MHz RF, such as supplied by an amplified RF function generator, while the other two rods/blades remain under Direct Current (DC), connected to a digital-to-analog converter. This standard configuration provides longitudinal trapping (x, y) ensuring that the ion beam remains collimated into a one-dimensional axial crystal (z). The DC rods may be segmented (with different DC voltages) to provide control of the axial transport of the ion beam. In this way, the ion beam can be continuously transported along the collimator with a well controlled velocity profile. This speed control is very beneficial when the frequency reference is an ultra-narrow frequency reference.

Unlike conventional RF ion traps, the linear collimator preferably does not include a DC end cap that would cause harmonic axial trapping. Instead, the ion collimator produces a slowly moving ion beam that is not trapped in all three dimensions. The linear design of the ion collimator may be similar to an ion-based filter, which typically operates in a high vacuum range. However, since long trap lifetimes are not required, vacuum levels can be relaxed compared to typical ion traps.

The rods/blades of the ion collimator may be machined and aligned in a (e.g., macor) support structure, such as byThe structure manufactured by glass-ceramic (corning corporation (Corning Incorporated), corning, new york, united states) may be machined. The rods/blades may be made of metal in strips deposited on the walls of hollowed out, machined (e.g. laser machined) parts such as pieces of fused silica. Typical dimensions of the Macor structure are about 30cm by 10cm, and typical dimensions of the laser machining system are about 10cm by 3cm by 1mm. Smaller laser machining designs are preferred if stability and simplicity are priorities.

The ion collimator may be a non-linear collimator, such as a racetrack collimator. A racetrack collimator (see fig. 3) essentially bends the linear collimator and connects the ends together to form a racetrack shape. In this configuration, the remaining Doppler shift can be offset by interrogating two ion beams of opposite momentum. A racetrack collimator, or other recirculation configuration, may utilize a commercial ion pump to maintain the vacuum. Ion collimators with recirculation configurations provide long atomic source lifetimes.

Ions exiting the ion collimator may be collected by ion clusters for recycling. Ion sinks are optional components that may be particularly beneficial in the case of linear collimators. An ion sink may be positioned on the output port of the ion collimator to collect the ion beam after use. The ion sink may be an electrochemical solid state atomic sink, which may be similar to an electrochemical solid state atomic source but designed to act as an atomic sink. In some embodiments, the atomic source is reused as an ion sink, which can significantly increase the lifetime of the device. For example, when the atomic source is exhausted, the ion sink may be reused as a new source, directing the atomic beam in the opposite direction along the ion collimator. The ion beam may then be collected by the original atomic source (which is now itself reused as the ion sink).

Other implementations of atomic sinks include, but are not limited to, graphite intercalation compounds, mixtures of atomic species with alkali or alkaline earth metals, or cold surfaces. An atomic sink, once it contains a high amount of absorbed, adsorbed, or intercalated atoms, may be heated to release the atomic species of interest. The initial atomic source may be cooled to convert it to an atomic sink, reversing the flow of atoms and ions, allowing the atoms to be reused, and allowing longer equipment life and/or smaller atomic source size.

The laser array includes an optional cool laser, one or more probe lasers, and a doppler laser that acts as a readout laser. The laser array is preferably arranged orthogonal to the direction of propagation of the ions. The laser array is configured to sequence the ion beam with a lamb Ji Tanxun as the ions pass through the ion collimator.

A doppler laser, or other cooled laser, may be used to initialize the ion beam to the S state in preparation for the lamb Ji Tanxun. The doppler laser cools the ion beam to a doppler limit (e.g., a temperature of about 70 mK) and enters a Lamb-dick state where the first order doppler shift can separate into moving sidebands, with a slight red detuning with respect to the s→p electrical dipole transition of the ion (a broad cyclic transition with high scattering rate). The laser may be a medium power (a few mW) compact External Cavity Diode Laser (ECDL) that is locked to prevent accidental blue detuning heating of the ions. For this purpose, a small commercial cavity with a round-Drever-Hall (PDH) lock may be used. Depending on the atomic species selected, one or more red wavelength re-pump lasers may also be utilized to keep the ions in a doppler cooling cycle. Such re-pumped lasers have even more relaxed power and locking requirements; an inexpensive Distributed Feedback (DFB) laser can be used, locked to only the slow wavemeter.

The probe laser is locked to a narrow transition in the ion via optical lamb Ji Guangpu method. At Ca ⁺ Or Sr ⁺ In the case of (a), the narrow transition is an approximately Hz wide electrical quadrupole s→d transition. Quadrupole transitions are clock transitions that do not emit light very well, have long coherence, and have a high quality factor (Q). To perform spectroscopy with sufficient accuracy to resolve the lamb Ji Tiaowen pattern, the laser is preferably pre-stabilized, locked to the super via the PDHThe low expansion (ULE) cavity narrows to about kHz laser linewidth. It should be noted that the cavity need not be narrowed to the mHz laser linewidth. To scan the laser frequency, a small amount of tuning (kHz of 100 s) is achieved by directing the probe laser beam (after locking) through an acousto-optic modulator (AOM).

Table 1 below lists the Sr used in the exemplary embodiment ⁺ And Ca ⁺ Cooling/detection of ions, quadrupole transitions and laser wavelength of re-pumping.

	Sr ⁺	Ca ⁺
			Cooling/inspection	421.7nm	396.8nm
Re-pump 1	1091.5nm	866.2nm
			Re-pump 2	1033nm	729nm
Quadrupoles	674nm	854nm

Table 1: the laser wavelengths of strontium and calcium ions used in the interferometric frequency reference.

Both lamb Ji Hela sequences of the lambda-bode spectra can be used for operation of the device. A lambda sequence may be understood as consisting of only the first two pulses from a lambda-bode pulse sequence. The lambda-bode spectral sequence is now described in detail as seen by the ions in their own frame of reference as they pass through the array of continuous wave lasers. In the reference frame of the ion, the sequence consists of four coherent pi/2 pulses, all preferably at the same frequency.

(1) The first pi/2 pulse facilitates coherent addition of ions from the S-state to the S-and D-states. After this pi/2 pulse, the ions evolve freely over a period of time τ, which may be referred to as the lambda interrogation time. If measured in a rotating reference frame during this time, the phase delay between the local oscillator (probe laser) and the rotation of the state vector in the bloch sphere will develop if and only if the probe laser is detuned from the atomic transition.

(2) The second pi/2 pulse is pulsed at the end of the lambda probe time tau. Depending on the phase delay obtained during the interrogation time, the ions will either return to the ground state S with a well-defined probability or will be excited to the D state.

(3) The third pi/2 pulse is a counter-propagating pulse that excites ions with a small delay T after the first lambda interrogation time. The pi/2 pulse causes the atoms to again become a coherent superposition of S and D states during time t. However, a phase is now obtained that is negative with respect to the first interrogation time τ. This excites the echo, effectively eliminating low frequency dephasing from unwanted noise sources. This is a well known technique, commonly referred to as stimulated photon echo, which is an optical simulation of stimulated spin echo. Preferably, it is ensured that τ=t for all measurements.

