A Path towards Thresholdless Colloidal Quantum Dot Lasers by Solving Decades of Mythology on Optical Gain

The semiconductor quantum dot (CQD) was first conceived in the 1980s as offering potential for future lasers. Following high quality solution phase synthesis of colloidal CQD (CCQD) in 1993, optical gain was first demonstrated in 2000 via stimulated emission (SE) measurements. Decades of phenomenology have given rise to a Standard Model of optical gain in CCQD based upon two assumptions: a biexciton is required to achieve optical gain, and short biexciton lifetimes limit the efficient development of amplified spontaneous emission (ASE). The Standard Model predicts the solution to efficient ASE is slowing Auger recombination, a task which now consumes the CCQD field. Here, we show that the Standard Model is physically incorrect, leading to misdirected materials development. Inspection of the phenomenology reveals a Simple Model which uniquely reproduces all observed phenomena. The Simple Model provides the physical foundation for developing CCQD lasers with quantum leaps in performance, including thresholdless gain.