Compact and efficient Nd:YVO 4 laser that generates a tunable single-frequency green output

We demonstrate 250 mW of single-frequency 532-nm output from a simple intracavity-doubled Nd:YVO(4) laser, pumped with 1.2 W from a fiber-coupled diode laser. The laser can be frequency chirped smoothly over ~17 GHz while maintaining a single-frequency green output of greater than 200 mW. A short Fabry-Perot cavity is used, and single-frequency operation is enforced by means of a birefringent filter that utilizes the birefringence of both the KTP doubling crystal and the Nd:YVO(4) laser crystal with polarization-dependent loss from a glass Brewster plate combined with polarization-dependent gain from the laser crystal.     

Four watt long-term stable intracavity frequency-doubling Nd:YVO(4) laser of single-frequency operation pumped by a fiber-coupled laser diode

The longitudinal-mode stability of a single-frequency intracavity frequency-doubling laser can be enhanced by increasing the ratio between the nonlinear spectral bandwidth and the gain bandwidth of the laser. A 4 W long-term stable cw single-frequency green laser is obtained using an etalon inside the laser cavity as a spectral filter. No mode hopping is observed when the laser operates for 6 h and the power fluctuation is less than +/-1.2%. In contrast, in the situation of no etalon inside the laser cavity, mode hopping can be observed at irregular intervals and the power fluctuation is +/-3.8% when the laser operates for 4 h.     

Suppression of intensity noise of a laser-diode-pumped single-frequency Nd:YVO4 laser by optoelectronic control

The intensity-noise reduction of a laser-diode-pumped single-frequency ring Nd:YVO4 laser when different optoelectronic control systems are used is theoretically and experimentally investigated. It has been demonstrated that combining two techniques, optoelectronic feedback control of the drive current of the pump laser diode and feed-forward control of the output laser beam, is a good way to significantly suppress the intensity noise of a laser at low frequency.     

Unidirectional single-mode Nd:YAG laser with a planar semimonolithic ring cavity

Unidirectional single-mode operation of a diode-pumped Nd:YAG laser with a planar semimonolithic ring cavity has been demonstrated at 1064 nm. The semimonolithic cavity consists of a laser active medium placed in a magnetic field, a crystal quartz plate, and an output coupling mirror, which form an optical diode by acting as a Faraday rotator, a reciprocal polarization rotator, and a partial polarizer, respectively. A single-mode output power of 155 mW and a slope efficiency of 17% were obtained with a 1.2-W diode laser at 809 nm. A laser linewidth of less than 100 kHz is inferred from a beat note frequency spectrum between two identical laser systems and continuous tuning to greater than 2 GHz was observed.     

Doubled single-frequency Nd:YLF ring laser coupled to a passive nonresonant cavity

We demonstrate an original solution to obtain a single-frequency ring laser coupled to an external passive nonresonant ring cavity, which plays the role of an optical diode. This system provides more output power than systems with an intracavity unidirectional device. To the best of our knowledge, this work marks the first demonstration of a unidirectional planar ring laser at 1.3 microm. Using 12 W at 797 nm to pump a Nd:YLF laser, combined with intracavity second-harmonic generation, we achieve yields of 440 mW at 661.3 nm and 340 mW at 656.0 nm.     

High-repetition rate Q-switched Nd:YVO4 laser with a composite semiconductor absorber

A diode-pumped Nd:YVO4 laser passively Q switched by a semiconductor absorber is demonstrated. The Q-switched operation of the laser has an average output power of 135 mW with a 1.6 W incident pump power. The minimum pulse width is measured to be about 8.3 ns with a repetition rate of 2 MHz. To our knowledge, this is the first demonstration of a solid-state laser passively Q-switched by such a composite semiconductor absorber.     

Passively Q-switched multi-wavelength Nd:YVO4 self-Raman laser

Abstract

Multi-wavelength self-Raman laser from a passively Q-switched c-cut Nd: YVO₄ laser at 1066.8 nm to four discrete Stokes lines at 1097.2, 1129.2, 1168.3 and 1178.8 nm is demonstrated simultaneously for the first time. With a 0.27 at% c-cut Nd:YVO₄ crystal, the total output power of Stokes lines is 267 mW at a pump power of 5.0 W.     

