Dispersion of effective refractive indices of mid-infrared quantum cascade lasers

Abstract

We point out the difference between the two mostly used methods for calculating the effective refractive index of mid-infrared quantum cascade lasers, namely by solving the Maxwell's wave equation and by analyzing the frequency spacing of the longitudinal modes of the Fabry-Perot cavity. The effective refractive indices obtained by these methods are shown to be different, as one refers to the phase effective refractive index while the other refers to the group effective refractive index, respectively. Dispersion relationships for these two effective refractive indices are deduced for mid-infrared quantum cascade lasers, which show an increase in group refractive index and a decrease in phase refractive index with wavelength. Experiments are conducted to obtain the group effective refractive indices of quantum cascade lasers emitting at various wavelengths, and good agreement has been achieved between the experimental data and theory

Parametric Thermo-Optical Simulations of Quantum Cascade Laser Waveguides

“…Rigorous optimization of active region geometry, and that of the waveguide, is expected to reduce experimental redundancy by way of reducing the number of samples grown for characterization. In fact, various thermal and optical properties of QCL waveguides specifically have already been extensively investigated [3,4].…”

Parametric Thermo-Optical Simulations of Quantum Cascade Laser Waveguides

“…Rigorous optimization of active region geometry is expected to reduce experimental redundancy by virtue of reducing the number of samples grown for characterization. Despite the QCL being a relatively novel technology, there is already an abundance of fruitful results (such as those in [3] and [4]) from research on waveguides designed specifically for this demanding application.…”

Effective group dispersion of terahertz quantum-cascade lasers

“…For THz QCLs, this method is implemented by using THz time-domain spectroscopy, which employs the phase-sensitive detection of broadband THz pulses for the determination of n g,eff [14,15]. A second method, which we employ in this work, relies on the mode spacing in the emission spectrum of THz QCLs with Fabry-Pérot resonators [13,26].…”