Greater than 20%-efficient frequency doubling of 1532-nm nanosecond pulses in quasi-phase-matched germanosilicate optical fibers

Abstract

We fabricated second-order nonlinear gratings in D-shaped germanosilicate fibers, using thermal poling and periodic electrodes defined by standard photolithography. These gratings, which are up to 75 mm long, were used for efficient quasi-phase-matched frequency doubling of 1.532-mum nanosecond pulses from a high-power erbium-doped fiber amplifier. Average second-harmonic powers as high as 6.8 mW and peak powers greater than 1.2 kW at 766 nm were generated, with average and peak conversion efficiencies as high as 21% and 30%, respectively.

236mW average second-harmonic power generated from periodically poled silica fibres

“…The almost perfect sinc 2 profile of the tuning curve is a testament to the extremely good quality of the quasi-phase matched grating over the whole 32cm length (Figure 1(a)). From this measurement, the normalised conversion efficiency was estimated to be 7.34x10 -2 %/W, translating to a 3.3-fold improvement in comparison to the previously best reported value [2] and 14-fold over [1]. A high power tunable Er/Yb fibre laser MOPA source of 3MHz repetition rate and 2.5ns pulse duration was employed to characterise the PPSF device.…”

“…The result shows the ability of the PPSF to handle high average pump powers (∼1.6W) without any signs of decay of the second-order nonlinearity from day to day operation. The average power shows a 35-times improvement over the best results on PPSF to date and the corresponding average efficiency exceeding 15% was achieved with 20-times lower peak power [1]. The PPSF device was fabricated by the insertion of wire electrodes into the holes of a specialty twin-hole germanosilicate fibre (Figure 1(a) -inset).…”

A Long-Period Grating Sensor forWind Turbine Blades

“…Alignment to a base-plate also provides a suitable method/process for a sensor when embedded on a turbine, as the risk for error placing the sensors in the production-line is decreased. Furthermore, these fibres have been commercially available and utilized in other applications [77,80,81] and are more distributed than CCE fibres. D-shape fibres can also be fabricated with standard fibre production facilities.…”

Raman probes based on optically-poled double-clad fiber and coupler

“…In this way, the all-fiber design is preserved and both the generation of fundamental and second harmonic (SH), as well as its delivery to the sample can be done in-fiber. Frequency doubling by thermal poling followed by periodic erasure allows for generation of red [9], green [10] and blue [11] wavelengths and recently as much as 236mW of green light were produced in a fiber with this technique [12]. Ultimately, thermal poling should be used for in-fiber SHG.…”