Flowcell and system with improved collection efficiency for Raman spectroscopy

A Raman analysis system, comprising:

• a laser source operative to generate a laser excitation beam;
• a spectrograph operative to receive and operate on a signal collection beam, which includes Raman scattered radiation;
• a computer configured to receive signals from the spectrograph to analyze Raman signatures present in the signal collection beam;
• optical components operative and arranged to combine the laser excitation beam and the signal collection beam into a combined counter-propagating, collimated, excitation/collection beam;
• a flowcell configured to convey a sample, the flowcell including a flow channel therethrough, the flow channel having opposing first and second sides, and a longitudinal axis defining a flow direction;
• first and second optical materials disposed on the first and second sides of the flow channel, respectively;
• and
• a single concave aspheric reflective surface, wherein the concave aspheric reflective surface is a parabolic, biconic, or freeform optical surface;
• wherein the collimated excitation/collection combined beam is configured to pass through the first optical material, intersect the flow channel at a substantially transverse angle, pass through the second optical material, and then impinge upon the concave aspheric reflective surface;
• and
• wherein the concave aspheric reflective surface is configured to focus the laser excitation beam of the combined beam to a region within the sample within the flow channel and to re-collimate the signal collection beam into the combined beam from the region within the flow channel.