Understanding the Mechanism of Linear Optical Tweezers for Cell Stretching"

[crina]

Hi,

I work with a diode laser, astigmatic Gaussian beam (elliptic), that has two foci positions. One is for to focus the width of the beam and the other one to focus the length of the beam. I trap particles using the first focus. The two parts of the beam act as two orthogonal beams. So, the particles see the trap from the first focus and the light that was not focused due to the orthogonal component of the beam. If I put a deformable object (cells), the object start to stretch along the first focus which looks like a line. What mechanism is acting there? If I increase the laser power, the trap goes stronger across the linear trap but the stretching is along the trap. The stretching is because the radiation pressure caused by the unfocused orthogonal beam (going to the focus) or because of the other beam that focuses first and after that diverges perpendicular to the other beam.

Thanks,

 

[BigJDubs]

The stretching of the deformable object is likely due to a combination of both radiation pressure and the focused beam. The radiation pressure from the unfocused orthogonal beam is pushing the object, while the focused beam provides an additional force that helps stretch the object in the direction of the focused beam. Depending on the power levels of each beam, one force may be stronger than the other and the object may be stretched more in one direction.