Some technical publications about the optics use with SPR.

Prabowo, B. A., A. Purwidyantri and K.-C. Liu - Surface Plasmon Resonance Optical Sensor: A Review on Light Source Technology. Biosensors 8: 80; (2018). Goto reference

The notion of surface plasmon resonance (SPR) sensor research emerged more than eight decades ago from the first observed phenomena in 1902 until the first introduced principles for gas sensing and biosensing in 1983. The sensing platform has been hand-in-hand with the plethora of sensing technology advancement including nanostructuring, optical technology, fluidic technology, and light source technology, which contribute to substantial progress in SPR sensor evolution. Nevertheless, the commercial products of SPR sensors in the market still require high-cost investment, component, and operation, leading to unaffordability for their implementation in a low-cost point of care (PoC) or laboratories. In this article, we present a comprehensive review of SPR sensor development including the state of the art from a perspective of light source technology trends. Based on our review, the trend of SPR sensor configurations, as well as its methodology and optical designs are strongly influenced by the development of light source technology as a critical component. These simultaneously offer new underlying principles of SPR sensor towards miniaturization, portability, and disposability features. The low-cost solid-state light source technology, such as laser diode, light-emitting diode (LED), organic light emitting diode (OLED) and smartphone display have been reported as proof of concept for the future of low-cost SPR sensor platforms. Finally, this review provides a comprehensive overview, particularly for SPR sensor designers, including emerging engineers or experts in this field.

Wang, T. J. et al. Integrated-optic biosensor by electro-optically modulated surface plasmon resonance. Biosens.Bioelectron. 22: 1441-1446; (2007).

This publication presents an integrated-optic surface plasmon resonance (SPR) biosensor based on electro-optical modulation. Two measurement methods, electro-optically modulated SPR spectral measurement and electro-optically modulated SPR intensity measurement, are demonstrated and their measurands are the SPR wavelength and the output optical intensity, respectively. Experimental results measured by the electro-optically modulated SPR methods are compared with those measured by the conventional spectral and intensity methods, and the effects of waveguide width on the biosensor performance are discussed.

Akimoto, T. et al. Effect of incident angle of light on sensitivity and detection limit for layers of antibody with surface plasmon resonance spectroscopy. Biosens.Bioelectron. 15: 355-362; (2000).

The effect of the incident angle of light on sensitivity and the detection limit for surface-plasmon resonance spectroscopy were examined. The sensitivities and the detection limit were experimentally measured using an antibody as a modeled analyte in the incident angles of a light region of 66-76 degrees. The results showed that the sensitivity of a smaller incident angle was higher than that of a larger one.

Ma, S. C., R. Gupta, N. A. P. Ondevilla, et al. - Voltage-modulated surface plasmon resonance biosensors integrated with gold nanohole arrays. Biomed Opt Express 14: 182-193; (2023). Goto reference

Surface plasmon resonance (SPR) has emerged as one of the most efficient and attractive techniques for optical sensors in biological applications. The traditional approach of an EC (electrochemical)-SPR biosensor to generate SPR is by adopting a prism underneath the sensing substrate, and an angular scan is performed to characterize the reflectivity of target analytes. In this paper, we designed and investigated a novel optical biosensor based on a hybrid plasmonic and electrochemical phenomenon. The SPR was generated from a thin layer of gold nanohole array on a glass substrate. Using C-Reactive Protein (CRP) as the target analyte, we tested our device for different concentrations and observed the optical response under various voltage bias conditions. We observed that SPR response is concentration-dependent and can be modulated by varying DC voltages or AC bias frequencies. For CRP concentrations ranging from 1 to 1000 µg/mL, at the applied voltage of -600 mV, we obtained a limit of detection for this device of 16.5 ng/mL at the resonance peak wavelength of 690 nm. The phenomenon is due to spatial re-distribution of electron concentration at the metal-solution interface. The results suggest that CRP concentration can be determined from the SPR peak wavelength shift by scanning the voltages. The proposed new sensor structure is permissible for various future optoelectronic integration for plasmonic and electrochemical sensing.