A fiber-ribbon-based coupling method is presented as a practical way to enhance light sensitivity in spectroscopic and similar systems employing a multialkali photomultiplier tube as a detector. The sensitivity enhancement is achieved by an increase in absorption in the photocathode through multiple total internal reflection in the photomultiplier entrance window. Improvements by factors of (blue-green) to more than 10 (near infrared) have been measured. Implications for spectroscopic applications are discussed.
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