Apparatus and method for coupling electromagnetic energy into cavity of resonator comprising one or more loop-gap resonators

Abstract

To provide techniques for efficiently coupling radio frequency spectrum electromagnetic energy into a central cavity of a resonator comprising one or more loop-gap resonators.SOLUTION: Electromagnetic energy is first coupled into each loop-gap resonator 112-1, 112-2, 112-3, 112-N. Each portion of the electromagnetic energy is coupled from each loop-gap resonator into a central cavity 101.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT This invention was made with government support under Contract No. N00014-22-C-1043 awarded by the Office of Naval Research. The government has certain rights in this invention. [Background technology]

[0002] An electromagnetic resonator including a central cavity and two or more peripheral cavities coupled to the central cavity via capacitive gaps is used in an atomic clock to provide an electromagnetic field in a radio frequency spectrum, which changes the energy state of electrons in the atoms in the central cavity. Within the central cavity, the electromagnetic field has a substantially stable phase and amplitude. Recent applications require compact atomic clocks with reduced power consumption. Correspondingly, an electromagnetic energy source in the radio frequency spectrum and configured to provide the electromagnetic field has a reduced power level. Summary of the Invention

[0003] In some aspects, techniques described herein relate to an apparatus for efficiently coupling electromagnetic energy to a central cavity of a primary resonator within a conductive ring, the apparatus including: a central cavity within the conductive ring; one or more satellite cavities within the conductive ring; and one or more gaps within the conductive ring, each gap beginning with a unique satellite cavity and terminating at the central cavity, wherein each gap, the central cavity, and each satellite cavity is an air gap within the conductive ring; the apparatus further including: one or more gaps; and one or more loop gap resonators, each loop gap resonator including a unique satellite cavity and a unique gap between its unique satellite cavity and the central cavity, wherein each loop gap resonator is configured to receive radio frequency spectrum electromagnetic energy from a source external to the conductive ring; and a primary resonator including each loop gap resonator and the central cavity, wherein each loop gap resonator is configured to electromagnetically couple at least a portion of the radio frequency spectrum electromagnetic energy to the central cavity.

[0004] In some aspects, techniques described herein relate to a method for efficiently coupling electromagnetic energy to a central cavity of a primary resonator within a conductive ring, the method including receiving the radio frequency spectrum electromagnetic energy in one or more loop gap resonators, each loop gap resonator configured to receive radio frequency spectrum electromagnetic energy from a source external to the conductive ring, each loop gap resonator including a unique satellite cavity and a unique gap connecting its unique satellite cavity to a central cavity, each gap, each satellite cavity, and each central cavity within the conductive ring, each gap, each central cavity, and each satellite cavity being an air gap within the conductive ring; and electromagnetically coupling at least a portion of the radio frequency spectrum electromagnetic energy from the one or more loop gap resonators to the central cavity, wherein the primary resonator includes each loop gap resonator and the central cavity.

[0005] In some aspects, the techniques described herein relate to an apparatus configured to efficiently couple electromagnetic energy to a central cavity within a conductive ring, the apparatus comprising: a conductive ring including a conductor, a central cavity within the conductor defined by an inner radius, a plurality of gaps within the conductor, and a plurality of satellite cavities within the conductor, each satellite cavity disposed around the central cavity and equally spaced with respect to each adjacent satellite cavity and equally spaced with respect to the central cavity, each satellite cavity being connected by a unique gap, each satellite cavity having a satellite cavity radius, and each gap, central cavity, and each satellite cavity being an air gap within the conductor; at least one loop gap resonator, each loop gap resonator including a unique satellite cavity and a gap connecting the unique satellite cavity to the central cavity; a primary resonator including each loop gap resonator and the central cavity; and a plurality of sets of at least one shielded transmission line and electromagnetic coupling element, each shielded transmission line of the set electromagnetically coupled to a coupling element, each coupling element configured to electromagnetically couple radio frequency spectrum electromagnetic energy to a unique loop gap resonator, and each loop gap resonator configured to electromagnetically couple at least one portion of the radio frequency spectrum electromagnetic energy to the central cavity. [Brief explanation of the drawings]

[0006] Example embodiments will be described with additional specificity and detail using the accompanying drawings, with the understanding that the drawings illustrate example embodiments only and therefore should not be considered limiting in scope. [Figure 1] 1 shows a diagram of one embodiment of a resonator including one or more loop gap resonators. [Figure 2] 1 illustrates a schematic diagram of one embodiment of an electromagnetic feed network configured to provide electromagnetic energy to one or more loop gap resonators. [Figure 3] 1 shows a schematic diagram of one embodiment of a set of shielded transmission line networks electrically connected to an electromagnetic coupling element. [Figure 4] 1 illustrates a cross-sectional view of one embodiment of an electronic sensor. [Figure 5] 1 illustrates a flow diagram of an exemplary method for efficiently coupling electromagnetic energy into a central cavity of a resonator that also includes one or more loop gap resonators.

