Abstract
Quantum noise limits the sensitivity of laser interferometric gravitational-wave detectors. Given the state-of-the-art optics, the optical losses define the lower bound of the best possible quantum-limited detector sensitivity. In this work, we come up with a broadband signal recycling scheme which gives a potential solution to approaching this lower bound by converting the signal recycling cavity to be a broadband signal amplifier using an active optomechanical filter. We will show the difference and advantage of such a scheme compared with the previous white light cavity scheme using the optomechanical filter in [Phys.Rev.Lett.115.211104 (2015)]. The drawback is that the new scheme is more susceptible to the thermal noise of the mechanical oscillator.
Highlights
IntroductionBroadband Signal Recycling Scheme for Approaching the Quantum Limit from Optical Losses
In the optomechanical filter cavity, the thermal noise contribution of the mechanical oscillator can be modelled as effective signal-recycling cavity (SRC) loss [8]: ee f f =
We show one scheme whose shot noise limited sensitivity can almost reach the optical-loss limit
Summary
Broadband Signal Recycling Scheme for Approaching the Quantum Limit from Optical Losses. The SRC loss limited sensitivity rises at higher frequencies above the arm cavity bandwidth due to the decrease of signal response It is independent of any optical modules inside the SRC. The black line illustrates the resulting shot noise of the aLIGO configuration with the BSR scheme discussed in this work It approaches the SRC loss limit at high frequencies and arm cavity loss limit at low frequencies. It is due to the accumulation of the phase of the sideband traveling inside the cavity (positive dispersion), which leads to a destructive interference when the frequency is larger than the cavity bandwidth Another recent work on high-frequency detector design uses the coupled-cavity resonance of the arm cavity and the SRC. The scheme proposed in this work realises the coupled SRC and arm cavity resonance in a broad frequency band We name it as the broadband signal recycling (BSR) scheme
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