Continuous wave energy transfer dye lasers in the near infrared spectral region: Theory, modeling, simulation, performance

Energy transfer processes in dye mixture lasers in which optical excitation energy is absorbed by one dye (the donor) and transferred to a second dye (the acceptor) in which laser action takes place, have been extensively studied to improve the efficiency and broaden the attainable spectral range of pulsed dye lasers. We developed a theoretical simulation model which predicts the attainable gain spectrum of CW laser pumped energy transfer dye lasers (ETDL) as a function of donor and acceptor concentrations, their spectral parameters, energy transfer parameters, laser cavity, and pumped power and excitation wavelength. The model takes into account contributions due to both radiative and nonradiative energy transfer. Numerical simulation results applied the model to different dyes. The model predicts that there are a number of useful dye candidate pairs that would benefit from the ETDL approach in terms of reduced power and attainable spectral range. Analysis of the relevant gain parameters of CW EDTL's, together with results for a representative and practically useful donor-acceptor pair, is presented. We used the argon ion laser to excite an ETDL with Rhodamine 610 as donor and Nile Blue 690 as acceptor to demonstrate laser action in the near infrared, with operational parameters very close to those predicted by our theoretical simulation model. It is believed that the results obtained in this work open up a new and practically useful avenue for CW laser operation with improved spectral capabilities and reduced pump requirement.