Thermoelectric Effect in Quantum Cascade Lasers

• Published in: IEEE photonics journal Vol. 2; no. 3; pp. 500 - 509
• Main Authors: Escarra, Matthew D, Benz, Alexander, Bhatt, Anjali M, Hoffman, Anthony J, Xiaojun Wang, Jen-Yu Fan, Gmachl, Claire
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.06.2010; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Continuous wave; Design engineering; Electrons; Heat sinks; Lasers; Optical design; optoelectronic materials; Performance analysis; Performance evaluation; Polarity; Pulse measurements; Quality control; Quantum cascade lasers; superlattice devices; Thermal loading; thermal modeling; thermoelectric effect; Thermoelectricity; Threshold current; Threshold currents
• ISSN: 1943-0655; 1943-0655; 1943-0647
• DOI: 10.1109/JPHOT.2010.2050304

The choice of polarity of operation in a quantum cascade (QC) laser is made at the beginning of every QC laser design and growth, yet little work has been done to ascertain any performance benefits of one polarity versus the other. In this paper, we compare two QC lasers of the same design, differentiated only by the reversing of the growth order of the heterostructure layers in the laser core, which results in opposite polarities of operation. Analysis is performed through continuous wave (CW) and pulsed threshold current measurements to observe the change in active core temperature with input power. A thermoelectric effect is observed, where the direction of current flow improves thermal transport in negative polarity lasers (electron flow toward the heat sink) over positive polarity (electron flow away from the heat sink), leading to a maximum observed reduction in laser core heating of 10.0 ± 5.5 K for a thermal load of 7.2 kW/cm 2 in CW operation.