High-power and narrow-linewidth optimizations of mid-infrared quantum cascade lasers

A novel design of high peak power mid-infrared quantum cascade lasers has been modeled, implemented and characterized. Emitting 23.5 W peak power at room temperature, it demonstrated high beam quality, owing to the gain guiding effect, which has not been reported in quantum cascade lasers before.
A new concept of constant power laser current source has been proposed and designed in a circuit performing reduction of optical frequency noise by reducing the amount of the electrical power fluctuations generated by the laser itself. Significant reduction of optical frequency noise has been measured without locking the laser frequency to any optical reference.
Quantum cascade lasers operating at two frequencies simultaneously have been characterized in terms of frequency stability. A high value of correlation observed between instant frequencies of the two modes allowed to implement a scheme with indirect frequency locking, where the mode not locked to an optical reference experienced frequency noise reduction while the other one was used for stabilization.