Sensor

A method of coupling electromagnetic radiation into a sample using a sensor measurement device, the sensor measurement device comprising:

• an impedance analyzer to determine an impedance of a sample;
• a first antenna configured to generate electromagnetic radiation having a first wavelength;
• an impedance-matching device, positioned in a radiation path between the first antenna and the sample, to receive the electromagnetic radiation from the first antenna and transmit electromagnetic radiation of the first wavelength into the sample, the impedance-matching device comprising a metasurface including:
• a substrate having a thickness no greater than the first wavelength of the electromagnetic radiation;
• and
• a plurality of elements supported by the substrate, wherein:
• the plurality of elements are spaced apart from one another across the substrate,
• each element has a first dimension no greater than the first wavelength of the electromagnetic radiation, and
• at least two elements of the plurality of elements differ in one or more of shape or size;
• and
• a second antenna configured to receive electromagnetic radiation from the sample;
• the method comprising:
• positioning the sensor measurement device with respect to the sample such that the first antenna is disposed on a first side of the sample and the second antenna is disposed on a second side of the sample;
• determine an impedance of a sample;
• tuning one or both of the first antenna or the impedance-matching device based on the determined impedance to reduce an impedance mismatch along the radiation path;
• providing electromagnetic radiation having the first wavelength from the first antenna to the impedance-matching device;
• transmitting, by the impedance-matching device, electromagnetic radiation having the first wavelength from the first antenna into the sample;
• receiving, by the second antenna, electromagnetic radiation from the sample;
• and
• characterizing the sample based on the received electromagnetic radiation.

A method for designing an impedance-matching device for a sensor measurement device, the sensor measurement device comprising:

• a first antenna configured to generate electromagnetic radiation having a first wavelength;
• the impedance-matching device, positioned in a radiation path between the first antenna and a test sample, to receive the electromagnetic radiation from the first antenna and transmit the electromagnetic radiation into the test sample, the impedance-matching device comprising a metasurface including:
• a substrate having a thickness no greater than the first wavelength of the electromagnetic radiation;
• and
• a plurality of elements supported by the substrate, wherein:
• the plurality of elements are spaced apart from one another across the substrate,
• each element has a first dimension no greater than the first wavelength of the electromagnetic radiation, and
• at least two elements of the plurality of elements differ in one or more of shape or size;
• and
• a second antenna configured to receive electromagnetic radiation from the sample;
• the method comprising:
• positioning the first antenna on a first side of the test sample and the second antenna on a second side of the test sample;
• determining an impedance of the test sample;
• calculating a sheet impedance for the metasurface that will couple the electromagnetic radiation of the first wavelength into the sample with maximum transmission;
• and
• using analytical modelling to design the plurality of elements of the metasurface such that, when the plurality of elements are combined together in a pattern, cause the metasurface to have the calculated sheet impedance.