Kang Kang Chen

Picosecond fiber MOPA pumped supercontinuum source with 39 W output power

We report picosecond fiber MOPA pumped supercontinuum source with 39W output, spanning at least 0.4–1.75µm with high and relatively uniform spectral power density of ∼31.7mW/nm corresponding to peak power density of ∼12.5W/nm in 20ps pulse.

High power pulsed fiber MOPA system incorporating electro-optic modulator based adaptive pulse shaping

We demonstrate active pulse shaping using an Electro-Optic Modulator in order to compensate the pulse shaping effects caused by Gain Saturation in a high power Yb doped fiber amplifier chain and to generate various custom-defined output pulse shapes. Square, step and smooth pulse shapes are achieved, with mJ pulse energies. Use of a modulator to shape pulses rather than direct modulation of the diode drive current allows us to eliminate undesired transients due to laser start up dynamics. The required shaping is calculated based on a simple measurement of amplifier performance, and does not require detailed modeling of the amplifier dynamics.

Polarisation maintaining 100-W Yb-fiber MOPA producing micro-J pulses tunable in duration from 1-21 ps

This paper demonstrates a single polarisation, 1.06 microm Yb-doped fiber MOPA, delivering 21 ps pulses in a diffraction limited beam at repetition rates of up to 908 MHz and average output power of 100 W. The maximum pulse energy was 1.7 microJ at a repetition rate of 56 MHz, with corresponding peak power of 85 kW. The 100 W power was limited by available diode pump power and scaling to higher power levels is discussed. We also report self-phase-modulation based pulse compression which produced pulse durations as short as 1.1 ps from an external grating compressor. Using 4.2 ps pulses at a repetition rate of 227 MHz enabled 26 W of visible laser power (50% SHG efficiency) to be demonstrated.

PPMgLN-Based High-Power Optical Parametric Oscillator Pumped by Yb

We report a periodically poled magnesium-oxide-doped lithium niobate (PPMgLN) based optical parametric oscillator (OPO) pumped by a diode-seeded, linearly polarized, high-power, pulsed, ytterbium fiber master oscillator power amplifier (MOPA). Using adaptive pulse shaping of the seed laser (using an external modulator), we demonstrate a reduction in the impact of dynamic gain saturation and optical Kerr/Raman nonlinearities within the fiber MOPA, obtaining shaped signal and idler pulses at the OPO output and reduced spectral bandwidths. A maximum average output power of 26.5 W was obtained from the MOPA at 1062 nm. An output power as high as 11 W from the OPO at an overall slope efficiency of 67% was achieved, with 2.7 W of output power obtained at a wavelength of 3.5 mum. Our experiments were pump-power-limited and considerable scope remains for further power scaling of such OPOs using this approach.

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We demonstrate the selective excitation of individual Raman Stokes lines of up to the ninth order by pumping with rectangular-shaped optical pulses at 530 nm from a frequency-doubled adaptively pulse shaped fiber master oscillator power amplifier. We achieve extinction ratios of up to 15 dB between selected and adjacent Raman orders in a 1-km-long fiber.

-Doped Fiber Amplifier Incorporates Active Pulse Shaping

We report a frequency-doubled green source at 530 nm pumped based on an all-fiber, picosecond, single-polarization Yb 3+-doped fiber master oscillator power amplifier (MOPA) delivering 20-ps pulses at user selectable repetition rates of up to 910 MHz and an average output power in excess of 100 W at 1.06 ¿m. The output of the MOPA was frequency-doubled using a lithium triborate crystal. Up to 56 W of green light was generated at a corresponding repetition rate of 227 MHz at an overall conversion efficiency of 56%. The diode-to-green optical power conversion efficiency was 37%.

Excitation of individual Raman Stokes lines in the visible regime using rectangular-shaped nanosecond optical pulses at 530 nm

We report a rapidly tunable, wavelength agile fiber laser system capable of the synchronous generation of sequences of pulses with different wavelengths in the visible region of the spectrum using stimulated Raman scattering of multi-step pump pulses in a 250 m length of fiber. The frequency doubled output of a single polarization all-fiber Yb-doped MOPA operating at 1060 nm was used as the pump source. By adjusting the pump power and the pulse profiles we achieved the sequential excitation of green (1st Stokes), yellow (4th Stokes) and red light (6th Stokes) using 3-step pulses, or the combination of any two using 2-step pulses. The wavelength switching time was <5 ns and was limited only by the pulse shaping drive electronics.

56-W Frequency-Doubled Source at 530 nm Pumped by a Single-Mode, Single-Polarization, Picosecond, Yb

We report a tunable synchronously pumped fiber Raman laser (SPFRL) in the near-infrared (NIR) and visible wavebands pumped by a pulsed, all-fiber PM 1060 nm master oscillator power amplifier (MOPA) and its frequency-doubled output, respectively. The seed was adaptively shaped to deliver rectangular output pulses, thereby enabling selective excitation of individual Raman Stokes lines. Using filtered synchronous feedback of the desired Raman Stokes line, the linewidth of the SPFRL was reduced by a factor of 4 and the extinction ratio of the desired Raman Stokes was improved by more than 3 dB relative to a simple single-pass conversion scheme. A continuous tuning range of 2.2 THz was obtained for each of the Raman Stokes orders in the visible (spanning from green to orange-first to fifth Stokes lines). A larger 5.0 THz tunable range was achieved in the NIR spectral region.

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We report a PM, picosecond fiber MOPA delivering 20ps pulses at repetition rates upto 910MHz and average output power in excess of 100W at 1.06μm. The output was frequency doubled generating 45W of green light.

-Doped Fiber MOPA

Raman lasers have attracted much interest since they allow a very wide range of wavelengths to be generated [1]. Operation in the pulsed regime is compromised by the power dependen (b) he gain (c) different parts of the pulse with different instantaneous power will undergo differing amounts of Raman scattering leading to major variations in spectral content across the pulse (varying amounts of light in different Raman orders). To address this issue active pulse shaping technique can be applied to obtain rectangular shaped output pulses so that constant Raman gain can be ensured across the pulse profile [2]. Here we demonstrate a new approach combining pulse shaping with a synchronously pumped scheme [3] to produce narrower linewidths as well as higher extinction ratios between neighboring Raman Stokes lines. Several tens of nanometer of tuning range for each Stokes order and a total tuning range of over 200 nm was achieved using resonant feedback from an external bulk grating.