Optical Tweezers — Iris Lab

Laser & Trap

Laser power P: 100 mW Beam waist w₀: 1.5 μm Particle radius a: 0.5 μm Particle n: 1.59 (polystyrene)

Environment

Viscosity η: 1.0 mPa·s (water) Temperature T: 293 K

Trap Data

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κ (pN/μm)

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F_max (pN)

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⟨Δx⟩ (nm)

Trapped

Physics

F_grad = −∇U
U = −½α⟨E²⟩

For Rayleigh (a≪λ):
F_grad = (2πn_m a³/c)·
((m²−1)/(m²+2))·∇I

κ = 2·I₀·α/(c·w₀²)

⟨Δx²⟩ = k_B T / κ
(Brownian fluctuations)

Click canvas to move laser trap. Particles feel gradient force toward focus. Brownian motion adds thermal fluctuations.