Xiuquan Ma

Single-mode chirally-coupled-core fibers with larger than 50µm diameter cores

In this paper, we report an advance in increasing core size of effective single-mode chirally-coupled-core (CCC) Ge-doped and Yb-doped double-clad fibers into 55 µm to 60 µm range, and experimentally demonstrate their robust single-mode performance. Theoretical and numerical description of CCC fibers structures with multiple side cores and polygon-shaped central core is consistent with experimental results. Detailed experimental characterization of 55 µm-core CCC fibers based on spatially and spectrally resolved broadband measurements (S(2) technique) shows that modal performance of these large core fibers well exceeds that of standard 20 μm core step-index large mode area fibers.

Angular-momentum coupled optical waves in chirally-coupled-core fibers

A new type of interaction between optical waves occurs in chirally-coupled-core (CCC) fibers. Instead of linear-translational symmetry of conventional cylindrical fibers, CCC fibers are helical-translation symmetric, and, consequently, interaction between CCC fiber modes involves both spin and orbital angular momentum of the waves. Experimentally this has been verified by observing a multitude of new phase-matching resonances in the transmitted super-continuum spectrum, and theoretically explained through modal theory developed in helical reference frame. This enables new degrees of freedom in controlling fiber modal properties.

Power adjustable visible supercontinuum generation using amplified nanosecond gain-switched laser diode

Supercontinuum covering 0.45-1.2 mum is scaled from 250-740 mW by varying the repetition rate of a frequency doubled telecom laser diode. Efficient SC generation requires minimal non-linearity in the amplifier and fiber dispersion matched to the pump.

Propagation-length independent SRS threshold in chirally-coupled-core fibers.

Both analytical study and numerical simulations show that the propagation-length independent Stimulated Raman Scattering (SRS) threshold can be achieved by Stokes wave suppression in optical fibers. We propose a specific design based on Chirally-Coupled-Core (CCC) fibers with spectrally-tailored wavelength-selective transmission to suppress the Stokes wave of Raman scattering. Fibers with length-independent nonlinearity threshold could be particularly advantageous for high power lasers and fiber beam delivery for material processing applications.

3C Yb-doped fiber based high energy and power pulsed fiber lasers

3C fiber technology advances the performance frontier of practical, high-pulse-energy fiber lasers by providing very large core fibers with the handling and packaging benefits associated with single mode fibers. First-generation fibers demonstrate scaling to > 240 W average power coincident with 100-kW peak power in 1-mJ, 10-ns pulses while maintaining single-mode beam quality, polarized output, and efficiencies > 70%. Peak powers over 0.5 MW with negligible spectral distortion can be achieved with sub ns, near-transform-limited pulses. In-development second-generation 3C Yb-fiber based on core sizes around 55 μm1 have produced >8 mJ, 13 ns pulses with peak powers exceeding 600 kW.

Single-frequency and single-transverse mode Yb-doped CCC fiber MOPA with robust polarization SBS-free 511W output

We demonstrate 511W single-frequency (Δν << 40MHz), single-transverse mode and robust linear polarization output fiber MOPA based on 37µm diameter Yb-doped Chirally-Coupled-Core air-clad fiber.

Experimental demonstration of SRS suppression in chirally-coupled-core fibers

We experimentally demonstrate suppression of Stimulated Raman Scattering using a spectrally tailored transmission of a large-core effectively-single-mode Chirally-Coupled-Core fiber with a large loss at Stokes wavelengths.

Characterization of single-mode performance of Chirally-Coupled-Core fibers with cores larger than 50μm

We demonstrate robust single-spatial mode performance in fabricated Ge-doped 50μm -60μm core Chirally-Coupled-Core fibers using spatially and spectrally resolved (S²) measurements.

Compact high-power FCPA enabled by chirped volume bragg grating and chirally-coupled-core fiber technologies

Ultrafast fiber-based lasers have always been a promising technological path towards uniquely high power and potentially very compact and robust femtosecond laser systems. However, combining power scaling with compactness and robustness in such systems so far remained quite elusive due to two main constraints: (i) the absence of compact monolithic pulse compressors, which could provide nanosecond-stretched pulse compression at high powers and energies, and (ii) the use of large core fibers with limited robustness, such as LMA or photonic-crystal rods. Due to these constraints, all demonstrated ultrashort-pulse and high power fiber lasers are essentially laboratory type systems, with free-space coupling and pumping arrangements and, more importantly, using cumbersomely large pulse compressors based on diffraction gratings. Over last few years, we have been developing new solutions to both these constraints: chirped volume Bragg grating compact pulse compressors [1] and robustly single-mode large-core fibers using chirally-coupled-core (CCC) structures [2], recently demonstrating high average power and 200fs FCPA based on these new components.

Power scalable visible supercontinuum generation using amplified nanosecond gain-switched laser diode

Supercontinuum covering 0.45-1.2 mum is scaled from 250-740 mW by varying the repetition rate of a frequency doubled telecom laser diode. Efficient SC generation requires minimal non-linearity in the amplifier and fiber dispersion matched to the pump.