Double-end-pumped Nd:YVO4 slab laser at 1064 nm

We demonstrate a high-power laser diode stacks double-end-pumped Nd:YVO4 1064 nm slab laser with a folded stable-unstable hybrid resonator. An output power of 220 W was obtained at the pump power of 490 W with optical conversion efficiency of 44.9%. At the output power of 202 W, the M2 factors in the unstable direction and in the stable direction were 1.7 and 2.3, respectively.     

The characteristics of Kerr lens mode-locked Nd:YVO4 laser with a symmetrical z-shaped cavity

In this paper, a diode-pumped CW Kerr lens mode-locked Nd:YVO₄ laser is demonstrated in the megahertz (MHz) oscillations mode-locked regime for the first time. Considered the beam mode size in the laser crystal and the Kerr lens sensitivity, an effective laser system with a symmetrical z-shaped cavity is strictly designed by the ABCD matrix and experimentally researched. The laser system can be self-starting without the need of any additional components. When an incident pump power is of 8 W, the maximum output power is 1.65 W, with a slope efficiency of 23.8%. The mode-locked repetition rate and pulse width are 530 MHz and 15.1 ps, respectively.     

Passively Q-switched Nd:YVO4 waveguide laser using graphene as a saturable absorber

We report on passively Q-switched lasers in femtosecond laser written waveguide in Nd:YVO₄ crystal. Using graphene as a saturable absorber, passively Q-switched waveguide laser operations are achieved along both TE and TM polarizations with single modal profiles. Furthermore, all-angle linear light pump was utilized to investigate the thorough information of the polarization effects of the laser, showing that the optimum polarization for laser generation is TE. The maximum average output power is estimated to be 129 mW with 12.2% slope efficiency, corresponding to single-pulse energy of 8.1 nJ, pulse duration of 25.0 ns and repetition rate of 16.3 MHz.     

Transverse-mode astigmatism in a diode-pumped unstable resonator Nd:YVO(4) laser

We have observed a sizable astigmatism in the output beam from a diode-pumped unstable resonator Nd:YVO(4) laser operating in a single polarization and a single-longitudinal and transverse mode. The anisotropic index of refraction of the vanadate crystal has been identified as the source of this astigmatism. A theoretical prediction of the eigenmode astigmatism based on this index anisotropy is consistent with our experimental measurements.     

抽运条件对Nd:YVO4增益开关激光器输出特性的影响

通过数值求解增益开关速率方程,模拟得到Nd:YVO4增益开关激光器输出脉宽和峰值功率随抽运条件的理论变化曲线,在此基础上提出了减小增益开关固体激光器输出脉宽的方法,即:令抽运源LD的直流驱动电流接近阈值,叠加脉冲电流高于2倍阈值,并调节抽运脉宽保证单脉冲激光输出。实验结果与理论曲线符合较好,证实了这一方法的有效性。利用此方法最终获得了脉宽20ns、重复频率在1Hz-4kHz精确可控的1.064μm脉冲激光输出。     

Comparison on performance of passively Q-switched laser properties of continuous-grown composite GdVO4/Nd:GdVO4 and YVO4/Nd:YVO4 crystals under direct pumping

The comparison on performance of passively Q-switched laser properties of continuous-grown composite GdVO(4)/Nd:GdVO(4) and YVO(4)/Nd:YVO(4) crystals under direct pumping to the emitting level was demonstrated. A Cr(4+):YAG crystal was used as saturable absorber. At an incident pump power of 10 W, the average output power, the pulse width, the repetition rate, the pulse energy, and the peak power for a GdVO(4)/Nd:GdVO(4) laser were 1.22 W, 48.1 ns, 121 kHz, 10.1 μJ, and 209.6 W, respectively. And for a YVO(4)/Nd:YVO(4) laser under the same conditions, these output characteristics were 1.26 W, 44.9 ns, 218 kHz, 5.8 μJ, and 128.7 W, respectively.     

