Source: Optris

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Transmissivity in Optics

Definition

The transmissivity of a surface in optics is the ratio of transmitted optical power to the incident optical power. It is commonly used for flat unstructured surfaces and is measured with a light beam.

Transmissivity vs. Transmittance

Transmissivity refers to transmission through a single surface, while transmittance is more appropriate for transmission through extended objects like glass plates or optical resonators. Laser mirrors, despite being dielectric, are often specified in terms of transmissivity.

Non-Normal Incidence

For non-normal incidence, the ratio of transmitted to incident optical intensity does not directly correspond to transmissivity due to changes in propagation direction and beam area.

Transmission Coefficients

The transmission through an optical surface can be described using complex transmission coefficients, where the squared modulus represents transmissivity and carries a complex phase related to optical phase changes.

Fresnel Equations

Complex transmission coefficients and transmissivity for optical interfaces can be calculated using Fresnel equations, which depend on the refractive indexes of the optical materials involved.

Further Exploration

Understanding transmissivity in optics is crucial for various applications in photonics and optical engineering. It plays a significant role in the design and analysis of optical systems.

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