High-average-power picosecond mid-infrared OP-GaAs OPO.

We report a high-average-power mid-infrared picosecond (ps) optical parametric oscillator (OPO) based on orientation-patterned gallium arsenide (OP-GaAs), with wide wavelength tunability. The OP-GaAs OPO is synchronously pumped by a thulium-doped-fiber (TDF) master oscillator power amplifier (MOPA), seeded by a gain-switched laser diode. At a pump power of 35.3 W and a repetition rate of 100 MHz, a maximum OPO total average output power of 9.7 W (signal 5.7 W (0.60 kW peak power), idler 4.0 W (0.42 kW peak power)) is obtained at signal and idler wavelengths of 3093 nm and 5598 nm, and a thermally induced power roll-off is observed. To mitigate the thermal effects, an optical chopper is placed before the OPO to provide burst mode operation and a reduced thermal load. We achieved a linear growth in OPO output power over the full range of available pump powers in this instance confirming thermal effects as the origin of the roll-off observed under continuous pumping. We estimate the maximum peak powers of the signal and idler are estimated to be over 0.79 kW and 0.58 kW, respectively in this instance. A wide mid-infrared wavelength tuning range of 2895-3342 nm (signal) and 4935-6389 nm (idler) is demonstrated.

Controllable duration and repetition-rate picosecond pulses from a high-average-power OP-GaAs OPO.

We report an orientation-patterned gallium arsenide (OP-GaAs) optical parametric oscillator (OPO) offering a high degree of temporal flexibility with controllable pulse repetition rates from 100 MHz to 1 GHz and pulse durations from ∼95 ps to ∼1.1 ns. The maximum average power of 9.2-W signal (3.3 µm) and 4.5-W idler (4.9 µm) was obtained at a repetition rate of 100 MHz and a pulse duration of ∼95 ps, with a pump power of 34.3 W and at a slope efficiency of 45.4%. The corresponding total average output power of 13.7 W is the highest power achieved to date from an OP-GaAs OPO, to the best of our knowledge.

295-kW peak power picosecond pulses from a thulium-doped-fiber MOPA and the generation of watt-level >2.5-octave supercontinuum extending up to 5 µm.

We report a gain-switched diode-seeded thulium doped fiber master oscillator power amplifier (MOPA) producing up to 295-kW picosecond pulses (35 ps) at a repetition rate of 1 MHz with a good beam quality (M2 ~1.3). A narrow-band, grating-based filter was incorporated within the amplifier chain to restrict the accumulation of nonlinear spectral broadening and counter-pumping of a short length of large-mode-area (LMA) fiber was used in the final stage amplifier to further reduce nonlinear effects. Finally, we generated watt-level >2.5-octave supercontinuum spanning from 750 nm to 5000 nm by using the MOPA output to pump an indium fluoride fiber.

Highly efficient frequency doubling and quadrupling of a short-pulsed thulium fiber laser.

We report the second harmonic generation and fourth harmonic generation of the output from a short-pulsed (~ 80 ps) thulium-doped fiber laser, generating 976 and 488 nm wavelengths with high efficiency. With a narrow-linewidth (0.5 nm) pump at a power of 3.2 W, a second harmonic power of 2.4 W was generated at 976 nm with a conversion efficiency reaching 75%. For FHG, 690 mW of power at 488 nm was obtained from frequency doubling of 976 nm with a conversion efficiency of 30%.

High-energy, near- and mid-IR picosecond pulses generated by a fiber-MOPA-pumped optical parametric generator and amplifier.

We report a high-energy picosecond optical parametric generator/amplifier (OPG/A) based on a MgO:PPLN crystal pumped by a fiber master-oscillator-power-amplifier (MOPA) employing direct amplification. An OPG tuning range of 1450-3615 nm is demonstrated with pulse energies as high as 2.6 µJ (signal) and 1.2 µJ (idler). When seeded with a ~100 MHz linewidth diode laser, damage-limited pulse energies of 3.1 µJ (signal) and 1.3 µJ (idler) have been achieved and the signal pulse time-bandwidth product is improved to ~2 times transform-limited. When seeded with a 0.3 nm-bandwidth filtered amplified spontaneous emission source, crystal damage is avoided and maximum pulse energies of 3.8 µJ (signal) and 1.7 µJ (idler) are obtained at an overall conversion efficiency of 45%.

