Loss-Compensated and Enhanced Midinfrared Interaction-Free Sensing with Undetected Photons

Sensing with undetected photons enables the measurement of absorption and phase shifts at wavelengths different from those detected. Here, we experimentally map the balance and loss parameter space in a nondegenerate nonlinear interferometer, showing the recovery of sensitivity despite internal losses at the detection wavelength. We further explore an interaction-free operation mode with a detector-to-sample incident optical power ratio of over 200. This allows changes in attowatt levels of power at 3.4 mu m wavelength to be detected at 1550 nm, immune to the level of thermal black-body background. This reveals an ultrasensitive infrared imaging methodology capable of probing samples effectively in the dark.

Automated summary

Sensing with undetected photons allows measurement of absorption and phase shifts at different wavelengths. Experimental mapping in a nondegenerate nonlinear interferometer shows sensitivity recovery despite internal losses at the detection wavelength. An ultrasensitive infrared imaging methodology capable of probing samples effectively in the dark is demonstrated.