Many optical measurements that are subject to high levels of background illumination rely on phase sensitive lock-in detection to extract the useful signal. If modulation is applied to the portion of the signal that contains information, lockin detection can perform very narrowband (and hence low noise) detection at frequencies well away from noise sources such as 1/f and instrumental drift. Lock-in detection is therefore used in many optical imaging and measurement techniques, including optical coherence tomography, heterodyne interferometry, optoacoustic tomography and a range of pump-probe techniques. Phase sensitive imaging is generally performed sequentially with a single photodetector and a lock-in amplifier. However, this approach severely limits the rate of multi-dimensional image acquisition. We present a novel linear array chip that can perform phase sensitive, shot-noise limited optical detection in up to 256 parallel channels. This has been achieved by employing four independent wells in each pixel, and massively enhancing the intrinsic well depth to suppress the effect of optical shot noise. Thus the array can reduce the number of dimensions that need to be sequentially scanned and greatly speed up acquisition. Results demonstrating spatial and spectral parallelism in pump-probe experiments are presented where the a.c. amplitude to background ratio approaches 1 part in one million.

Date Published: 24 February 2010
PDF: 10 pages
Proc. SPIE 7570, Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XVII, 75700U (24 February 2010); doi: 10.1117/12.842083

Published in SPIE Proceedings Vol. 7570:
Three-Dimensional and Multidimensional Microscopy: Image Acquisition and Processing XVII
Jose-Angel Conchello; Carol J. Cogswell; Tony Wilson; Thomas G. Brown, Editor(s)