[0007] According to common practice, the various features described are not drawn to scale but are drawn to emphasize particular features relevant to the exemplary embodiments. Reference characters denote like elements throughout the figures and text. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which specific exemplary embodiments are shown by way of illustration. However, it is to be understood that other embodiments may be utilized and structural, mechanical, and / or electrical changes may be made. Furthermore, the methods presented in the drawings and specification should not be construed as limiting the order in which the individual steps may be performed. The following detailed description is not to be construed in a limiting sense.

[0009] An embodiment of the present invention efficiently couples electromagnetic energy in a radio frequency spectrum (e.g., 1 kHz to 300 GHz) into a central cavity of a resonator (or primary resonator), which also includes one or more loop gap resonators. Optionally, the frequency of the electromagnetic energy is 6.8 GHz. Each satellite cavity is distributed around the central cavity and is connected to the central cavity by a gap, i.e., a capacitive gap. Thus, each gap connects the central cavity to its own satellite cavity. Each gap, each satellite cavity, and the central cavity are each air gaps within a conductive ring. Unless expressly stated otherwise elsewhere in this specification, cavity does not refer to a primary resonator.

[0010] The satellite cavities and the gaps connecting the satellite cavities with the central cavity form a loop gap resonator, which may be referred to herein as a satellite resonator. The central cavity and each satellite cavity, and each gap connecting the central cavity to a satellite cavity, form a primary resonator. Each gap may be referred to herein as a capacitive gap or slot.

[0011] Electromagnetic energy at a first frequency from an external source is coupled through each coupling element of a set of one or more coupling elements to each loop gap resonator having a first resonant frequency. A portion of the electromagnetic energy is electromagnetically coupled to each loop gap resonator through near-field radiation from a unique coupling element. Optionally, each coupling element may be a conductive loop, such as a wire coil. Optionally, each loop gap resonator has a first resonant frequency. At least a portion of the electromagnetic energy is then electromagnetically coupled from the loop gap resonator to the central cavity of the primary resonator. The primary resonator has a second resonant frequency. The foregoing technique efficiently couples electromagnetic energy from an external source to the central cavity of the primary resonator. As a result, a lower-power, and optionally lower-cost and / or smaller, electromagnetic energy source may be utilized.

[0012] Optionally, the primary resonator has a second resonance centered about a second resonant frequency, and each loop gap resonator has a first resonance centered about the first resonant frequency. Optionally, the difference between the first resonant frequency and the second resonant frequency is no more than one linewidth, two linewidths, or three linewidths of the widest of the first and second resonances. Optionally, the first resonant frequency and the second resonant frequency are substantially equal. Optionally, the first frequency is substantially equal to the first and second resonant frequencies.

[0013] Optionally, the primary resonator may be used in an atomic sensor. Optionally, the atomic sensor is an atomic clock. However, the atomic sensor may alternatively be another type of atomic sensor.

[0014] Optionally, embodiments of the present invention provide a substantially uniform electromagnetic field amplitude and phase throughout the central cavity of the primary resonator that confines the atoms. Optionally, any atom within the central cavity is exposed to an electromagnetic field that differs in phase by less than 0.1% from the electromagnetic fields to which other atoms are exposed. This results in improved accuracy of the atomic sensor.

[0015] FIG. 1 shows a diagram of one embodiment of a primary resonator (or primary resonator) 100 that includes one or more loop gap resonators. The dimensions (e.g., length and radius) of the primary resonator 100 may vary in each embodiment. The relative dimensions shown in FIG. 1 are for instructional purposes only. For instructional purposes, FIG. 1 depicts the satellite and central cavities as cylindrical cavities. Alternatively, two or more of the cavities may be non-cylindrical cavities.

[0016] The primary resonator 100 includes a conductive ring 105 that includes a central cavity 101 surrounded by N satellite cavities 102-1, 102-2, 102-3, 102-N, where N is an integer greater than 0, such as 1, 2, 3, 4, or greater than 4. For instructional purposes, the conductive ring 105 is shown as having a circular perimeter, although the perimeter may alternatively have a perimeter of another shape, such as a square.

[0017] The illustrated conductive ring 105 has an outer radius Ro, an inner radius Ri, and a length L. The outer radius Ro and inner radius Ri are projected from a central axis 118 of the primary resonator 100 and, therefore, the conductive ring 105. The central cavity 101 is therefore centered about the central axis 118. Optionally, the length (cylinder length) L lies within the Z-axis Z, and the central axis 118 is parallel to the Z-axis Z.

