1. Principle of multi-layer thin film interference

-Basic structure: Laser line long wave pass filters are usually composed of multiple layers of dielectric thin films, which are alternately deposited on optical substrates to form a complex optical structure.

-Design principle: The thickness and refractive index of these films are precisely controlled, allowing specific wavelengths of light to interfere at the interfaces of the films. When the interference condition is met, light of a specific wavelength will pass through the filter, while light of other wavelengths will be reflected or absorbed.
-Mathematical description: The formula for transmittance is:

2. High transmittance and depth cutoff capability

-High transmittance: Edmund Optics' laser line long wave pass filters have a transmittance of up to 93% within the passband, which means they can effectively transmit the desired optical signal and reduce signal loss.

-Depth cutoff capability: These filters have a depth cutoff capability greater than OD 6, which can largely reject the light of the laser line and ensure that the light signal within the cutoff band is effectively blocked.

3. Steep edge characteristics

-Edge characteristics: The portion between the position with an optical density of 6.0 and the position with a transmittance of 50% is very steep, which allows the filter to measure the minimum Raman shift.

-Application advantages: This steep edge characteristic makes the laser line long wave pass filter an alternative to expensive holographic notch filters used in Stokes Raman scattering measurements.

4. Materials and Manufacturing Processes

-Substrate materials: Commonly used substrate materials include optical glass (such as BK7, B270), quartz (suitable for UV), sapphire (hard and corrosion-resistant), silicon/germanium (suitable for infrared), etc.

-Coating materials: Common dielectric film materials include silicon dioxide (SiO?), titanium dioxide (TiO?), tantalum pentoxide (Ta? O?), etc.

-Manufacturing process: Interference filters are mainly manufactured through vacuum coating technology, including electron beam evaporation, ion beam sputtering, etc. These processes need to be carried out in an ultra-high vacuum environment, ensuring product performance through precise control of film thickness and rate.

5. Application Fields

-Raman spectroscopy: In Raman spectroscopy analysis, laser line long wave pass filters can effectively separate laser lines and Raman scattering signals, improving signal detection sensitivity.

-Confocal microscopy: In confocal microscopy, these filters can be used to improve the contrast and resolution of imaging.

-Biotechnology instruments: In biotechnology instruments, laser line long wave pass filters can be used to separate light signals of specific wavelengths, improving detection accuracy.

Through the above optical principles and characteristics, Edmund Optics' laser line long wave pass filter performs excellently in various optical applications, providing strong support for scientific research and industrial applications.