Development of a 1.54µm Yb:Er:glass laser pumped by a Nd:YAG laser

Abstract

The development of a laser source, operating at the wavelength of 1.54µm, using the scheme of ytterbium:erbium:glass, longitudinally pumped by a Nd:YAG laser at 1.064µm, has been investigated. The first pulsed Nd:YAG laser pumped Yb:Er:glass laser system was successfully demonstrated. This system was operated free-running, Q-switched, mode-locked, and combined Q-switched and mode-locked, all with good output characteristics. A free-running output power of 2.25W in a 3.5ms pulse was achieved, with 13% slope efficiency, and a threshold incident pump power of 37W. Q-switched pulses of 10kW peak power and 60ns width were obtained, using a LiNbO3 electro-optic device. Active mode-locking, using an acousto-optic device, gave pulses of 50W peak power and 70ps duration. Combined Q-switched and mode-locked operation, gave a peak power of 2kW with pulses 85ps wide.

The first cw laser operation o bulk Yb:Er:glass, pumped by a cw Nd:YAG laser, was also demonstrated. Using high reflectivity mirrors an absorbed power threshold as low as 500mW was achieved. An output of 21mW was obtained for 1.05W absorbed pump power. Q-switched, and mode-locked operation, for this cw laser, have also been demonstrated, with good characteristics.

A detailed discussion is given of the design considerations leading to successful laser performance. A rate equation analysis, including energy transfer from Yb to Er, and volumetric considerations, is presented. A detailed study is made of the theoretical aspects of thermal effects, such as lensing and birefringence, and their practical implications, which are an important feature of the laser design.

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