Highly stable chip-scale atomic beam clocks using miniaturized atomic beams and monolithic clock chips
地域：
CA
CA Malibu
摘要
A low-power, chip-scale atomic beam clock is provided that maintains high precision for at least one week at any practical temperature. In some variations, the invention provides a chip-scale atomic beam clock comprising: a micro-optical bench; an atom collimator configured to generate a collimated atomic beam via differential pumping through microchannels; a VCSEL configured to emit laser photons horizontally in the plane of the micro-optical bench; an in-plane lithographically defined diffraction grating configured to split the laser photons into a first photon beam and a second photon beam; in-plane lithographically defined mirrors configured to retroflect the photon beams; in-plane photodetectors configured to detect the photon beams after being retroflected, wherein the first photon beam and the second photon beam interrogate the collimated atomic beam in-plane with the micro-optical bench. The chip-scale atomic beam clocks is capable of maintaining precise positioning, navigation, and timing in case of GPS denial or failure.
說(shuō)明書
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The present invention generally relates to chip-scale atomic beam clocks, and methods of making and using chip-scale atomic beam clocks.
Frequency stability is required for modern, high-speed communications, navigation, electronic instrumentation, and many other applications. Atomic frequency references are devices for producing or probing frequencies and are based on the energy difference between two or more energy levels of a quantum system. In an atom, quantum mechanics requires that the electrons exist only in certain states with specific, discrete energies. Differences between the energies of these states define correspondingly specific frequencies. Therefore, atoms can be excellent frequency references.
A dipole moment, oscillating at one of these frequencies, can be excited by an electromagnetic wave propagating in the same space as the atom. Frequency references are widely available that employ an excitation scheme in which microwave fields excite the atoms of a sample. When the microwave frequency is near the atomic oscillation frequency, a change in the atomic state can be detected by measuring the absorption or phase shift of the atomic sample. The microwave excitation technique works well but poses significant problems for miniaturization, since the microwaves are usually confined in a cavity with size scale constrained by the microwave wavelength. Such devices are rather large.
權(quán)利要求
What is claimed is:1. A chip-scale atomic beam clock comprising:(a) a micro-optical bench that is fabricated from a silicon-containing material; (b) an atom collimator configured to generate a collimated atomic beam via differential pumping through microchannels within said micro-optical bench; (c) a vertical-cavity surface-emitting laser configured to emit laser photons horizontally in the plane of said micro-optical bench; (d) an in-plane diffraction grating configured to split said laser photons into a first photon beam and a second photon beam; and (e) a first in-plane mirror configured to retroflect said first photon beam, and a second in-plane mirror configured to retroflect said second photon beam, wherein said first and second in-plane mirrors are lithographically defined within said micro-optical bench, wherein said first photon beam and said second photon beam interrogate said collimated atomic beam in-plane with said micro-optical bench. 2. The chip-scale atomic beam clock of claim 1 , wherein said silicon-containing material is silicon, silica, fused silica, silicates, aluminosilicates, borosilicates, silicon nitrides, silicon oxynitrides, silicon carbides, silicon oxycarbides, or combinations thereof. 3. The chip-scale atomic beam clock of claim 1 , wherein said collimated atomic beam contains Rb atoms, Cs atoms, Yb atoms, Hg atoms, Sr atoms, Al atoms, Ca atoms, H atoms, or a combination thereof. 4. The chip-scale atomic beam clock of claim 1 , wherein said in-plane diffraction grating is lithographically defined within said micro-optical bench. 5. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock further comprises a first in-plane photodetector configured to detect said first photon beam after being retroflected by said first in-plane mirror, and a second in-plane photodetector configured to detect said second photon beam after being retroflected by said second in-plane mirror. 6. The chip-scale atomic beam clock of claim 1 , wherein said microchannels are bonded to a contiguous top layer to form a closed environment under vacuum. 7. The chip-scale atomic beam clock of claim 6 , wherein said microchannels are bonded to said contiguous top layer via direct wafer bonding, anodic bonding, metal-metal bonding, or a combination thereof. 8. The chip-scale atomic beam clock of claim 6 , wherein said contiguous top layer is a different composition than said silicon-containing material. 9. The chip-scale atomic beam clock of claim 6 , wherein said contiguous top layer is fabricated from a material that has a coefficient of thermal expansion less than 0.05 ppm/° C. between 25° C. and 300° C. 10. The chip-scale atomic beam clock of claim 6 , wherein said contiguous top layer is fabricated from alkali-free glass. 11. The chip-scale atomic beam clock of claim 6 , wherein said contiguous top layer is fabricated from borosilicate glass. 12. The chip-scale atomic beam clock of claim 6 , wherein a photodetector is mounted on said contiguous top layer to collect photoluminescence from an atom-photon interaction region. 13. The chip-scale atomic beam clock of claim 1 , wherein said vertical-cavity surface-emitting laser is configured to emit circularly polarized light. 14. The chip-scale atomic beam clock of claim 13 , wherein said first in-plane mirror is configured to flip the polarization of said first photon beam between left and right, and wherein said second in-plane mirror is configured to flip the polarization of said second photon beam between left and right. 15. The chip-scale atomic beam clock of claim 1 , wherein said vertical-cavity surface-emitting laser is configured to emit photons with one or more wavelengths selected from about 500 nm to about 2000 nm. 16. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock comprises an atom-beam tube configured to contain said collimated atomic beam generated by said atom collimator. 17. The chip-scale atomic beam clock of claim 16 , wherein said atom-beam tube is configured to be perpendicular to said first photon beam at a first atom-photon interaction region, and wherein said atom-beam tube is configured to be perpendicular to said second photon beam at a second atom-photon interaction region. 18. The chip-scale atomic beam clock of claim 1 , wherein said atom collimator and said vertical-cavity surface-emitting laser are configured so that collimated atomic beam height and laser photon beam height are the same or about the same. 19. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock further comprises an actuator configured to mitigate mis-alignment between said vertical-cavity surface-emitting laser and said micro-optical bench. 20. The chip-scale atomic beam clock of claim 1 , wherein an outer surface of said chip-scale atomic beam clock is coated with a low-emissivity coating to suppress radiative heat loss. 21. The chip-scale atomic beam clock of claim 20 , wherein said low-emissivity coating contains gold, silver, copper, aluminum, or a combination thereof. 22. The chip-scale atomic beam clock of claim 1 , wherein a Helmholtz coil is wrapped around both sides of said micro-optical bench. 23. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock is characterized by a long-term ADEV drift less than 6×10?13 after one week of operation. 24. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock has a volume of about 10 cm3 or less. 25. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock has a weight of about 25 grams or less. 26. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock has a power requirement of about 200 mW or less. 27. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock is operable over a temperature range from ?40° C. to 85° C. 28. The chip-scale atomic beam clock of claim 1 , wherein said chip-scale atomic beam clock is operable without Global Positioning System calibration.
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