METHODS FOR DETERMINING OPTICAL POWER, FOR POWER NORMALIZING LASER MEASUREMENTS, AND FOR STABILIZING POWER OF LASERS VIA COMPLIANCE VOLTAGE SENSING
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.
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.