Toward integrated sensors for optimized optical coherence tomography with undetected photons

<jats:p> The development of practical sensors for optical coherence tomography (OCT) with undetected photons requires miniaturization via integration. To be practical, these sensors must exhibit a large spectral bandwidth and a high brightness, which are linked to a high axial resolution and a sufficient signal-to-noise ratio, respectively. Here, we combine these requirements in a scheme for OCT measurements with undetected photons based on nonlinear <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mi>Ti</a:mi> <a:mo>:</a:mo> <a:msub> <a:mrow> <a:mi>Li</a:mi> <a:mi>Nb</a:mi> <a:mi mathvariant="normal">O</a:mi> </a:mrow> <a:mn>3</a:mn> </a:msub> </a:math> waveguides. We investigate the performance benchmarks of the commonly used SU(1,1) scheme in comparison to an induced-coherence scheme and find that the latter is actually better suited when implementing measurements with undetected photons in integrated systems. In both schemes, we perform pump-gain optimization and OCT measurements with undetected photons with an axial resolution as low as <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mn>28</d:mn> <d:mspace width="0.2em"/> <d:mtext fontfamily="times">μ</d:mtext> <d:mrow> <d:mi mathvariant="normal">m</d:mi> </d:mrow> </d:math> . </jats:p>