Tag: Agnese Callegari

OTGO published in JOSA B

Computational toolbox for optical tweezers in geometrical optics

Computational toolbox for optical tweezers in geometrical optics
Agnese Callegari, Mite Mijalkov, Burak Gököz & Giovanni Volpe
Journal of the Optical Society of America B 32(5), B11—B19 (2015)
DOI: 10.1364/JOSAB.32.000B11
arXiv: 1402.5439

Optical tweezers have found widespread application in many fields, from physics to biology. Here, we explain in detail how optical forces and torques can be described within the geometrical optics approximation, and we show that this approximation provides reliable results in agreement with experiments for particles whose characteristic dimensions are larger than the wavelength of the trapping light. Furthermore, we provide an object-oriented software package implemented in MATLAB for the calculation of optical forces and torques in the geometrical optics regime: Optical Tweezers in Geometrical Optics (OTGO). We provide all source codes for OTGO as well as documentation and code examples—e.g., standard optical tweezers, optical tweezers with elon- gated particles, the windmill effect, and Kramers transitions between two optical traps—necessary to enable users to effectively employ it in their research.

Speckle Optical Tweezers published in Opt. Express

Speckle optical tweezers: Micromanipulation with random light fields

Speckle optical tweezers: Micromanipulation with random light fields
Giorgio Volpe, Lisa Kurz, Agnese Callegari, Giovanni Volpe & Sylvain Gigan
Optics Express 22(15), 18159—18167 (2014)
DOI: 10.1364/OE.22.018159
arXiv: 1403.0364

Current optical manipulation techniques rely on carefully engineered setups and samples. Although similar conditions are routinely met in research laboratories, it is still a challenge to manipulate microparticles when the environment is not well controlled and known a priori, since optical imperfections and scattering limit the applicability of this technique to real-life situations, such as in biomedical or microfluidic applications. Nonetheless, scattering of coherent light by disordered structures gives rise to speckles, random diffraction patterns with well- defined statistical properties. Here, we experimentally demonstrate how speckle fields can become a versatile tool to efficiently perform fundamental optical manipulation tasks such as trapping, guiding and sorting. We anticipate that the simplicity of these “speckle optical tweezers” will greatly broaden the perspectives of optical manipulation for real-life applications.