| Supercontinuum(SC)is a kind of broadband light source.When a high power laser is transmitted in the fiber,various nonlinear effects induced by the high power laser participate in the formation of broadband spectrum in optical fibers and finally get SC output.SC has broad applications in medical,military,communications,and spectroscopy because of its ultra-wide spectrum and excellent laser characteristics.Compact,low-cost,high-performance SC light sources further extends the applications of SC in those fields.In this paper,generation of SC in a single-mode fiber is studied by adopting passively Q-switch microchip laser as a pump source.High power,broadband SC light has been generated in a commercial standard single-mode fiber,which confirms the potential on developing high performance,compact and economical SC source using this pump configuration.The femtosecond mode-locked laser pumped photonic crystal fiber(PCF)has been extensively used in developing broadband SC sources because the dispersion of the PCF is easily designed for improving the performance of SC source.However,high cost,difficult to maintain and complex SC sources constructed with both specially designed PCFs and mode-locked femtosecond lasers limit the applications on portable instruments.Besides,the average output power of the SC generated in this pump configuration is very low which will further limit the applications of such SC sources.Therefore,SC generation in standard communication fibers pumped with a compact light source is the most effective solution.Passively Q-switched microchip lasers not only have good beam quality and compact structure but it can achieve high peak power laser output with a pulse width of sub-nanoseconds,and are widely used in laser processing,laser ignition,and nonlinear frequency conversion.Therefore,in order to obtain a compact and high-performance SC light source,this paper uses Yb:YAG laser crystal and Cr4+:YAG passively Q-switched crystal to build a high-performance passively Q-switched microchip laser,then we use it to pump SMF-28 fiber.The experimental results were analyzed by numerical simulation and the mechanism of SC generation in a single-mode fiber pumped by high peak power passive Q-switched microchip laser was clarified.First,a 940 nm continuous-wave laser diode pumped Yb:YAG/Cr4+:YAG passively Q-switch microchip laser was constructed,and pulsed laser oscillating at 1.03 ?m was achieved with the highest peak power and the highest average output power of 43 kW and 880 mW.With this high peak power laser as pump source,The SC was obtained in a SMF-28 fiber.The obtained SC spectrum covers from 600 nm to 1750 nm,the average output power is 181 mW,and the optical conversion efficiency is 21%.The nonlinear effects participating for spectral broadening have been studied in a single-mode fiber pumped with a high peak power laser.In the experiment,the evolution of spectra of SC generated in a single-mode fiber was investigated by controlling the average output power from Yb:YAG/Cr4+:YAG passively Q-switch microchip laser.Based on SC spectrum evolution at different pump powers,the reasons of SC spectrum formation in a single-mode fiber are analyzed and explained in detail,which includes various nonlinear effects such as Stimulated Raman Scattering(SRS)and Four-Wave Mixing(FWM).Besides,the intermodal Four-Wave Mixing(IMFWM)effect in the single-mode fiber is studied by numerical simulation.And results shows that the IMFWM effect is the main mechanism for broadening the spectrum of SC in the visible range.Using the IMFWM effect,combining with single-mode fiber transmission characteristics for different modes,theoretically explains well the broadband SC coverage to orange produced in the single-mode fiber.SC with spectral coverage ranging from 600 nm to 1750 nm was obtained in SMF-28 single-mode fiber pumped by 1030 nm passive Q-switched microchip laser.It is the widest result obtained using a SMF-28 fiber pumped at a wavelength of 1030 nm which is 280 nm away from the fiber's zero-dispersion wavelength.This work provides new research ideas and implementation methods for studying high-peak power passively Q-switched microchip laser pumped single-mode fiber to obtain ultra-broad band SC,which has very high scientific value and practical significance. |
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