CMOS lock-in optical sensor for parallel detection in pump-probe systems

Roger A. Light, Richard J. Smith, Nicholas S. Johnston, Michael Geoffrey Somekh, Mark C. Pitter

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review


In pump-probe type experiments the signal of interest is often a very small fraction of the overall light intensity reaching the detector. This is beyond the capabilities of conventional cameras due to the necessarily high light intensity at the detector and its limited dynamic range. To overcome these problems, phase-sensitive or lock-in detection with a single photodiode is generally used. In phase-sensitive detection, the pump beam is modulated and the probe beam is captured with a photodiode connected to a lock-in amplifier running from the same reference. This provides very narrowband detection and moves the signal away from low frequency noise. We have developed a linear array detector that can perform shot-noise limited lock-in detection in 256 parallel channels. Each pixel has four independent wells to allow phase-sensitive detection. The depth of each well is massively increased and can be controlled on a per-pixel basis allowing the gain of the sensor to be matched to the incident light intensity, improving noise performance. The array reduces the number of dimensions that need to be sequentially scanned and so greatly speeds up acquisition. Results demonstrating spectral parallelism in pump-probe experiments are presented where the a.c. amplitude to background ratio approaches 1 part in one million.
Original languageEnglish
Title of host publicationOptical Sensors 2011; and Photonic Crystal Fibers V
Publication statusPublished - 15 Jun 2011
Externally publishedYes
EventOptical Sensors 2011; and Photonic Crystal Fibers V - Prague, Czech Republic
Duration: 18 Apr 201120 Apr 2011


ConferenceOptical Sensors 2011; and Photonic Crystal Fibers V
Country/TerritoryCzech Republic


  • Active pixel sensor
  • CMOS image sensor
  • Modulated light
  • Phase sensitive detection

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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