An experimental investigation of high-frequency noise, i.e., up to 3 GHz, exhibited by a 9.7 μm quantum cascade laser, is described. Noise characteristics and measurements of a liquid-nitrogen-cooled continuous-wave distributed-feedback laser are presented. Well defined sets of narrow and intense resonance peaks have been observed in the 10–300 MHz range. Measurements of relative intensity noise have been performed. It is also shown that quantum-cascade lasers are sensitive to optical feedback. The excess noise generated by the feedback has been investigated under well defined conditions. A description of the experimental phenomenon is presented along with methods of minimizing optical feedback.
© 2007 Optical Society of America
Lasers and Laser Optics
Original Manuscript: August 14, 2006
Manuscript Accepted: November 24, 2006
Published: February 2, 2007
Damien Weidmann, Kevin Smith, and Brian Ellison, "Experimental investigation of high-frequency noise and optical feedback effects using a 9.7 μm continuous-wave distributed-feedback quantum-cascade laser," Appl. Opt. 46, 947-953 (2007)