High-temperature quantum sensor

Abstract

A vapor cell comprises a cell body and a cell window, which is anodically connected to the cell body. The cell window and the cell body define a vapor cavity designed to contain a vapor comprising a variety of alkali atoms.

Description

[0001] This application claims priority over the preliminary US patent application 63 / 536,153 filed on September 1, 2023, the entire contents of which are hereby incorporated by reference. RIGHTS OF THE GOVERNMENT

[0002] This invention was developed with government support under contract number HR00112390115, awarded by the Defense Advanced Research Projects Agency (DARPA). The government holds certain rights to the invention. TECHNICAL AREA

[0003] This revelation applies generally to quantum sensors. BACKGROUND

[0004] Quantum sensors utilize quantum phenomena such as superposition, entanglement, and quantum tunneling to measure physical quantities with very high precision. They can detect minute changes in environmental conditions, including magnetic fields, electric fields, temperature, pressure, and gravitational fields. Quantum sensors can be used in atomic clocks, gyroscopes, magnetometers, interferometers, and other devices that precisely measure relatively small changes in parameters such as time and acceleration. In some cases, quantum sensors use atomic spectroscopy and light-atom interactions to detect changes in the properties of gas-phase atoms and obtain precise measurements of parameters acting on these atoms.To dissociate alkali atoms into gas-phase atoms and maintain the thermal equilibrium of the gas-phase atoms, atom sensors can be operated at high temperatures and consume large amounts of energy to maintain these high temperatures. SUMMARY

[0005] In general, systems and techniques for quantum sensors are described that can operate at high temperatures, e.g., temperatures greater than or equal to 150 degrees Celsius (°C) or temperatures above approximately 150 °C. A quantum sensor comprises a vapor cell designed to withstand high temperatures, e.g., mechanical survivability of the vapor cell, and designed to control the density of the alkali atoms vaporized in the vapor cell. In some examples, a quantum sensor comprises a vapor cell containing materials that are unreactive with alkali atoms and are anodically bonded, e.g., for mechanical survivability. In some examples, a quantum sensor comprises a vapor cell with an intermetallic alloy comprising a metal and a variety of alkali atoms, e.g., to control the density of the alkali atoms vaporized in the vapor cell.

[0006] In one example, this disclosure describes a vapor cell comprising: a cell body; and a cell window anodically bonded to the cell body, the cell window and the cell body defining a vapor cavity configured to contain a vapor comprising a plurality of alkali atoms.

[0007] In another example, this disclosure describes a sensor comprising: a vapor cell, comprising: a cell body; a cell window, wherein the cell window and the cell body define a vapor cavity and are configured to contain a vapor comprising a plurality of alkali atoms; and an intermetallic alloy comprising a metal and the plurality of alkali atoms; and a detector configured to receive a probe light transmitted through the vapor cell.

[0008] In another example, this disclosure describes a method for producing a vapor cell, wherein the method comprises: arranging at least one silicon or germanium on at least one of a cell window or a cell body, wherein the cell window and the cell body define a vapor cavity; and anodic bonding of the cell window to the cell body via the at least one silicon or germanium.

[0009] The details of one or more examples of the disclosure are set forth in the accompanying drawings and in the description below. Further features, subject matter and advantages of the disclosure will become apparent from the description and the drawings as well as from the claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a block diagram illustrating an example of a sensor system according to the techniques of revelation. Fig.Figure 2A is a cross-sectional diagram of an exemplary vapor cell of a quantum sensor according to the techniques of the revelation. Fig. 2B is a cross-sectional diagram of the exemplary steam cell from Fig. 2A in another configuration of a quantum sensor according to the techniques of revelation. Fig. Figure 3 is a cross-sectional diagram of another exemplary vapor cell of a quantum sensor according to the techniques of the revelation. Fig. Figure 4 is a flowchart of an exemplary process for manufacturing a steam cell according to the techniques disclosed. DETAILED DESCRIPTION

[0010] In general, systems and techniques for quantum sensors are described that can operate at high temperatures, e.g., temperatures above approximately 150 degrees Celsius (°C). In some examples, a quantum sensor can operate at temperatures greater than or equal to 500 °C, e.g., above approximately 500 °C. Quantum sensors can include a magnetometer (scalar or vectorial), an atomic clock, a Rydberg sensor for electromagnetic (EM) radiation (e.g., EM waves and / or EM energy), or another suitable quantum sensor.

[0011] Conventional quantum sensors can be affected at very high temperatures. For example, fluxgate magnetometers can experience failure of the insulating coatings on the magnet wires, problems related to differences in the coefficients of thermal expansion (CTE) of the components, and temperature effects on the microcircuits mounted close to the fluxgate sensors. Typical vapor cell magnetometers contain alkali atoms that are kept at relatively low temperatures, such as 100 °C or less. At higher temperatures, the alkali atoms used to detect the magnetic field react with the walls of the vapor cell, which are usually made of borosilicate glass. This depletes the alkali atoms and "darkens" the cell, reducing the optical transmission of the probe light, such as excitation and / or probing laser light.In other words, the material of the vapor cell can react with the vaporized alkali atoms, and the inner surfaces of the vapor cell can then exhibit reduced optical transmission and / or become essentially opaque to excitation and / or probing radiation (e.g., light), in addition to the depletion of the alkali atom vapor, thereby reducing the detection capability of the quantum sensor.

