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EP-4741766-A1 - LASER-BASED ATOMIC SENSOR SYSTEM COMPRISING A FABRY-PÉROT RESONATOR

EP4741766A1EP 4741766 A1EP4741766 A1EP 4741766A1EP-4741766-A1

Abstract

The present invention relates to an atomic sensor system (1) with a vapor cell (2) comprising an alkali metal vapor, a pump laser system (3) configured to generate an optical pump beam (4) along a first axis (5) through the vapor cell (2), a magnetic field system (6) configured to generate a magnetic field along the first axis (5) through the vapor cell (2) and a probe laser system (7) configured to generate an optical probe beam (8) along a second axis (9) through the vapor cell (2). The present invention is based on the general idea that the atomic sensor system (1) comprises a Fabry-Pérot resonator (10), wherein the alkali metal vapor of the vapor cell (2) is located inside the Fabry-Pérot resonator (10).

Inventors

  • Torralbo-Campo, Lara
  • Padniuk, Mikhail
  • KONRAD, ALEXANDER

Assignees

  • Arda Atomics GmbH

Dates

Publication Date
20260513
Application Date
20251106

Claims (15)

  1. An atomic sensor system (1) comprising: - a vapor cell (2) comprising an alkali metal vapor; - a pump laser system (3) configured to generate an optical pump beam (4) along a first axis (5) through the vapor cell (2); - a magnetic field system (6) configured to generate a magnetic field along the first axis (5) through the vapor cell (2); - a probe laser system (7) configured to generate an optical probe beam (8) along a second axis (9) through the vapor cell (2); characterized in that - the atomic sensor system (1) comprises a Fabry-Pérot resonator (10), wherein the alkali metal vapor of the vapor cell (2) is located inside the Fabry-Pérot resonator (10), wherein the atomic sensor system (1) comprises an optical detection system (23) configured to measure the probe beam (8, 25) emanating from the vapor cell (2), wherein the pump laser system (3) comprises a probe laser control unit (36) configured to adjust optical frequency of the probe optical beam (8), wherein the probe laser control unit (36) is configured to modulate the optical frequency of the probe optical beam (8) of at least 1 MHz to perform a FM lock and/or phase lock.
  2. The atomic sensor system (1) according to claim 1, characterized in that - the Fabry-Pérot resonator (10) comprises a first reflective surface (11) and a second reflective surface (12), - wherein the first reflective surface (11) and the second reflective surface (12) are spaced apart from each other with respect to the second axis (9).
  3. The atomic sensor system (1) according to claim 2, characterized in that - the first reflective surface (11) and the second reflective surface (12) are each planar and/or flat formed, and/or - wherein the first reflective surface (11) and the second reflective surface (12) are spaced apart from each other by a distance (13), in particular by an invariable distance (13), with respect to the second axis (9).
  4. The atomic sensor system (1) according to claim 2 or 3, characterized in that - at least one reflective surface (11, 12) of the Fabry-Pérot resonator (10) is formed by a reflective coating of the vapor cell (2), and/or - at least one reflective surface (11, 12) of the Fabry-Pérot resonator (10) is formed by a mirror, wherein this mirror is formed separately from the vapor cell (2).
  5. The atomic sensor system (1) according to any of claims 2 to 4, characterized in that - the vapor cell (2) comprises a casing (14) with a first section (15) and a second section (16) which are transparent and/or permeable, - wherein the first reflective surface (11) of the Fabry-Pérot resonator (10) is formed by a reflective coating of the first section (15), - wherein the second reflective surface (12) of the Fabry-Pérot resonator (10) is formed by a reflective coating of the second section (16).
  6. The atomic sensor system (1) according to claim 5, characterized in that the first section (15) comprises a first outer surface (17) of the casing (14) and a first inside surface (18) of the casing (14), while the second section (16) comprises a second inside surface (19) of the casing (14) and a second outer surface (20) of the casing (14).
  7. The atomic sensor system (1) according to claim 6, characterized in that - the first outer surface (17), the first inside surface (18), the second inside surface (19) and the second outer surface (20) are each formed planar, and/or - wherein the first outer surface (17) has a surface vector, said surface vector of the first outer surface (17) being parallel to the second axis (9), and/or - wherein the first inside surface (18) has a surface vector, said surface vector of the first inside surface (18) being parallel to the second axis (9), and/or - wherein the second inside surface (19) has a surface vector, said surface vector of the second inside surface (19) being parallel to the second axis (9), and/or - wherein the second outer surface (20) has a surface vector, said surface vector of the second outer surface (20) being parallel to the second axis (9).
  8. The atomic sensor system (1) according to claim 6 or 7, characterized in that - the first reflective surface (11) of the Fabry-Pérot resonator (10) is formed by a reflective coating of the first outer surface (17), and/or - the first reflective surface (11) of the Fabry-Pérot resonator (10) is formed by a reflective coating of the first inside surface (18).
  9. The atomic sensor system (1) according to any of claims 6 to 8, characterized in that - the second reflective surface (12) of the Fabry-Pérot resonator (10) is formed by a reflective coating, in particular a dielectric reflective coating, of the second inside surface (19), and/or - the second reflective surface (12) of the Fabry-Pérot resonator (10) is formed by a reflective coating, in particular a dielectric reflective coating, of the second outer surface (20).
  10. The atomic sensor system (1) according to any one of the preceding claims, characterized in that - the Fabry-Pérot resonator (10) comprises a free spectral range (21) smaller than an absorption spectral range (22) of the alkali vapor, and/or - wherein the free spectral range (21) of the Fabry-Pérot resonator (10) is configured and/or formed by a distance (13) between the first reflective surface (11) and the second reflective surface (12), and/or - wherein the free spectral range (21) of the Fabry-Pérot resonator (10) is configured and/or formed by a reflectivity of the first reflective surface (11) and the second reflective surface (12).
  11. The atomic sensor system (1) according to any one of the preceding claims, characterized in that - the probe laser control unit (36) is configured to scan the optical frequency of the probe optical beam (8) over an optical frequency range in order to identify an optimal optical frequency (35) based on the measurement by the optical detection system (23).
  12. The atomic sensor system (1) according to claim 11, characterized in that - the probe laser control unit (36) is configured to scan the optical frequency of the probe optical beam (8) over several GHz, in particular several hundreds of GHz, to find the optimal optical frequency (35), and/or - wherein the optimal optical frequency (35) is a frequency at which the derivation of the measured signal (33) has a maximum or minimum, and/or - wherein the optimal optical frequency (35) is a frequency between a minimum and a maximum of the alkali metal vapor absorption spectrum (34), and/or - wherein the optimum optical frequency (35) is a frequency at which the measurement of the probe beam (8, 25) by the optical detection system (23) is more sensitive than at other optical frequencies.
  13. The atomic sensor system (1) according to any one of the preceding claims, characterized in that - the atomic sensor system (1) comprises a heating control system (26), in particular an external or internal temperature control system, configured to control the alkali-metal vapour density, and/or - wherein the heating control system (26), in particular the temperature control system, comprises a feedback system that is configured to stabilize the temperature of the alkali metal vapour.
  14. A gyroscope system comprising at least one atomic sensor system (1) according to any one of the preceding claims in order to determine an orientation of the gyroscope system.
  15. A satellite, and/or a vehicle, in particular a ground, land, sea and/or air vehicle, and/or a spacecraft comprising at least one gyroscope system according to claim 14 in order to determine an orientation of the device comprising this gyroscope system.

