End-Close-Pumped Passively Q-Switched Composite Nd:YAG/Cr4+:YAG Laser

We designed a compact diode-end-close-pumped passively Q-switched composite Nd:YAG/Cr4+:YAG laser. By a single F-mount packaged fast-collimated laser diode without any optical pump coupling components, we achieved a 1.7 ns pulse width output with an 11.4 kHz pulse repetition rate at a 2 W continuous wave pump power in the resonator formed by the coated end surfaces of the crystal, and this agrees with numerical simulations. The corresponding pulse energy and average output power is 21 mu J and 240 mW at 1,064 nm, and the beam is near-diffraction-limited with M (2)similar to 1.5. To the best of our knowledge, these are the highest pulse energy and average power in directly close-pumped passive lasers. The laser overall size without the forced air cooling system is smaller than a one-pound coin, and such miniaturization will lead to more widespread applications.