Efficient Green Light Generation Research Articles

Large mode area double-clad ytterbium-doped spun tapered fiber

We performed a comparative study of Yb-doped double-clad large mode area ( M F D = 31 µ m ) spun tapered fibers with different pitch lengths. A novel type of spun tapered fibers with constant pitch lengths of 7.5, 15, and 30 mm, internal birefringence as low as ∼ 10 − 8 , and perfect output beam quality ( M 2 < 1.2 ) has been manufactured and investigated. We demonstrated the efficient direct amplification of a picosecond pulsed signal (95 ps/100 MHz, 1064 nm) in the spun active tapered fiber with optimized geometry providing an average output power of 71 W (gain 32 dB, 74% slope efficiency). Efficient green light generation ( λ = 532 n m ) with 17 W average power (1.7 µJ) and 80 pm linewidth was demonstrated using the developed master oscillator power amplifier system.

Integrated 13 GHz ps-pulse-source at 1064 nm

We present an integrated pulse source at 1064 nm and discuss design, fabrication and measurement results of the 3.5 mm long ridge-waveguide distributed Bragg reflector laser. The optical pulses with a peak power of 0.9 W, a temporal duration of 12.4 ps and a repetition frequency of 13 GHz are generated by passive mode-locking and are well suited for seeding master oscillator power amplifier systems for efficient green light generation with nonlinear frequency doubling in single pass configuration.

466 mW green light generation using annealed proton-exchanged periodically poled MgO: LiNbO_3 ridge waveguides

We report high-power efficient green light generation by frequency doubling from a periodically poled MgO doped LiNbO(3) ridge waveguide. The ridge waveguide is fabricated by the annealed proton-exchanging and precise diamond blade dicing techniques. The ridge structure exhibits a surface roughness of only 3.7 nm, and near-90° vertical sidewall. The total insertion loss of an 8.5 µm wide and 1.4 cm long uncoated waveguide is 3.0 dB under direct fiber coupling. 466 mW of continuous-wave green light with an optical-to-optical conversion efficiency of 69.7% is obtained. To the best of our knowledge, this is the highest green light output power reached to date using a ridge-type LiNbO(3) waveguide device. Phase-matching temperature shift, tuning curve distortion, and waveguide loss increase are observed under high power operation. Our analysis shows that the photorefractive effect and the green induced infrared absorption are responsible for the observed phenomena, which becomes prominent under several megawatt per square centimeter power density.

Efficient green-light generation by proton-exchanged periodically poled MgO:LiNbO_3 ridge waveguide

Efficient cw 532 nm green-light generation is demonstrated using a periodically poled MgO:LiNbO3 ridge waveguide prepared by a process that combines annealed proton exchange and precise dicing. Performance of waveguides with different widths has been investigated. The 6-μm-wide, 1.6-cm-long uncoated ridge waveguide has achieved a green output power of 127 mW under a coupled fundamental light power of 250 mW. The highest conversion efficiency achieved is 53%.

Efficient green-light generation by frequency doubling of a picosecond all-fiber ytterbium-doped fiber amplifier in PPKTP waveguide inscribed by femtosecond laser direct writing

We have demonstrated an ultrashort, compact green light radiation by frequency doubling of an all-fiber ytterbium-doped fiber laser source in a PPKTP waveguide fabricated by femtosecond laser pulses. Using the fabricated PPKTP waveguide crystal containing a 10 mm single grating with a period of 9.0 μm, we generate 310 mW of picosecond radiation at 532 nm for a fundamental power of 1.6W, corresponding to a conversion efficiency of 19.3%. The temperature tuning range of 8°C is achieved for a fixed fundamental wavelength of 1064 nm, the FWHM of the wavelength tuning curve is 4.2 nm at room temperature. The generated ultrashort pulses at 532 nm are of great importance and have comprehensive applications in photobiology research and high-resolution spectroscopy.

Master-oscillator power-amplifier scheme for efficient green-light generation in a planar MgO:PPLN waveguide

We developed a new master-oscillator power-amplifier scheme consisting of a tapered semiconductor amplifier and a fiber-grating-stabilized laser diode for efficient green-light generation in a planar MgO:PPLN waveguide, and demonstrated cw green-light generation of 346 mW.

Efficient green-light generation from waveguide crystal

Data are presented of efficient single-pass green-light second-harmonic generation from a periodically-poled LiNbO3 waveguide crystal. Over 220 mW maximum green light output power with an optical-to-optical conversion efficiency of over 70% is measured. Green-induced infrared absorption is indicated to be the major absorption loss in this waveguide. A simple analytic expression is derived and used to estimate the crystal waveguide absorption coefficient, which was found to be 7×10−3 cm−1.

Highly efficient green-light generation by quasi-phase-matched frequency doubling of picosecond pulses from an amplified mode-locked Nd:YLF laser

We report on first-order quasi-phase-matched frequency doubling of picosecond pulses to the green, using a sample of periodically poled lithium niobate. In cw mode-locked operation, 330 mW of average green power was generated with an average conversion efficiency of ~52%. With a quasi-cw mode-locked pulse train an average conversion efficiency of ~65% was achieved, and 1.3 W of green power (average power within the 10-micros pulse envelope) was produced. At these powers there was no significant photorefractive damage, as confirmed by measured M(2) beam-quality factors of ~1.1 for both output fundamental and second-harmonic beams.

Stable and efficient green light generation by intracavity frequency doubling of Nd:YVO4 lasers

A green light source of 11 mW (maximum) has been obtained by frequency doubling in 3 at. % Nd:YVO4 lasers pumped by a single longitudinal mode laser diode (LD), for a 50 mW incident pumping power, with grating feedback optics. When the temperature of the LD was changed within the range of 23±10 °C, the oscillated wavelength of the LD remained unchanged, and the relative intensity noise of the green light was maintained to less than −140 dB/Hz (at 2.5 MHz).