High Spatially Resolved Idler Image With a Compact Noncollinear Optical Parametric Amplifier Using a CW Laser as Signal

We realize a high spatially resolved idler imaging with a compact noncollinear optical parametric amplifier, which is based on type-II phase matching (PM). Using an intense femtosecond laser pulse train as the pump, this amplifier can amplify a separate continuous-wave (CW) signal with high gain and broad gain bandwidth with no need for time synchronization between the pump and the signal. In spite of the noncollinear arrangement of the amplifier, the spatial geometric smearing (SGS) is eliminated inside the amplifier due to the collinear Poynting vectors of the signal and the idler, which promotes the horizontal spatial resolution of the idler image to approach its vertical spatial resolution. Our experiments show that this design can improve the 2-D space-bandwidth product (SBP) of the idler imaging by a factor of 2.8, compared with the noncollinear type-I PM amplifier. The measured 2-D SBP is more than 73 000, which, to our knowledge, is the highest value for idler imaging to date.