Abstract
Optical coherence tomography (OCT) has been utilized in a rapidly growing number of clinical and scientific applications. In particular, swept source OCT (SS-OCT) has attracted many attentions due to its excellent performance. So far however, the limitations of existing photon detectors have prevented achieving shot-noise-limited sensitivity without using balanced-detection scheme in SS-OCT, even when superconducting single-photon detectors were used. Unfortunately, balanced-detection increases OCT system size and cost, as it requires many additional components to boost the laser power and maintain near ideal balanced performance across the whole optical bandwidth. Here we show for the first time that a photon detector is capable of achieving shot noise limited performance without using the balanced-detection technique in SS-OCT. We built a system using a so-called electron-injection photodetector, with a cutoff-wavelength of 1700 nm. Our system achieves a shot-noise-limited sensitivity of about −105 dB at a reference laser power of ~350 nW, which is more than 30 times lower laser power compared with the best-reported results. The high sensitivity of the electron-injection detector allows utilization of micron-scale tunable laser sources (e.g. VCSEL) and eliminates the need for fiber amplifiers and highly precise couplers, which are an essential part of the conventional SS-OCT systems.
Highlights
Optical coherence tomography (OCT) is a tomographic imaging technique that has revolutionized biomedicine since its invention in 19911–3
One important figure of merit in an OCT system is the signal-to-noise-ratio (SNR), where the signal is proportional to the optical power from the sample and the noise is defined as the variance of the background
Since the signal power produced by the photodetector in an OCT system is proportional to the intensity of the reference beam, a high reference power is typically needed to amplify the signal above the detector noise
Summary
Vala Fathipour[1], Tilman Schmoll[2], Alireza Bonakdar[1], Skylar Wheaton1 & Hooman Mohseni[1]. In order to evaluate the merits of using electron-injection detectors in an SS-OCT system, we measured the noise equivalent power of the EI detector and compared it to the state-of-the art balanced photodetectors at frequencies relevant to high-speed SS-OCT systems. Utilizing the measured detector parameters provided, in equation (4) of the “Methods” section, one can conclude that EI detector shot noise would surpass amplifier noise ( provided in Table 1), at a reference power of 350 nW This is confirmed experimentally in our SS-OCT system. The typical optimum reference power level for a balanced detection system is in the few mW range[14, 15, 37] with the lowest reported value of ~15 μW17 This is the first report of shot-noise-limited performance, without the use of balanced detection in an SS-OCT setup
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
