Optical design and sensitivity optimization of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS)
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| Format: | Preprint |
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2025
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| _version_ | 1866911462175277056 |
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| author | Inoue, Yuki Tanabe, Daiki Ismail, M. Afif Kumar, Vivek Onglao III, Mario Juvenal S Yu, Ta-Chun |
| author_facet | Inoue, Yuki Tanabe, Daiki Ismail, M. Afif Kumar, Vivek Onglao III, Mario Juvenal S Yu, Ta-Chun |
| contents | We present the optical design and sensitivity modeling of the 2.5 m Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter (CHRONOS), a triangular Sagnac speed-meter interferometer incorporating power- and signal-recycling techniques. Using ABCD-matrix analysis and Finesse3 simulations, we show that stable eigenmodes are obtained with optimized mirror curvatures and focal placements, achieving mode-matching efficiencies above 99.5 %. The resulting configuration reaches a quantum-noise-limited strain sensitivity of $h \simeq 3\times10^{-18},\mathrm{Hz^{-1/2}}$ at 1 Hz, with a ring-cavity finesse $\mathcal{F}\simeq3.1\times10^{4}$ and round-trip Gouy phase $ψ_{\mathrm{rt}}\approx153^{\circ}$. The power-recycling cavity detuning ($ϕ_p=-85^{\circ}$) dominates the low-frequency quantum noise, while the signal-recycling cavity detuning ($ϕ_s=0^{\circ}$) mainly introduces a uniform quadrature rotation. The optimal homodyne angle ($ζ_{\mathrm{opt}}\simeq46^{\circ}$) balances shot-noise and radiation-pressure effects to give the best sensitivity near 1 Hz. Assuming end-mirror reflectivity $R_{\mathrm{ETM}}=99.9999\%$ under cryogenic operation at 10 K, CHRONOS can achieve quantum-noise-limited performance on a laboratory scale and serve as a testbed for future long-baseline, cryogenic interferometers probing sub-hertz gravitational waves. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2510_24780 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Optical design and sensitivity optimization of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) Inoue, Yuki Tanabe, Daiki Ismail, M. Afif Kumar, Vivek Onglao III, Mario Juvenal S Yu, Ta-Chun Instrumentation and Detectors Cosmology and Nongalactic Astrophysics Instrumentation and Methods for Astrophysics General Relativity and Quantum Cosmology We present the optical design and sensitivity modeling of the 2.5 m Cryogenic sub-Hz cROss torsion-bar detector with quantum NOn-demolition Speed meter (CHRONOS), a triangular Sagnac speed-meter interferometer incorporating power- and signal-recycling techniques. Using ABCD-matrix analysis and Finesse3 simulations, we show that stable eigenmodes are obtained with optimized mirror curvatures and focal placements, achieving mode-matching efficiencies above 99.5 %. The resulting configuration reaches a quantum-noise-limited strain sensitivity of $h \simeq 3\times10^{-18},\mathrm{Hz^{-1/2}}$ at 1 Hz, with a ring-cavity finesse $\mathcal{F}\simeq3.1\times10^{4}$ and round-trip Gouy phase $ψ_{\mathrm{rt}}\approx153^{\circ}$. The power-recycling cavity detuning ($ϕ_p=-85^{\circ}$) dominates the low-frequency quantum noise, while the signal-recycling cavity detuning ($ϕ_s=0^{\circ}$) mainly introduces a uniform quadrature rotation. The optimal homodyne angle ($ζ_{\mathrm{opt}}\simeq46^{\circ}$) balances shot-noise and radiation-pressure effects to give the best sensitivity near 1 Hz. Assuming end-mirror reflectivity $R_{\mathrm{ETM}}=99.9999\%$ under cryogenic operation at 10 K, CHRONOS can achieve quantum-noise-limited performance on a laboratory scale and serve as a testbed for future long-baseline, cryogenic interferometers probing sub-hertz gravitational waves. |
| title | Optical design and sensitivity optimization of Cryogenic sub-Hz cROss torsion bar detector with quantum NOn-demolition Speed meter (CHRONOS) |
| topic | Instrumentation and Detectors Cosmology and Nongalactic Astrophysics Instrumentation and Methods for Astrophysics General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2510.24780 |