[0012] The amount of alkali atoms in the vapor cell may need to be carefully controlled. For example, changes in alkali atom density can lead to pressure fluctuations within the vapor cell or enhance collisions between alkali atoms and a buffer gas. Typically, a vapor cell can be operated at a constant temperature, with a reservoir of liquid droplets of alkali atoms within the cell serving to compensate for the loss of alkali atoms to atom sinks (e.g., reactions with other materials such as the cell body, the cell window, or other materials) and to maintain a substantially constant density of vaporized alkali atoms. Such a configuration may not be usable over a wide temperature range because the optical density of the vapor can vary considerably, and the density can increase to such an extent that the vapor becomes too dense for probing light and / or excitation radiation (e.g., from a ray tube)."Pump radiation") essentially becomes opaque.

[0013] According to the techniques, systems, devices, and / or sensors disclosed herein, a quantum sensor comprises a vapor cell designed to withstand high temperatures, e.g., mechanical survivability of the vapor cell, and designed to control the density of the alkali atoms vaporized in the vapor cell. The alkali or vaporized alkali atoms may be lithium, sodium, potassium, rubidium, cesium, or any other suitable alkali. In some examples, a quantum sensor comprises a vapor cell that includes materials unreactive with alkali atoms and anodically bonded, e.g., for mechanical survivability. For example, a vapor cell may include a cell body comprising a material unreactive with respect to alkali atoms or alkali vapor (e.g.,non-reactive or chemically unreactive), for example materials such as sapphire, titanium, germanium or any other material that is non-reactive towards vaporized alkali atoms.

[0014] The vapor cell may also include a cell window for probing the contents of the vapor cell. The cell window is configured to form a seal with the cell body to retain a vapor containing a variety of alkali atoms within a volume (e.g., the cell volume) defined by the cell body and the cell window. For example, the cell body may be essentially hollow and open at opposite ends, which are hermetically sealed by cell windows at both ends. The cell window may, for instance, comprise a material that is unreactive with alkali atoms, such as sapphire, titanium, germanium, or any other material that is unreactive with vaporized alkali atoms, and may be configured to be anodically bonded to the cell body. The window may also be essentially optically transparent to at least certain frequencies of light, such as excitation radiation and probing light.For example, a vapor cell can include a sapphire cell window that is anodically bonded to a sapphire cell body with amorphous silicon.

[0015] Instead of a homogeneous source of alkali atoms, the vapor cells described here can include a heterogeneous source of alkali atoms, chemically designed to release the alkali atoms at a reduced rate at high temperatures. The vapor cell can comprise an intermetallic alloy consisting of a metal and a variety of alkali atoms. The intermetallic alloy can be designed to control the density of the vaporized alkali atoms within the vapor cell based on temperature. In some examples, the intermetallic alloy can be designed to retain the alkali atoms at substantially high temperatures, e.g., above about 150 °C, so that the alkali atoms do not vaporize further and increase the density of the vaporized alkali atoms.For example, a steam cell containing the intermetallic alloy can be sealed and heated to an initial high temperature, which may be equal to or greater than the phase transition temperature of the intermetallic alloy. This initial temperature can be significantly higher than the operating temperature of the steam cell, e.g., above 500 °C, and alkali atoms can evaporate from the intermetallic alloy. The intermetallic alloy can be heated to this initial temperature for a period of time designed to produce an alkali atom vapor with a specific, desired density. The intermetallic alloy can then be cooled or allowed to cool, and the steam cell can maintain a relatively constant density of evaporated alkali atoms as a function of temperature, even at temperatures of 150 °C or higher.For example, the intermetallic alloy can include an alkali gold alloy, which may have a melting point of 495 °C, 490 °C, or approximately 500 °C. The alkali gold alloy can be heated above its melting point while monitoring the absorption of a probe beam (by vaporized alkali atoms) to deliver a known density of alkali atoms to the vapor.

[0016] The sensors and techniques described here can provide a quantum sensor with improved temperature stability and a wider operating temperature range. These sensors and techniques can also provide improved control over the density of vaporized alkali atoms within the vapor cell and the ability to modify the density of alkali atoms within the vapor cell, for example, by heating an intermetallic alloy. For instance, a quantum sensor comprising a vapor cell with inert or non-reactive materials for the vapor cell body and window (to eliminate alkali sinks, for example), and employing a controllable source, such as an intermetallic alloy, can control the number and / or density of alkali atoms to remain essentially constant over a wide temperature range, including temperatures of 150 °C or higher.The sensor may include a vapor cell that improves sensitivity at normal or relatively high temperatures (e.g., 150 °C or more). For example, the vapor cell may prevent and / or reduce darkening of the vapor cell, e.g., by deposition of materials such as alkali atoms on a cell window, and / or by increasing the density of vaporized alkali atoms, thereby increasing the optical density of the cell to probe light and / or excitation radiation that may impair a sensor signal, signal strength, or signal-to-noise ratio. The sensors and techniques described herein may provide improved sensor survivability. For example, the vapor cells disclosed herein may provide improved survivability of the bond and / or the seal of the window to the cell body (e.g.,by anodic bonding and / or sealing, such as a sapphire-to-sapphire bond or seal) at relatively higher temperatures, e.g. reduced impairment of bond / seal, leakage, penetration of materials into the vapor cell or the like at temperatures of 150 °C or more, of 500 °C or more or any suitable relatively high temperature or more.

[0017] Fig.Figure 1 is a block diagram illustrating an example of a quantum sensor system 100 according to the techniques of disclosure. In the example shown, the quantum sensor system 100 comprises a sensor 112 and a computing device 106. The sensor 112 comprises a vapor cell 102, a detection system 104, and a processing system 108. Although the sensor 112 is described here as a magnetometer, the quantum sensor system 100 and / or the sensor 112 can be configured to detect magnetic fields, incident electromagnetic radiation, and / or other suitable stimuli.