[0018] The central cavity 101 has a radius equal to the inner radius Ri and a length equal to the length L. The cross section 117 of the central cavity 101 has a perimeter Pc defined by the inner radius Ri.

[0019] Each satellite cavity 102-1, 102-2, 102-3, 102-N has a radius Rs projected from the central axis of the satellite cavity and a length equal to the length L. A cross section 116 of the satellite cavity has a perimeter Ps defined by the radius Rs of the satellite cavity. Optionally, the central axes 114-1, 114-2, 114-3, 114-N of each satellite cavity 102-1, 102-2, 102-3, 102-N are equidistant from the central axis 118 of the central cavity 101.

[0020] The conductive ring 105 has a first surface FS and a second surface SS. The first surface FS is opposite the second surface SS. The first surface FS is spaced from the second surface SS by a length L. Thus, the central cavity 101 and each of the satellite cavities 102-1, 102-2, 102-3, 102-N are formed within the conductive ring 105 between the first surface FS and the second surface SS. Optionally, the length L is perpendicular to the first surface FS and the second surface SS.

[0021] Each satellite cavity 102-1, 102-2, 102-3, 102-N is connected to the central cavity 101 by a gap 107-1, 107-2, 107-3, 107-N in the primary resonator 100. Each gap 107-1, 107-2, 107-3, 107-N extends from the surface Sc of the central cavity 101 to the surface Ss of the satellite cavity. Optionally, each gap 107-1, 107-2, 107-3, 107-N is a rectangular parallelepiped and extends between the region of the periphery Pc of the central cavity 101 that is closest to the region of the periphery Ps of the satellite cavity connected to the central cavity by that gap.

[0022] The area of the surface Sc of the central cavity 101 is defined by the perimeter Pc of the central cavity 101 and the conductive ring 105, e.g., the cylindrical length L of the central cavity 101. The area of the surface Ss of each satellite cavity 102-1, 102-2, 102-3, 102-N is defined by the perimeter Ps of the satellite cavity and the conductive ring 105, e.g., the cylindrical length L of the satellite cavity.

[0023] Optionally, the central axis of each satellite cavity 102-1, 102-2, 102-3, 102-N is spaced apart from the central axis of each adjacent satellite cavity by angle A (with respect to central axis 118) when the first and second satellite cavities are adjacent to one another. In such a case, angle A is equal to 360 degrees divided by N. Optionally, each central axis of each satellite cavity 102-1, 102-2, 102-3, 102-N is displaced the same distance from central axis 118 of central cavity 101. Thus, optionally, each pair of adjacent satellite cavities is equally spaced within the conductive ring. Furthermore, optionally, if gap length 104 is the same for each gap, each satellite cavity is equally spaced from central cavity 101. Optionally, the gap width 106 is the same for each gap.

[0024] Optionally, the closest points on the perimeter Ps of each satellite cavity 102-1, 102-2, 102-3, 102-N and the perimeter Pc of the central cavity 101 are separated by a gap length 104 of gaps 107-1, 107-2, 107-3, 107-N. Optionally, each gap is separated from each adjacent gap by an angle A (with respect to the central axis 118).

[0025] The primary resonator 100 includes (i) a central cavity 101 and (ii) N loop gap resonators 112-1, 112-2, 112-3, 112-N, i.e., a respective satellite cavity and a respective gap 107-1, 107-2, 107-3, 107-N connecting the central cavity 101 to the satellite cavity 102-1, 102-2, 102-3, 102-N. Each of the N loop gap resonators 112-1, 112-2, 112-3, 112-N includes a satellite cavity and a gap connecting the central cavity 101 to that satellite cavity.

[0026] 2 shows a schematic diagram of one embodiment of an electromagnetic feed network 220 configured to supply electromagnetic energy to one or more of the N loop gap resonators. The electromagnetic feed network 220 includes M sets 222-1, 222-M of shielded transmission line networks 221-1, 221-M electrically connected to electromagnetic coupling elements 224-1, 224-M, where M is an integer greater than or equal to 0 and less than or equal to N, and optionally M is equal to N.

[0027] Each of the shielded transmission line networks 221-1, 221-M is electromagnetically shielded so as not to emit electromagnetic energy, and may be formed by a stripline, a coaxial cable, or any other electromagnetically shielded transmission line.

[0028] Each electromagnetic coupling element 224-1, 224-M of one of the M sets 222-1, 222-M is configured to electromagnetically couple electromagnetic energy from the shielded transmission line network 221-1, 221-M to a unique loop gap resonator. Each electromagnetic coupling element 224-1, 224-M is configured to be positioned adjacent to the first surface FS or the second surface SS of the primary resonator 100 and adjacent to a unique satellite cavity. Each electromagnetic coupling element 224-1, 224-M may be formed by a loop of conductive material, such as a wire. Optionally, each coupling element has a radius equal to, less than, or greater than the radius of the satellite cavity on which the coupling element is positioned.

