Broadband amplitude squeezing in a periodically poled KTiOPO_4 waveguide

We generated -2.2 dB of broadband amplitude squeezing at 1064 nm in a periodically poled KTiOPO4 (PPKTP) waveguide by coupling of the fundamental and second-harmonic cw fields. This is the largest amount of squeezing obtained to date in a KTP waveguide, limited by propagation losses. This result paves the way for further improvements by use of lower-loss buried ion-exchanged waveguides.