[0018] The vapor cell 102 can contain a vapor of atoms, for example alkali atoms, which, due to their precisely defined electronic structure and the precision with which their resonant frequencies and energy levels can be manipulated and detected, are suitable for probing and measuring optical and magnetic properties. In some examples, the vapor cell 102 can be configured as a transducer to convert physical phenomena 110 into electrical information via the detection system 104. Although referred to below as magnetic field 110 for simplicity, physical phenomena 110 can include magnetic fields (e.g., strength, direction, and / or relative changes of magnetic fields), incident electromagnetic radiation (e.g., electromagnetic energy, light, radio waves, or the like), or other physical phenomena.For example, the steam cell 102 can be configured to convert at least a portion of the energy of a scalar or vectorial magnetic field 110 and / or an EM radiation 110 (e.g. with frequencies in a first frequency range such as MHz, THz or GHz radio waves) into a signal that can be a light signal (e.g. EM radiation with frequencies in a second range such as infrared or visible light) that can be detected by a photodiode, or into an ionization state of the atoms in the steam cell, or into any suitable detectable signal.

[0019] The detection system 104 can comprise one or more detectors, circuits, measuring instruments, and the like, configured to detect a response of the alkali atoms to the magnetic field 110 after the alkali atoms have been processed via the processing system 108, e.g., after a large number of alkali atoms have been processed to be in a Rydberg state. For example, the detection system 104 can comprise an optical detector configured to detect a quantity of probe light from the processing system 108 passing through the vapor cell 102 and to record an absorption spectrum of the alkali atoms as a function of the frequency detuning of the probe light, thus indicating / quantifying the electromagnetically induced transparency (EIT) of the alkali atom vapor.The detection system 104 can be designed to detect a reaction of the alkali atoms, when they are prepared in a Rydberg state, to a magnetic field 110 and to convert the detected reaction into one or more signals, e.g. analog and / or digital signals.

[0020] The computing device 106 can be configured to receive analog and / or digital signals from the detection system 104. For example, the computing device 106 can be configured to process, record, and / or store signals received from the detection system 104, and can be configured to store and / or output raw and / or processed data indicating incident EM radiation 110, e.g., the quantity and / or spectral content of the EM radiation 110. The computing device 106 can comprise one or more processors, memory, and interface components.

[0021] For example, the one or more processors of the computing device 106 may comprise one or more processing circuits, a microprocessor, a control unit, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or an equivalent discrete or integrated logic circuit. The functions assigned to the processors described here may be provided by processing circuits of a hardware device, e.g., supported by software and / or firmware.

[0022] In some examples, the memory of the computing device 106 can comprise any volatile or non-volatile media, such as random-access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), electrically erasable programmable ROM (EEPROM), flash memory, and the like. The memory can be a storage device or other non-volatile medium and can be used by the processing circuits, for example, to store information related to the sensor system 100, such as information relating to the steam cell 102, the detection system 104, the processing system 108, and the incident electromagnetic radiation 110. In some examples, the memory can store information or data previously received from the detection system 104 for later retrieval. In some examples, the memory can store settings, fixed values, and / or calculated values ​​for later retrieval.

[0023] In some examples, the interface components of the computing device may include output devices such as a screen, a sound card, a video graphics adapter card, a speaker, a presence-sensitive display, one or more USB interfaces, video and / or audio output interfaces, or any other type of device capable of producing tactile, acoustic, visual, or other outputs. A display device may use technologies such as liquid crystal displays (LCDs), quantum dot displays, dot matrix displays, light-emitting diode (LED) displays, organic light-emitting diode (OLED) displays, cathode ray tube (CRT) displays, E-Ink, or monochrome, color, or other types of displays capable of producing tactile, acoustic, and / or visual outputs.

[0024] In some examples, the computing device 106 can be integrated into the sensor system 100, e.g., integrated into one or more of the steam cell 102, the detection system 104, and the processing system 108. In other examples, the computing device 106 can be an external device, e.g., a computing device separate from the sensor system 100, designed to communicate with the sensor system 100.

[0025] The processing system 108 can be configured to emit one or more EM radiation frequencies that are designed or can be used to process alkali atoms within the vapor cell 102 from a first quantum energy state, which may be a ground state of the alkali atom vapor, to a second, higher quantum energy state, e.g., a Rydberg state. In some examples, the processing system 108 can include any hardware suitable for processing the atoms for the Rydberg state. For example, the processing system 108 can include a variety of EM radiation sources and physical / optical elements designed to direct EM radiation from the one or more EM radiation sources. In some examples, the processing system 108 can be entirely optical, e.g.,EM radiation sources can include optical sources such as lasers, light-emitting diodes, incandescent lamps, fluorescent lamps, or the like. Physical / optical elements can include lenses, mirrors, diffraction gratings, windows, filters, waveguides, fibers, or any other physical / optical element used to direct and / or shape EM radiation from a radiation source (e.g., beam shaping) so that it is directed onto the alkali atoms in the vapor cell 102.

[0026] In some examples, the processing system 108 can be configured to emit a multitude of EM stream frequencies arranged to incident on alkali atoms within the vapor cell 102. For example, the processing system 108 can be configured to emit a multitude of EM "beams," each having one or more frequencies (e.g., wavelengths) directed into the vapor cell 102. In some examples, the processing system 108 can include three EM frequencies configured to excite alkali atoms to a Rydberg state (e.g., a "three-photon" system). In some examples, the processing system 108 can include more or fewer than three EM radiation frequencies, e.g., one EM radiation frequency, two EM radiation frequencies, or four or more EM radiation frequencies.In some examples, the multitude of EM radiation frequencies of the processing system 108 can be configured to process alkali atoms within the vapor cell 102 into a Rydberg state via one or more intermediate quantum energy states.

