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| Format: | Preprint |
| Published: |
2026
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| Online Access: | https://arxiv.org/abs/2603.28805 |
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| _version_ | 1866915900774416384 |
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| author | Bray-Ali, Noah |
| author_facet | Bray-Ali, Noah |
| contents | A precision measurement is proposed to determine, in a couple hours of integration time, the axion Compton frequency using a modest power (3 mW) tunable external-cavity diode laser at 2458 nm as input to drive a free-space table-top Mach-Zehnder interferometer whose sensing arm passes the expanded beam-waist ($3~{\rm mm}$) light beam through a $1~{\rm T}$ strong, $40~{\rm cm}$ long dipole magnetic field created by a custom-built permanent-magnet assembly with a large but achievable ($6~{\rm mm}$) gap between poles. As the laser frequency is slowly modulated at 1 kHz through a 65 MHz wide window that is well within the 30 GHz fine-tuning range of the laser, a small but readily observable modulation appears in the dark-port optical power of the dark-fringe phase-locked interferometer due to photons converting into axions within the light beam as it passes through the magnetic field. Measuring the axion Compton frequency, $ν_A\approx{\rm 122~THz}$, where the dark-port power modulation peaks, to within the line-width of the laser, $Δν_A=1~{\rm MHz}$, then determines $G$ to 38 ppb, a roughly 600-fold improvement, through a relation between $ν_A$ and $G$, involving $h$, $c$, and nucleon masses. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2603_28805 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Determining $G$ with Laser Spectroscopy to 38 ppb Bray-Ali, Noah High Energy Physics - Phenomenology Optics A precision measurement is proposed to determine, in a couple hours of integration time, the axion Compton frequency using a modest power (3 mW) tunable external-cavity diode laser at 2458 nm as input to drive a free-space table-top Mach-Zehnder interferometer whose sensing arm passes the expanded beam-waist ($3~{\rm mm}$) light beam through a $1~{\rm T}$ strong, $40~{\rm cm}$ long dipole magnetic field created by a custom-built permanent-magnet assembly with a large but achievable ($6~{\rm mm}$) gap between poles. As the laser frequency is slowly modulated at 1 kHz through a 65 MHz wide window that is well within the 30 GHz fine-tuning range of the laser, a small but readily observable modulation appears in the dark-port optical power of the dark-fringe phase-locked interferometer due to photons converting into axions within the light beam as it passes through the magnetic field. Measuring the axion Compton frequency, $ν_A\approx{\rm 122~THz}$, where the dark-port power modulation peaks, to within the line-width of the laser, $Δν_A=1~{\rm MHz}$, then determines $G$ to 38 ppb, a roughly 600-fold improvement, through a relation between $ν_A$ and $G$, involving $h$, $c$, and nucleon masses. |
| title | Determining $G$ with Laser Spectroscopy to 38 ppb |
| topic | High Energy Physics - Phenomenology Optics |
| url | https://arxiv.org/abs/2603.28805 |