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Enhanced coupling to vertical radiation is obtained from a light-emitting diode using a two-dimensional photonic crystal that lies entirely inside the upper cladding layer of an asymmetric quantum well structure. A sixfold enhancement in light extraction in the vertical direction is obtained without the photonic crystal penetrating the active material. The photonic crystal is also used to couple pump light at normal incidence into the structure, providing strong optical excitation.

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Thermo-optic materials properties of laser host materials have been measured to enable solid-state laser performance modeling. The thermo-optic properties include thermal diffusivity (β), specific heat at constant pressure (Cp), thermal conductivity (κ), coefficient of thermal expansion (α), thermal coefficient of the optical path length (γ) equal to (dO∕dT)∕L, and thermal coefficient of refractive index (dn∕dT) at 1064nm; O denotes the optical path length, which is equal to the product of the refractive index (n) and sample length (L). Thermal diffusivity and specific heat were measured using laser-flash method. Thermal conductivity was deduced using measured values of β, Cp, and the density (ρ). Thermal expansion was measured using a Michelson laser interferometer. Thermal coefficient of the optical path length was measured at 1064nm, using interference between light reflected from the front and rear facets of the sample. Thermal coefficient of the refractive index was determined, using the measured values of γ, α, and n. β and κ of Y3Al5O12, YAIO3, and LiYF4 were found to decrease, as expected, upon doping with Yb.