Timing jitter reduction and single-frequency operation in an acousto-optic Q-switched Cr,Nd:YAG laser

A laser-diode-pumped watt-level single-frequency combined actively and passively Q-switched (CAPQ) laser with a wavelength of 1064 nm that simultaneously uses a codoped Cr(4+),Nd(3+):YAG crystal as the gain medium and mode selector is presented. The optimum repetition period of the CAPQ laser is approximately 1.5 times the natural repetition period of the passively Q-switched laser. The averaged timing jitter is approximately 400 ns in the CAPQ laser and the repetition rate of the CAPQ laser is experimentally shown to reach a time instability of 0.2% over 10(6) pulses. The output is a stable single frequency with a linewidth of 400 MHz at 20 W pump power.     

Passively Q-switched Nd:YVO(4) laser with a Cr(4+):YAG crystal saturable absorber

We demonstrate, for the first time as far as we know, a passively Q-switched operation of a Nd:YVO(4) laser in which a Cr(4+):YAG crystal and a laser-diode bar are used as the saturable absorber and the pump source, respectively. Stable laser pulses as short as 28 ns with 20-muJ energy can be generated with this laser, which has the advantages of simplicity, high efficiency, and good long-term stability.     

Fluorescence feedback control of an active Q-switched diode-pumped Nd:YVO4 laser

We have implemented active feedback control in a Q-switched diode-pumped Nd:YVO(4) laser by monitoring the fluorescence intensity from the laser crystal. When the initial inversion level indicated by the detected fluorescence has reached a predetermined value, Q switching is initiated. This scheme allowed us to vary the reproducibility of the output pulse peak power and pulse width. The novel active Q-switching approach can reduce the shot-to-shot variations of the output pulse peak power and the pulse width.     

Near shot-noise-level relative frequency stabilization of a laser-diode-pumped Nd:YVO(4) microchip laser

A laser-diode-pumped Nd:YVO(4) microchip laser was built and actively frequency stabilized relative to a Fabry-Perot cavity with the frequency-modulated sideband technique. The error signal reaches the shot-noise level of 7.4 mHz/√Hz around 1 kHz. Excess intensity noise sets a lower limit of16.5 mHz/√Hz for the relative frequency noise, corresponding to a spectral linewidth of 860 μHz. We discuss the method for reconstructing the actual frequency deviation from the observed error signal.     

Diode-end-pumped,electro-optically Q-switched Nd:YVO4 slab laser and its second-harmonic generation

We describe the operation of a near-diffraction-limited, 1,064-nm electro-optically Q-switched Nd:YVO4 slab laser that is end pumped by laser-diode stacks and its efficient second-harmonic generation by using a lithium triborate (LBO) crystal. The energy per pulse of 3.6 and 0.8 mJ and pulse widths of 5 and 13.5 ns were obtained at repetition of 5 and 40 kHz, respectively. With a LBO crystal, a maximum output power of 15.6 W at 532 nm was obtained at the repetition rate of 40 kHz, the corresponding conversion efficiency was 60%, and the pulse width was 11.3 ns. At 10 kHz, the pulse energy of 532 nm was 1.2 mJ, and the pulse width was 5 ns.     

Periodic pulse oscillation in an intracavity-doubled Nd:YVO(4) laser

We report periodic pulse oscillation in an intracavity-doubled Nd:YVO(4) laser. The pulse oscillation is caused by alternate oscillation between two modes. We investigated improvement of green-light power with the pulse oscillation in a Nd:YVO(4) laser. The pulse oscillation gave a factor of approximately 2 higher average green-light power than that for cw oscillation at the same pumping power.     

Diode-laser-array end-pumped 1W CW Nd:YVO4/BIBO green laser

Abstract

This paper discusses a diode-laser-array end-pumped Nd:YVO₄/BIBO green laser. Using a three-mirror folded cavity (V-shaped), a 1.06 W CW green output was obtained at an incident pump power of 8.5 W; the corresponding optical conversion efficiency was 12.5%. The relationship between the green output and the temperature of the BIBO crystal was investigated. The laser damage threshold of BIBO crystal was measured to be 600 MW cm^?2 and 400 MW cm^?2 at 1064 nm and 532 nm, respectively.