[0029] The electromagnetic feed network 220 is configured to be mounted on one of the first surface FS and the second surface of the primary resonator, Optionally, the first electromagnetic feed network is mounted on the first surface FS and the second electromagnetic feed network is mounted on the second surface SS.

[0030] Optionally, each electromagnetic feed network 225 has a center point Cefm configured such that the central axis 118 of the primary resonator 100 protrudes therethrough, and the plane 227 on which the electromagnetic feed network 225 resides is orthogonal to the central axis 118 of the primary resonator 100. For teaching purposes, the location of the central cavity 101 is represented by the dashed circle 223.

[0031] Optionally, each electromagnetic coupling element 224-1, 224-M includes a center point Cer through which a central axis of a unique satellite cavity is configured to protrude, with plane 227 being perpendicular to the central axis of the central axis. Optionally, each electromagnetic coupling element includes a perimeter Per defined by the conductors of that electromagnetic coupling element that are farthest from the center point Cer of that electromagnetic coupling element. Optionally, the perimeter Per of the electromagnetic coupling element has a radius Rr. Optionally, the perimeter Per of the electromagnetic coupling element is confined within a perimeter Ps of a satellite cavity whose central axis protrudes through the center point Cer of that electromagnetic coupling element.

[0032] 3 shows a schematic diagram of one embodiment of a set of shielded transmission line networks 322 electrically connected to an electromagnetic coupling element 324. The set of shielded transmission line networks 322 includes a first shielded transmission line 322-A, an optional second shielded transmission line 322-B, and an impedance element 322-C.

[0033] The first shielded transmission line 322-A has a first transmission line port TP1 and a termination impedance ZT. The first shielded transmission line 322-A is configured to receive a radio frequency spectrum electromagnetic signal RFS at the first transmission line port TP1, e.g., from a radio frequency spectrum signal source, e.g., an oscillator. Such radio frequency spectrum electromagnetic signal RFS is configured to propagate to the second transmission line port TP2.

[0034] The electromagnetic coupling element 324 is configured to couple at least some portion of the radio frequency spectrum electromagnetic signal RFS from the shielded transmission line network 322. For example, as discussed elsewhere herein, when positioned adjacent to the satellite cavity, the electromagnetic coupling element 324 is configured to couple at least some portion of the radio frequency spectrum electromagnetic signal RFS to the loop gap resonator by electromagnetic near-field coupling.

[0035] The electromagnetic coupling element 324 includes a first coupling element port RP1 and a second coupling element port RP2. The first coupling element port RP1 is electrically coupled to the second transmission line port TP2. The second coupling element port RP2 is electrically connected to a termination impedance ZT or electrical ground GND. The impedance value of the termination impedance ZT is selected to enhance, e.g., optimize, the amount of power in the radio frequency spectrum electromagnetic signal RFS radiated from the electromagnetic coupling element 324 and thus coupled to the loop gap resonator.

[0036] For instructional purposes, the termination impedance ZT is shown as an impedance element 322-C electrically connected to the optional second shielded transmission line 322-B. The impedance element 322-C is electrically connected to ground. The optional second shielded transmission line 322-B is electrically connected to the second coupling element port RP2. However, alternative implementations of the termination impedance ZT may be used.

[0037] In the embodiment shown in FIG. 3, the termination impedance ZT is implemented as follows: The optional second shielded transmission line 322-B includes a third transmission line port TP3 and a fourth transmission line port TP4. The impedance element 322-C includes a first impedance element port ZP1 and a second impedance element port ZP2. For instructional purposes, the impedance element 322-C is shown as a resistor. However, the impedance element 322-C may be any type of impedance element. The third transmission line port TP3 is electrically coupled to the second coupling element port RP2. The fourth transmission line port TP4 is electrically coupled to the first impedance element port ZP1. The second impedance element port ZP2 is electrically connected to electrical ground GND.

[0038] 4 shows a cross-sectional view of one embodiment of an atomic sensor 440. The atomic sensor may be implemented in a variety of ways. For example, each pair of light beams may be generated by a single laser whose light beam passes through the atomic vapor and is reflected back into the atomic vapor by an optical reflector, e.g., a mirror. Thus, the optional second light source described below may be replaced by an optical reflector.

[0039] The atomic sensor 440 comprises a primary resonator 400, a first cap 443-1, a second cap 443-2, an optional at least one conductive coil 447, a first light source OS1, an optional second light source OS2, and at least one photodetector PD. As discussed elsewhere herein, the primary resonator 400 includes a first surface FS, a second surface SS, a central cavity 401, at least one, e.g., two or more, satellite cavities 402, and a cylindrical length L.