[0027] The steam cell 102 can comprise a cell body and one or more cell windows that are anodically bonded to the cell body. The cell body and cell windows can define a steam cavity, e.g., a volume within the steam cell 102, and the steam cell 102 can be configured to contain a vapor comprising a variety of alkali atoms, e.g., within the steam cavity. The anodic bonding between the cell body and the cell window(s) can form a hermetic seal, whereby the steam cell 102 can exhibit relatively low or no vapor permeability, e.g., little or no loss of alkali vapor, and / or little or no ingress or egress of gas or vapor into the steam cell 102, e.g., little or no ingress of water, oxygen, or helium. In some examples, the cell body and the cell window can have essentially the same CTE, e.g.,an adapted CTE, and the anodic bond may also have a CTE that is essentially adapted to the CTE of the cell body and / or the cell window.

[0028] Fig. 2A and Fig. Figure 2B shows cross-sectional diagrams of an exemplary vapor cell 202 of a quantum sensor according to the techniques revealed. Fig. Figure 2A illustrates the steam cell 202 and a first configuration of the probe light 208A and the excitation radiation 208B, and Fig. Figure 2B illustrates a second configuration of the probe light 208A and the excitation radiation 208B. The vapor cell 202 can be essentially similar to the vapor cell 102 described above.

[0029] In the example shown, the vapor cell 202 comprises a cell body 204, a cell window 206a, and a cell window 206b on a side of the cell body 204 opposite cell window 206a. The cell body 204 may comprise sapphire or germanium. The cell windows 206a and 206b may each be anodically bonded to the cell body 204 via anodic bonds 222a and 222b, respectively. The cell windows 206a and 206b (collectively, "cell windows 206") may comprise sapphire and exhibit high optical transparency to the probing light 208A and / or the excitation radiation 208B; for example, the cell windows 206 may be essentially optically transparent to the probing light 208A and / or the excitation radiation 208B. The cell body 204 and the cell windows 206 can define the vapor cell cavity 212 and be designed to contain a vapor comprising a variety of alkali atoms within the vapor cell cavity 212.

[0030] The probe light 208A can be electromagnetic radiation with radio wave frequencies or optical frequencies that are detectable via the detection system 104. The probe light 208A and the excitation radiation 208B can be arranged such that they propagate to and / or through the vapor cell cavity 212, e.g., to and / or through the multitude of alkali atoms. In the example of Fig. In 2A, both the probe light 208A and the excitation radiation 208B are arranged such that they propagate through a vapor cell window, e.g. 206a, to and / or through the vapor cell cavity 212, and at least a portion of the probe light 208A (e.g., a section not absorbed by the alkali vapor) is arranged such that it propagates from the vapor cell cavity 212 through the cell window 206b, e.g., for detection by the detection system 104. Fig.In 2A, the probe light 208A and the excitation radiation 208B propagate in the same direction. In the Fig. In the example shown in Figure 2B, the probe lights 208A and 208B are arranged such that they propagate in different directions to and / or through the vapor cell cavity 212. For example, the cell body 204 can also be substantially transparent to at least one of the excitation radiation 208B or, as shown in the example, the probe light 208A.

[0031] The probe light 208A and the excitation radiation 208B can have frequencies that can excite at least a fraction of the multitude of alkali atoms within the vapor cell cavity 212 into an excited quantum state, for example, a Rydberg state. For example, the probe light 208A can be infrared, visible, or ultraviolet laser light, such as 780 nanometer (nm) laser light. The excitation radiation 208B can be electromagnetic radiation with radio or optical frequencies, such as 480 nm laser light. A fraction of the probe light 208A can excite a fraction of the multitude of alkali atoms within the vapor cell 202 into a first quantum state, and the excitation radiation 208B can excite the fraction of the multitude of alkali atoms into a second, Rydberg quantum state. The quantum state of the alkali atoms excited to the Rydberg state can be disturbed, e.g., by... B.They are sensitive to magnetic fields, radio waves, or other physical phenomena, such that the alkali atoms can be "detuned" from the Rydberg state, thereby changing the amplitude of the probe light 208A that propagates through the vapor cell 202 to the detection system 104. In some examples, the excitation radiation 208B can include multiple radiation frequencies (e.g., from multiple radiation sources) designed to excite alkali atoms, along with the probe light 208A, into a Rydberg state via one or more intermediate quantum states. For example, the excitation radiation 208B can include laser light at 776 nanometers (nm) and laser light at 1260 nm.

[0032] The steam cell 202 is designed to control the ratio and / or quantity of alkali atoms excited to the Rydberg state for the detection of magnetic fields or external EM radiation, such as radio waves, even at relatively high temperatures, e.g., temperatures above about 150 °C or about 250 °C or about 490 °C or about 495 °C or any other suitable elevated temperature (e.g., elevated above room temperature).For example, the steam cell 202 can be configured to maintain a substantially constant seal at temperatures above about 150 °C or about 250 °C, or about 495 °C, to maintain the density of the plurality of alkali atoms in the steam cell cavity 212, which is substantially constant as a function of temperature for temperatures of the steam cell 202 above about 150 °C or about 250 °C or about 490 °C or about 495 °C, and to prevent vaporized alkali atoms from reacting with the cell body 204 and / or the cell windows 206 at temperatures above about 150 °C or about 250 °C or about 490 °C or about 495 °C.

