Generation of Kerr combs centered at 4.5 µm in crystalline microresonators pumped with quantum-cascade lasers.

We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF2 and MgF2 whispering-gallery-mode resonators pumped with continuous-wave room-temperature quantum cascade lasers. The combs were centered at 4.5 µm, the longest wavelength to date. A frequency comb wider than one half of an octave was demonstrated when approximately 20 mW of pump power was coupled to an MgF2 resonator characterized with quality factor exceeding 10(8).

Coherent combining of pulsed fiber amplifiers in the nonlinear chirp regime with intra-pulse phase control.

Two high pulse contrast (> 95 dB) polarization maintaining all-fiber amplifier chains were coherently combined to generate 0.42 mJ, 1 ns 25 kHz pulses with 79% efficiency despite 38 radians of intra-pulse phase distortion. A recursive intra-pulse phase compensation method was utilized to correct for the large nonlinear chirp providing a path for improved coherent waveform control of nanosecond pulse trains.

High-gain Er-doped fiber amplifier generating eye-safe MW peak-power, mJ-energy pulses.

We report on a large-core, Er-doped fiber amplifier that generates pulses of approximately 1.1 ns duration and maximum pulse energy/peak power approximately 1.4 mJ/1.2 MW, at 1567 nm wavelength, while concurrently providing optical gain in excess of 25 dB, in a multi-mode output beam (M(2) approximately 8.5).

Watt-level, high-repetition-rate, mid-infrared pulses generated by wavelength conversion of an eye-safe fiber source.

We report on a mid-infrared (mid-IR) source consisting of an approximately 10 W average-power, linearly polarized 1.54 microm wavelength pulsed fiber source pumping an optical parametric oscillator. From this source, we obtained average power in excess of 1 W in the 3.8-4.0 microm wavelength range at a pulse repetition frequency of 100 kHz. With a slightly different setup, we also achieved an average power of 0.25 W at 4.5 microm wavelength. To our knowledge, these values represent the highest mid-IR power obtained through wavelength conversion of an eye-safe fiber source.

1.1 MW peak-power, 7 W average-power, high-spectral-brightness, diffraction-limited pulses from a photonic crystal fiber amplifier.

We report a large-core, Yb-doped photonic crystal fiber amplifier generating diffraction-limited (M2 = 1.04), approximately 0.45 ns, approximately 8 GHz linewidth pulses with energies of 540 microJ, peak power in excess of 1.1 MW, and average power of approximately 7.2 W at a repetition rate of 13.4 kHz. The pulse peak spectral brightness exceeds 10 kW/(sr Hz cm2) and is the highest generated by a fiber source, to our knowledge.

1-mJ energy, 1-MW peak-power, 10-W average-power, spectrally narrow, diffraction-limited pulses from a photonic-crystal fiber amplifier.

We report on a diode-pumped master-oscillator/fiber-amplifier (MOFA) system consisting of a passively Q-switched, single-frequency Nd:LSB microchip laser that seeds a dual-stage Yb-doped fiber amplifier. A large-core, single-mode photonic crystal fiber was used for the final amplifier. The MOFA generated 1062nm wavelength, 1-ns long, ~10kHz repetition-rate, diffraction-limited pulses of energy >1mJ, peak power >1MW, average power >10W, and spectral linewidth ~9 GHz.

Multistage Yb-doped fiber amplifier generating megawatt peak-power, subnanosecond pulses.

A Q-switched microchip laser generating 1064 nm wavelength, subnanosecond pulses at a 13.4 kHz repetition rate was used to seed a dual-stage amplifier featuring a 40 microm core Yb-doped photonic-crystal fiber (PCF) as the power amplifier. From this source, we obtained diffraction-limited (M2 = 1.05), approximately 450 ps pulses of energy > 0.7 mJ, peak power in excess of 1.5 MW, and an average power of approximately 9.5 W. By further amplifying the PCF output in a multimode 140 microm core Yb-doped fiber, we generated a peak power in excess of 4.5 MW, the highest obtained in a fiber source to our knowledge.