Detailed Description
Reichert Inc.’s SR7000DC Dual Channel Surface Plasmon Resonance (SPR) Spectrometer is a Kretschmann (1) principle SPR instrument. Figure 1. Depicts the optical configuration of the instrument.
Figure 1: Optical-Mechanical layout of the SR7000DC
Twin 780 nm 60 LED banks illuminate an integrating sphere to fully homogenize the source light. Light exits the integrating sphere through twin apertures, one for each channel, and is collimated, p polarized, focused and directed through a sapphire prism in optical contact with a glass slide coated with 50 nm of gold. The light illuminates 2.2 mm x 0.8 mm oval spots on the gold surface over a 60° to 80° range of angles (see Figure 2). Reflected light is projected and focused on twin linear photodiode (pd) arrays. Onboard computer capability is used to analyze the photodiode array output and determine the SPR minimum angle. The glass slide is placed in contact with the sapphire prism using an optical coupling liquid. This maintains strict optical continuity with the prism and contributes to signal regularity and integrity over the entire range of angles. A spot, as opposed to a focal point on the gold surface is used to promote heat dissipation and minimize artifacts due to high local heating. Sapphire is used as the prism material to prevent surface scratches and deterioration common with glass prisms. The high thermal conduction of sapphire contributes to the overall temperature control capabilities of the instrument.
Figure2: Illumination path of the SR7000DC (not to scale).
|
