Nd-Doped Polymer Waveguide Amplifiers

Nd³⁺-complex-doped polymer channel waveguide amplifiers with various lengths and Nd³⁺ concentrations are fabricated by a simple procedure. Internal net gain at 840-950 nm and 1064 nm is experimentally and theoretically investigated under continuous-wave excitation at 800 nm. Internal net gain in the range 865-930 nm is observed and a peak gain of 2.8 dB at 873 nm is obtained in a 1.9-cm-long waveguide with a Nd³⁺ concentration of 0.6 × 10²⁰ cm^-3 at a launched pump power of 25 mW. The small-signal gain measured in a 1-cm-long sample with a Nd³⁺ concentration of 1.03 × 10²⁰ cm^-3 is 2.0 dB/cm and 5.7 dB/cm at 873 nm and 1064 nm, respectively. By use of a rate-equation model, the internal net gain at these two wavelengths is calculated and the macroscopic parameter of energy-transfer upconversion as a function of Nd³⁺ concentration is derived. Ease of fabrication, compatibility with other materials, and low cost make such rare-earth-ion-doped polymer waveguide amplifiers suitable for providing gain in many integrated optical devices.