Dual-wavelength Pumping Research Articles

High efficiency, dual-wavelength fibre Raman pump laser for U-band fibre Raman amplifiers

A dual-wavelength, continuous wave, high efficiency fibre Raman ring laser for pumping U-band (1625–1675 nm) fibre Raman amplifiers is demonstrated. Two fibre Bragg gratings were used as wavelength-selective elements resulting in lasing lines at 1529.7 and 1558.7 nm with respective maximum powers of 209.0 and 390.9 mW. A simple U-band Raman amplifier was constructed to test the dual-wavelength pump laser and on:off gain with a peak of 7.3 dB and a 3-dB bandwidth of 73 nm was obtained.

Noise and gain band management of thulium-doped fiber amplifier with dual-wavelength pumping schemes

Three dual-wavelength pumping schemes (1550 nm + 1064, 1047, or 1400 nm) have been experimentally assessed for the thulium-doped fiber amplifier in terms of power and noise performance. It is shown that 1047- and 1550-nm pumping gives a better power performance than 1064- and 1550-nm pumping at fixed gain peak wavelength (GPW). In addition, the most efficient pumping scheme appears to be 1400- and 1550-nm pumping for GPW higher than 1475 nm, and 1047 and 1550 nm for lower GPW. Noise figures lower than 6 db (with -5-dBm signal input power) are exhibited regardless the pumping schemes (although a 0.8-dB increase is reported for the 1400- and 1550-nm pumping).

Gain-Shifted Thulium-Doped Fiber Amplifier.

The growing need for increases in the transmission capacity of optical communications has driven research efforts of broadband fiber amplifiers that can fully exploit the low-loss region of silica fibers (1450-1650 nm, <0.25dB/km). The so-called S-band (1480-1530nm) is becoming more promising as a candidate for the next-generation transmission band. By using 1.05- and 1.56-?Em dual-wavelength pumping, we first demonstrated a gain-shifted thulium-doped fiber amplifier (GS-TDFA) operating at the S-band. We have then demonstrated a highly-efficient (29%) and high-power (+21.5dBm) GS-TDFA by use of practical laser-diode pumping of 1.4 and 1.56?Em. With the GS-TDFA, a record 10.92-Tb/s capacity WDM transmission has recently been demonstrated. In this paper, we review these recent results by starting from thebasic operational concept of gain shifting. Amplification and transmission characteristics confirm the applicability of GS-TDFAs to large-capacity field-use WDM networks.

Ultrafast carrier dynamics in InGaAsP grown by He-plasma-assisted epitaxy

We perform dual-wavelength pump–probe measurements on InGaAsP grown by He-plasma-assisted molecular beam epitaxy with Be doping concentrations ranging from 0 to 6×10 18 cm −3. The material response times obtained vary from 1 to >70 ps depending on doping concentration, pump pulse energy, and probe wavelength. A two-trap-level rate equation model is presented to explain the various response times observed, and trap densities of 2.5×10 17 and 12×10 17 cm −3, electron-capture cross-sections of 12×10 −15 and 2.8×10 −15 cm 2, and hole-capture cross-sections of 1.4×10 −16 and 1.8×10 −15 cm 2 are derived by fitting the experimental data. Dual-pulse pump–probe measurements indicate that a fast repeated switching on a ∼10 ps timescale using Be-doped materials can be achieved despite the slow hole-capture rate associated with one of the trap levels.

150-µm-band gain-shifted thulium-doped fiber amplifier with 105- and 156-µm dual-wavelength pumping

We propose and demonstrate a 1.50-mum- band gain-shifted thulium-doped fiber amplifier (TDFA) by using a novel dual-wavelength (1.05and1.56 -mum) pumping scheme for what we believe is the first time. By providing a small amount of 1.56-mum power to a conventional upconversion-pumped TDFA, we successfully demonstrated a small-signal gain larger than 25 dB and a noise figure of 5 dB in a 1475-1510-nm band.

Subnanosecond pulse generation in the VUV by dual-wavelength pumped stimulated rotational Raman scattering

A novel scheme to generate a subnanosecond pulse in VUV spectral region is proposed, by applying a dual-wavelength pumping method in conjunction with polarization switching technique to the stimulated rotational Raman scattering process. Optimum conditions for the efficient conversion and short pulse generation are presented through numerical model calculations. It is theoretically shown that the duration of the first anti-Stokes pulse of a VUV pump laser can be shorten to 0.72 ns. Since the anti-Stokes pulse is generated at a frequency within the gain profile of the pump laser, the proposed process is applicable to a seed pulse generation for subnanosecond pulse amplification by the pump laser medium in the VUV region.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Generation of dual-wavelength, synchronized, tunable, high energy, femtosecond laser pulses with nearly perfect gaussian spatial profile

We use self-phase modulation in a single-mode fiber to produce broadband femtosecond laser pulses. Subsequent amplification through two Bethune cells yields high-energy, tunable, pulses synchronized with the output of an amplified colliding-pulse-modelocked (CPM) laser. We routinely obtain tunable 200 μJ pulses of 42 fs (fwhm) duration with a nearly perfect gaussian spatial profile. Although self-phase modulation in a single-mode fiber is widely used in femtosecond laser systems, amplification of a fiber-generated supercontinuum in a Bethune cell amplifier is a new feature which maintains the high-quality spatial profile while providing high gain. This laser system is particularly well suited for high energy dual-wavelength pump=probe experiments and time-resolved four-wave mixing spectroscopy.