Abstract: A measurement device characterizes an environment. The measurement device includes a transmitter and a receiver. The transmitter transmits a transmitted light. The transmitter includes an atomically two-dimensional material for emitting the transmitted light. The atomically two-dimensional material is tunable to select a predominate wavelength of the transmitted light within a tunable range of wavelengths. The receiver receives a received light, which is the transmitted light after encountering the environment. The receiver characterizes the environment from a measured change between the received light and the transmitted light.