Single-longitudinal-mode Ho:YVO₄ MOPA system with a passively Q-switched unidirectional ring oscillator

A 2052.96 nm single-longitudinal-mode pulsed Ho:YVO₄ MOPA system was demonstrated for the first time. The pulsed Ho:YVO₄ MOPA system consisted of a unidirectional ring passively Q-switched oscillator and a single-pass amplifier. By inserting an isolator, a half-wave plate and a Cr²⁺:ZnS plate into the ring Ho:YVO₄ oscillator cavity, the single-longitudinal-mode pulsed laser was achieved with an average output power of 1.02 W with pulse width of 910 ns and pulse repetition frequency (PRF) of 67 kHz. Using the residual (non-absorbed) pump power of the oscillator as pump, the single-pass pulsed Ho:YVO₄ amplifier obtained an average output power of 1.67 W. The total optical-to-optical efficiency of the pulsed Ho:YVO₄ MOPA system was 14.3%. Single-longitudinal-mode pulsed MOPA system based on isolator and Cr²⁺:ZnS around 2 µm has not been reported yet to the best of our knowledge.