Hybrid optic rf spectrum analyzer using waveguide type Bragg cell coupled with focusing lens and glass waveguide

The acousto-optic spectrum analyzer (AOSA) using a waveguide type Bragg cell, which consists of a Ti indiffused waveguide and a surface acoustic wave(SAW) transducer fabricated on a LiN´bOJ substrate, is promising as a compact RF signal analyzer. The integrated optic spectrum analyzer(IOSA) has been investigated as an AOSA using a waveguide type Bragg cell. In the IOSA, a Ti indiffused waveguide,a SAW transducer and two waveguide lenses are integrated on a LiNb03 substrate. However,the dynamic range of the IOSA is limited to less than 25dB by the scattered light in the Ti indiffused waveguide and the waveguide lenses. Scattering loss of the Ti indiffused waveguide is about 3dB since the waveguide length and the propagation loss caused by scattering are about 6cm and O.SdB/cm,respectively. Scattering loss of the waveguide lenses is about SdB. We developed a hybrid optic spectrum analyzer (HOSA) with a dynamic range of more than 30dB. In the HOSA, the scattered light is suppressed by setting the focusing lens outside of waveguides, limiting the Ti indiffused waveguide to the area where the guided light is diffracted by the SAW and leading the diffracted light to a photodiode(PD) array through the glass waveguide.