Ultralow lasing thresholds of VCSEL-type resonators with periodically structured quantum wells

Widely used in photonics vertical cavity surface emitting lasers (VCSEL) commonly have quantum wells as active regions. Besides many advantages of that model we propose enhancing its properties by replacing a quantum well with periodically structured quantum wires. Thus the properties of specific high Q-factor grating resonances of the grating consisting of periodically placed circular cylinders [1,2] can be combined with those of a VCSEL-type resonator. In the latter device, two distributed Bragg reflectors (DBR) sandwiching a cavity in the middle forge a high-intensity field in the cavity. First time the grating resonances were explained in [1]. Then we investigated in [2] the natural grating-type modes of similar structure made of quantum wires, in the framework of the Lasing Eigenvalue Problem (LEP) with two parameters (σ, γ). The first is the normalized by period lasing frequency and the second is the material gain necessary to bring the mode to lasing. Therefore it is interesting to find geometrical and material parameters which lead to the lowest lasing threshold. In the previous study, besides other interesting facts it was discovered that, if the quantum-wire grating in the free space becomes sparser, the lasing thresholds decrease in exponential manner and can reach the values γ ≈ 10⁻³ if the period is ten times larger than the wire diameter.