Integrated IR Modulator with a Quantum Cascade Laser

Abstract

This paper presents an infrared pulsed modulator into which quantum cascade lasers and a current driver are integrated. The main goal of this study was to determine the capabilities of a new modulator design based on the results of its electrical model simulation and laboratory experiments. A simulation model is a unique tool because it includes the electrical performance of the lasing structure, signal wiring, and driving unit. In the laboratory model, a lasing structure was mounted on the interfacing poles as close to the switching electronics as possible with direct wire bonding. The radiation pulses and laser biasing voltage were registered to analyze the influence of laser module impedance. Both simulation and experimental results demonstrated that the quantum cascade laser (QC laser) design strongly influenced the shape of light, driving current, and biasing voltage pulses. It is a complex phenomenon depending on the laser construction and many other factors, e.g., the amplitude and time parameters of the supplying current pulses. However, this work presents important data to develop or modify numerical models describing QC laser operation. The integrated modulator provided pulses with a 20–100 ns duration and a frequency of 1 MHz without any active cooling. The designed modulator ensured the construction of a sensor based on direct laser absorption spectroscopy, applying the QC laser with spectral characteristics matched to absorption lines of the detected substances. It can also be used in optical ranging and recognition systems.