Diode Laser Spectroscopy Combiners

Power of diode pumped solid-state laser(abbreviated to DPSSL) is hard to improve continually for thermal effect.Beam combining is a better way to acquire high power.Beam combining is divided into two sorts:coherent combining and incoherent combining. Incoherent combining can also be divided into two sorts:polarized combining and spectral beam combining(abbreviated to SBC).Polarized combining limits number of the combining laser just two.Spectral beam combining,which forces beams to overlap with dispersive apparatus,has caused great concern for no precise phase control.SBC based on PTR grating and SBC based on grating-cavity have been analytically studied. The main results obtained in the dissertation can be summarized as follows:Firstly,factors on angular selectivity and wavelength selectivity of transmitting gratings are analyzed:angular selectivity and wavelength selectivity decrease with increase of thickness and spatial frequency,and refractive index modulation must be changed accordingly to maintain diffraction efficiency.According to critical that two diffraction orders of reflection grating overlap,critical incidence angle is concluded.Diffraction efficiency model of nonplanar light is established with Fourier transform.With the modal the Gaussian beams and super-Gaussian beams were simulated.The results indicate that the diffraction efficiency reduce with the increase of divergence angle and order of Gaussian beams.The propagation distance has no influence on diffraction efficiency.The diffraction efficiency increase when the waist radius of super-Gaussian beams increase or when the super-Gaussian order decrease. The combining efficiency model of Multi-beams spectral beam combining is established,and we got the expression of combining power and combining efficiency with cross-talk and without cross-talk.Efficiency of spectral beam combining based on grating-cavity mostly depends on coupling efficiency between emitter and cavity.Base on diffraction integral equation,coupling efficiency model with abaxial aberration is established.Then,the effect of the system parameters on coupling efficiency is analyzed quantitatively.The results show that coupling efficiency decrease when abaxial distance or the order of mode increase,or when mode field radius increase,or when grating plane or array plane deviate from focal plane.Grating's tilt angle and distance between grating plane and OCM have few influence on coupling efficiency. For the system with bi-convex lens of 500-mm focal length and 10-mm array,mode field radius in fast axis should be more than 0.15 mm,and mode field radius in slow axis should be more than 20μm,and array plane's deviation should be no more than 0.5 mm,and grating plane's deviation should be no more than 0.2 mm,and the linewidth of each element is no more than 0.1 nm.Spectral beam combining of diode laser based on grating-cavity was investigated experimentally.LDA comprised of 19 elements was spectrally combined.10 W under CW operation was measured with a beam quality of M_x~2=16.7 and M_y~2=10.8.With feedback the slope efficiency is 0.45W/A as compared to 0.91W/A for the free-running laser.