Saturated absorption spectroscopy of acetylene molecules with an optical nanofiber

We performed saturated absorption spectroscopy of acetylene (C?H?) ν? + ν? band transitions with an optical nanofiber (ONF). Owing to high-intensity light around the ONF, we observed a Lamb dip at relatively low-power laser (~10 mW) without a cavity. Our results showed that the simple ONF spectrometer is advantageous for performing saturation absorption spectroscopy and serves as a practical low-cost wavelength reference in the optical fiber communication band.