[0040] The first cap 443-1 is configured to be mounted on a first surface FS of the primary resonator 400. Thus, the first cap 443-1 encloses a first end (at the first surface FS) of the central cavity 401. The second cap 443-2 is configured to be mounted on a second surface SS of the primary resonator 400. Thus, the second cap 443-2 encloses a second end (at the second surface SS) of the central cavity 401.

[0041] The illustrated atomic sensor 440 operates by placing an atomic vapor cell 449 containing a vapor of atoms 448, such as a vapor of alkali atoms, within the central cavity 401. The atomic vapor cell 449 may be within a chamber formed by the surface of the central cavity 401, a first surface FF, and a second surface SS. Alternatively, the atomic vapor cell 449 may be formed differently, for example, within an optically transparent, insulating container, for example made of quartz, inserted within the chamber formed by the surface of the central cavity 401, the first surface FF, and the second surface SS.

[0042] The first light source OS1 and optional second light source OS2 are configured to emit a first coherent light beam 445-1 and a second coherent light beam 445-2, respectively, directed toward the atomic vapor 448. The first coherent light beam 445-1 is projected from the first surface FS, and the second coherent light beam 445-2 is projected from the second surface FS. The first coherent light beam 445-1 and the second coherent light beam 445-2 are directed toward each other and configured to meet within a volume 462 in the central cavity 401. Optionally, the first coherent light source OS1 is attached to a first cap 443-1, and the optional second light source OS2 is attached to a second cap 443-2. For this reason, and because the frequencies of each of the first coherent light beam 445-1 and the second coherent light beam 445-2 are configured to cool the atomic vapor 448, the atomic vapor 448 is trapped (or confined) within a volume 462 within the central cavity 401.

[0043] While FIG. 4 shows one pair of light beams (or, e.g., laser beams or laser light) for instructional purposes, optionally, more than one pair of light beams for trapping atomic vapor 448 within volume 462. Optionally, each light source is configured to provide a coherent light beam. Optionally, each light source is a laser, a grating utilized to emit light generated by a laser, or another device configured to emit an optical signal or light beam. Each pair of light beams includes a beam emitted from either side of length L of primary resonator 400, e.g., from first cap 443-1 and second cap 443-2.

[0044] Optional at least one conductive coil 447 is configured to generate a constant magnetic field within volume 462 that aligns the spins of atoms trapped within volume 462 and reduces the effects of external magnetic fields. Optional at least one conductive coil 447 is configured to be electrically coupled to optional direct current (DC) voltage source 441. The optional DC voltage source is coupled between optional at least one conductive coil 447 and electrical ground GND. Optionally, atomic sensor 440 includes DC voltage source 441.

[0045] An optional radio frequency spectrum signal source 444 generates a radio frequency spectrum electromagnetic signal RFS. The optional radio frequency spectrum signal source 444 is electrically coupled to the at least one electromagnetic feed network 420-1, 420-2 and configured to provide the radio frequency spectrum electromagnetic signal RFS to each of the at least one electromagnetic feed network 420-1, 420-2. Optionally, the atomic sensor 440 includes the optional radio frequency spectrum signal source 444.

[0046] A radio frequency spectrum electromagnetic signal RFS is configured to be provided to at least one end of each satellite cavity 402 in a manner described elsewhere herein. For instructional purposes, FIG. 4 shows that the radio frequency spectrum electromagnetic signal RFS is provided to both ends of the satellite cavities 402. The radio frequency spectrum electromagnetic signal RFS is configured to be provided to the ends of the satellite cavities by electromagnetic feed networks 420-1, 420-2 in a manner described elsewhere herein.

[0047] The frequencies of the radio frequency spectrum electromagnetic signal RFS cause electrons of the atoms of the atomic vapor 448 to transition between energy levels. Using standard techniques of atomic fluorescence spectroscopy, the atoms may be stimulated to emit light after transitioning between energy levels, and the atomic sensor is configured to detect the emitted light with at least one photodetector PD. In response to receiving the emitted light, the at least one photodetector PD generates an electrical signal. The at least one photodetector PD is configured to be mounted above the central cavity 401 on the first side FS and / or the second side SS. For instructional purposes, FIG. 4 shows the at least one photodetector PD as being mounted above the central cavity 401 on the first side.

[0048] An optional processing system (or processing circuit) 446 is configured to receive the electrical signals. The optional processing system 446 is optionally further configured to process the electrical signals from the at least one photodetector PD to accurately infer the presence of a fluctuating external influence on the atomic vapor, such as a magnetic field, an electric field, a gravitational field, or an inertial force. Optionally, for example, when there are substantially no fluctuating external influences on the atomic vapor and the optional processing system 446 is configured to process the electrical signals from the photodetector PD to generate a control signal CS, for example, to control the frequency of a radio frequency spectrum electromagnetic signal RFS generated by the optional radio frequency spectrum signal source 444, the optional radio frequency spectrum signal source 444 becomes an atomically stable frequency reference when so controlled.

