Controlling intersubband nonlinear dynamics for secure communications, high-power lasers and optical countermeasures
Abstract
Quantum cascade lasers (QCLs) are unipolar semiconductor lasers offering access to a wide range of optical wavelengths from the mid-infrared (IR) to the terahertz domain and promising impact on various applications such as free-space encrypted communications, high-resolution spectroscopy, LIDAR remote sensing or optical countermeasures [1]. Unlike bipolar semiconductor lasers, stimulated emission in QCLs is obtained via electronic transitions between discrete energy states inside the conduction band. Recent technological progress has led to QCLs operating in pulsed or continuous wave (CW) mode, at room temperature in single- or multimode operation, with high powers up to a few watts for mid-IR devices. This spectacular development raises interrogations regarding the stability of QCLs as little is known on their dynamical properties. Over the years, spotty experimental work has shown the possibility of improving QCL features under external control. In particular, optical feedback has demonstrated its potential for e.g. noise reduction or mode selection for widely tunable sources. Our experiments based on optical spectrum measurements have unveiled for the first time the existence of five distinct feedback regimes without, however, identifying the complex dynamics dwelling within the QCL. Our recent work has evidence for the first ever route to chaos in a QCL emitting at mid-IR wavelength. When applying an optical feedback with an increasing strength, the QCL dynamics was found to bifurcate to periodic dynamics at the external cavity frequency and later to chaos without an undamping of relaxation oscillations. In contrast with the spatial chaos observed earlier in quantum cascade micro-resonators, our discovery does not originate from ray dynamics in a laser cavity but from the temporal nonlinear dynamics driving the evolution of both photon and carrier densities.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Sep 19, 2018
- Source ID
- FA95501817001
Entities
People
- Frédéric Grillot
Organizations
- Air Force Office of Scientific Research
- Institut Mines-Télécom
- United States Air Force