Preferably, the first, second and third pi/2 pulses maintain maximum phase coherence. Otherwise, the phase jitter of the probe laser relative to the ion beam-physically moving the laser output due to acoustic vibration and possibly causing doppler shift-can significantly reduce the lambda Ji Tiaowen contrast. Thus, in a preferred embodiment, the phase stability of the laser beam path is actively stabilized via a small Mach-Zehnder (MZ) beam splitter interferometer.

(4) The fourth and last pi/2 pulse converts the ion to either the S or D state. The probability of becoming excited (D-state) or unexcited (S-state) is determined by the phase obtained during the time of the lambda Ji Tanxun (τ, t). As population status, readout is determined by measuring fluorescence achieved by a cyclic/doppler laser. Since the likelihood of being in the S or D state is in part a function of the detuning of the probe laser from atomic transitions, scanning the probe laser frequency via the post-lock AOM discussed above results in the occurrence of a lambda stripe to which the probe laser can be locked Ji Tiaowen (the locking electronics discussed below).

In some embodiments, the velocity profile of the ion beam is similar to a delta-function (delta-function-like) to ensure a constant lambda interrogation time τ from ion to ion, thereby minimizing loss of lambda Ji Tiaowen contrast. It should also be noted that the stripe feature has a width of 1/τ, so τ is preferably as long as possible, limited by the decoherence time and readout speed, as well as the lock-in bandwidth. The speed control of the ion beam provided by the ion collimator is a substantial benefit.

A readout laser is employed to make quantum transition measurements to determine the number of ground state population after a lambda interrogation. The readout laser may be the same doppler laser used for cooling via beam splitting, or may be a different doppler laser. Quantum transition measurement utilizes fluorescence from the s→p cycling transition. If the measurement collapses the wave function of the ion to the S ground state, the ion will cycle over the S→P transition and will fluoresce. Otherwise, if the wave function collapses to the excited D state, the ions will be outside the cycling transition and in the dark state. Repeated fluorescence measurements using an imaging system quickly give a measure of the probability of successful quantum transitions.

The imaging system includes a photomultiplier tube (PMT) and a lens to focus the ion fluorescence onto the PMT aperture. The readings may be taken as an average of the ions as they pass, or a single pass (ion-by-ion) of the photons arriving as they pass using a field programmable gate arrayAnd (5) gating. Eventually, the ion velocity and spacing will set the readout time, as well as the scattering rate of the cycling transitions. The estimated readout time can be realized by the following equation. Consider the time of ion passage through an ion filter. This is defined by T _a1 ＝d _RB /V _Atoms Given, wherein d _RB Is the well length and V _Atoms Is the velocity of the ion beam. Subsequently, it is necessary at time T _a2 ＝d _RB /V _Atoms +d _Atoms /V _Atoms Reading a second ion immediately after the first ion, wherein d _Atoms Is the atom-atom spacing. Thus, the measurement update time is defined by T _m ＝d _Atoms /V _Atoms The setup, i.e. it is the time between successive ion-ion measurements. The upper limit of the measurement time/bandwidth can be found by considering a 7.62-cm-long ion trap and a speed of 76 m/s-this corresponds to T _m =65 nanoseconds, a rate of about 15MHz (1/T _m ). This would be the fastest rate at which the laser linewidth can be updated for readout. It should be noted that for Ca ⁺ And Sr ⁺ The cyclic transition linewidth is about 20MHz. Finally, having a faster ion-ion update rate of over about 20MHz has no benefit, as the fastest rate at which individual ions can be read out is essentially set by that rate.

The interferometric frequency reference is preferably configured with locking electronics for frequency locking, with PID-proportional (P), integral (I) and derivative (D) feedback control. A conventional op-amp with a feedback loop can be used to keep the probe laser frequency locked to one side of the lamb Ji Tiaowen. The lamb Ji Tiaowen width is set by 1/τ and the narrower the stripe, the tighter the lock (and thus the narrower the locked laser). However, the stripe must not be so narrow that the locking range is narrow, which may be easy to unlock. The input to the feedback loop may be an error calculated as the reading minus the set point, where the reading is the measured, calibrated quantum transition probability determined by the readout laser, and the set point is determined on-line (in-circle). The output of the feedback loop may be P x error + I, where I is the integral of the error as a function of time. Feedback is transmitted to the acousto-optic modulator described above. In some embodiments, feedback is also transmitted in part to the probe laser, depending on the type of laser.

The interferometric frequency reference may comprise a residual amplitude modulation feedback system. The interferometric frequency reference may be configured to stabilize or polarize input light to an electro-optical modulator (EOM).

The interferometric frequency reference is described primarily as an independent optical frequency reference. If the desired operation is for an ultra-stable microwave frequency source, a high repetition rate frequency comb (e.g., 10 GHz) is preferably locked to an ultra-stable narrow linewidth laser using a similar PID lock as disclosed above. Locking the comb line to the ultra-narrow linewidth transfers the stability of the narrow linewidth laser to the frequency comb. In a fully self-referencing system, the rate at which about 200 femtosecond pulses of the frequency comb emanate from the laser (a rate of about 10 GHz) is locked with the stability of the optical reference. Detecting these pulses on the photodiode creates an ultra-stable microwave frequency reference. Frequency combs can be purchased commercially for this purpose. Alternatively, two or more devices (as disclosed herein) may be used for frequency transfer. In some embodiments, the microwave frequency reference is generated by beating two separate devices against each other. The resulting beat note may have a relative stability of the optical frequency reference.

The invention is applicable to portable atomic instruments, sensors and lasers. Current electronic warfare systems would benefit from a highly stable local oscillator, which would enable the analog-to-digital converter to operate at higher frequencies and at more bits. Similarly, radar systems benefit from lower local oscillator noise, enabling detection of slow moving objects and use of SAR on higher or geosynchronous orbits. In addition, ultra-narrow lasers for remote legal seismology (explosion detection) using fiber optic cables below water are needed.

Interferometric frequency references can be manufactured in a wide variety of sizes, such as, for example, from about 1cm ³ To about 100cm ³ Is used for the total equipment volume of the equipment. In some embodiments, the interferometric frequency reference has a size of less than 100cm ³ Less than 10cm ³ Or less than 1cm ³ 。

The interferometric frequency reference may operate according to the following examples, which are in no way limiting.

In one example, the interferometric frequency reference and its output are considered to act as a "black box" for the ultra-stable laser. Ultrastable lasers have a variety of applications in timing, sensing, and spectroscopy.

In another example, an interferometric frequency reference is utilized for generating the RF timing. Two or more devices may be used to generate the RF clock by beating the output lasers to each other. The beat note will then contain the relative stability of the two devices, down-converted to radio frequency.

