Large aperture disk standing-wave unstable resonator with intra-cavity adaptive correction

An unstable resonator with seven large aperture ceramic disks and intra-cavity adaptive correction is presented.The composite ceramic disks with absorption rings were adopted to suppress amplified spontaneous emission.An intra-cavity aberration non-conjugate correction based on round-trip wavefront and relaxation iteration was applied in the resonator.After tilt and defocus were corrected in turn,an average output power of 4.5 kW was obtained.The corresponding beam quality factorβwas 19.5.After tilt,defocus,and high order aberrations were corrected,the average output power was increased to 5.4 kW,and the beam quality factorβwas improved to 6.8.

Investigations on beam quality improvement of an NCPM-KTA-based high energy optical parametric oscillator using an unstable resonator with a Gaussian reflectivity mirror

Beam quality improvements by a large margin for signal and idler beams of a high energy 100 Hz KTiOAsO_(4)(KTA)non-critical phase matching(NCPM)optical parametric oscillator(OPO)were demonstrated using an unstable resonator configuration instead of a plane-parallel one.Theoretically,influences of cavity lengths and transmission of an output coupler on the OPO conversion efficiency for both were numerically simulated.For OPO based on an unstable resonator with a Gaussian reflectivity mirror,the maximum pulse energies at the signal(1.53μm)and idler(3.47μm)were about 75 mJ and 26 mJ,respectively.The corresponding beam quality factors of the signal were M_(x)^(2)=9.8 and M_(y)^(2)=9.9,and M_(x)^(2)=11.2 and M_(y)^(2)=11.5 for the idler.As a comparison,128 mJ of signal and 48 mJ of idler were obtained with the plane-parallel resonator,and the M~2 factors of the signal were M_(x)^(2)=39.8 and M_(y)^(2)=38.4,and M_(x)^(2)=32.1 and M_(y)^(2)=31.4 for the idler.Compared with a plane-parallel cavity,over eight times and three times brightness improvements were realized for the signal and idler light,respectively.

Development of an injection-seeded single-frequency laser by using the phase modulated technique

An injection-seeded single-frequency Q-switched Nd：YAG laser is accomplished by using a phase modulated rampfire technique. A RbTiOPO4（RTP） electro-optic crystal is selected for effective optical path length modulation of the slave self-filtering unstable resonator. This single-frequency laser is capable of producing 50 m J pulse energy at 1 Hz repetition rate with a pulse width of 16 ns. The standard deviation of laser pulse intensity for consecutive 100 shots from the mean pulse intensity is less than 1.05%. A spectral linewidth of less than 0.5 pm with a frequency jitter of about 14 fm over30 min is obtained.

Beam quality improvement of the high-energy KTA-OPO based on a confocal unstable cavity with Gaussian reflectivity mirror

A high-energy 100-Hz optical parametric oscillator(OPO)based on a confocal unstable resonator with a Gaussian reflectivity mirror was demonstrated.A KTA-based OPO with a good beam quality was obtained when the magnification factor was 1.5,corresponding to the maximum signal(1.53μm)energy of 56 m J and idler(3.47μm)energy of 20 m J,respectively.The beam quality factors(M^(2))were measured to be M^(2)_(x)=5.7,M^(2)_(y)=5.9 for signal and M^(2)_(x)=8.4,M^(2)_(y)=8.1 for idler accordingly.The experimental results indicated that the beam quality positively changed with the increase of magnification factors,accompanied by an acceptable loss of pulse energy.