Broadband filter using cladding profile linearly tapered long-period waveguide grating

► Profile chirped long-period waveguide gratings can generate broadened filtering bandwidth. ► A large coupling constant is used together with a linearly tapered cladding in our simulation. ► The 20-dB bandwidth can be 14 times broader while the grating strength keeps large. ► The bandwidth broadening and large filtering strength are observed experimentally.