Another method for generating an RF clock may be achieved by locking an optical frequency comb to an ultra-stable laser. In this case, the repetition rate of the frequency comb is used as an RF clock, wherein the stability of the ultra-stable laser translates into a stability of the comb repetition rate.

The interferometric frequency reference may be used as a stable clock. On a satellite, submarine, or other vehicle, the stable clock allows secure communications for long periods of time (years), even in a GPS-refused environment. This is in contrast to existing prior art secure communications, which are only on the timescale of a few minutes.

For space-based radars, the disclosed interferometric frequency reference-operating as a stable clock-is capable of (i) identifying slow moving targets, (ii) removing clutter from radar echo signals, (iii) having the ability to geosynchronous Synthetic Aperture Radars (SAR) with millimeter resolution, and (iv) longer integration times of SAR satellites.

The disclosed interferometric frequency reference may be an ultra-stable laser in an optical atomic clock. In an optical atomic clock, an ultra-stable laser is a key component for miniaturization of the optical atomic clock. The ultra-stable laser replaces the low temperature cavity used to generate stable laser light in prior art optical clocks.

The disclosed interferometric frequency reference may be an ultrastable laser in spectrometry. In spectroscopy, an ultrastable laser provides a tool to study various narrow radioactive elements (nuclear transitions) by transferring its stability to another laser. Thus, the devices disclosed herein may be used for nuclear material status experiments. In addition, in spectroscopy, an ultra-stable laser locked to an atomic reference may act as an absolute frequency calibration source in connection with future astronomical experiments.

Solid state electrochemical atomic source

Some variations utilize an atomic beam source apparatus as a solid state electrochemical atomic source, wherein the atomic beam source apparatus comprises:

a first electrode;

a second electrode electrically isolated from the first electrode; and

a first ion conductor interposed between the first electrode and the second electrode, wherein the first ion conductor is capable of transporting metal ions, and wherein the first ion conductor is in contact with the first electrode and the second electrode.

The atoms emitted from the atomic beam source device (as atomic vapor) may be alkali metal atoms, alkaline earth metal atoms, rare earth metal atoms, mercury, or combinations thereof. For example, the metal atom may be selected from the group consisting of Rb, cs, ca, na, K, sr, li, yb, hg and combinations thereof. Other metal atoms may be emitted from the atomic beam source device, including, for example, si, ga, al, in, as, sb, ge, sn, pb, mg, ba, te, au, pt, cr and Cd.

A voltage may be applied to the source atoms on two electrodes located on opposite sides of the first ion conductor for a given duration. The voltage polarity may be switched such that the atomic beam source device becomes an atomic sink. The voltage amplitude is selected to control atomic flux.

In various embodiments, the applied voltage between the two electrodes is from about 0.01V to about 100V, such as from about 0.1V to about 10V. The device power input for obtaining metal atoms is preferably less than about 500mW, more preferably less than about 200mW, and most preferably less than about 100mW.

An "electrode" is a region that is electrically conductive or includes one or more material phases that are electrically conductive in nature. The first electrode allows conduction of electrons and is in contact with a first ion conductor (discussed below). The first electrode allows for (a) conduction of the same ionic species as conducted by the first ionic conductor, (b) diffusion of reduced forms of the same ionic species as conducted by the first ionic conductor, or both (a) and (b).

In some embodiments, the first electrode is a porous conductive structure. In some embodiments, the first electrode is a selectively permeable conductive layer. See, for example, U.S. patent No. 10,545,461 to Roper et al, which is incorporated herein by reference. In this patent application, "selectively permeable" refers to the transport of metal atoms through an electrode (by diffusion or conduction). In some embodiments, the first electrode is a mixed ion-electron conductor. See, for example, U.S. patent No. 10,828,618 to Roper et al, which is incorporated herein by reference.

The first electrode is preferably a porous conductive layer. The porous conductive layer is preferably a patterned metal layer directly on one surface of the first ion conductor. The metal layer is preferably thin, such as less than 1 micron thick, more preferably less than 200 nanometers thick or less than 100 nanometers thick. The pattern of the metal layer is preferably such that the metal area pitch is small, such as less than 100-micron line pitch, more preferably less than 10-micron line pitch, and most preferably less than 2-micron line pitch. The metal layer may be patterned using photolithography, electron beam lithography, direct write metal deposition (e.g., ion beam induced deposition), interference lithography, and the like.

Exemplary electrode materials for the porous conductive layer include Pt, mo, W, ni, cu, fe, al and combinations thereof. The porous conductive layer may also require more than one layer, such as a Ti adhesion layer and a Pt layer.

The porous conductive layer preferably does not chemically interact with the ionic species conducted by the first ionic conductor. For example, the porous conductive layer preferably does not form intermetallic phases and does not chemically react with ionic species other than to enable electrochemical oxidation and reduction. In addition, the porous conductive layer preferably does not chemically interact with the first ionic conductor itself, except possibly chemically bonded to adhere to the surface of the first ionic conductor. For example, portions of the porous conductive layer preferably do not form mobile ions that are transported to the first ion conductor.

In some embodiments, the first electrode has a high diffusivity for the source metal atoms. The metal atoms comprising the atomic vapor have a molecular weight of preferably at least about 10 as measured at 25 ℃ or operating temperature ^-10 cm ² S and more preferably at least about 10 ^-6 cm ² Diffusivity in the first electrode of/s.

The first electrode is at least a uniform electrical conductor. The resistivity of the first electrode measured at 25 ℃ is preferably less than 10kΩ·cm, more preferably less than 1kΩ·cm, and most preferably less than 1 Ω·cm.

In some embodiments, the first electrode comprises an intercalation compound that is a material capable of being intercalated by atoms of the atomic vapor. In some embodiments, the intercalation compound is, for example, graphite, moS ₂ 、TaS ₂ Or a combination thereof. The intercalation compound may be disposed in a uniform layer consisting essentially of the intercalation compound and any intercalation atoms. The thickness of the intercalated compound layer is preferably less than 100 microns and more preferably less than 10 microns.

In some embodiments, the first electrode comprises particles of an intercalation compound in a matrix. The matrix is preferably a polymeric binder such as, but not limited to, poly (vinyl pyrrolidone), poly (methacrylate), poly (methyl methacrylate), poly (ethyl methacrylate), poly (2-hydroxyethyl methacrylate), fluoroelastomers, cellulosic resins, or combinations thereof. The polymeric binder preferably has low outgassing at the operating temperature of the equipment and is compatible with ultra-high vacuum. Matrix additives may be included to increase the conductivity of the first electrode. For example, small conductive carbon particles (e.g. Carbon black).

