We report thermally stable latched operation of a nonlinear Fabry-Perot device without heat sinking other than through the 0.5-mm GaAs substrate. The device has a 2-μm GaAs spacer and integrated dielectric mirrors with reflectivities of 91% and 99%. Operated in reflection at a wavelength of 886 nm, thresholds as low as 1 mW, and contrast ratios of 10:1 have been observed. Measurements of the threshold dependence on the size of the excited spot give evidence for carrier diffusion and light-diffraction effects.