Raman based detection instrument and method of detection

A method for distinguishing an active pathogen from an inactivated pathogen using Raman based spectroscopic analysis, the method comprising:

• radiating coherent light onto a sample;
• collecting a Raman signal from the sample;
• collimating the Raman signal;
• dispersing the collimated Raman signal;
• directing the dispersed Raman signal to an optical filter;
• detecting the filtered Raman signal by an imaging sensor array, the imaging sensor array comprising a plurality of detection areas to separately detect each of a plurality of different spectral bands of the filtered Raman signal;
• analyzing the Raman signal for the presence of a pathogen;
• and
• analyzing the Raman signal for a Raman peak spectral shift indicative of a change in activity of the pathogen.

A method of making a graded optical filter, comprising:

• depositing an Indium Aluminum Nitride (InAlN) alloy coating on a substrate by hollow cathode-based low energy plasma deposition;
• sliding the substrate during the deposition;
• and
• changing Indium depositing rate to coordinate with sliding of the substrate to create a graded InAlN coating having a band gap between 1 eV and 6 eV.