The first electrode may further include a region and/or layer having high conductivity to minimize sheet resistance of the first electrode. For example, the first electrode may be composed of two layers: a layer that is substantially graphite and a layer that is a porous conductive layer, such as a thin platinum mesh. This layered configuration may be beneficial to ensure that the potential does not vary significantly across the electrode surface when applied (e.g., < 0.1V), even if the intercalation material has moderate conductivity or even if the intercalation material is very thin. The highly conductive layer may include Pt, mo, W, or a combination thereof. The highly conductive layer may also require more than one sub-layer, such as a Ti adhesion sub-layer and a Pt sub-layer. The highly conductive layer preferably does not form intermetallic phases with the ionic species or otherwise chemically react with the ionic species. The highly conductive layer preferably does not chemically interact with the first ion conductor.

In some embodiments, the first electrode is a mixed ion-electron conductor, meaning that the first electrode is both an ion conductor and an electron conductor. The mixed ion-electron conductor preferably has a sheet resistance of less than 10mΩ/∈h & (1000 kohms/square), more preferably less than 100kΩ/∈h &, and most preferably less than 1kΩ/∈h +. The resistivity of the mixed ion-electron conductor is preferably less than 100kΩ·cm, more preferably less than 10kΩ·cm, and most preferably less than 100 Ω·cm. The ionic conductivity of the mixed ion-electron conductor is preferably at least 10 ^-12 Ω ^-1 ·cm ^-1 More preferably at least 10 ^-9 Ω ^-1 ·cm ^-1 And most preferably at least 10 ^-6 Ω ^-1 ·cm ^-1 . The ionic conductance of the mixed ion-electron conductor through the thickness of the electrode is preferably less than 10k omega, more preferably less than 1k omega, and most preferably less than 100 omega.

Exemplary doped mixed ion-electron conductors include, but are not limited to, rb _1-2x M _x AlO ₂ (x is from 0 to less than 0.5), wherein m=pb, cd, and/or Ca; rb (Rb) _2-2x Fe _2-x M _x O ₄ (x is from 0 to 1), wherein m= P, V, nb and/or Ta; rb (Rb) _2-2x Ga _2-x M _x O ₄ (x is from 0 to 1), wherein m= P, V, nb and/or Ta; rb (Rb) _2-2x Al _2-x M _x O ₄ Wherein m= P, V, nb and/or Ta; rb _1- _x Al _1-x M _x O ₂ (x is from 0 to less than 1), where m=si, ti, and/or Ge.

In some embodiments, the mixed ion-electron conductor material may be selected from alkali metalsPyrophosphates, e.g. Rb ₄ P ₂ O ₇ . The alkali metal pyrophosphate is optionally doped with one or more atoms selected from Ca, sr, ba, pb, Y, la, and/or Nd, for example. Exemplary compounds of doped alkali metal pyrophosphates include, but are not limited to, rb _4-2x M _x P ₂ O ₇ (x is from 0 to less than 2), wherein M = Ca, sr, ba, and/or Pb; rb _3-3x M _x PO ₄ (x is from 0 to less than 1), where m= Y, la, and/or Nd.

In some embodiments, the mixed ion-electron conductor is a uniform layer consisting essentially of the mixed ion-electron conductor. The thickness of the mixed ion-electron conductor material is preferably about 500 microns or less, and more preferably about 100 microns or less.

In some embodiments employing a hybrid ion-electron conductor, the first electrode includes a region or layer having a high electrical conductivity to minimize sheet resistance of the first electrode. For example, the first electrode may include two layers: a layer that is a hybrid ion-electron conductor and a layer that is a highly conductive layer (e.g., a thin Pt mesh). This layered configuration allows the potential to be applied without significant change on the electrode surface (e.g.,<0.1V), even if the mixed ion-electron conductor has moderate conductivity or even if the mixed ion-electron conductor is very thin. The highly conductive layer may include Pt, mo, W, or a combination thereof. The highly conductive layer itself may include sublayers such as Ti adhesion sublayers and Pt sublayers. The highly conductive layer preferably does not chemically interact with the ionic species and preferably does not form intermetallic phases with the ionic species. In addition, the highly conductive layer preferably does not chemically interact with the first ion conductor. For example, when the highly conductive layer contains Pt, pt is preferable ²⁺ Or other platinum ions, will not become mobile ions within the first ion conductor.

The second electrode is preferably in contact with the first ion conductor. The second electrode is not in electrical contact with the first electrode. The second electrode contains at least a second electrode first phase that stores and transports neutral atoms. The transport of neutral atoms is preferably via diffusion and the storage of neutral atoms is preferably via intercalation.

The atomic species contained within the first phase of the second electrode are preferably reduced versions of the same ionic species as in the first ionic conductor. Alternatively, or in addition, different atomic species may be contained within the reservoir. For example, when the device obtains atoms, na may be contained within the second electrode/reservoir and may be oxidized while Rb may be reduced at the first electrode.

The second electrode first phase is preferably graphite. The first phase of the second electrode may mainly comprise sp ² -bonded carbon. sp (sp) ² Examples of bonded carbon include, but are not limited to, graphite, single-layer graphene, few-layer graphene, graphene sheets, porous graphene (perforated graphene), carbon nanotubes, fullerenes (e.g., C ₆₀ 、C ₇₀ Etc.), polycyclic aromatic hydrocarbons (e.g., pentacene, rubrene, hexabenzocoronene, coronene, etc.), chemical vapor deposited graphitic carbon, pyrolyzed carbonaceous molecules or polymers including pyrolyzed parylene (e.g., pyrolyzed poly (p-xylene) or the like), or combinations of the foregoing.

The second electrode first phase may alternatively or additionally comprise a metal dichalcogenide. In various embodiments, the second electrode first phase includes a transition metal oxide (e.g., znO), a transition metal sulfide (e.g., moS) ₂ Or TaS ₂ ) Transition metal selenides (e.g. TiSe ₂ ) Or transition metal telluride (e.g. TiTe ₂ )。

The second electrode first phase is preferably in the form of particles. Preferably, the particles have at least one relatively short dimension to reduce the diffusion length of neutral atoms, thereby increasing the transport rate. For example, the particles of the first phase of the second electrode may have a smallest dimension (e.g., diameter of a sphere or rod) of less than 1000 microns, less than 500 microns, less than 100 microns, less than 50 microns, less than 10 microns, less than 5 microns, less than 1 micron, or less than 500 nanometers. In a preferred embodiment, the particles of the first phase of the second electrode have a minimum dimension selected from about 100 nanometers to about 20 microns. Particle size may be measured by a variety of techniques including, for example, dynamic light scattering, laser diffraction, image analysis, or sieve separation.

The second electrode first phase is preferably a continuous phase or a semi-continuous phase. For example, the second electrode first phase may be or include a carbon aerogel, carbonized polymer, or reticulated vitreous carbon foam.

The second electrode is preferably electrically conductive. In different embodiments, the resistivity of the second electrode measured at 25 ℃ is preferably less than 10kΩ·cm, more preferably less than 1kΩ·cm, even more preferably less than 100 Ω·cm, and most preferably less than 10 Ω·cm.

The thickness of the second electrode may be selected from about 1 micron (or less) to about 100 microns (or more). Typically, the second electrode is thicker than the first electrode or the third electrode.

