Dan Nguyen

Mid-IR supercontinuum generation in ultra-low loss, dispersion-zero shifted tellurite glass fiber with extended coverage beyond 4.5 μm

Mid-infrared sources are a key enabling technology for various applications such as remote chemical sensing, defense communications and countermeasures, and bio-photonic diagnostics and therapeutics. Conventional mid-IR sources include optical parametric amplifiers, quantum cascade lasers, synchrotron and free electron lasers. An all-fiber approach to generate a high power, single mode beam with extremely wide (1μm-5μm) and simultaneous wavelength coverage has significant advantages in terms of reliability (no moving parts or alignment), room temperature operation, size, weight, and power efficiency. Here, we report single mode, high power extended wavelength coverage (1μm to 5μm) supercontinuum generation using a tellurite-based dispersion managed nonlinear fiber and an all-fiber based short pulse (20 ps), single mode pump source. We have developed this mid IR supercontinuum source based on highly purified solid-core tellurite glass fibers that are waveguide engineered for dispersion-zero matching with Tm-doped pulsed fiber laser pumps. The conversion efficiency from 1922nm pump to mid IR (2μm-5μm) supercontinuum is greater than 30%, and approaching 60% for the full spectrum. We have achieved > 1.2W covering from 1μm to 5μm with 2W of pump. In particular, the wavelength region above 4μm has been difficult to cover with supercontinuum sources based on ZBLAN or chalcogenide fibers. In contrast to that, our nonlinear tellurite fibers have a wider transparency window free of unwanted absorption, and are highly suited for extending the long wavelength emission above 4μm. We achieve spectral power density at 4.1μm already exceeding 0.2mW/nm and with potential for higher by scaling of pump power.

976 nm single-frequency distributed Bragg reflector fiber laser

A single-frequency distributed Bragg reflector (DBR) fiber laser at 976 nm was developed with a 2 cm long highly ytterbium-doped phosphate fiber and a pair of silica fiber Bragg gratings. More than 100 mW of linearly polarized output was achieved from the all-fiber DBR laser with a linewidth less than 3 kHz. The outstanding features of this single-frequency laser also include ultralow relative intensity noise and high wavelength stability. This fiber laser is an excellent seeder for high-power 976 nm narrow-linewidth laser amplifiers that can be used for efficient coherent blue-light generation through frequency doubling.

All-fiber fundamentally mode-locked 12 GHz laser oscillator based on an Er/Yb-doped phosphate glass fiber

We have developed a compact and stable all-fiber fundamentally mode-locked 12xa0GHz laser system. The passively mode-locked laser centered at 1535xa0nm has temporal pulse width of ∼2u2009u2009ps and average power of 5xa0mW. The timing jitter, which is cumulative from pulse-to-pulse, has been measured using an optical cross-correlation method and found to be 44u2009u2009fs/pulse. The self-starting, mode-locked laser consists of a semiconductor-based saturable absorber with high modulation depth and a high gain per unit length, polarization-maintaining 0.8xa0cm long Er/Yb phosphate fiber as a gain medium.

976 nm Single-Polarization Single-Frequency Ytterbium-Doped Phosphate Fiber Amplifiers

Core-pumped 976 nm single-polarization single-frequency fiber amplifiers based on several centimeter long polarization maintaining 6 wt% ytterbium (Yb3+) doped phosphate fibers are investigated experimentally and numerically. A 350 mW linearly polarized output with >20 dB polarization extinction ratio and >50 dB optical signal-to-noise ratio is obtained from a 4 cm fiber amplifier at maximum available pump power of 793 mW. The slope efficiency of the 4 cm fiber amplifier is 52.5%. A small signal net gain of 25 dB, corresponding to a unit gain of over 6 dB/cm is achieved in this fiber. It is predicted that a watt level 976 nm core-pumped fiber amplifier can be achieved using more powerful pumps and low insertion loss optical components.

Low loss, wide transparency, robust tellurite glass fibers for mid-IR (2-5 μm) applications

Mid Infrared (MIR) fiber optics has gained a great deal of interest over the past several decades. Applications range from passive transport to fiber lasers and nonlinear applications. These fibers have found use in a wide array of fields such as sensing, military countermeasures, scientific instrumentation, medical instrumentation, and in research laboratories. As with all fiber development there is a continual urge to seek better performance characteristics including transparency over a wide wavelength range, corrosion resistance, high power handling and low loss. We report on development of tellurite glass fibers displaying exceptionally high performance for various applications including wide band, low loss passive transport for mid IR, high efficiency, wide wavelength range and high power supercontinuum generation from visible to MIR wavelengths >4.5um, and active doping in fibers for use in laser cooling. High performance in each of these areas of interest has been brought about by development of a stable glass formulation and advanced processing techniques to remove impurities ions, entrapped hydroxyl, and scatter centers which allow fibers to be made with exceptionally low losses ~0.2dB/m.

New approach to image amplification based on an optically pumped multi-core optical fiber

This paper describes a new approach to amplify optical images by using optically pumped doped cores in a multi-core optical fiber structure. This approach combines the high gain and high efficiency properties of cladding pumped optical amplifiers with the imaging properties of coherent fiber bundles. The individual cores correspond to the pixels in the image amplifier. We have demonstrated 3x3 arrays in an ytterbium-doped phosphate fiber energized by one multimode semiconductor diode. Each pixel is capable of high gain (> 20 dB), low noise, and large acceptance angle (>12 degrees). We expect our glass and preform fabrication method to scale to over 100 pixels. The amplified image can preserve coherence (phase and wavelength) - or scramble the coherence depending on the design of the cores. This image amplifier is an enabling technology for any type of imaging system that is photon-starved and requires a compact and low noise image amplifier.

Ultra-wide mid-IR supercontinuum generation in W-type tellurite fiber pumped by 2 micron ultrashort laser

We have demonstrated heretofore ultra-wide mid-IR supercontinuum spanning from 0.9 µm to 4.2µm in a low-loss W-type tellurite based optical fiber. The W-fiber was pumped by passively mode-locked 2 micron Thulium doped fiber laser.

An optical Ising machine based on multi-core fiber lasers

Summary form only given. In this work, an optical Ising machine that is based on multi-core fiber lasers (MCFL), which play the role of slave lasers, is demonstrated. Specifically, we use a 19-core Yb-doped fiber lasers in the experimental setups. The system is very compact with the length of the multi-core fiber is of about few cm, and the fiber diameter is of 120-micron. In general, the number of cores can be scaled up to a very large number, hundreds or even higher. 2 spatial light modulators, SLM1 and SLM2 is proposed for polarization control of the couplings from master to slave lasers, and to control the mutual coupling among slave lasers corresponding to Zeeman term, and mutual coupling term, respectively, in Ising Hamiltonian.

Solitonic supercontinuum of fs mid-IR pulses in W-type index tellurite fibers with two zero dispersion wavelengths

We are able to generate red-shifted dispersive waves up to a wavelength of 5.1 µm by pumping a W-type index tellurite fiber in the anomalous dispersion regime between its two zero dispersion wavelengths.

All-fiber fundamentally mode locked 12 GHz laser comb for stable microwave generation

We have developed a compact, yet very stable all-fiber fundamentally mode-locked 12 GHz laser system. The passively mode-locked laser centered at 1535 nm has temporal bandwidth of ~2 ps, average power of 3mW and timing jitter of 44 fs/pulse.