[0033] For example, the vapor cell 202 comprises anodic bonds 222a and 222b (collectively, “anodic bonds 222”) that can maintain a hermetic seal between the cell body 204 and the cell windows 206. The anodic bonds 222 can comprise silicon, germanium, and / or glass. In the example shown, the anodic bond 222a comprises three layers, namely two layers 218a and 220a of amorphous silicon, which are adjacent to opposite sides of the glass 216a, and similarly, the anodic bond 222b comprises three layers—two layers 218b and 220b of amorphous silicon, which are adjacent to opposite sides of the glass 216b. In some examples, the layers 218a, 218b (collectively referred to as “layers 218”) may consist of silicon or germanium and may be arranged on an inner surface of the cell window 206, a surface of the glass 216a or both.Likewise, the layers 220a, 220b (collectively “silicon 220”) can consist of silicon or germanium and can be arranged on a surface of the glass 216b, a surface of the cell body 204, or both. In some examples, the anodic bonds 222 can have a thickness (e.g., that shown in ). Fig. 3. The thickness 348 shown is less than or equal to approximately 10 micrometers, e.g., in the x-direction shown. For example, the glasses 216a and / or 216b may have a thickness of less than 10 micrometers, and the layers 218a, 218b, 220a, 220b may each have a thickness of approximately 200 nanometers or less. Although shown as three layers, the anodic bonds 222 may comprise more or fewer layers. For example, the anodic bonds 222 may comprise a single layer 218 (or 220) of amorphous silicon or germanium between the cell window 206 and the cell body 204.

[0034] The vapor cell 202 can be inert in the presence of alkali metals, e.g., at elevated temperatures such as temperatures above approximately 150 °C, 250 °C, 490 °C, or 495 °C. For example, the cell body 204 and the cell windows 206 can be made of sapphire, which remains essentially transparent to the probe light 208A and / or the excitation radiation 208B and does not act as a sink for vaporized alkali atoms, e.g., it does not react with alkali atoms, so that the atoms are deposited on the inner surfaces of the cell body 204 and / or the cell windows 206. The cell windows 206, the cell body 204, and / or the anodic bonds 222 can exhibit a CTE of more than approximately 6 parts per million per degree Celsius (ppm / °C). For example, the cell windows 206 may have a CTE that is substantially adapted to the cell body 204 and / or the anodic bonds 222.The glass 216a and the glass 216b can comprise D-263 Schott glass, BK-7 optical glass, soda-lime glass, or any other suitable glass that has, for example, a CTE greater than about 6 ppm / °C. The steam cell 202 can be made of materials as listed in Table 1 below. In some examples, the steam cell 202 can comprise silicon, which may have a CTE of less than about 6 ppm / °C; however, the amount of silicon (e.g., a thin layer) for anodic bonding can be such that the CTE of the silicon does not significantly contribute to differential thermal expansion or contraction. For example, the silicon can have such a small mass that it does not negate the CTE matching of the materials of the steam cell 202. Table 1 material comment temperature CTE (x 10 -6 / °C) sapphire Parallel to the z-axis 40 - 4000 °C 7,7 sapphire Perpendicular to the z-axis 40 - 4000 °C 7,0 D-263 glass Schott Glass 20 - 300 °C 7,2 Germanium 0 - 300 °C 7,0 BK-7 glass Optical glass 20 - 300 °C 8.3 lime soda 0 - 300 °C 8,6 silicon 0 - 300 °C 3,8

[0035] In general, the steam cell can incorporate 202 materials and processes and be assembled using the same that can tolerate significant temperature ranges. For example, the optics for alkali atom processing and signal readout can be made of high-quality quartz and quartz glass and bonded with high-temperature ceramic adhesives.

[0036] Fig. Figure 3 is a cross-sectional diagram of an exemplary vapor cell 302 of a quantum sensor according to the techniques of disclosure. The vapor cell 302 may be essentially the same as the vapor cell 102 from Fig. 1 and the steam cell 202 from the Fig. 2A and Fig. 2B, except for the differences described here. In the example shown, the steam cell 302 comprises an alkali source 330 formed from an intermetallic alloy and thermal control elements 332.

[0037] The alkali source 330 can comprise a metal and an alkali, for example, an intermetallic alloy containing a variety of alkali atoms. For instance, the alkali source 330 can comprise gold and / or silver and rubidium. The alkali source 330 can have a relatively high decomposition temperature, for example, a decomposition temperature above approximately 150 °C, above approximately 250 °C, above approximately 490 °C, or above approximately 495 °C. At or above the decomposition temperature, the alkali atoms can be released from the alkali source 330 and evaporate. In some examples, the alkali source 330 can be heated to a desired density of alkali atoms released and evaporated. In some examples, the alkali source 330 can exhibit a decomposition temperature significantly higher than the operating temperature of the steam cell 302.For example, the alkali source 330 may have a decomposition temperature of approximately 495 °C and may be heated to a temperature of 495 °C or higher for a specific period (or heated for a specific period according to a temperature profile as a function of time) to release alkali atoms from the alkali source 330, such that a specific desired density of the vaporized alkali atoms is achieved within the cavity 212 of the steam cell. Subsequently, the steam cell 302 may be operated at relatively high temperatures during use, e.g., at temperatures of approximately 150 °C or higher, but below the decomposition temperature of the alkali source 330 (e.g., less than approximately 495 °C), in order to maintain the density of the vaporized alkali atoms within the steam cell 302 even at relatively high temperatures.If the density of the vaporized alkali atoms in the vapor cell 302 changes over time, the desired density can be restored via the alkali source 330, which can serve, for example, as a source or sink for alkali atoms to maintain the density of the vaporized alkali atoms. For instance, the alkali source 330 can be heated to a temperature equal to or greater than its decomposition temperature to increase the density of the vaporized alkali atoms, or the temperature of the alkali source 330 can be controlled to decrease the density of the vaporized alkali atoms within the vapor cell cavity 212.