The second electrode may contain one or more other phases in addition to the first phase to form a composite electrode/reservoir. See, for example, U.S. patent No. 10,545,461 to Roper et al, which is incorporated herein by reference. The additional phase may be an atom transfer phase that stores and transfers neutral atoms. The transport of neutral atoms is preferably via diffusion. At a fixed point in time, the neutral atom may be in the process of being transported into or out of the atom transfer phase, may be stored at a fixed location within the atom transfer phase, or may move within the atom transfer phase but not across its phase boundaries, and thus be stored within that phase. The transport of neutral atoms within and/or across the phase boundaries of the atom transport phase may occur via a variety of diffusion mechanisms such as, but not limited to, bulk solid phase diffusion, porous diffusion, surface diffusion, grain boundary diffusion, permeation, dissolution diffusion, and the like. The storage of neutral atoms is preferably via intercalation. When the diffusion rate of metal atoms is negligible (e.g., less than 10 ^-10 cm ² S) also results in the storage of neutral atoms.

In the atom transfer phase of the second electrode, the selected metal atoms may have at least about 10 measured at the device operating temperature (such as 25 ℃, 100 ℃, 150 ℃, or 200 ℃) ^-10 cm ² /s、10 ^-9 cm ² /s、10 ^-8 cm ² /s、10 ^-7 cm ² /s、10 ^-6 cm ² /s, or 10 ^-5 cm ² Diffusion coefficient/s. The whole secondThe diffusion of metal atoms in the electrode will depend on the bulk diffusivity of the atom transport phase, the volume fraction of the atom transport phase, and the connectivity/tortuosity of the atom transport phase.

The atomic species contained in the atomic transport phase are preferably reduced (neutral charge) forms of at least one ionic species contained in the first ionic conductor. Alternatively, or in addition, the atom transfer phase may contain an atomic species different from the species contained in the first ion conductor. For example, when the device is configured to obtain atoms, na may be contained within the atom transport phase, na may be oxidized to Na at the second electrode ⁺ ，Rb ⁺ Can be reduced to Rb at the first electrode and the first ion conductor can contain Na at the same time ⁺ And Rb ⁺ 。

The atom transfer phase and/or the second electrode first phase preferably contains an intercalated compound capable of being intercalated with at least one element in ionic and/or neutral form. As used herein, an "intercalation (intercalation) compound" is a host material capable of forming an intercalation compound with guest atoms, including atomic vapors whose density is controlled. In other words, the intercalated compound is intercalated (capable of intercalation) with at least some of the atoms in the atomic vapor. The intercalated guest atoms may be neutral atoms, ionic species, or a combination thereof. Typically, the guest atom is inserted as a neutral atom.

In some embodiments, the host material actually contains guest species, resulting in a material that may be referred to as an "intercalation compound". It should be noted that for the purposes of this patent application, any reference to an intercalated compound may be replaced by an intercalated compound, and vice versa, as the intercalated compound must be capable of intercalating the guest species, but may or may not actually contain the intercalated guest species.

"intercalation" herein is not limited to the reversible inclusion or intercalation of atoms, ions, or molecules sandwiched between layers present in a compound, and shall be referred to herein as "intercalation". Intercalation also involves the absorption of neutral or ionic species into the bulk phase of the compound, whether the phase is amorphous or crystalline; adsorbing neutral atoms or ionic species onto an external or internal surface (e.g., phase boundary) present in the compound; and reversible chemical bonding between neutral atoms or ionic species and compounds.

Some embodiments of the invention utilize intercalation in which guest species such as K expand van der waals gaps between sheets of layered compounds such as graphite. The layer expansion requires energy. Without being limited by theory, energy may be supplied by an electric current to induce charge transfer between the guest (e.g., K) and the host solid (e.g., graphite). In this example, a potassium graphite compound, such as KC, may be formed ₈ And KC ₂₄ . These compounds are reversible such that when the current is regulated, the potassium graphite compound may cross the inserted atom (K). For example, those previously inserted atoms may be released into the gas phase or into the first ion conductor. Electrical energy may be supplied to cause a chemical potential change at the interface with the intercalated compound, which then causes the layer to expand.

In some embodiments, the intercalated compound is a carbonaceous material, such as a material selected from the group consisting of: graphite, graphite oxide, graphene oxide, porous graphene, graphene flakes, carbon nanotubes, fullerenes, activated carbon, coke, pitch coke, petroleum coke, carbon black, amorphous carbon, glassy carbon, pyrolyzed carbon-containing molecules, pyrolyzed parylene, polycyclic aromatic hydrocarbons, and combinations thereof.

The intercalated carbonaceous material may be at least 50wt% carbon, preferably at least 75wt% carbon, more preferably at least 90wt% carbon, most preferably at least 95wt% carbon. In some embodiments, the carbonaceous material is substantially pure carbon, except for impurities. The carbonaceous material may include mesoporous carbon, microporous carbon, nanoporous carbon, or a combination thereof.

The intercalated carbonaceous material may be predominantly sp ² And the form of the bonded carbon. sp (sp) ² Examples of bonded carbon include, but are not limited to, graphite, graphene, carbon nanotubes, carbon fibers, fullerenes (e.g., C ₆₀ Or C ₇₀ ) Pyrolyzed carbonaceous molecules or polymers (such as pyrolysisParylene such as parylene-N, parylene-C, or parylene-AF-4) and macropoly-aromatics such as pentacene, rubrene, hexabenzocoronene, or coronene. In the case of graphene (which is basically a single-layer graphite), the graphene may be a single-layer graphene or a multi-layer graphene. Graphene sheets (few-layer graphene) may be utilized. Certain embodiments utilize a single layer of porous graphene, multiple layers of porous graphene, or graphene sheets.

In certain embodiments, the carbonaceous material comprises graphite. Graphite is composed of carbon sheet planes. Metal atoms, especially alkali metal atoms, are easily intercalated between these carbon sheets, resulting in a high diffusivity of these atoms. Graphite electrodes enable rapid metal transport at low voltages and low power consumption per atom removed. Graphite not only transports atoms through intercalation, but also conducts electricity due to electron delocalization within the carbon layer. Valence electrons in carbon can move freely and thus conduct electricity through graphite.

The graphite may be natural graphite (e.g., mined graphite) or synthetic graphite produced by various techniques. For example, graphite may be obtained from chemical vapor deposited graphitic carbon, carbide derived graphite, recycled graphite, waste from graphene fabrication, and the like. Crystalline flake graphite exists as isolated, flat, plate-like particles with hexagonal edges without cracking; when broken, the edges may be irregular or angular. Amorphous graphite is very fine flake graphite. Bulk graphite is present in the fracture veins or fractures and appears as giant platy co-organisms of fibrous or needle-like crystalline aggregates. Highly oriented pyrolytic graphite is graphite having an angular spread between graphite sheets of less than 1 °.

