Quantum Cascade Ring Laser Systems

Jul 20, 2023, 10:00 am11:30 am
EQUAD B327 & Zoom (see abstract)



Event Description

Mid-infrared light is a powerful tool for spectroscopy and sensing due to its strong interaction with many molecules through their ro-vibrational resonances. The development of mid-infrared light sources was limited until the advent of quantum cascade (QC) lasers. These lasers, composed of atomically thin heterostructures, offer unparalleled engineerability, inspiring continuous innovation over the past three decades.  

The focus of this dissertation is the exploration of QC ring laser systems. These cavity geometries are attractive due to their favorable attributes such as low loss, low lasing threshold and high internal optical power. Additionally, the fast gain recovery time of QC lasers enables them to efficiently generate frequency combs. Coupled with dual-comb spectroscopy, ring QC lasers are poised to revolutionize compact and high-precision spectrometers in the mid-infrared. However, several technological challenges stand in the way of realizing commercial spectrometers from standalone QC lasers. 

To bridge this technological gap, we demonstrate the monolithic integration of ring QC lasers with other optoelectronic components. We develop novel fabrication methods suited to building chip-scale systems on conventional QC laser wafers. Leveraging these methods, we develop active waveguide couplers that offer a three-order-of-magnitude enhancement of the output power of ring lasers compared to standalone devices, while also providing precise control over the direction of emission. We demonstrate the successful integration of fast and efficient photodetectors on the same chip eliminating the need for free-space components which allows us to scale the number of optical outputs. We then expand this system to include two coupled lasers in a photonic molecule arrangement and explore the degeneracies of this highly multimode system. We find that degenerate combs of frequencies give rise to discrete energy bands instead of the typical two-level anti-crossing. The versatility of this active system is such that the same components may perform several functions acting as lasers, detectors, waveguides, amplifiers, filters, switches, and frequency combs. Finally, we develop efficient computation methods to study such systems focusing on coherent multimode instabilities in ring lasers. 

This research advances our understanding of novel laser physics and contributes to the development of commercial on-chip sensing systems operating in the mid-infrared range. 

Adviser: Claire Gmachl

Zoom: : https://princeton.zoom.us/j/92162780943