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Title: Dispersion dynamics of quantum cascade lasers

A key parameter underlying the efficacy of any nonlinear optical process is group velocity dispersion. In quantum cascade lasers (QCLs), there have been several recent demonstrations of devices exploiting nonlinearities in both the mid-infrared and the terahertz. Though the gain of QCLs has been well studied, the dispersion has been much less investigated, and several questions remain about its dynamics and precise origin. In this work, we use time-domain spectroscopy to investigate the dispersion of broadband terahertz QCLs, and demonstrate that contributions from both the material and the intersubband transitions are relevant. We show that in contrast to the laser gain—which is clamped to a fixed value above lasing threshold—the dispersion changes with bias even above threshold, which is a consequence of shifting intersubband populations. In conclusion, we also examine the role of higher-order dispersion in QCLs and discuss the ramifications of our result for devices utilizing nonlinear effects, such as frequency combs.
Authors:
 [1] ;  [1] ;  [2] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Report Number(s):
SAND-2016-8988J
Journal ID: ISSN 2334-2536; 647328
Grant/Contract Number:
AC04-94AL85000
Type:
Accepted Manuscript
Journal Name:
Optica
Additional Journal Information:
Journal Volume: 3; Journal Issue: 12; Journal ID: ISSN 2334-2536
Publisher:
Optical Society of America
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; semiconductor lasers; quantum cascade
OSTI Identifier:
1339651

Burghoff, David, Yang, Yang, Reno, John L., and Hu, Qing. Dispersion dynamics of quantum cascade lasers. United States: N. p., Web. doi:10.1364/OPTICA.3.001362.
Burghoff, David, Yang, Yang, Reno, John L., & Hu, Qing. Dispersion dynamics of quantum cascade lasers. United States. doi:10.1364/OPTICA.3.001362.
Burghoff, David, Yang, Yang, Reno, John L., and Hu, Qing. 2016. "Dispersion dynamics of quantum cascade lasers". United States. doi:10.1364/OPTICA.3.001362. https://www.osti.gov/servlets/purl/1339651.
@article{osti_1339651,
title = {Dispersion dynamics of quantum cascade lasers},
author = {Burghoff, David and Yang, Yang and Reno, John L. and Hu, Qing},
abstractNote = {A key parameter underlying the efficacy of any nonlinear optical process is group velocity dispersion. In quantum cascade lasers (QCLs), there have been several recent demonstrations of devices exploiting nonlinearities in both the mid-infrared and the terahertz. Though the gain of QCLs has been well studied, the dispersion has been much less investigated, and several questions remain about its dynamics and precise origin. In this work, we use time-domain spectroscopy to investigate the dispersion of broadband terahertz QCLs, and demonstrate that contributions from both the material and the intersubband transitions are relevant. We show that in contrast to the laser gain—which is clamped to a fixed value above lasing threshold—the dispersion changes with bias even above threshold, which is a consequence of shifting intersubband populations. In conclusion, we also examine the role of higher-order dispersion in QCLs and discuss the ramifications of our result for devices utilizing nonlinear effects, such as frequency combs.},
doi = {10.1364/OPTICA.3.001362},
journal = {Optica},
number = 12,
volume = 3,
place = {United States},
year = {2016},
month = {12}
}