Optical interrogation of targets enables a non-destructive way by which to extract useful information on critical target parameters. Such methods predominantly employ either angular or spectral interrogation, in which the target is illuminated at different incidence angles or wavelengths, respectively. The reflected (or transmitted) light is then used to extract information on the target. These techniques are pivotal in the arsenal of available tools for critical parameter extractions on a wide range of targets for a wide range of applications. For example, ellipsometry systems employ both spectral and angular interrogation, and are amongst the most sensitive of such methods. Another example is Surface Plasmon Resonance (SPR) phenomena. This resonant physical phenomenon allows real-time sensing of environmental changes at a several hundred nanometer range of a metal surface. These methods are usually used for metrology and biosensing of molecular and protein interactions.
The sensitivity of SPR imposes significant limitations for sensing of small proteins or molecules, as well as very low concentrations of analytes. It is also limited in the ability to distinguish between changes in refractive index caused by the targeted specific interaction, and those caused from other non-specific interactions, which inevitably leads to higher measurement noise. Overcoming this issue requires sample preparation which decreases cost-effectiveness, and reduces robustness.
Measuring the phase of a reflected or transmitted beam from a target simultaneously (no scanning) for a range of illumination wavelengths and incidence angles (spectro-angular interrogation) allows rapid detection of unique phase features, that can be applied for exceptionally high optical sensitivity and resolution in detection in a cost effective and robust manner.
- Increased sensitivity
- Rapid measurement
- High resolution
Applications and Opportunities
- Real-time optical target monitoring, and SPR biosensing
- Fast ellipsometry