Exploiting the short wavelength gain of silica-based thulium-doped fiber amplifiers.

Short wavelength operation (1650-1800 nm) of silica-based thulium-doped fiber amplifiers (TDFAs) is investigated. We report the first demonstration of in-band diode-pumped silica-based TDFAs working in the 1700-1800 nm waveband. Up to 29 dB of small-signal gain is achieved in this spectral region, with an operation wavelength accessible by diode pumping as short as 1710 nm. Further gain extension toward shorter wavelengths is realized in a fiber laser pumped configuration. A silica-based TDFA working in the 1650-1700 nm range with up to 29 dB small-signal gain and noise figure as low as 6.5 dB is presented.

First demonstration of a 2µm few-mode TDFA for mode division multiplexing.

We report the first demonstration of an inline few-mode thulium doped fiber amplifier (TDFA) operating at 2µm for mode division multiplexed transmission. Similar gain and noise figure performance for both the LP(01) and LP(11) modes are obtained in a cladding pumped 2-mode group TDFA. A maximum gain of 18.3dB was measured at 1970nm with a 3dB gain bandwidth of 75nm while the average noise figure was measured to be between 7 and 8dB for wavelengths longer than 1970nm.

High-energy diode-seeded nanosecond 2 µm fiber MOPA systems incorporating active pulse shaping.

We report on high-energy nanosecond-pulsed fiber master oscillator power amplifier (MOPA) systems seeded by semiconductor laser diodes at 2 µm incorporating arbitrary pulse-shaping capabilities. Two MOPA systems, one based on direct diode modulation and the second using additional electro-optic modulator (EOM) based shaping, are investigated, with up to 0.5 mJ (25 kHz) and 1.0 mJ (12.5 kHz) pulse energies achieved, respectively, for 100 ns pulses with user-defined pulse shapes. Our results indicate that further energy scaling with shaped output pulses is primarily limited by the maximum pulse peak power available from the seed laser diode and the dynamic range offered by the first generation of EOMs at 2 µm.

All-fiber, ultra-wideband tunable laser at 2 µm.

We report a direct diode-pumped all-fiber tunable laser source at 2 µm with a tuning range of more than 250 nm. A 3 dB power flatness of 200 nm with a maximum output power of 30 mW at 1930 nm was achieved. The laser has a high optical signal-to-noise ratio (OSNR) of more than 40 dB across the whole tuning range.

Diode-pumped wideband thulium-doped fiber amplifiers for optical communications in the 1800 - 2050 nm window.

We present the first in-band diode-pumped TDFAs operating in the 2 µm wavelength region and test their suitability as high performance amplifiers in potential future telecommunication networks. We demonstrate amplification over a 240 nm wide window in the range 1810 - 2050 nm with up to 36 dB gain and noise figure as low as 4.5 dB.

Mid-infrared ZBLAN fiber supercontinuum source using picosecond diode-pumping at 2 µm.

We present the first demonstration of mid-IR supercontinuum generation directly pumped with picosecond pulses from a Thulium fiber-amplified gain-switched laser diode at 2 µm. We achieve more than two octaves of bandwidth from 750 - 4000 nm in step-index ZBLAN fiber with Watt-level average power and spectral flatness of less than 1.5 dB over a 1300 nm range in the mid-IR from 2450 - 3750 nm. The system offers high stability, power-scaling capability to the 10 W regime, and demonstrates an attractive route towards relatively inexpensive, versatile and practical sources of high power broadband mid-IR radiation.

100 kW peak power picosecond thulium-doped fiber amplifier system seeded by a gain-switched diode laser at 2 µm.

We report on the generation of picosecond pulses at 2 µm directly from a gain-switched discrete-mode diode laser and their amplification in a multistage thulium-doped fiber amplifier chain. The system is capable of operating at repetition rates in the range of 2 MHz-1.5 GHz without change of configuration, delivering high-quality 33 ps pulses with up to 3.5 µJ energy and 100 kW peak power, as well as up to 18 W of average power. These results represent a major technological advance and a 1 order of magnitude increase in peak power and pulse energy compared to existing picosecond sources at 2 µm.

Thulium-doped fiber amplifier for optical communications at 2 µm.

We report the first experimental realization and detailed characterization of thulium doped fiber amplifiers (TDFAs) specifically designed for optical communications providing high gain (>35 dB), noise figure as low as 5 dB, and over 100 nm wide bandwidth around 2 µm. A maximum saturated output power of 1.2 W was achieved with a slope efficiency of 50%. The gain dynamics of the amplifier were also examined. Our results show that TDFAs are well qualified as high performance amplifiers for possible future telecommunication networks operating around 2 µm.

Demonstration of amplified data transmission at 2 µm in a low-loss wide bandwidth hollow core photonic bandgap fiber.

The first demonstration of a hollow core photonic bandgap fiber (HC-PBGF) suitable for high-rate data transmission in the 2 µm waveband is presented. The fiber has a record low loss for this wavelength region (4.5 dB/km at 1980 nm) and a >150 nm wide surface-mode-free transmission window at the center of the bandgap. Detailed analysis of the optical modes and their propagation along the fiber, carried out using a time-of-flight technique in conjunction with spatially and spectrally resolved (S2) imaging, provides clear evidence that the HC-PBGF can be operated as quasi-single mode even though it supports up to four mode groups. Through the use of a custom built Thulium doped fiber amplifier with gain bandwidth closely matched to the fiber's low loss window, error-free 8 Gbit/s transmission in an optically amplified data channel at 2008 nm over 290 m of 19 cell HC-PBGF is reported.

High power and high energy ultrashort pulse generation with a frequency shifted feedback fiber laser.

The highest average power that has been achieved with a frequency-shifted feedback modelocked fiber laser is reported. Subpicosecond pulses with 40 kW peak power are obtained by this technique for the first time by using external pulse compression. The pulsing is self starting and environmentally stable. The measured pulse energy in modelocked operation is 120 nJ. The pulses could be compressed to 855 fs. The pulse energy was increased to 1muJ with controlled Q-switched modelocking.