1342 nm 2.8ns electro-optical cavity damping Nd: YVO₄ laser

Abstract

1.3 μm Nd laser has significant practical applications in various fields, such as fiber communication, medical treatment, frequency conversion, and scientific research, etc. Many applications of a 1.3 μm laser, especially like frequency conversion, benefit much from a short pulse width with high peak power. In the paper, an electro-optical cavity dumping Nd:YVO₄ laser at 1342 nm wavelength has been studied theoretically and experimentally. The pulse width for an electro-optical cavity dumping laser is determined by the optical length of the cavity. A narrower pulse width can be obtained by reducing the length of the cavity and the round trip time of the laser in the cavity. However, when the round trip time in the cavity approaches to the falling edge time of the electro-optical switch, shortening the length of the cavity will not get a narrower pulse width, and the falling edge time of the electro-optical switch will influence the laser pulse width. The temporal characteristics of the laser pulse are simulated when the falling edge time of the electro-optical switch is close to the round trip time in the cavity. Influences of the falling edge time of the electro-optical switch on the laser pulse duration are analyzed theoretically. The modified rate equation is used to study the relationship between the falling edge time and the laser pulse width. We demonstrate an electro-optical cavity dumping Nd:YVO₄ laser. The 0.3 at.% Nd:YVO₄ placed in a short Plano-concave cavity is in-band pumped by an 880 nm quasi-continuous-wave diode. A fiber-coupled diode laser module (NA=0.22) with a power of 30 W was used. A LiNbO₃ electro-optical switch was employed for the cavity-dumping. The 1342 nm cavity-dumping laser operates at a repetition rate of 1kHz, and a single-pulse energy of 0.21 mJ is obtained with a pulse width of 2.8 ns. Near-diffraction-limited beam quality with an M² value of < l.2 is achieved. The setup provides efficient second harmonic generation at 671 nm using a MgO:PPLN crystal, and the pulse width is 1.8 ns. To the best of our knowledge, this is the shortest pulse duration obtained from 1.3μm actively Q-switched Nd-doped laser.