Low threshold gain metal coated laser nanoresonators

Abstract

We introduce a low refractive index layer between the metal and the gain medium in metal-coated laser resonators and demonstrate that it can significantly reduce the dissipation losses. Analysis of a gain medium waveguide shows that for a given waveguide radius, the low index layer has an optimal thickness for which the lasing threshold gain is minimal. The waveguide analysis is used for the design of a novel three-dimensional cylindrical resonator that is smaller than the vacuum wavelength in all three dimensions and exhibits a low enough threshold gain to lase at room temperature.

Temperature effects in metal-clad semiconductor nanolasers

“…The mode is only supported in the central region where the high-index gain material resides. Figure 3C shows the numerically determined optimal SiO 2 shield thickness and its corresponding threshold gain for this infinite waveguide, for a total device radius of 460 nm [39]. This optimal shield thickness depends on the real part of the material permittivities, which depend weakly on temperature, as discussed in Section 2.2.…”

“…The optimum shield thickness for a given total device diameter can be calculated using the numerical technique outlined in [39], or by the analytical approximations outlined in [40]. Both techniques involve first finding the optimal shield thickness in a composite gain 2D waveguide, which shares the same optimal shield thickness with its 3D counterpart.…”

“…Hence, photonic lasing modes typically have higher Q-factors and lower threshold gain values, albeit at the expense of reduced mode confinement. For metal-clad nanolasers based on photonic modes, metal losses may be minimized using a metallo-dielectric composite structure, in which a shield layer is placed between the active region and the metal cladding [39]. From a purely electromagnetic perspective, the optimal shield thickness for a given total device size, corresponding to minimal threshold gain of a photonic mode, can be determined numerically [39], and may be approximated analytically [40].…”

“…For metal-clad nanolasers based on photonic modes, metal losses may be minimized using a metallo-dielectric composite structure, in which a shield layer is placed between the active region and the metal cladding [39]. From a purely electromagnetic perspective, the optimal shield thickness for a given total device size, corresponding to minimal threshold gain of a photonic mode, can be determined numerically [39], and may be approximated analytically [40]. Lasing in an optically-pumped metallo-dielectric subwavelength laser, with such an optimized thickness of SiO 2 shield, was demonstrated at room temperature [41].…”

An electrical injection metallic cavity nanolaser with azimuthal polarization

“…An InP/InGaAs/InP layer stack grown by metal organic chemical vapor deposition (MOCVD) is etched into circular pillars and then we deposit SiN layer via plasma enhanced chemical vapor deposition (PECVD) for insulating purpose and also as a buffer layer to push away optical field from lossy metal to improve cavity quality factor (Q). 25 Finally, the whole structure is encapsulated in silver to form a metallic cavity. Electrical injection is enabled through top and bottom contacts.…”