[0038] In the example shown, the alkali source 330 is arranged on an inner surface of the cell body 204. In other examples, the alkali source 330 can have any shape and be located at any point within the steam cell cavity 212. For example, the alkali source 330 can be a pellet arranged within the steam cell cavity 212.

[0039] In the example shown, the steam cell 302 comprises thermal control elements 332. The thermal control elements 332 can be configured to heat and / or cool the alkali source 330 within the steam cell cavity 212. For example, the thermal control elements 332 can be a heating device and / or heating elements configured to heat the alkali source 330 to at least the alloy decomposition temperature. In the example shown, the thermal control elements 332 are platinum heating devices configured as coils within the steam cell body 204 and positioned close enough to the alkali source 330 to heat or cool it. In other examples, thermal control elements 332 can be arranged on an inner surface of the cell body 204 or on an outer surface of the cell body 204.In some examples, the steam cell 302 may not include thermal control elements 332, but may be configured such that the alkali source 330 can be thermally controlled. For example, the steam cell 302 may be essentially transparent to radiation that can be directed at the alkali source 330 to change its temperature, or the steam cell 302 may be configured such that the alkali source 330 can be inductively heated, e.g., via an induction coil. In some examples, the thermal control elements 332 may function as induction coils.

[0040] In the example shown, the steam cell 302 can be essentially cylindrical with a circular cross-section. The steam cell 302 can have a diameter 340, a cell body thickness 342, and a steam cavity diameter 344, for example, along the y-direction in the example shown. In some examples, the diameter 340 can be about 3 millimeters (mm), or about 5 mm, or about 7 mm, or about 10 mm, or any suitable diameter. The cell body thickness 342 can be about 0.5 mm, about 1 mm, about 3 mm, about 5 mm, or any suitable thickness. The steam cavity diameter 344 can be about 2 mm, about 5 mm, about 7 mm, or any suitable diameter. The cell windows 206 can have a thickness 346 (e.g., along the x-direction, as shown), which can be approximately 0.1 mm, approximately 0.5 mm, approximately 1 mm, or any suitable thickness. The steam cell 302 can have a total length 350 (e.g.,along the x-direction, as shown) of approximately 2 mm, approximately 5 mm, approximately 10 mm or any suitable total length.

[0041] The vapor cell 302 can have sources and sinks for evaporated alkali atoms, which are removed under operating conditions, and the number and / or density of the evaporated alkali atoms within the vapor cell cavity 212 can remain essentially constant, e.g., as a function of temperature. In some examples, the vapor cell 302 can include glass layers 216a and 216b with anodic bonds 222a and 222b, which can be sinks for evaporated alkali atoms; however, the diffusion of alkali atoms into the glass layers 216a and 216b can be less than 10 10Remove alkali atoms from the cell (e.g., less than one picogram for rubidium atoms), and the diffusion rate of the alkali atoms can decrease exponentially until the sink is effectively saturated. Since the glass layers 216a and 216b are not in the optical access area (i.e., the probing light 208A and / or the excitation radiation 208B do not propagate to or through the glass layers 216a and 216b), any darkening of the glass layers 216a and 216b associated with this diffusion has no effect on the sensor signal using the vapor cell 302.

[0042] The steam cell 302 can be designed such that the density of alkali atoms within the steam cell cavity 212 is essentially constant as a function of temperature via the alkali source 330. For example, the number density of alkali atoms can be comparable to the equilibrium number of alkali atoms at 100 °C, which is 1.927 × 10 -7Amagat (amg) or, converted, 5.178 × 10 18 atoms / m 3 Using the density of gold as a metal, an alloy volume of 0.175 cubic micrometers is required to create a 1 cm³ 3 -to fill the vapor cell cavity 212 when the alkali source 330 is completely used up. By using up only 1% of the alkali source 330, the volume of the alkali source 330 would only increase to 17.5 cubic micrometers to fill a 1-cm 3-to fill the vapor cell. The alkali source 330 can be arranged so that it does not affect the free aperture of the vapor cell 302 or the sensor (e.g., magnetometer) during operation. To release 1% of the alkali atoms, e.g., for rubidium, the temperature of the alkali source 330 can be raised by approximately 25 °C above its melting point before it resolidifies, thus allowing significant control over the final number density of the alkali atoms in the vapor cell 302. In some examples, the release of the alkali atoms from the alkali source 330 can also be monitored in situ using Doppler-free saturated absorption spectroscopy to ensure the correct number density in the vapor cell 302 before operation.

[0043] Fig.Figure 4 is a flowchart of an exemplary process for manufacturing a steam cell according to the techniques disclosed. Although the process refers to the sensor system 100 and the steam cell 102 made of Fig. 1 as well as steam cells 202 and 302 from Fig. As described in 2A-3, the procedures discussed herein may also include and / or utilize other systems and procedures in other examples.

[0044] A manufacturer can arrange at least one silicon or germanium 218, 220 on at least one of a cell window 206 or a cell body 204 (402). For example, the manufacturer can arrange silicon or germanium by coating, sputtering, depositing, or evaporating (e.g., by atomic layer deposition) silicon or germanium layers 218, 220 directly onto a surface of the cell window 206 or the cell body 204 or onto the glass layers 216. In some examples, the manufacturer can arrange glass on the silicon or germanium layers 218, 220, which are already arranged, for example, on a surface of the cell window 206 or a cell body 204.

