1 / 11

Innovative Heterodyne Readout for Advanced LIGO Instrumentation

Delve into the novel Heterodyne Readout method for Advanced LIGO, surpassing limitations of conventional Homodyne Readout. Explore the significance of balanced heterodyne detection, signal tuning, offset arm cavity lengths, and more, revolutionizing GW detection. Discover the complex interplay of optical and mechanical resonances, coupled with detailed quantum mechanical formulations, to enhance signal extraction. Learn about ongoing research on optimizing readout schemes and considering technical noise effects for comprehensive advancements in gravitational wave detection.

earlpatel
Download Presentation

Innovative Heterodyne Readout for Advanced LIGO Instrumentation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Heterodyne Readout for Advanced LIGO Alessandra Buonanno Yanbei Chen Nergis Mavalvala and valuable discussions with Kip Thorne, Ken Strain, Peter Fritschel …

  2. Background of the problem • "Conventional" power-recycled interferometer • GW-induced audio-freq SB beat with a pair of RF SB at anti-symmetric port • RF SB resonant in power-recycling cavity for maximum transmission to AS port • Balanced heterodyne detection (immunity to technical noise sources due to cancellations) • Signal-tuned interferometer with detuned RSE • RF sidebands moved off resonance in signal extraction cavity • Can compensate detuning with RF freq change, e.g., BUT can only make one of the two RF SB resonant • Unbalanced heterodyne detection (technical noise sources couple differently, fewer cancellations)

  3. Homodyne readout • Revisit homodyne (DC) readout (Strain, Fritschel, Mueller, others) • Offset arm cavity lengths to make DC component of carrier the LO • Find optimum homodyne phase by looking at ifo response to an inspiraling binary source (Fritschel) • Calculate optical noise with full quantum mechanical formulation of the EM field in ifo (Buonanno and Chen, 2000) • Find coupling of shot noise and radiation pressure noise due to SEC detuning (the two quadratures are mixed by the detuning) • This coupling gives rise to an optical-mechanical resonance • Limitation of homodyne readout • Can't demodulate with both quadratures to find frequency-dependent optimum • Heterodyne readout circumvents this, since we can phase shift LO arbitrarily

  4. Heterodyne readout • Do full QM calculation of RF modulated-demodulated EM field (Buonanno and Chen, 2002) • Find additional noise term due to quantum noise at 2 fm • Similar to work of Niebauer et al (1991) and Meers and Strain (1991) BUT includes • Imbalanced modulation necessary for detuned RSE • Includes radiation pressure noise • Use realistic (baseline) ifo parameters to calculate transmission of RF SB to detection port

  5. Homodyne (DC) readout • z0 = homodyne phase • k = coupling constant (ISQL, I0, W, g) • F, f = GW sideband, carrier phase gain in SR cavity • = GW sideband phase gain in arm cavity r, t = SRM reflection, transmission coefficient Cij, M, D1,2 = f(r, f, F, k, b)

  6. Heterodyne (RF) readout Extra term due to noise at 2 fm z0 = “Homodyne” phase fD = RF demodulation phase D+,- = (complex) amplitude of upper, lower RF sideband

  7. SQL Opt. DC fD = 0 fD = p/2 Frequency-dependent fD h (1/rtHz) frequency (Hz)

  8. SQL Opt. RF fDC = 0 fDC = p/2 Frequency-dependent to fD minimize noise spectral density h (1/rtHz) frequency (Hz)

  9. Opt. RF Opt. DC If frequency-dependent homodyne angle were possible… h (1/rtHz) frequency (Hz)

  10. Effect of the additional noise term: conventional interferometer h (1/rtHz) frequency (Hz)

  11. Work still in progress • Preliminary results, need to iron out details of contrast defect, modulation index,… • Optimization of the readout scheme for different GW sources • So far, we have considered only fundamental quantum noise on the light • So need to consider technical noise as well (already begun by Mueller, Fritschel, others)

More Related