Description

The present invention relates to a laser-based atomic sensor system with a vapor cell comprising an alkali metal vapor. The invention also relates to a gyroscope system comprising such an atomic sensor system and/or to a system comprising this gyroscope system. US2023273278A1 describes an atomic vapor cell, for atomic or molecular spectroscopy, optical pumping, and/or spin-based atomic sensing, that includes a host substrate and defined there within a buried or non-buried chamber laser written in the host substrate without the need of a mask or photoresist, with either planar or three-dimensional geometry, and intended to contain an atomic vapor. The problem addressed by the present invention is to improve the measurement sensitivity with respect to the Faraday rotation of the optical probe beam, which is caused by the embedded atoms of the alkali metal vapour and the magnetic field. This problem is solved according to the invention by the subject-matter of the independent claims. The dependent claims relate to advantageous embodiments. The invention is based on the general idea that the alkali metal vapor is enclosed by an optical resonator. This optical resonator is a Fabry-Pérot resonator, in particular a Fabry-Pérot interferometer (FPI) and/or etalon. Thus, the atomic sensor system comprises a Fabry-Pérot resonator, wherein the alkali metal vapor of the vapor cell is located inside the Fabry-Pérot resonator. The probe beam emanating from the Fabry-Pérot resonator may be used to improve the measurement sensitivity of the laser-based atomic sensor system. As a result, magnetic field changes may be detected much more accurately and may form the basis for generating control signals of systems that comprise such an atomic sensor system according to the invention. The laser-based atomic sensor system comprises a pump laser system configured to generate an optical pump beam, in particular an optical laser pump beam, along a first axis through the vapor cell, a magnetic field system configured to generate a magnetic field along the first axis through the vapor cell and a probe laser system configured to generate an optical probe beam, in particular an optical laser probe beam, along a second axis through the vapor cell. The first axis and the second axis may be perpendicular to one another. In an advantageous embodiment, the Fabry-Pérot resonator comprises a first reflective surface and a second reflective surface, wherein the first reflective surface and the second reflective surface are spaced apart from each other with respect to the second axis. This provides an optimal system structure. The pump laser system may be configured to generate the optical pump beam such that the optical pump beam propagates through the vapor cell but not through the first reflective surface and/or the second reflective surface of the Fabry-Pérot resonator. In other words, the optical pump beam propagates through the vapor cell between the first reflective surface and the second reflective surface of the Fabry-Pérot resonator. The magnetic field system may be configured to generate the magnetic field such that the magnetic field permeates the vapor cell and/or the Fabry-Pérot resonator, in particular the first reflective surface and/or the second reflective surface of the Fabry-Pérot resonator. The pump laser system may be configured to generate the optical probe beam such that the optical probe beam propagates through the vapor cell and through the first reflective surface and the second reflective surface of the Fabry-Pérot resonator. In an advantageous embodiment, the first reflective surface and the second reflective surface are each planar and/or flat formed. Alternatively or additionally, the first reflective surface and the second reflective surface are spaced apart from each other by a distance, in particular by an invariable distance, with respect to the second axis. The distance between the first reflective surface and the second reflective surface may be greater than or equal to 10 mm. The distance between the first reflective surface and the second reflective surface may be greater than or equal to 15 mm. The distance between the first reflective surface and the second reflective surface may be greater than or equal to 20 mm. The first reflective surface and the second reflective surface form two parallel reflective planar and/or flat surfaces, whereby the optical probe beam only propagates through the Fabry-Pérot cavity when it is in resonance with it. The invariable distance, in particular a constant and/or unchangeable distance, has the advantage of counteracting unwanted changes of the Fabry-Pérot cavity resonance. In an advantageous embodiment, at least one reflective surface, in particular both reflective surfaces, of the Fabry-Pérot resonator is formed by a reflective coating of the vapor cell. This has the advantage that the vapor cell, which includes the Fabry-Pérot resonator, can be made very compact and pro