The graphite may be crystalline, amorphous, or a combination thereof. For example, the crystallinity of the graphite may range from about 10% to about 90%. The mixture of crystalline and amorphous graphite may be beneficial not only for intercalation between crystalline layers, but also for intercalation between crystalline and amorphous regions of graphite. In the case where the crystallinity is too high, the diffusivity becomes highly anisotropic. If highly crystalline (i.e., highly anisotropic) graphite is oriented with the low diffusivity axis perpendicular to the device surface (this is typical orientation), it will result in reduced alkali metal flux and thus reduced performance.

In some embodiments, the intercalated compound of the atom transfer phase is a transition metal oxide, a transition metal dichalcogenide, or a combination thereof. The intercalated compound may also be a mixture of carbonaceous material and transition metal oxide, or a mixture of carbonaceous material and transition metal dichalcogenide, or a mixture of all of these materials. In particular, the insertable compound may be selected from MoS ₂ 、TaS ₂ 、TiTe ₂ Or any other metal dichalcogenide of a transition metal dioxide, disulfide, diselenide, or ditelluride.

The second electrode is preferably encapsulated by the first ion conductor and one or more reservoir walls. For example, the package may be a single package (e.g., UHV epoxy) or an adhesive substrate using UHV epoxy or thermo-compression bonded silicon, borosilicate glass, or alumina mold (aluminum die).

For the selected ion species, the first ion conductor preferably has a high ionic conductivity. The ionic conductivity measured at 25℃or at the operating temperature of the apparatus is preferably at least 10 ^-7 S/cm, and more preferably at least 10 ^-5 S/cm. The ionic species may be in the ionized form of atoms of interest in atomic physics and atomic measurement instruments. In various embodiments, the ionic species is selected from the group consisting of: li (Li) ⁺ 、Na ⁺ 、K ⁺ 、Rb ⁺ 、Cs ⁺ 、Sr ⁺ 、Sr ²⁺ 、Ca ⁺ 、Ca ²⁺ 、Ba ⁺ 、Yb ²⁺ 、Yb ³⁺ 、Hg ⁺ 、Hg ²⁺ And combinations thereof (i.e., multiple ions may be present in the device).

The first ion conductor preferably comprises a solid electrolyte. For example, the first ion conductor may be a majority (by weight>50%), beta-alumina, beta "-alumina, or a combination of beta-alumina and beta" -alumina. Beta-alumina and beta "-alumina are good conductors of their mobile ions, but allow negligible non-ionic (i.e., electron) transportConductivity. Beta "-alumina is a hard polycrystalline or monocrystalline ceramic material. Beta-alumina and/or beta "-alumina are also referred to herein as" beta-alumina ". When prepared as a solid electrolyte, beta-alumina is combined with mobile ions (such as Na ⁺ 、K ⁺ 、Li ⁺ 、Rb ⁺ 、Cs ⁺ 、Sr ²⁺ Or Ca ²⁺ ) Complexing, in which case the material becomes sodium-beta-alumina, potassium-beta-alumina, lithium-beta-alumina, rubidium-beta-alumina, cesium-beta-alumina, strontium-beta-alumina, or calcium-beta-alumina, respectively.

Other possible solid electrolyte materials for the first ion conductor include yttria stabilized zirconia, NASICON, LISICON, KSICON, alkali metal ion exchanged forms thereof, and combinations of any of the foregoing. In these or other embodiments, chalcogenide glass may be used as the solid electrolyte material of the first ion conductor. Exemplary chalcogenide glasses include, but are not limited to, rbI-GeSe ₂ -Ga ₂ Ge ₃ And CsI-GeSe ₂ -Ga ₂ Ge ₃ 。

The atomic beam source device may comprise an atomic reservoir different from the second electrode/reservoir. The further atom reservoir is preferably in contact with the second electrode. The atomic reservoir may be partially or fully composed of graphite or graphitic carbon. Graphite or graphitic carbon provides conductivity and also means for storing atoms, such as in graphite intercalation compounds.

The atomic reservoirs may contain metal in the vapor phase and may also contain metal in the solid and/or liquid phase. The atomic species contained within the atomic reservoir are preferably reduced versions of the same ionic species as in the first ion conductor. Alternatively, a different atomic species may be contained within the atomic reservoir.

The atomic reservoir and/or the second electrode may be designed to accommodate any mechanical strain from the reservoir volume that varies due to the loss or introduction of atoms. For example, a gap may be located between the intercalated compound and the reservoir wall to allow the intercalated compound to expand without tensioning the reservoir wall. The reservoir walls may be designed to deform elastically and/or plastically. This configuration may be achieved by material selection (e.g., metal, polymer, or a combination thereof). Alternatively, or in addition, this configuration may be achieved by a reservoir design (e.g., bellows).

The atomic reservoir and/or the second electrode has a wall that is preferably impermeable to the atomic species contained within the reservoir. The wall is preferably a thin film and is supported by a substrate (e.g., glass, si, alumina, etc.). The side or sides of the reservoir wall facing the interior of the reservoir preferably do not chemically interact with the ionic species. For example, the reservoir walls do not form intermetallic phases with the ionic species and do not chemically react with the ionic species. Exemplary reservoir wall materials include Pt, mo, W, or combinations thereof for walls facing the interior of the reservoir. When one or more sides of the reservoir wall contact the first ion conductor, the reservoir wall preferably does not chemically interact with the first ion conductor other than to chemically bond to adhere to the first ion conductor. Exemplary reservoir wall materials include Pt, mo, W, or combinations thereof for contacting the walls of the first ion conductor (if any).

Multiple ion conductors may be present in a single device, each with its own electrode. The plurality of first electrodes may or may not be electrically connected by electrical leads or electrical traces. Likewise, the plurality of second electrodes may or may not be electrically connected by electrical leads or electrical traces.

There may typically be multiple sets of first electrodes, ion conductors and second electrodes. In some embodiments, two or more first (front) electrodes are employed. In these or other embodiments, two or more second (back) electrodes are employed. In any of these embodiments, or other embodiments, two or more ion conductors are employed.

Each electrode is typically connected to an electrical lead made of an electrically conductive material. A lead is an electrical connection made up of a length of wire, metal pad, metal trace, or other conductive structure. Leads are used to transfer power and may also provide physical support and possibly a heat sink. In some embodiments, a device is provided without such leads, which may be added at a later time before use.

There are many options for electrical connection to the first and second electrodes of the atomic beam source device. The electrical connection may be connected to the bond pad for connection to an external circuit. The electrical connection may include a through-wafer via, a patterned conductive film, a doped region of a semiconductor, a wire bond, or a combination thereof. The patterned film may be parallel to the first electrode, such as when the first electrode is substantially planar. Portions of the patterned film may be at an angle to the first electrode. In some embodiments, the electrode connector travels out of the plane of the electrode to which it is connected.

