Observation of Saturation Spectrum of the 2ν3 Band of Methane

We have carried out intracavity saturated absorption spectroscopy of the 2ν3 band of methane using a 1.6-µm-grating feedback external-cavity semiconductor laser. Since the narrowest linewidth of observed saturation dips is only 0.9 MHz (half-width at half-maximum), a high potential exists for the use of this band as a precise frequency standard, especially when considering that the ν3 band of methane is currently a well-established frequency standard.