Optics & Optical Coatings


Selection of optics

Prepare a diagram featuring your desired optical path based on your experimental principles for the optical system.
Check the required specifications of each optical component stated on the optical path and select the correct components.
As the options available are extensive, we can assist you by introducing the following two important factors when selecting your optics.
(Laser Specifications & Classification of Optical Systems)

Optical Coatings

Laser Specifications

When selecting optics, determine the type of “light” to be used.
As there are various types of light sources in the market, our Sigma Koki catalog offers Laser, LED, Halogen and Metal Halide solutions.
Laser typically offers various wavelengths and the accompanied optics to be used can differ depending on the wavelengths.
In addition to the wavelength of laser, there are some elements to consider when deciding the specification of optics.

Check Items for Laser Example 1 Example 2 Related Spec
Laser Type He-Ne YAG Compatible Wavelength
Wavelength [nm] 632.8nm 532nm
Calculation of Energy Density [J/cm2]
(User should calculate)
Example 1 : Any
Example 2 : 78J/cm2
Output beam diameter
(1/e2, diameter) [mm]
0.59mm 0.7mm Not applicable for CW of laser
damage threshold of 0.5W
or lower
Not applicable for pulse of
100mJ/cm2 or lower
For continuous wave (CW) laser
Output [W]
1mW -
For pulse laser
Energy [J], Pulse width [s],
Repetition frequency [Hz]
- 300mJ
10ns, 20Hz
Beam Spread Angle (Full) [rad] 1.35mrad 1.3mrad Clear aperture
Transverse Mode TEM00 Single Focus spot diameter
Polarization Orientation
(Vertical, horizontal, or random)
Vertical Horizontal Reflectance, transmittance

If the information provided above is still uncertain, please check with the manufacturer of the Laser and they will provide you with the necessary information and specifications.Compare the specifications of the optics listed in our catalog against the laser and select the optics that is compatible especially in the area of laser damage threshold and polarization orientation.

Classification of Optical System

Confirm the type and degree of precision required for your optical system.
If uncertain, you may classify by its intended usage.
Illumination by itself does not require precision but more towards functionality and purpose.
Please see chart below to have a better understanding.

Class Surface Accuracy Surface Quality Product Example Usage
System Class
About λ About 60-40 Biconvex lens
Aspheric lens
Lamp illumination of microscope
Condensing beam to a detector, etc.
Simplified Optical
System Class
λ/4 or lower 40-20 or lower Plano convex lens
Achromatic lens
Aluminum* /
Dielectric multi-layer mirror coating
Various imaging systems
Interferometers for small diameter beam
λ/10 or lower 20-10 or lower Surface accuracy guaranteed mirror
Femto high power mirror
Focusing lens
Interferometers for wavefront
observation, laser processing devices
Optical experiments with higher resolution

The above classification is a rough guide. The classification may not apply depending on products or materials.
For selection of each product, refer to the selection guide.
Also refer to the explanations in the selection guides or application notes such as “Beam Expanding Method”
or “How to Use Polarizers”.
If you have any question, contact our International Sales Division.
When making an inquiry, do let us know your laser specifications or intended usage,
we can provide you with a quicker and more comprehensive answer or solution.

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