Development of a passively Q-switched eye-safe microchip laser for pulsed laser range-finding

Microchip lasers emitting at 1535nm are a valued tool for laser range-finding owing to their compactness, increased eye-safety, and ability to generate short laser pulses. We present the development of a longitudinally diode-pumped, passively Q-switched eye-safe laser utilizing an Er³⁺ and Yb³⁺ doped phosphate laser glass and a Co²⁺:MgAl₂O₄ crystal acting as a saturable absorber. The laser and its solid-state components are designed to produce 5 ns short laser pulses at 1535 nm. The design process is aided by analytical expressions derived from the coupled laser rate equations, which are also solved numerically. For verification, an experimental setup of the passively Q-switched laser emitting at 1535nm is built and several measurements will be presented, including the laser pulse duration, the pulse energy statistics, and the transverse intensity profile of the passively Q-switched laser. Very good agreement is achieved between the predicted and measured laser pulse duration with a lowest obtained value of 7.3 ns. The maximum laser pulse energy is 15.7 μJ in lowest-order transverse mode operation of the laser.