[0049] 5 shows a flow diagram of an exemplary method 550 for efficiently coupling electromagnetic energy into a cavity of a primary resonator that also includes one or more loop gap resonators. The exemplary method 550 may be implemented by one or more of the devices shown in FIGS. 1-4. To the extent that the methods herein are described herein as being implemented by one or more of the devices shown in FIGS. 1-4, it should be understood that other embodiments may be implemented in other manners. Techniques described with respect to the embodiments shown in FIGS. 1-4 may be applicable to the method 550.

[0050] The blocks of the flow diagrams herein are generally organized sequentially for ease of explanation. However, it should be understood that this organization is merely exemplary and that the operations associated with the methods (and illustrated blocks) may occur in a different order (e.g., at least some of the operations associated with the blocks may be performed in a parallel and / or event-driven manner).

[0051] At block 551, radio frequency spectrum electromagnetic energy, e.g., at a first frequency, is received at one or more loop gap resonators within the conductive ring, with each loop gap resonator receiving the radio frequency spectrum electromagnetic energy from a unique coupling element, as discussed elsewhere herein.

[0052] At least a portion of radio frequency spectrum electromagnetic energy is electromagnetically coupled from one or more loop gap resonators to a central cavity of a primary resonator at block 552. As described elsewhere herein, the primary resonator includes a central cavity and one or more loop gap resonators.

[0053] In optional block 553, atoms, e.g., alkali atoms, are confined within the central cavity, e.g., using at least one pair of opposing light beams, e.g., each generated by a laser, and directed at the vapor of atoms within the cavity, e.g., as further described elsewhere herein. Further, the atoms within the cavity are exposed to at least a portion of that portion of the radio frequency spectrum electromagnetic energy.

[0054] At optional block 554, the optical signal emitted from the atoms in the central cavity generates an electrical signal, for example, in a photodetector. The optical signal is emitted by the atoms in the central cavity when they are exposed to at least a portion of at least some portion of the radio frequency spectrum electromagnetic energy. For purposes of clarity, at least a portion of the at least some portion of the radio frequency spectrum electromagnetic energy is within the central cavity.

[0055] In optional block 555, a control signal is generated using the electrical signal, for example by a processing system. In optional block 556, a frequency of the radio frequency spectrum electromagnetic energy is controlled, for example stabilized, using the control signal.

[0056] While the present teachings have been presented with respect to one or more embodiments, changes and / or modifications to the presented embodiments may be made without departing from the scope of the appended claims. In addition, while certain features of the present disclosure may be described with respect to only one of several embodiments, such features may be combined with one or more features of other embodiments as may be desirable or advantageous for any given or particular function. Furthermore, to the extent that terms such as "including," "includes," "having," "has," "with," or variations thereof are used in either the Detailed Description and / or the Claims, such terms are intended to be as inclusive as the term "comprising." The term "at least one of" is used to mean that one or more of the listed items may be selected. As used herein, the term "one or more of," with respect to a list of items, such as A and B, or A and / or B, means A only, B only, or A and B. The term "at least one of" is used to mean that one or more of the listed items may be selected.

[0057] Relative position terms used in this application are defined based on a plane parallel to a conventional plane or working surface of a material (e.g., a layer or substrate), regardless of orientation. Terms such as "on," "higher," "lower," "over," "top," and "under" are defined with respect to a conventional plane or working surface that is on top of a layer or substrate, regardless of orientation. The terms "about" or "substantially" indicate that a specified value or parameter may be slightly modified unless such modification results in non-compliance of the process or structure with the illustrated embodiment. Finally, "exemplary" indicates that the description does not imply ideality but is used as an example. While specific embodiments have been shown and described herein, those skilled in the art will recognize that any configuration expected to achieve the same purpose may be substituted for the specific embodiment shown. Therefore, it is manifestly intended that this invention be limited only by the claims and equivalents thereof. Example

[0058] Example 1 includes an apparatus for efficiently coupling electromagnetic energy into a central cavity of a primary resonator within a conductive ring, the apparatus comprising: a central cavity within the conductive ring; one or more satellite cavities within the conductive ring; one or more gaps within the conductive ring, each gap beginning with a unique satellite cavity and terminating at the central cavity, each gap, central cavity, and each satellite cavity being an air gap within the conductive ring; and one or more loop gap resonators, each loop gap resonator comprising a unique satellite cavity and a unique gap between its unique satellite cavity and the central cavity, each loop gap resonator configured to receive radio frequency spectrum electromagnetic energy from a source external to the conductive ring; and a primary resonator comprising each loop gap resonator and the central cavity, each loop gap resonator configured to electromagnetically couple at least a portion of the radio frequency spectrum electromagnetic energy to the central cavity.

