Optical lock-in camera for gravitational wave detectors

Abstract

Knowledge of the intensity and phase profiles of spectral components in a coherent optical field is critical for a wide range of high-precision optical applications. One of these is interferometric gravitational wave detectors, which rely on such fields for precise control of the experiment. Here we demonstrate a new device, an optical lock-in camera, and highlight how they can be used within a gravitational wave interferometer to directly image fields at a higher spatial and temporal resolution than previously possible. This improvement is achieved using a Pockels cell as a fast optical switch which transforms each pixel on a sCMOS array into an optical lock-in amplifier. We demonstrate that the optical lock-in camera can image fields with 2 Mpx resolution at 10 Hz with a sensitivity of -62 dBc when averaged over 2s. arXiv:1907.05224v1 [astro-ph.IM]

Observing the optical modes of parametric instability

“…4. Photon shot noise fundamentally limits the floor of this subtraction [19], however in this experiment intensity fluctuations and movement of the beam on the camera between frames is the dominating noise source.…”

“…Assuming a mode overlap β = 10% and an optical gain of G ∼ 130 the relative amplitude of the sideband to the carrier is E sb /E c ∼ π λ aβG ≈ 1.2 × 10 −4 . Following the notation of [19], imaging this sideband field would require a sensitivity of 10 log 10 |E sb | 2 /|E c | 2 = −78 dBc The single pixel sensitivity demonstrated in [19] of this type of optical lock-in camera was −62 dBc, limited by uncontrolled laser intensity noise. The camera is ultimately limited by its dynamic range and readout noise ( 86 dBc for the Zyla 4.2) and photo-electron shot noise.…”

“…Our technique uses an optical lock-in camera [19] to image the transverse amplitude and phase of the beat between the main cavity field and the sideband field generated by PI. We demonstrated this experimentally at the Gingin High Optical Power Test Facility [20] (HOPTF) facility.…”

“…A detailed description of the optical lock-in camera can be found in [19]. The operating principle is analogous to demodulation with a photodiode, where information of particular spectral components in a signal are recovered via mixing and lowpassing the signal with a local oscillator at the frequency of interest.…”

Resonant Electro-optic Imaging for Microscopy at Nanosecond Resolution

“…We recently demonstrated the use of Pockels cells for time-resolved microscopy detection, showing wide-field electro-optic FLIM (EO-FLIM) of single molecules at kilohertz excitation rates. 22 Electrooptic imaging has since been applied to threedimensional modulation-enhanced localization microscopy, 23,24 lock-in profiling of optical modes, 25 and kilohertz imaging. 26 To enable practical applications in lifetime microscopy, improving the repetition rate while maintaining a usable field of view is essential.…”