Coherently Enhanced Axion-Photon Conversion via Seeded Photons for Short-Pulse Axion Detection

TL;DR

The paper tackles the limited sensitivity of pulsed light-shining-through-a-wall axion searches by introducing a coherent seed electromagnetic field in the regeneration region, enabling constructive interference with the axion-induced photons. It derives the seed-enhanced photon yield, $N'_\gamma = n_s + n_0 + 2\sqrt{n_s n_0}\cos\delta$, and analyzes the statistical impact of seed fluctuations under Poisson counting, showing substantial gains in sensitivity under favorable seed numbers and phase control. The authors quantify the improvement in the axion-photon coupling reach, finding that unseeded scenarios yield $g_{a\gamma\gamma}^\text{sens}$ around $4.3\times10^{-10}\ \mathrm{GeV}^{-1}$, while seeded runs with modest seeds (e.g., $n_s=100$) can reach $\sim3\times10^{-12}\ \mathrm{GeV}^{-1}$, potentially surpassing current laboratory limits in some regimes. This time-domain approach circumvents the need for resonant cavities in femtosecond-pulse experiments and offers a promising pathway to extend laboratory axion searches, provided seed-phase and intensity fluctuations are well characterized.

Abstract

We propose a seeded axion-photon conversion scheme to enhance the sensitivity of light-shining-through-a-wall (LSW) experiments for axion detection, where the axions are generated from short pulse lasers and the usual resonant cavity is not applicable. By injecting a weak, coherent seed electromagnetic (EM) field into the axion-photon conversion region, the axion-induced EM field can constructively interfere with the seed field, amplifying the number of regenerated photons to a level exceeding that of the unseeded scenario. We evaluate the expected signal enhancement, statistical limits from Poisson counting with seed fluctuations and background, and the potential improvement in coupling sensitivity. Compared to a standard LSW setup, the seeded scheme can achieve orders-of-magnitude higher photon yield per axion, potentially surpassing resonance-enhanced experiments in certain parameter regimes. This approach presents a promising pathway to extend the reach of laboratory axion searches, particularly in scenarios where the resonant cavities are impractical.

Figures (3)

• Figure 1: Conceptual scheme of coherently enhanced axion-photon conversion via seeded photons.
• Figure 2: (a) Median sensitivity (sens) on $n_0$ at 90% CL versus $n_s$ at fixed $N_{\text{shot}}=30\,\text{days}\times 1\,\text{Hz}$ and $n_b=0.1$. (b) Same sensitivities versus $n_b$ at fixed $n_s=100$ and $N_{\text{shot}}=30\,\text{days}\times 1\,\text{Hz}$. All sensitivities use the statistical configurations in Table \ref{['tab:cases']}.
• Figure 3: Projected sensitivity to $g_{a\gamma\gamma}$ for a pulsed LSW experiment with and without seeding, compared to ALPS experiment bahre_any_2013AxionLimits.