[0045] The manufacturer can anodically bond the cell window 206 to the cell body 204 via at least one silicon or germanium 218, 220 (404). For example, the manufacturer can compress the silicon or germanium layers 218, 220 and optionally the glass layers 216 between the cell window 206 and a cell body 204 while heating the cell window 206 or a cell body 204 and / or applying a voltage or electric current to the silicon or germanium layers 218, 220 to form anodic bonds 222.

[0046] In some examples, the manufacturer can heat the alkali source 330 within the vapor cell cavity 212 to an alloy decomposition temperature in order to release at least a fraction of the multitude of alkali atoms from the alloy as vapor within the vapor cell cavity 212. The manufacturer can heat the alkali source 330 before the anodic bonding of the cell window 206 to the cell body 204, e.g., in a vacuum or inert gas environment, in which the alkali source 330 may be located inside or outside the vapor cell cavity 212, but configured to vaporize alkali atoms into the vapor cell cavity 212; or the manufacturer can heat the alkali source 330 after the anodic bonding of the cell window 206 to the cell body 204.

[0047] The following examples illustrate one or more aspects of the revelation:

[0048] Example 1: Vapor cell comprising: a cell body; and a cell window anodically bonded to the cell body, wherein the cell window and the cell body define a vapor cavity configured to contain a vapor comprising a plurality of alkali atoms.

[0049] Example 2: Steam cell according to Example 1, wherein the cell window is essentially optically transparent for a probe light.

[0050] Example 3: Steam cell according to Example 1 or Example 2, wherein the cell window comprises sapphire, wherein the cell window has a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C).

[0051] Example 4: Steam cell according to one of Examples 1 to 3, wherein the anodic bond comprises at least one of silicon or germanium and wherein the cell body comprises at least one of silicon or germanium.

[0052] Example 5: Steam cell according to one of Examples 1 to 4, wherein the cell body and the cell window are not reactive with the multitude of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C).

[0053] Example 6: Steam cell according to one of Examples 1 to 5, wherein the steam cell is designed to maintain a density of the plurality of alkali atoms within the steam cavity which is essentially constant as a function of temperature for temperatures of the steam cell above about 150 °C.

[0054] Example 7: Steam cell according to one of Examples 1 to 6, further comprising an intermetallic alloy comprising a metal and the plurality of alkali atoms.

[0055] Example 8: Steam cell according to Example 7, wherein the metal comprises at least one of gold or silver.

[0056] Example 9: Steam cell according to Example 7 or Example 8, wherein the intermetallic alloy has an alloy decomposition temperature above about 150 °C.

[0057] Example 10: Steam cell according to one of Examples 7 to 9, further comprising a heating device designed to heat the intermetallic alloy to at least the alloy decomposition temperature.

[0058] Example 11: Sensor comprising: a vapor cell, comprising: a cell body; a cell window, wherein the cell window and the cell body define a vapor cavity and are configured to contain a vapor comprising a plurality of alkali atoms; and an intermetallic alloy comprising a metal and the plurality of alkali atoms; and a detector configured to receive a probe light transmitted through the vapor cell.

[0059] Example 12: Sensor according to Example 11, wherein the cell window is essentially optically transparent to the probing light.

[0060] Example 13: Sensor according to Example 11 or Example 12, wherein the cell window comprises sapphire, wherein the cell window has a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C).

[0061] Example 14: Sensor according to one of Examples 11 to 13, wherein the cell window is anodically bonded to the cell body.

[0062] Example 15: Sensor according to Example 14, wherein the cell body comprises at least one of sapphire or germanium and wherein the anodic bond comprises at least one of silicon or germanium.

[0063] Example 16: Sensor according to one of Examples 11 to 15, wherein the cell body and the cell window are non-reactive with the multitude of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C).

[0064] Example 17: Sensor according to one of Examples 11 to 16, wherein the vapor cell is configured to maintain a density of the plurality of alkali atoms within the vapor cavity which is essentially constant as a function of temperature for vapor cell temperatures above about 150 °C.

[0065] Example 18: Sensor according to one of Examples 11 to 17, wherein the metal comprises at least one of gold or silver.

[0066] Example 19: Sensor according to one of Examples 11 to 18, wherein the intermetallic alloy has a decomposition temperature above about 150 °C.

[0067] Example 20: Sensor according to one of Examples 11 to 19, further comprising a heating device designed to heat the alloy to at least the alloy decomposition temperature.

[0068] Example 21: Method for producing a steam cell, wherein the method comprises: arranging at least one silicon or germanium on at least one of a cell window or a cell body, wherein the cell window and the cell body define a steam cavity; and anodic bonding of the cell window to the cell body via the at least one silicon or germanium.

[0069] Example 22: Method according to Example 21, further comprising: arranging glass on at least one of the silicon, the germanium, the cell window or the cell body; and anodic bonding of the cell window to the cell body via the glass.

[0070] Example 23: Method according to Example 21 or Example 22, further comprising: heating an intermetallic alloy within the vapor cavity, wherein the intermetallic alloy comprises a metal and a plurality of alkali atoms, to an alloy decomposition temperature in order to release at least a proportion of the plurality of alkali atoms from the alloy as vapor within the vapor cavity.

[0071] Example 24: Steam cell comprising: a cell body; a cell window having a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C), wherein the cell window is anodically bonded to the cell body, wherein the cell window and the cell body define a steam cavity configured to contain a steam comprising a plurality of alkali atoms, the anodic bond comprising at least one of silicon or germanium, wherein the cell body and the cell window are non-reactive with the plurality of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C); and an intermetallic alloy comprising a metal and the plurality of alkali atoms, wherein the intermetallic alloy has an alloy decomposition temperature above about 490 °C.

