PPLN green frequency doubling light source pumped by tunable DFB laser
To develop a high repetition rate nanosecond narrow-pulse light source with with pulse width,repetition frequency and output power tunable to the single-photon level for the visible wavelength with high repetition frequen-cy,a green frequency-doubling light source design based on a gain-modulated DFB laser and a PPLN crystal is pro-posed.The DFB laser is driven by a homemade nanosecond high-speed driver circuit in a pulsed mode to generate a fixed-wavelength pump source;using a fiber optic semiconductor attenuator to adjust the attenuation amount and mod-ulate the intensity of pump light;using PPLN crystal as a nonlinear crystal material,a quasi phase matched green fre-quency doubling laser output was obtained through its tunable properties.The experimental results show that the pump power and center wavelength of the gain modulated DFB laser are stable,with a pulse width of 1.02～10.25 ns and an operating frequency of 1 Hz～10 MHz that can be continuously and independently adjusted.When the power of pump light decays to-44.61 dB,the average photon number of the green frequency doubling light output pulse is about 384N,and the conversion efficiency of the frequency doubling light to light is 9.3％.
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