The atomic beam source apparatus may be contained within a furnace. For example, the purpose of the oven may be to control the temperature of the device at a temperature above ambient temperature. In principle, the atomic beam source device may be comprised in any type of temperature control system for heating or cooling the device.

The atomic beam source apparatus can operate over a wide range of temperatures and pressures. In various embodiments, the atomic beam source apparatus may be operated at a temperature from about-200 ℃ to about 500 ℃, preferably from about-50 ℃ to about 250 ℃, and more preferably from about 10 ℃ to about 200 ℃. After the atoms are emitted from the atomic beam source device, the atoms may be cooled to ultra-low temperatures (e.g., 10 f, according to the needs of some applications or measurements ^-7 K to 10 ^-3 K) A. The invention relates to a method for producing a fibre-reinforced plastic composite In various embodiments, the atomic beam source apparatus may be in the range of from about 7600 Torr (10 atm) to about 10 ^-14 A tray, preferably from about 10 ^-3 To about 10 ^-13 A tray, and more preferably from about 10 ^-7 To about 10 ^-12 Operating under the pressure of the tray.

The atomic beam source apparatus may include an integrated heater. The integrated heater may be a resistive heater such as a thin wire or patterned thin metal trace (e.g., pt or nickel-chromium alloy). For example, the integrated heater may also be a radiant heater or a thermoelectric heater. The integrated heater preferably includes a temperature sensor, such as a thermocouple or a resistive temperature detector (e.g., pt). Preferably, the heater is in good thermal communication with a region of the first ion conductor proximate the first electrode.

In some embodiments, the atomic beam source device is a chip-scale device that is mounted or integrated on a microelectromechanical system (MEMS) heater level to minimize heater power.

When an integrated heater is included in the device, the heater may further include one or more insulating structures. The insulating structure minimizes heat transfer from the heated area of the device to the cooler ambient environment. The insulating structure is configured to minimize heat loss from the heating zone to the cold zone by functioning as an insulator to retain heat within the heating zone. The insulating structure preferably has a high thermal resistance value, as explained further below.

In some embodiments, the insulating structure may be made of the same material and layer as the atomic reservoir walls. In these or other embodiments, the insulating structure may be made of the same material and layer as the first ion conductor. The insulating structure is preferably a polymer, ceramic, or glass, or a combination of the foregoing, although metals may also be utilized.

In some embodiments, the insulating structure is made of a material selected from the group consisting of beta-alumina (e.g., rb-beta-alumina, na-beta-alumina, or Sr-beta-alumina), beta "-alumina (e.g., rb-beta" -alumina, na-beta "-alumina, or Sr-beta" -alumina), alpha-alumina, silica, fused silica, quartz, borosilicate glass, silicon nitride, silicon carbide, and combinations thereof.

The insulating structure may be designed to accommodate materials having any thermal conductivity. High thermal conductivity materials would benefit from long, high aspect ratio connections, while lower thermal conductivity materials may utilize shorter, thicker connections.

An important design parameter of the insulating structure (when present) is the thermal resistance. The thermal resistance is the temperature difference across the insulation structure as the unit thermal energy flows through the insulation structure in a unit time; or equivalently, in steady state, causes a temperature difference between two defined surfaces of the insulating structure per unit of thermal flow rate. Because a low heat flow rate is desired, a high temperature difference, i.e., a high thermal resistance, is desired. The thermal resistance of the insulating structure is preferably at least 100K/W, more preferably at least 1,000K/W, and most preferably at least 10,000K/W.

The insulating structure may also be configured to impart mechanical strain relief, thereby preventing mechanical damage due to accumulated thermal strain when the first ion conductor is heated to a higher temperature than the base substrate. In some embodiments, the insulating structure is mechanically coupled to the base substrate, such as by a frame. Preferably, the insulation structure is designed to reduce thermal or residual stress by at least 2×, preferably at least 10×, and more preferably at least 100× from one side of the insulation structure to the other. The thermal or residual stress reduction is not an inherent material property, but rather a function of the geometric design of the insulation structure and its material properties.

In some embodiments, the insulating structure is a hanging beam. Typically, there will be a plurality of suspension beams to connect the heated area to the cold area. The heating zone is in contact with the cold zone only through the suspension beams. The suspension beam may be a straight beam, a folded beam, a bent beam, a round beam, etc. The suspension beams may be made in any layer(s) in a planar process such as surface or bulk micromachining. The remainder of the heated zone may be surrounded by a vacuum or vapor phase (e.g., containing an inert gas), any of which has a high thermal resistance to the cold zone. Alternatively, the vapor/vacuum region may comprise an insulating material, such as aerogel.

In some embodiments, the insulating structure has a thin metal film patterned thereon for electrical interconnection. In some preferred embodiments, the resistive heater and the temperature sensor are patterned on (in contact with) the same layer as the at least one insulating structure. Preferably, the electrical connections to the heater and the temperature sensor are also patterned on one or more insulating structures. Optionally, part or all of the heater may be patterned on one or more insulating structures. In some embodiments, the thin film resistive heater is patterned on one or more sides of the same layer as the insulating structure. In the case where the first ion conductor is separate from the insulating structure, the heater may be patterned on the same side or on the opposite side of the insulating structure as compared to the location of the first ion conductor. In the case where the first ion conductor is the same as the insulating structure or layer thereof, the heater may be patterned on either side of the first ion conductor (i.e. on the first electrode side and/or the second electrode side). See commonly owned U.S. patent application Ser. No. 16/573,684, filed on publication No. 9/17 at 2019, which is hereby incorporated by reference.

Integrating the heater and insulation structure within the system achieves low system power input. The system power input for controlling the vapor density of the metal atoms is preferably less than about 500mW, more preferably less than about 200mW, and most preferably less than about 100mW. In various embodiments, the system power input for obtaining and/or sinking metal atoms is about 1000, 500, 400, 300, 200, 100, 50, 25, or 10mW.

In some embodiments where a high vapor density is desired, the density of metal atoms may be at least 10 ⁹ Atoms/cm ³ Preferably at least 10 ¹⁰ Individual/cm ³ And more preferably at least 10 ¹¹ Individual/cm ³ . In some embodiments where a low vapor density is desired, the density of metal atoms may be less than 10 ⁸ Atoms/cm ³ Preferably below 10 ⁷ Atoms/cm ³ . In various embodiments, the density of metal atoms is about, at least about, or at most about 10 ⁶ Atoms/cm ³ 、10 ⁷ Atoms/cm ³ 、10 ⁸ Atoms/cm ³ 、10 ⁹ Atoms/cm ³ 、10 ¹⁰ Atoms/cm ³ 、10 ¹¹ Atoms/cm ³ Or 10 ¹² Atoms/cm ³ 。

Atomic beam source devices can be manufactured on a variety of length scales. The length scale may be characterized by the square root of the area of the first electrode. The length scale may vary from 10m to 1 micron, with 1m to 10mm being typical for macro-scale atomic timing and navigation systems and 30mm to 10 microns being typical for chip-scale atomic timing and navigation systems.

