Methods for determining optical power, for power normalizing laser measurements, and for stabilizing power of lasers via compliance voltage sensing

Abstract

A method is disclosed for power normalization of spectroscopic signatures obtained from laser based chemical sensors that employs the compliance voltage across a quantum cascade laser device within an external cavity laser. The method obviates the need for a dedicated optical detector used specifically for power normalization purposes. A method is also disclosed that employs the compliance voltage developed across the laser device within an external cavity semiconductor laser to power-stabilize the laser mode of the semiconductor laser by adjusting drive current to the laser such that the output optical power from the external cavity semiconductor laser remains constant.

What is claimed is: 
     
         1 . A method of stabilizing an optical power of an external cavity laser, comprising the steps of:
 driving a laser device disposed within the external cavity laser with a current through the laser device from a current controller;   measuring the compliance voltage across the laser device;   applying a mathematical function to the compliance voltage to produce an optical power signal proportional to an optical power of the external cavity laser;   feeding the optical power signal back to the current controller to change the current delivered to the laser device; and   adjusting feedback parameters to stabilize the optical power of the external cavity laser.   
     
     
         2 . The method of  claim 1 , wherein the feedback parameters include: phase, amplitude, and bandwidth of the optical power signal. 
     
     
         3 . The method of  claim 1 , wherein the optical power is a circulating optical power. 
     
     
         4 . The method of  claim 1 , wherein the optical power is an output optical power.