All-in-fiber amplification and compression of coherent frequency-shifted solitons tunable in the 1800–2000  nm range

Abstract

We report an all-fiber, all-polarization maintaining (PM) source of widely tunable (1800-2000 nm) ultrashort pulses based on the amplification of coherent self-frequency-shifted solitons generated in a highly nonlinear fiber pumped with an Er-doped fiber laser. The system delivers sub-100 fs pulses with energies up to 8.6 nJ and is built entirely from PM optical fibers, without any free-space optics. The all-fiber alignment-free design significantly increases the suitability of such a source for field deployments.

Low noise all-fiber amplification of a coherent supercontinuum at 2 µm and its limits imposed by polarization noise

“…We report a broadband, ultrafast Tm/Ho co-doped all-fiber chirped pulse amplifier, seeded by an Er-fiber system spectrally broadened in an ANDi PCF, supporting a − 20 dB bandwidth of more than 300 nm and delivering high quality 66 fs pulses with more than 70 kW peak power directly from the output fiber. This is amongst the shortest reported pulse durations for similar systems that do not use nonlinear post-compression schemes [10][11][12][13]15,16 . The total RIN integrated from 10 Hz to 20 MHz is 0.07%, which to our knowledge is the lowest reported RIN for wideband ultrafast amplifiers operating at 2 µm to date.…”

“…Direct laser emission in the 2 µm wavelength regime is possible through Thulium (Tm)- or Holmium (Ho)-doped silica fiber lasers, which have been scaled to the kilowatt average power level even in ultrafast operation, but with limited spectral bandwidths 6 . Spectrally broadband sources, which take advantage of the very broad gain bandwidth provided by Tm- and Ho-ions 7 – 9 , are often based on Tm- and Ho-doped fiber amplifiers seeded by modelocked Erbium (Er)-fiber systems, which are spectrally broadened to the 2 µm region via the generation of Raman-shifted solitons, four-wave mixing, or supercontinuum generation in the anomalous dispersion region of a highly nonlinear fiber (HNLF) 4 , 10 – 16 . In this way, the maturity, robustness, and excellent performance parameters of Er:fiber technology operating in the 1.55 µm window can be conveniently extended to longer wavelengths and are easily power-scaled.…”

The Adoption of Chalcogenide Glass Fiber as Pulse Stretcher in an All-Fiber Structured 2 μm Chirped Pulse Amplification System

“…All-fiber 2 µm ultrashort pulsed laser sources with good beam quality and high stability have attracted much attentions owed to their potential applications in such fields as optical frequency comb [1,2], multi-modal imaging [3,4], cascaded Raman laser realization [5,6], and mid-infrared supercontinuum (Mid-IR SC) generation in soft-glass fibers [7,8]. Thus far, two approaches, direct mode-locking [9][10][11] and Raman soliton self-frequency shift (SSFS) [12][13][14][15][16][17][18], are usually used to realize all-fiber 2 µm femtosecond sources. Compared with direct mode locking, SSFS enabled 2 µm sources in silica fiber pumped by 1.55 µm Er-doped femtosecond fiber laser is more advantageous in terms of long-term stability, signal-to-noise ratio (SNR), compactness and costs.…”

Demonstration of supercontinuum and frequency shifted solitons pumped at 1.56 µm as seed sources for Tm-doped fiber amplifiers

“…Nonlinear effects that occur in microstructured silica fibers, e.g. soliton self-frequency shift (SSFS) [1] or supercontinuum (SC) generation [2] can be exploited to build such sources as an alternative to lasers based on conventional gain media, e.g. Ho-or Tm-doped fibers combined with different mode-locking techniques.…”

“…Nowadays, the possibility of using dispersionengineered fibers with their structure consisting of numerous air-holes in the cladding gives the opportunity to control the nonlinearities in such fibers which makes it a powerful tool for nonlinear optics. Since both SSFS and SC were already used as seed sources for Tm-doped amplifiers [1,3] (as an alternative to a Tm-doped mode-locked laser), the aim of the presented work is to directly compare their performance in terms of power, noise, coherence and stability.…”