THORLABS EDU-OT2, Руководство пользователя

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Portable Optical Tweezers Kit Chapter 4: Principles of Optical Tweezers
Page 8 MTN012639-D02
Reflection and Transmission of an Incident Partial Beam on the
Inside and Outside Surfaces of a Sample Bead with a Refractive Index
Higher than the Immersion Medium
Inside the sphere, the beam is reflected and transmitted numerous times. Part of the beam
is repeatedly reflected on the sphere's internal wall and remains in the sphere, while the
rest exits the sphere again through transmission. The beams which exit the sphere again
were thus subject to a change in momentum
𝑑𝑝
𝑑𝑡
. The force on the sphere is equal to the
momentum per unit time that remains in the sphere, based on equation (9). Now, the force
on the sphere is once again divided into two components: a component in the direction of
the incident beam (corresponds to the Z direction) and a perpendicular component
(corresponds to the Y axis). This results in the following for both forces:
𝐹
𝑠
≔ 𝐹
𝑧
= 𝑛
𝑚
𝑃
𝐵𝑒𝑎𝑚
𝑐
𝑄
𝑠
(13)
with the Q factor
𝑄
𝑠
= 1 + 𝑅
𝑟
cos
(
2𝜃
)
−
𝑇
2
(
cos
(
2𝜃 − 2𝑡
)
+ 𝑅
𝑟
cos
(
2𝜃
))
1 + 𝑅
𝑟
2
+ 2𝑅
𝑟
cos
(
2𝑡
)
(14)
and
𝐹
𝑔

𝐹
𝑦
= 𝑛
𝑚
𝑃
𝐵𝑒𝑎𝑚
𝑐
𝑄
𝑔
(15)
with the Q factor