Pulsed laser deposited diode-pumped 7.4 W Yb:Lu2O3 planar waveguide laser.

Fabrication, characterization, and laser performance of an Yb:Lu2O3 planar waveguide laser are reported. Pulsed laser deposition was employed to grow an 8 µm-thick Yb-doped lutetia waveguide on a YAG substrate. X-ray diffraction was used to determine the crystallinity, and spectroscopic characterization showed the absorption and emission cross-sections were indistinguishable from those reported for bulk material. When end-pumped by a diode-laser bar an output power of 7.4 W was achieved, limited by the available pump power, at a wavelength of 1033 nm and a slope efficiency of 38% with respect to the absorbed pump power.

Broadband telecom to mid-infrared supercontinuum generation in a dispersion-engineered silicon germanium waveguide.

We demonstrate broadband supercontinuum generation (SCG) in a dispersion-engineered silicon-germanium waveguide. The 3 cm long waveguide is pumped by femtosecond pulses at 2.4 µm, and the generated supercontinuum extends from 1.45 to 2.79 µm (at the -30 dB point). The broadening is mainly driven by the generation of a dispersive wave in the 1.5-1.8 µm region and soliton fission. The SCG was modeled numerically, and excellent agreement with the experimental results was obtained.

456-mW graphene Q-switched Yb:yttria waveguide laser by evanescent-field interaction.

In this Letter, we present a passively Q-switched Yb:Y2O3 waveguide laser using evanescent-field interaction with an atmospheric-pressure-chemical-vapor-deposited graphene saturable absorber. The waveguide, pumped by a broad area diode laser, produced an average output power of 456 mW at an absorbed power of 4.1 W. The corresponding pulse energy and peak power were 330 nJ and 2 W, respectively. No graphene damage was observed, demonstrating the suitability of top-deposited graphene for high-power operation.

Generation of mode-locked optical pulses at 1035 nm from a fiber Bragg grating stabilized semiconductor laser diode.

We report the generation of transform-limited, ~18 ps optical pulses from a fiber Bragg grating (FBG) stabilized semiconductor laser diode. Up to 7.2 pJ of pulse energy and a peak power of 400mW were achieved when operating at a repetition frequency of 832.6 MHz, a multiple of the cavity (diode + FBG) free spectral range (FSR). A small detuning in the repetition frequency resulted in broader optical pulses. We have shown experimentally the transition from a gain-switched regime of operation to mode-locked operation once the injection current modulation frequency is set to match a harmonic of the cavity FSR. The transition also results in a reduction in the timing jitter of the optical pulses.

Compact, high-pulse-energy, high-power, picosecond master oscillator power amplifier.

We report a compact, stable, gain-switched-diode-seeded master oscillator power amplifier (MOPA), employing direct amplification via conventional Yb(3+)-doped fibers, to generate picosecond pulses with energy of 17.7 µJ and 97-W average output power (excluding amplified spontaneous emission) at 5.47-MHz repetition frequency in a diffraction-limited and single-polarization beam. A maximum peak power of 197 kW is demonstrated. Such a high-energy, high-power, MHz, picosecond MOPA is of great interest for high-throughput material processing. With 13.8-µJ pulse energy confined in the 0.87-nm 3-dB spectral bandwidth, this MOPA is also a promising source for nonlinear frequency conversion to generate high-energy pulses in other spectral regions. We have explored the pulse energy scaling until the stimulated Raman Scattering (SRS) becomes significant (i.e. spectral peak intensity exceeds 1% of that of the signal).

Q-switched operation of a pulsed-laser-deposited Yb:Y(2)O(3) waveguide using graphene as a saturable absorber.

The first, to the best of our knowledge, Q-switched operation of a pulsed-laser-deposited waveguide laser is presented. A clad Yb:Y(2)O(3) waveguide was Q-switched using an output coupling mirror coated with a single layer of graphene deposited by atmospheric pressure chemical vapor deposition. During continuous-wave operation, a maximum power of 83 mW at a slope efficiency of 25% was obtained. During Q-switched operation, pulses as short as 98 ns were obtained at a repetition rate of 1.04 MHz and a central wavelength of 1030.8 nm.

Fundamentally mode-locked, femtosecond waveguide oscillators with multi-gigahertz repetition frequencies up to 15 GHz.