[0059] Example 2 includes the apparatus of example 1, further comprising one or more coupling elements each configured to electromagnetically couple radio frequency spectrum electromagnetic energy to a respective loop gap resonator, each coupling element configured to receive radio frequency spectrum electromagnetic energy from a source, the conductive ring comprising a first surface and a second surface spaced apart by a length of the conductive ring, and each coupling element disposed over a unique satellite cavity and over either the first surface or the second surface.

[0060] Example 3 includes the apparatus of example 2, wherein each coupling element is a loop of electrical conductor having a radius equal to, less than, or greater than the radius of the unique satellite cavity on which the coupling element is disposed.

[0061] Example 4 includes the apparatus of example 3, wherein each coupling element is centered on the central axis of a unique satellite cavity.

[0062] Example 5 includes the device of any of Examples 1 to 4, wherein each satellite cavity is cylindrical.

[0063] Example 6 includes the device of any of Examples 1-5, wherein the central cavity is cylindrical.

[0064] Example 7 includes the device of any of Examples 1-6, wherein each loop gap resonator has a first resonance centered at a first resonant frequency, and the primary resonator has a second resonance centered at a second resonant frequency, and a difference between the first resonant frequency and the second resonant frequency is less than or equal to three times the linewidth of the widest resonance among the first and second resonances.

[0065] Example 8 includes the device of any of Examples 1-7, further comprising: a first cap mounted on a first surface of the conductive ring and enclosing a first end of the central cavity; a second cap mounted on a second surface of the conductive ring and enclosing a second end of the central cavity, the first surface and the second surface being separated by a length of the conductive ring; a vapor of atoms in the central cavity; at least one laser light source in each of the first and second caps; at least one photodetector in at least one of the first and second caps configured to generate an electrical signal in response to an optical signal generated by the atoms in response to at least a portion of radio frequency spectrum electromagnetic energy in the central cavity; a processing circuit electrically coupled to the at least one photodetector and configured to generate a control signal used to control the frequency of the radio frequency spectrum electromagnetic energy; and one or more coupling elements, each configured to electromagnetically couple the radio frequency spectrum electromagnetic energy to a unique loop gap resonator, each coupling element disposed over a unique satellite cavity and on either the first surface or the second surface.

[0066] Example 9 includes a method for efficiently coupling electromagnetic energy to a central cavity of a primary resonator within a conductive ring, the method including receiving the radio frequency spectrum electromagnetic energy in one or more loop gap resonators, each loop gap resonator configured to receive radio frequency spectrum electromagnetic energy from a source external to the conductive ring, each loop gap resonator comprising a unique satellite cavity and a unique gap connecting the unique satellite cavity to the central cavity, each gap, each satellite cavity, and each central cavity within the conductive ring, each gap, each central cavity, and each satellite cavity being an air gap within the conductive ring; and electromagnetically coupling at least a portion of the radio frequency spectrum electromagnetic energy from the one or more loop gap resonators to the central cavity, wherein the primary resonator comprises each loop gap resonator and the central cavity.

[0067] Example 10 includes the method of example 9, wherein each loop gap resonator has a first resonance centered about a first resonant frequency, and the primary resonator has a second resonance centered about a second resonant frequency, wherein a difference between the first resonant frequency and the second resonant frequency is less than or equal to three times the linewidth of the widest resonance among the first and second resonances.

[0068] Example 11 includes the method of any of Examples 9-10, further including: confining the atoms within the central cavity using at least one pair of opposing optical beams; and generating electrical signals from optical signals emitted from the atoms in response to a corresponding portion of the radio frequency spectrum electromagnetic energy.

[0069] Example 12 includes the method of example 11, further including generating the control signal from the electrical signal and using the control signal to control a frequency of electromagnetic energy in the radio frequency spectrum.

[0070] Example 13 includes an apparatus configured to efficiently couple electromagnetic energy to a central cavity within a conductive ring, the apparatus including: a conductive ring comprising: a conductor; a central cavity within the conductor defined by an inner radius; a plurality of gaps within the conductor; and a plurality of satellite cavities within the conductor, each satellite cavity disposed about the central cavity and equally spaced with respect to each adjacent satellite cavity and equally spaced with respect to the central cavity, each satellite cavity connected by a unique gap, each satellite cavity having a satellite cavity radius, each gap, central cavity, and each satellite cavity being an air gap within the conductor; and at least one at least one loop gap resonator, each loop gap resonator comprising a unique satellite cavity and a gap connecting the unique satellite cavity to a central cavity; a primary resonator comprising each loop gap resonator and a central cavity; and a plurality of sets of at least one shielded transmission line and an electromagnetic coupling element, each shielded transmission line of the set electromagnetically coupled to a coupling element, each coupling element configured to electromagnetically couple radio frequency spectrum electromagnetic energy to a unique loop gap resonator, and each loop gap resonator configured to electromagnetically couple at least a portion of the radio frequency spectrum electromagnetic energy to the central cavity.

