457nm high-power single-frequency blue laser

457nm high-power single-frequency blue laser
Optical path design of a 457nm high-power single-frequency blue laser with single frequency
The pump source used is a 30 W fiber-coupled laser diode array. Secondly, a ring resonator is selected for mode selection. The end face is pumped with a 5 mm length Nd3+-doped yttrium vanadate (Nd:YVO4) crystal with a concentration of 0.1%. Then, through a I-type phase-matched lithium triborate (LBO) crystal cavity, the second harmonic is generated to achieve 457nm high-power single-frequency laser output. When the pump power is 30 W, the output power of the 457nm single-frequency laser is 5.43 W, the central wavelength is 457.06 nm, the light-to-light conversion efficiency is 18.1%, and the power stability within 1 hour is 0.464%. The 457nm laser operates in the fundamental mode within the resonator. The beam quality factors along the x and y directions are 1.04 and 1.07 respectively, and the ellipticity of the light spot is 97%.

Description of the optical path of the high-power blue light single-frequency laser
The pump source uses an optical fiber-coupled semiconductor laser diode array with a central wavelength of 808 nm, a continuous output power of 30 W, and a fiber core diameter of 400 μm, with a numerical aperture of 0.22.
The pump light is collimated and focused by two plano-convex lenses with a focal length of 20 mm and then incident on the laser crystal. The laser crystal is a 3 mm × 3 mm × 5 mm Nd:YVO4 crystal with a doping concentration of 0.1%, with 808 nm and 914 nm anti-reflection films deposited at both ends, and the crystal is wrapped with indium foil and placed in a copper clamping fixture. The copper clamping fixture is precisely temperature-controlled by a semiconductor cooler and set at 15℃.
The resonator is a four-mirror ring cavity composed of M1, M2, M3, and M4.
M1 is a plane mirror with 808 nm, 1064 nm, and 1342 nm anti-reflection films (R<0.05%), and a 914 nm total reflection film (R>99.8%); M4 is a plane output mirror with 914 nm total reflection film (R>99.8%), 457 nm and 1064 nm, 1342 nm anti-reflection films (R<0.02%); M2 and M3 are both plano-concave mirrors with a curvature radius of r = 100 mm, with 1064 nm and 1342 nm anti-reflection films (R<0.05%) on the plane and 914 nm and 457 nm total reflection films (R>99.8%) on the concave surface.
The half-wave plate and the TGG crystal placed in the magnetic field both have 914 nm anti-reflection films (R<0.02%). By introducing an optical unidirectional device composed of TGG and the half-wave plate, the laser is forced to run unidirectionally in the ring resonator, thus ensuring that the laser operates stably in a single-frequency state. FP is a standard piece with a thickness of 2 mm, with a double-sided coated reflectivity of 50%, and it performs secondary narrowing of the single-frequency operation of the laser in the cavity. The LBO crystal is selected as the frequency doubling crystal, with a size of 3 mm × 3 mm × 15 mm, and is coated with 914 nm and 457 nm anti-reflection films (R<0.02%), with I-type phase matching, cutting angle θ = 90°, φ = 21.9°.