Disclosed are ceramic honeycomb articles which possess a unique microstructure characterized by porosity between 40% and 70%, and the presence of coarse pores exhibiting a depth equivalent to the thickness of the cell wall and a dimensional width, in the plane of the cell wall, exhibiting a diameter that is at least as large as the thickness of the cell wall. The intensity of a wavelength-converted output \u03bbCONV of the device is monitored as the output beam of the laser is modulated and as the position of the modulated output beam \u03bbMOD on the input face of the wavelength conversion device is varied. The host material’s index of refraction may be chosen to maximize the effective active area of the device.