Understanding the linewidth of a quantum cascade laser

• Main Author: Leow, Amy Min Huay
• Other Authors: Wang Qijie
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/71304
• Institution: Nanyang Technological University

Quantum Cascade (QC) lasers are semiconductor injection lasers transmitting in the mid-infrared to the terahertz of the electromagnetic spectrum. QC laser is operated based on the intersubband transitions in a many alternating layers of semiconductor material compositions. This forms a many quantum-well heterostructure. There are several advantages of applying intersubband transition. Firstly, emission wavelength is based on the thickness of a quantum well layer. We are able to decide and choose the best suitable semiconductor laser within the wavelength range and not having to worry about the material’s energy bandgap. The next advantage will be the cascade process. One electron can produce many photons during the cascading process. This is because the electrons will recycle themselves within the conduction band, hence, electrons will be kept inside the conduction band, then move down towards the next action region. This cascading process has the ability to provide intrinsic high power to the lasers. Last but not least, the ability to have an ultra-fast carrier dynamics and absence of the linewidth enhancement factor of a QC laser, have proved that with this features, it can provide significant impact on the laser performance.