Light control through a nonlinear lensing effect in a colloid of biosynthesized gold nanoparticles

ABSTRACT

Biosynthesis of four samples of colloidal suspensions of gold nanoparticles is achieved using hydroalcoholic extract and three different separated compounds of the plant Bacopa procumbens. The nonlinear optical properties of each sample are characterized with the Z-scan technique. In all cases, the Z-scan curves indicate a negative or self-defocusing response, which is mainly attributed to thermal effects. Among the four samples, the hydroalcoholic extract was noted to have the highest nonlinear optical response and was selected to demonstrate the formation of self-collimated beams (SCBs). This kind of beams are obtained when a convergent CW laser, with only few tens of milliwatts of optical power, is introduced into the sample and induces a negative-lens effect that shifts the focal spot forward. As a result, the otherwise highly focused beam propagate with little divergence over lengths of up to 10 mm. Moreover, an SCB is capable of controlling and steering a weak probe beam of a different wavelength, since the probe experiences the lensing induced by the pump. Noteworthy, the response time of the material was found to be less than 0.07 s, which makes it a plausible candidate for photonic applications.

KEYWORDS:

• Nonlinear optics
• nonlinear optical materials
• gold nanoparticles
• self-effects

Acknowledgments

Authors acknowledge support from DGAPA-UNAM, grants PAPIIT IN114517, IA104917 and IPN with the Project SIP20170554. A. Balbuena-Ortega acknowledges support of CONACYT-Mexico.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Instituto Politécnico Nacional: [grant number SIP20170554]; DGAPA-UNAM: [grant number IA104917], [grant number PAPIIT IN114517].