Extended Data Fig. 3: System used for diffraction-assisted channel interference and spectral response measurements.
From: Time-asymmetric loop around an exceptional point over the full optical communications band
Coherent infrared light from a tunable diode laser (MG9638A, Anritsu) is coupled to the device through a lensed single-mode fibre at the input facet. The actual excitation wavelength is monitored with a spectrum analyser (MS9710B, Anritsu). For precise alignment and stable input coupling, the lensed fibre is mounted on a three-axis translation-stage assembly and the sample is mounted on a six-axis translation–rotation-stage assembly. The output light is collected by a z-scanning microscope objective (numerical aperture, 0.3; working distance, 10 mm; from Nachet) imaging tube lens and an infrared camera (Model 7290A Micron Viewer, Electrophysics) to acquire z-dependent diffraction-pattern images. A broadband linear polarizer (LPNIR100-MP2, Thorlabs) is located in front of the infrared camera to filter the transverse electric component (Ex) out of the acquired image. A motorized linear stage (M-505.4PD, Physik Instrumente) with 0.25-μm unit-step resolution is used for position control of the z-scanning microscope objective. The tunable diode laser, spectrum analyser, motorized linear stage and infrared camera are connected to a desktop computer that controls them in a programed order and integrates multiple camera images for high-quality data acquisition on demand.
