Chip-scale atomic gyroscope
View Patent ↗Apparatuses and methods for sensing rotations are provided. One embodiment provides an apparatus including a cell containing alkali and active nuclear magnetic resonance (NMR) isotope(s) atoms, a magnet providing a first magnetic field, a light source emitting diverging light that passes through the cell, and optics which circularly polarize the diverging light. A longitudinal component of the diverging light optically pumps the alkali atoms and, in conjunction with a second magnetic field orthogonal to the first magnetic field or a modulation of the diverging light, causes the alkali and NMR isotope atoms to precess about the first field. A transverse component of the diverging light acts as a probe beam for observing the precession. The apparatus further includes a polarizing beam splitter to split light that has passed through the cell into orthogonally polarized components detected by respective photodetectors and used to determine rotations relative to an inertial frame.
1. An apparatus for sensing rotations, the apparatus comprising:
a magnet that generates a first magnetic field;
a cell containing at least a vaporized source of alkali atoms and atoms of one or more active nuclear magnetic resonance (NMR) isotopes;
a light source configured to emit a diverging light that passes through the cell;
a polarizing beam splitter opposite the light source and configured to split the diverging light that has passed through the cell into orthogonally polarized components; and
a plurality of photodetectors, each of the photodetectors being configured to detect one of the orthogonally polarized components of the light that has passed through the cell and been split by the polarizing beam splitter and to generate a respective signal indicative of intensity of detected light for use in differential detection,
wherein a longitudinal component of the diverging light acts as a pump beam for optically pumping the alkali atoms in the cell and, in conjunction with at least a second magnetic field orthogonal to the first magnetic field or a modulation of the diverging light, causing the alkali atoms and the one or more active NMR isotope atoms to precess about the first magnetic field, and
wherein a transverse component of the diverging light acts as a probe beam for observing the precession about the first magnetic field.
2. The apparatus of claim 1 , further comprising, a circular polarizer configured to circularly polarize the diverging light prior to the diverging light entering the cell.
3. The apparatus of claim 2 , wherein the circular polarizer is a quarter-wavelength optical phase retarder oriented at 45 degrees relative to polarization of the diverging light emitted from the light source.
4. The apparatus of claim 1 , further comprising, a linear polarizer configured to linearly polarize the diverging light prior to the diverging light entering the cell.
5. The apparatus of claim 4 , further comprising, a quarter-wavelength optical phase retarder configured to rotate polarization of the diverging light that has passed through the cell by 45° for balanced detection with the photodetectors.
6. The apparatus of claim 1 ,
wherein the cell, the polarizing beam splitter, and the photodetectors are substantially rectangular, and
wherein the cell, the light source, the polarizing beam splitter, and the photodetectors are glued together into one piece.
7. The apparatus of claim 1 , wherein one or more walls of the cell include anti-relaxation coating.
8. The apparatus of claim 1 , further comprising, a spacer element between the light source and the cell.
9. A method for sensing rotations, the method comprising:
applying a first magnetic field;
emitting diverging light from a light source;
passing the diverging light through a cell containing at least a vaporized source of alkali atoms and atoms of one or more active nuclear magnetic resonance (NMR) isotopes;
splitting, via a polarizing beam splitter opposite the light source, the diverging light that has passed through the cell into orthogonally polarized components;
detecting, via a plurality of photodetectors, the orthogonally polarized components, wherein each of the photodetectors detects one of the orthogonally polarized components of the light that has passed through the cell and been split by the polarizing beam splitter and generates a respective signal indicative of intensity of detected light; and
determining using differential detection the rotations based on the signals produced by the photodetectors,
wherein a longitudinal component of the diverging light acts as a pump beam for optically pumping the alkali atoms in the cell and, in conjunction with at least a second magnetic field orthogonal to the first magnetic field or a modulation of the diverging light, causing the alkali atoms and the one or more active NMR isotope atoms to precess about the first magnetic field, and
wherein a transverse component of the diverging light acts as a probe beam for observing the precession about the first magnetic field.
10. The method of claim 9 , further comprising, circularly polarizing the diverging light prior to the diverging light entering the cell.
11. The method of claim 10 , wherein the diverging light is circularly polarized by a quarter-wavelength optical phase retarder oriented at 45 degrees relative to polarization of the diverging light emitted from the light source.
12. The method of claim 9 , further comprising, linearly polarizing the diverging light prior to the diverging light entering the cell.
13. The method of claim 12 , further comprising, rotating polarization of the diverging light that has passed through the cell by 45° for balanced detection with the photodetectors.
14. The method of claim 9 ,
wherein the cell, the polarizing beam splitter, and the photodetectors are substantially rectangular, and
wherein the cell, the light source, the polarizing beam splitter, and the photodetectors are glued together into one piece.
15. The method of claim 9 , wherein one or more walls of the cell include anti-relaxation coating.
16. The method of claim 9 , further comprising, passing the diverging light emitted from the light source through a spacer element between the light source and the cell.
17. An apparatus for sensing an external magnetic field, the apparatus comprising:
a magnet that generates a first magnetic field;
a cell containing at least a vaporized source of alkali atoms;
a light source configured to emit a diverging light that passes through the cell;
a polarizing beam splitter opposite the light source and configured to split the diverging light that has passed through the cell into orthogonally polarized components; and
a plurality of photodetectors, each of the photodetectors being configured to detect one of the orthogonally polarized components of the light that has passed through the cell and been split by the polarizing beam splitter and to generate a respective signal indicative of intensity of detected light for use in differential detection,
wherein a longitudinal component of the diverging light acts as a pump beam for optically pumping the alkali atoms in the cell and, in conjunction with at least a second magnetic field orthogonal to the first magnetic field or a modulation of the diverging light, causing the alkali atoms to precess about the first magnetic field, and
wherein a transverse component of the diverging light acts as a probe beam for observing the precession about the first magnetic field.