We demonstrate passively mode-locked Yb(3+)-doped glass waveguide lasers in a quasi-monolithic configuration with a maximum pulse repetition frequency up to 15.2 GHz. A semiconductor saturable absorber mirror (SESAM) is used to achieve stable mode-locking around 1050 nm with pulse durations as short as 811 fs and an average power up to 27 mW. Different waveguide samples are also employed to deliver pulses with repetition rates of 4.9 GHz, 10.4 GHz and 12 GHz with an average power of 32 mW, 60 mW and 45 mW, respectively. The group velocity dispersion control in the cavity is provided by changing the gap between the SESAM and the waveguide end-face to facilitate a soliton mode-locking regime.

Ion-exchanged Tm3+:glass channel waveguide laser.

Continuous wave laser action around 1.9 µm has been demonstrated in a Tm(3+)-doped germanate glass channel waveguide laser fabricated by ion-exchange. Laser action was observed with an absorbed power threshold of only 44 mW and a slope efficiency of up to 6.8% was achieved. Propagation loss at the lasing wavelength was measured to be 0.3 dB/cm. We believe this to be the first ion-exchanged Tm(3+)-doped glass waveguide laser.

High-power, high repetition-rate, green-pumped, picosecond LBO optical parametric oscillator.

We report on a picosecond, green-pumped, lithium triborate optical parametric oscillator with record-high output power. It was synchronously pumped by a frequency-doubled (530 nm), pulse-compressed (4.4 ps), high-repetition-rate (230 MHz), fiber-amplified gain-switched laser diode. For a pump power of 17 W, a maximum signal and idler power of 3.7 W and 1.8 W was obtained from the optical parametric oscillator. A signal pulse duration of ~3.2 ps was measured and wide tunability from 651 nm to 1040 nm for the signal and from 1081 nm to 2851 nm for the idler was achieved.

High-power, variable repetition rate, picosecond optical parametric oscillator pumped by an amplified gain-switched diode.

We demonstrate a picosecond optical parametric oscillator (OPO) that is synchronously pumped by a fiber-amplified gain-switched laser diode. At 24W of pump power, up to 7.3W at 1.54microm and 3.1W at 3.4microm is obtained in separate output beams. The periodically poled MgO-doped LiNbO(3) OPO operates with ~17ps pulses at a fundamental repetition rate of 114.8MHz but can be switched to higher repetition rates up to ~1GHz. Tunabilty between 1.4microm and 1.7microm (signal) and 2.9microm and 4.4microm (idler) is demonstrated by translating the nonlinear crystal to access different poling-period gratings and typical M(2) values of 1.1 by 1.2 (signal) and 1.6 by 3.2 (idler) are measured at high power for the singly resonant oscillator.

Compact, high-pulse-energy, picosecond optical parametric oscillator.

We report a high-energy optical parametric oscillator (OPO) synchronously pumped by a 7.19 MHz, Yb:fiber-amplified, picosecond, gain-switched laser diode. The 42-m-long ring cavity maintains a compact design through the use of an intracavity optical fiber. The periodically poled MgO-doped LiNbO(3) OPO provides output pulse energies as high as 0.49 µJ at 1.5 µm (signal) and 0.19 µJ at 3.6 µm (idler). Tunability from 1.5 to 1.7 µm and from 2.9 to 3.6 µm is demonstrated, and typical M(2) values of 1.5 × 1.3 and 2.8 × 1.9 are measured for the signal and idler, respectively, at high power.

High fidelity femtosecond pulses from an ultrafast fiber laser system via adaptive amplitude and phase pre-shaping.

The generation of high-fidelity femtosecond pulses is experimentally demonstrated in a fiber based chirped-pulse amplification (CPA) system through an adaptive amplitude and phase pre-shaping technique. A pulse shaper, based on a dual-layer liquid crystal spatial light modulator (LC-SLM), was implemented in the fiber CPA system for amplitude and phase shaping prior to amplification. The LC-SLM was controlled using a differential evolution algorithm, to maximize a two-photon absorption detector signal from the compressed fiber CPA output pulses. It is shown that this approach compensates for both accumulated phase from material dispersion and nonlinear phase modulation. A train of pulses was produced with an average power of 12.6W at a 50MHz repetition rate from our fiber CPA system, which were compressible to high fidelity pulses with a duration of 170 fs.