Compact 32-core multicore fibre isolator for high-density spatial division multiplexed transmission

We present a fully integrated 32-core multicore fibre isolator with low insertion loss (average loss <0.8dB, core-to-core variation <2dB) and low inter-core crosstalk (<-40dB)

Recent progress in SDM amplifiers

Space division multiplexing (SDM) utilizing few-mode fibers or multicore fibers supporting multiple spatial channels, is currently under intense investigation as an efficient approach to overcome the current capacity limit of high-speed long-haul transmission systems based on single mode optical fibers. In order to realize the potential energy and cost savings offered by SDM systems, the individual spatial channels should be simultaneously multiplexed, transmitted, amplified and switched with associated SDM components and subsystems. In this paper, recent progress on the implementation of various SDM amplifiers and its related SDM components is presented

High repetition rate, high pulse energy, Raman shifted wavelength selectable fiber laser source in the visible

We have demonstrated a Raman-shifted wavelength-selectable fiber laser source with fundamental spatial-mode output producing ~1µJ pulse-energy at 1MHz repetition-rate with 1.3ns pulse-width using a large-core photonic crystal fiber

Demonstration of ultra-low NA rare-earth doped step index fiber for applications in high power fiber lasers

In this paper, we report the mode area scaling of a rare-earth doped step index fiber by using low numerical aperture. Numerical simulations show the possibility of achieving an effective area of ~700µm2 (including bend induced effective area reduction) at a bend diameter of 32cm from a 35µm core fiber with a numerical aperture of 0.038. An effective single mode operation is ensured following the criterion of the fundamental mode loss to be lower than 0.1dB/m while ensuring the higher order modes loss to be higher than 10dB/m at a wavelength of 1060nm. Our optimized modified chemical vapor deposition process in conjunction with solution doping process allows fabrication of an Yb-doped step index fiber having an ultra-low numerical aperture of ~0.038. Experimental results confirm a Gaussian output beam from a 35µm core fiber validating our simulation results. Fiber shows an excellent laser efficiency of ~81% and a M2 less than 1.1

Generation of mode-locked optical pulses at 1035 nm from a fiber Bragg grating stabilized semiconductor laser diode

We report the generation of transform-limited, ~18 ps optical pulses from a fiber Bragg grating (FBG) stabilized semiconductor laser diode. Up to 7.2 pJ of pulse energy and a peak power of 400mW were achieved when operating at a repetition frequency of 832.6 MHz, a multiple of the cavity (diode + FBG) free spectral range (FSR). A small detuning in the repetition frequency resulted in broader optical pulses. We have shown experimentally the transition from a gain-switched regime of operation to mode-locked operation once the injection current modulation frequency is set to match a harmonic of the cavity FSR. The transition also results in a reduction in the timing jitter of the optical pulses

Broadband silica-based thulium doped fiber amplifier employing dual-wavelength pumping

We report a broadband and gain-flattened silica-based thulium-doped fiber amplifier with dual-wavelength pumping (790nm + 1600nm). 15dB gain bandwidth is more than 220nm ranging from 1700 to 1920nm with a maximum gain of 29dB and a noise figure of less than 5dB

High-energy, near- and mid-IR picosecond pulses generated by a fiber-MOPA-pumped optical parametric generator and amplifier

We report a high-energy picosecond optical parametric generator/amplifier (OPG/A) based on a MgO:PPLN crystal pumped by a fiber master-oscillator-power-amplifier (MOPA) employing direct amplification. An OPG tuning range of 1450-3615nm is demonstrated with pulse energies as high as 2.6µJ (signal) and 1.2µJ (idler). When seeded with a ~100 MHz linewidth diode laser, damage-limited pulse energies of 3.1µJ (signal) and 1.3µJ (idler) have been achieved and the signal pulse time-bandwidth product is improved to ~2 times transform-limited. When seeded with a 0.3nm-bandwidth filtered amplified spontaneous emission source, crystal damage is avoided and maximum pulse energies of 3.8µJ (signal) and 1.7µJ (idler) are obtained at an overall conversion efficiency of 45%

Green-pumped, picosecond MgO:PPLN optical parametric oscillator

We investigate the performance of a magnesium-oxide-doped periodically poled lithium niobate crystal (MgO:PPLN) in an optical parametric oscillator (OPO) synchronously-pumped by 530nm, 20ps, 230MHz pulses with an average power of up to 2W from a frequency-doubled, gain-switched laser diode seed and a multi-stage Yb:fiber amplifier system. The OPO produces ~165mW (signal, 845nm) and ~107mW (idler, 1421nm) of average power for ~1W of pump power and can be tuned from ~800nm to 900nm (signal) and 1.28µm to 1.54µm (idler). Observations of photo-refraction and green-induced infrared absorption (GRIIRA) in different operational regimes of the MgO:PPLN OPO are described and the role of peak intensity and average power are investigated, both with the aim to find the optimal operating regime for pulsed systems

The effect of source backing materials and excitation pulse durations on laser-generated ultrasound waveforms

In this article, it is shown experimentally that a planar laser-generated ultrasound source with a hard reflective backing will generate higher acoustic pressures than a comparable source with an acoustically matched backing when the stress confinement condition is not met. Furthermore, while the source with an acoustically matched backing will have a broader bandwidth when the laser pulse is short enough to ensure stress confinement, the bandwidths of both source types will converge as the laser pulse duration increases beyond stress confinement. The explanation of the results is supported by numerical simulations