The chip scale devices are preferably built using micro-fabrication techniques including some or all of photolithography, evaporation, shadow-masking, evaporation, sputtering, wafer bonding, tiling, anodic bonding, frit bonding, metal-to-metal bonding, and etching.

The present disclosure is hereby incorporated by reference for the following patents that teach solid state electrochemical atomic sources that are used as atomic sources and/or sinks in some embodiments: us patent No. 9,763,314, release 9 and 12, 2017; us patent No. 9,837,177, release 12/5 of 2017; us patent No. 10,056,913, 2018, 8, 21; us patent No. 10,545,461, 28, month 1 of 2020; us patent No. 10,775,748, release 9/15/2020; us patent No. 10,828,618, release 11/10/2020; U.S. patent No. 11,101,809, 2021, 24, 8. All publications, patents, and patent applications cited in this specification are herein incorporated by reference in their entirety as if each individual publication, patent, or patent application were specifically and individually indicated to be incorporated by reference herein.

In this detailed description, reference has been made to a number of embodiments and to the accompanying drawings in which specific exemplary embodiments of the invention are shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that modifications may be made to the various disclosed embodiments.

When the above-described methods and steps indicate that certain events occur in a certain order, those of ordinary skill in the art will recognize that the order of certain steps may be modified and that such modifications are made in accordance with the variations of the invention. In addition, some steps may be performed concurrently in parallel processes, if possible, or sequentially.

The above embodiments, variations and accompanying drawings should provide an indication of the utility and versatility of the present invention. Other embodiments that do not provide all of the features and advantages set forth herein may be used without departing from the spirit and scope of the invention. Such modifications and variations are considered to be within the scope of the invention as defined by the claims.

Claims

1. An interferometric frequency reference, the instrument comprising:

a vacuum chamber;

an atomic source configured to supply neutral atoms to be ionized;

an ionizer configured to excite the neutral atoms to form ionized atoms;

an ion collimator configured to form a collimated beam of the ionized atoms;

one or more probe lasers; and

a readout laser configured to determine a ground state population of the ionized atoms,

wherein the atomic source, the ionizer, and the ion collimator are disposed within the vacuum chamber.

2. The interferometric frequency reference of claim 1, wherein the atomic source is a solid state electrochemical atomic source.

3. The interferometric frequency reference of claim 1, wherein the ionizer is disposed inside the ion collimator.

4. The interferometric frequency reference of claim 1, wherein the ionizer is disposed outside of the ion collimator.

5. The interferometric frequency reference of claim 1, wherein the ion collimator is a linear collimator.

6. The interferometric frequency reference of claim 5, wherein the linear collimator is selected from the group consisting of a linear quadrupole trap, a penning trap, a surface ion trap, and a mass filter.

7. The interferometric frequency reference of claim 1, wherein the ion collimator is a non-linear collimator.

8. The interferometric frequency reference of claim 7, wherein the non-linear collimator is in a recirculating configuration.

9. The interferometric frequency reference of claim 1, wherein the ion collimator is configured such that the collimated beam of ionized atoms has a beam waist selected from about 10 nanometers to about 10 meters.

10. The interferometric frequency reference of claim 1, wherein the ion collimator is configured such that the collimated beam of ionized atoms has a beam velocity selected from the group consisting of about 1 micron/sec to about 0.99c, where c is the speed of light in vacuum.

11. The interferometric frequency reference of claim 1, wherein the one or more probe lasers are configured to perform a lamb Ji Guangpu method on the ionized atoms.

12. The interferometric frequency reference of claim 1, wherein the one or more probe lasers are two or more probe lasers.

13. The interferometric frequency reference of claim 1, wherein the one or more probe lasers are configured to detect quadrupole transitions or both dipole and quadrupole transitions of the ionized atoms.

14. The interferometric frequency reference of claim 1, wherein the interferometric frequency reference further comprises a cooling laser.

15. The interferometric frequency reference of claim 1, wherein the readout laser is further configured for cooling.

16. The interferometric frequency reference of claim 1, wherein the interferometric frequency reference further comprises an injection electrode.

17. The interferometric frequency reference of claim 1, wherein the interferometric frequency reference further comprises an ion sink configured to collect the ionized atoms exiting the ion collimator, and wherein the ion sink is disposed within the vacuum chamber.

18. The interferometric frequency reference of claim 1, wherein the interferometric frequency reference further comprises an imaging system configured to focus fluorescence from the ionized atoms.

19. The interferometric frequency reference of claim 1, in which the interferometric frequency reference provides an optical frequency reference.

20. The interferometric frequency reference of claim 1, in which the interferometric frequency reference provides a microwave frequency reference.

21. A method of generating a stable frequency reference, the method comprising:

(a) Generating atomic vapor;

(c) Collimating the ionized atoms in an ion collimator to form a collimated beam of the ionized atoms;

(d) Optionally, irradiating some of the ionized atoms with a cooled laser;

(g) Adjusting the first and second probe laser frequencies to an s→d transition of at least some of the ionized atoms using a lamb Ji Guangpu method; and

22. The method of claim 21, wherein the atomic vapor and/or the ionized atoms are obtained from a solid state electrochemical atomic source.

23. The method of claim 21, wherein the ionized atoms are Ca ⁺ And/or Sr ⁺ 。

24. The method of claim 21, wherein the ionized atoms provided in step (b) are formed within the ion collimator provided in step (c).

25. The method of claim 21, wherein the ionized atoms provided in step (b) are injected into the ion collimator.

26. The method of claim 21, wherein step (d) is performed to cool the ionized atoms in preparation for the lamb Ji Guangpu method.

27. The method of claim 21, wherein the ion collimator is a linear collimator.

28. The method of claim 27, wherein the linear collimator is selected from the group consisting of a linear quadrupole trap, a penning trap, a surface ion trap, and a mass filter.

29. The method of claim 21, wherein the ion collimator is a non-linear collimator.

30. The method of claim 29, wherein the non-linear collimator is in a recycling configuration.

31. The method of claim 21, wherein the collimated beam of ionized atoms has a beam waist selected from about 10 nanometers to about 10 meters.

32. The method of claim 21, wherein the collimated beam of ionized atoms has a beam velocity selected from the group consisting of about 1 micron/second to about 0.99c, where c is the speed of light in vacuum.

33. The method of claim 21, wherein the method further comprises irradiating at least some of the ionized atoms with a third probe laser.

34. The method of claim 33, further comprising irradiating at least some of the ionized atoms with a fourth probe laser after the irradiating at least some of the ionized atoms with the third probe laser.

35. The method of claim 21, wherein the method is continuous.

36. The method of claim 21, wherein the stable frequency reference is an optical frequency reference.

37. The method of claim 21, wherein the stable frequency reference is a microwave frequency reference.

38. The method of claim 21, wherein the method utilizes an interferometric frequency reference of claim 1.