[0071] Example 14 includes the apparatus of example 13, wherein each loop gap resonator has a first resonance centered about a first resonant frequency, and the primary resonator has a second resonance centered about a second resonant frequency, wherein a difference between the first resonant frequency and the second resonant frequency is less than or equal to three times the linewidth of the widest resonance of the first resonance and the second resonance.

[0072] Example 15 includes the device of any of Examples 13-14, wherein each coupling element is a loop of electrical conductor that is equal to, less than, or greater than the satellite cavity radius of the unique satellite cavity on which the coupling element is disposed.

[0073] Example 16 includes the device of any of Examples 13 to 15, wherein the angles between the central axes of each of two adjacent satellite cavities relative to the central axis of the central cavity are equal, and the distances between the central axis of the central cavity and the central axis of each satellite cavity are equal.

[0074] Example 17 includes the apparatus of any of Examples 13-16, further comprising: a first cap mounted on a first surface of the conductive ring and enclosing a first end of the central cavity; a second cap mounted on a second surface of the conductive ring and enclosing a second end of the central cavity, the first surface and the second surface being separated by a length of the conductive ring; a vapor of atoms in the central cavity; at least one laser light source in each of the first and second caps; and a laser light source generated by the atoms in response to at least a portion of the radio frequency spectrum electromagnetic energy in the central cavity. at least one photodetector in at least one of the first and second caps configured to generate an electrical signal in response to the optical signal; a processing circuit electrically coupled to the at least one photodetector and configured to generate a control signal used to control the frequency of the radio frequency spectrum electromagnetic energy; and one or more coupling elements, each configured to electromagnetically couple the radio frequency spectrum electromagnetic energy to a unique loop gap resonator, each coupling element disposed over a unique satellite cavity and on either the first surface or the second surface.

[0075] Example 18 includes the device of any one of Examples 13 to 17, and each shielded transmission line includes a stripline transmission line.

[0076] Example 19 includes the device of any of Examples 13-18, wherein the central cavity is cylindrical.

[0077] Example 20 includes the device of any of Examples 13-19, wherein each satellite cavity is cylindrical.

[0078] Although specific embodiments have been illustrated and described herein, those skilled in the art will recognize that any configuration which is expected to achieve the same purpose may be substituted for the specific embodiments shown. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.

Claims

1. 1. An apparatus for efficiently coupling electromagnetic energy into a central cavity of a primary resonator within a conductive ring, said apparatus comprising: the central cavity within the conductive ring; one or more satellite cavities within the conductive ring; one or more gaps in the conductive ring, each gap beginning with a unique satellite cavity and terminating at the central cavity, each gap, the central cavity, and each satellite cavity being an air gap in the conductive ring; The device, one or more loop gap resonators, each loop gap resonator comprising the unique satellite cavity and a unique gap between the unique satellite cavity and the central cavity; each loop gap resonator configured to receive radio frequency spectrum electromagnetic energy from a source external to the conductive ring; the primary resonator comprises a loop gap resonator and the central cavity; each loop gap resonator configured to electromagnetically couple at least a portion of the radio frequency spectrum electromagnetic energy to the central cavity; Device.

2. further comprising one or more coupling elements each configured to electromagnetically couple the radio frequency spectrum electromagnetic energy to a respective loop gap resonator, each coupling element configured to receive the radio frequency spectrum electromagnetic energy from the source; the conductive ring having a first surface and a second surface spaced apart by a length of the conductive ring; each coupling element is disposed above the unique satellite cavity and on either the first surface or the second surface; 10. The apparatus of claim 1.

3. a first cap mounted on a first surface of the conductive ring and enclosing a first end of the central cavity; a second cap mounted on a second surface of the conductive ring and enclosing a second end of the central cavity, the first surface and the second surface being separated by the length of the conductive ring; a vapor of atoms in the central cavity; at least one laser light source in each of the first and second caps; at least one photodetector in at least one of the first and second caps configured to generate an electrical signal in response to an optical signal generated by the atoms in response to at least some portion of the radio frequency spectrum electromagnetic energy within the central cavity; a processing circuit electrically coupled to the at least one photodetector and configured to generate a control signal used to control the frequency of the radio frequency spectrum electromagnetic energy; one or more coupling elements, each configured to electromagnetically couple the radio frequency spectrum electromagnetic energy to a unique loop gap resonator; each coupling element is disposed above the unique satellite cavity and on either the first surface or the second surface; 10. The apparatus of claim 1.

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