All-solid-state CW Single-frequency 266 Nm UV Laser

The all-solid-state single-frequency continuous-wave(CW)266 nm ultraviolet(UV)laser has the advantages of compact structure,narrow line width and high reliability.It also has the advantages of short wavelength,high resolution and concentrated photon energy.So,it has be widely used in scientific and industrial applications including the processing of channel routing in PCB in the electronics industry,the processing of large-capacity storage discs and the implementation of higher resolutions in microscopes.In this paper,a compact and stable all-solid-state single-frequency CW 266 nm UV laser was designed based on an external-cavity doubled resonator using a type I critical phase matched BBO crystal.A stable four-mirror external ring cavity structure was designed.By means of external polarization locking system,an all-solid-state single-frequency 266 nm UV laser with high-beam quality and high-conversion efficiency was realized.The main contents are as follows:1.Based on the three-wave coupling equation,the theory of second harmonic generation was introduced in details.The analysis of the frequency doubling efficiency under the approximation of large and small signals was derived.The theories of the type Ⅰ and type Ⅱ phase matching,phase matching angle,walk-off angle and phase matching width during the course of frequency doubling were introduced.The laser nonlinear crystals commonly used to produce 266 nm UV laser were introduced.And the BBO and CLBO crystals were emphatically explained.2.An efficient and stable four-mirror ring resonator structure was analyzed and designed by using the theory of resonant cavity.By shortening the cavity length,the radius of the waist spot at the BBO crystal was enlarged.Thereby the walk-off effect at the BBO crystal was minimized.And the transmission of the input-coupling mirror was calculated basing on the theory of the impedance matching of the resonant cavity.As a result,the beam quality of 266 nm UV light was optimized under the condition of high conversion efficiency.3.Based on theoretical research the all-solid-state CW 266 nm UV laser experimental setup was built.With the pump power of 3 W and the optimum design of the input-coupling mirror transmission of 2.5% at 532 nm,the highest output power of 810 m W at 266 nm has been obtained.The long-term stability(Peak-to-peak)within three hours and the beam quality factor M2 were Mx2=1.12,My2= 1.45 and ±1.5% at the output power of 730 m W,respectively.