A method for measuring the concentration of a gas includes heating a first gas with a pulse of light, the pulse of light having a wavelength absorbed by the first gas, wherein the first gas exerts pressure on a flexible membrane. The method includes receiving a first signal indicating a first deflection of the membrane, wherein the first deflection is due to a change in pressure of the first gas and receiving a second signal indicating a second deflection of the membrane occurring after the first signal, wherein the second deflection is due to the change in pressure of the first gas. The method includes determining a difference between the first signal and the second signal and, based on the difference between the first signal and the second signal, determining a first concentration of the first gas.