Gas sensing near exceptional points

Abstract

Abstract Here we investigate the possibility of gas sensing with ultrahigh sensitivity by exploiting the exceptional point (EP) in a non-Hermitian system. The underlying mechanism is that the transverse displacement induced by the photonic spin Hall effect (PSHE), which is significantly enhanced near EPs, is ultra-sensitive to the variation of refractive index in gas media. With the application of the weak measurement technique, we find that the sensitivity of the gas sensing can reach <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>6</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mtext>RIU </mml:mtext> </mml:mrow> <mml:mi>μ</mml:mi> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> . Moreover, if we further reduce the in-plane wavevector component of probe Gaussian light, the sensitivity can be readily improved, up to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mn>10</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>8</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> <mml:mrow> <mml:mtext>RIU </mml:mtext> </mml:mrow> <mml:mi>μ</mml:mi> <mml:mrow> <mml:msup> <mml:mrow> <mml:mtext>m</mml:mtext> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> , which is much better than that of previous PSHE-based gas sensors operating away from the EP. Therefore, our proposed scheme may be favorable for the development of high-performance sensors.