[0072] The techniques described in this disclosure may be implemented, at least in part, in hardware, software, firmware, or any combination thereof. For example, various aspects of the techniques may be implemented in one or more microprocessors, DSPs, ASICs, FPGAs, or other equivalent integrated or discrete logic QRS circuits, as well as in any combination of such components embodied in external devices. The terms "processor" and "processing circuit" may refer generally to any of the aforementioned logic circuits, alone or in combination with other logic circuits, or to any other equivalent circuit, alone or in combination with other digital or analog circuits.

[0073] For aspects implemented in software, at least some of the functions attributed to the systems and devices described in this disclosure may be embodied as instructions on a computer-readable storage medium such as RAM, DRAM, SRAM, magnetic disks, optical disks, flash memory, or forms of EPROM or EEPROM in their embodiment. The instructions may be executed to support one or more aspects of the functions described in this disclosure.

[0074] Furthermore, the functions described herein can, in some respects, be provided in dedicated hardware and / or software modules. Representing various features as modules or units serves to highlight different functional aspects and does not necessarily mean that such modules or units must be implemented by separate hardware or software components. Rather, functions associated with one or more modules or units can be performed by separate hardware or software components or integrated into common or separate hardware or software components. Moreover, the techniques can be implemented entirely within one or more circuits or logic elements. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 536,153

[0001] HR 00112390115

[0002]

Claims

Vapor cell comprising: a cell body; and a cell window anodically bonded to the cell body, the cell window and the cell body defining a vapor cavity configured to contain a vapor comprising a plurality of alkali atoms. Steam cell according to claim 1, wherein the cell window is essentially optically transparent for a probe light. Steam cell according to claim 1 or claim 2, wherein the cell window comprises sapphire, wherein the cell window has a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C). Steam cell according to one of claims 1 to 3, wherein the anodic bond comprises at least one of silicon or germanium and wherein the cell body comprises at least one of silicon or germanium. Steam cell according to one of claims 1 to 4, wherein the cell body and the cell window are non-reactive with the plurality of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C). Steam cell according to one of claims 1 to 5, wherein the steam cell is configured to maintain a density of the plurality of alkali atoms within the steam cavity which is substantially constant as a function of temperature for temperatures of the steam cell above about 150 °C. Steam cell according to one of claims 1 to 6, further comprising an intermetallic alloy comprising a metal and a plurality of alkali atoms. Steam cell according to claim 7, wherein the metal comprises at least one of gold or silver. Steam cell according to claim 7 or claim 8, wherein the intermetallic alloy has an alloy decomposition temperature above about 150 °C. Steam cell according to one of claims 7 to 9, further comprising a heating device configured to heat the intermetallic alloy to at least the alloy decomposition temperature. Sensor comprising: a vapor cell, comprising: a cell body; a cell window, wherein the cell window and the cell body define a vapor cavity configured to contain a vapor comprising a plurality of alkali atoms; and an intermetallic alloy comprising a metal and a plurality of alkali atoms; and a detector configured to receive a probe light transmitted through the vapor cell. Sensor according to claim 11, wherein the cell window is essentially optically transparent to the probing light. Sensor according to claim 11 or claim 12, wherein the cell window comprises sapphire, wherein the cell window has a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C). Sensor according to one of claims 11 to 13, wherein the cell window is anodically bonded to the cell body. Sensor according to claim 14, wherein the cell body comprises at least one of sapphire or germanium and wherein the anodic bond comprises at least one of silicon or germanium. Sensor according to one of claims 11 to 15, wherein the cell body and the cell window are non-reactive with the plurality of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C). Sensor according to one of claims 11 to 16, wherein the vapor cell is configured to maintain a density of the plurality of alkali atoms within the vapor cavity which is substantially constant as a function of temperature for vapor cell temperatures above about 150 °C. Sensor according to any one of claims 11 to 17, wherein the metal comprises at least one of gold or silver. Sensor according to one of claims 11 to 18, wherein the intermetallic alloy has a decomposition temperature above about 150 °C. Sensor according to one of claims 11 to 19, further comprising a heating device configured to heat the alloy to at least the alloy decomposition temperature. A method for producing a steam cell, the method comprising: arranging at least one silicon or germanium component on at least one component of a cell window or a cell body, wherein the cell window and the cell body define a steam cavity; and anodizing the cell window to the cell body via the at least one silicon or germanium component. The method of claim 21, further comprising: arranging glass on at least one of the silicon, the germanium, the cell window or the cell body; and undanodic bonding of the cell window to the cell body via the glass. The method of claim 21 or claim 22, further comprising: heating an intermetallic alloy within the vapor cavity, wherein the intermetallic alloy comprises a metal and a plurality of alkali atoms, to an alloy decomposition temperature in order to release at least a proportion of the plurality of alkali atoms from the alloy as vapor within the vapor cavity. Steam cell comprising: a cell body; a cell window having a coefficient of thermal expansion (CTE) of more than about 6 parts per million per degree Celsius (ppm / °C), wherein the cell window is anodically bonded to the cell body, wherein the cell window and the cell body define a steam cavity configured to contain a steam comprising a plurality of alkali atoms, wherein the anodic bond comprises at least one of silicon or germanium, wherein the cell body and the cell window are non-reactive with the plurality of alkali atoms at steam cell temperatures above about 150 degrees Celsius (°C); and an intermetallic alloy comprising a metal and a plurality of alkali atoms, wherein the intermetallic alloy has an alloy decomposition temperature above about 490 °C.

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