Fiber-optic spectroscopic rotational Raman lidar with visible wavelength fiber Bragg grating for atmospheric temperature measurement

- A rotational Raman lidar is demonstrated with visible wavelength fiber Bragg grating.
- Two rotational Raman signals are extracted by two sets of fiber Bragg gratings.
- Visible wavelength fiber Bragg grating is fabricated by zero-order nulled phase mask.
- The out-of-band rejection is tested to ensure rotational Raman spectral purity.
- Preliminary experiment is executed to assess capability of fiber-optic spectroscope.

A fiber-optic spectroscopic rotational Raman lidar is demonstrated with the visible wavelength fiber Bragg grating technique for profiling the atmospheric temperature. Two-channel pure rotational Raman optical signals are extracted from lidar echo signals by two sets of visible wavelength fiber Bragg gratings. The rejection-type of fiber Bragg grating in visible region is successfully fabricated through the zero-order nulled phase mask. Its most significant parameter, out-of-band rejection, for fiber-optic spectroscopic system is tested to ensure the spectral purity of rotational Raman channel. A temperature profile up to a 0.7-km height is obtained by pure rotational Raman lidar with 300-mJ laser pulse energy, and a 250-mm telescope. Preliminary results of observations show that this fiber-optic spectroscopic scheme with high mechanical stability has >70-dB suppression to elastic backscattering in lidar echo signals.