Their high selectivity and ability to reject interfering signals make them often used in industries as diverse as telecommunications and medical imaging. In this blog, we’ll look in-depth at what notch filters are, their importance in optical systems, and more.

Complex patterns and geometries are etched into thin film layers through techniques such as photolithography and reactive ion etching (RIE) to create precise wavelength-selective regions. This process allows the formation of high-quality optical structures with sharp transition edges between transmission and rejection bands.

Magnification: 0.25x – 10xDivergence Adjustability: YesAngle of Incidence: 0 ± 0.06°Pointing Stability: < 1 mradWavelength: 257 / 355 / 532 / 1064 / 1550 / 1940 / 2800 / 9400 / 10600nm

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Yes, a laser beam can become wider or narrower by a laser beam expander The magnification of the laser beam expander is decided by the focal length ratio of the divergent and collimated lens inside. When the laser beam in the exit side of the beam expander, the laser beam size will be decreased.

As shown in Figure 1, the Keplerian beam expander design involves a positive lens pair with focal positions coincident with each other. The total length between the lenses is the sum of the two focal lengths. The applications for the Keplerian beam expander design are:

Magnification: 1x – 50xBeam Divergence: AdjustableDesign Type: Galilean/KeplerianPointing Stability: < 1 mradWavelength: 266 / 355 / 405 / 532 / 633 / 1064 / 1550 / 2000 / 9400 / 10600nm

If you want to customize or purchase optical filters, including notch filters, bandpass filters, dichroic mirrors, or long and short pass filters, please visit Optolong’s official website to browse related products, or contact us for accurate quotes. We have a professional team to serve you!

Notchfilter design

Notch filters are widely used in astronomical imaging, telecommunications, biophotonics equipment, and Raman spectroscopy by selectively rejecting specific wavelengths without affecting other wavelengths.

These filters are often used to reduce or eliminate unwanted light, such as lasers or other specific wavelengths of light, without affecting the transmission of other wavelengths of light.

Bandpass filter

These filters are specially designed to attenuate a precise wavelength range while minimizing the intensity loss of the transmitted wavelength, which can effectively eliminate unwanted fluorescence, prevent laser radiation, and improve signal quality.

Notch filters work on the principle of phase cancellation interference, where the filtered wavelengths are phase-shifted, resulting in the wavelengths canceling each other. Through a clever combination of constructive and destructive interference, these filters effectively eliminate unwanted frequencies while maintaining the integrity of the desired signal.

Notchfilter transfer function

Broadband notch filters are designed to block or significantly attenuate various wavelengths of light while allowing other wavelengths to pass.Broadband notch filters can cover a wider wavelength region than narrowband notch filters. They are very effective in applications where multiple wavelengths or a wider range of wavelengths need to be suppressed simultaneously.

Laser beam expanders are critical optical devices that manipulate and enhance laser beams in various applications. They are pivotal in extending the beam’s width, collimation, and divergence, making them invaluable tools in research, manufacturing, telecommunications, and medical fields.

Notch filters, also known as band-stop filters, are key components in optical systems. These filters selectively attenuate specific frequencies while allowing others to pass through unaffected.

Now we understand the difference between Keplerian and Galilean beam expander design, let’s look into other different configurations. A laser beam expander can also be classified based on the viewing angle, whether the magnification is fixed or varying. For instance, a laser beam expander is either in a fixed or zoomed magnification. Additionally, based on its tuning method, the zoomed laser beam expanders can also be classified as manual or motorized zoomed configurations.

Narrowband Notch Filters are used to suppress light in a narrow range of wavelengths while allowing other wavelengths to pass through. These filters are commonly used in laser systems to exclude specific wavelengths of laser light to minimize scattering or fluorescence interference.

Thin film deposition and etching processes are two key technologies in the manufacturing process of notch filters. Thin film deposition techniques, including physical vapor deposition (PVD) and chemical vapor deposition (CVD), are used to form uniform and controlled optical coatings on the substrate surface, allowing precise control of coating thickness to optimize filter performance and tailor spectral characteristics to application requirements.

Matlabnotchfilter

Figure 4 shows a typical manual adjusted zoomed beam expander. There are two adjusting rings, one is to set magnifications whereas another is to set the focusing and divergence angle of the laser beam.

To reduce the thermal effects in high-power lasers as well as to eliminate the chromatic aberration in ultrafast lasers, we came up with new modules based on reflective focusing optics. It could be used as a stand-alone module, or integrated with other transmission-based beam expanders.

We value safety as much as we do and you can be assured that all our beam expanders are subjected to rigorous testing before market sales. All our fixed and zoom laser beam expanders are telescopic by nature and require a collimated beam input while delivering an expanded collimated beam at the output. All designs come with a detailed specification table and operation manual.

Wavelength Opto-Electronic designs and manufactures our in-house Ronar-Smith® brand of laser beam expanders, available in different magnification configurations and types of Galilean as well as Keplerian. With our state-of-the-art production facilities and design capabilities, you can be assured that our Ronar-Smith® laser beam expanders demand the highest quality in beam broadening and collimation without compromising on the expanded beam quality.

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In some applications, metal materials such as aluminum or gold are used to enhance reflective properties and effectively block unwanted wavelengths due to their unique optical properties.

Another type of classification is based on the refraction or reflection being applied. So, a laser beam expander can be classified as refractive (in most cases) or a reflective beam expander. There are laser beam expanders designed for CO2 laser applications.

CO2 laser beam expanders are developed to work with higher power (>100w) CO2 laser. We have developed below CO2 laser beam expanders for various CO2 laser applications:

In addition, etching processes such as photolithography and reactive ion etching (RIE) are used to create complex patterns and geometries on thin film layers, ensuring precise wavelength selection and high-quality optical structures, thereby achieving sharp transitions between transmission bands and rejection bands.

By adding metal layers to the filter stack, customized spectral control can be achieved and signal isolation can be improved, thereby improving the overall performance of the filter.

A notch filter is a special type of optical filter that blocks (filters out) light in one or several specific wavelength ranges while allowing other wavelengths to pass through.

The concept of zoomed laser beam expanders works on the internal translation stages and focusing mechanisms to adjust and account for the changes in magnification continuously. It also considers laser divergence and performs relative adjustments without affecting the overall housing length.

Galilean beam expanders do not have an internal focus, which makes them safer for high-power applications. Whereas Keplerian beam expanders have internal focus which can be used for spatial filtering.

Optical filter

By depositing thin films on the substrate surface, manufacturers can tailor the spectral characteristics of notch filters to specific application requirements.

Thin film deposition techniques are commonly used in the manufacture of notch filters to create uniform and controlled optical coatings. Methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD) can precisely control coating thickness to ensure optimal filter performance.

In the field of optical systems, there are two main types of notch filters: narrowband notch filters and wideband notch filters. Each type of notch filter has different uses depending on its design and operating characteristics.

In the design of optical notch filters, dielectric materials, and metal materials are two key material choices. Dielectric materials such as silicon dioxide or tantalum pentoxide have specific dielectric properties that enable them to accurately attenuate specific wavelengths of light, directly affecting the spectral response and transmission efficiency of the filter.

Following the global trend in automation, Wavelength Opto-Electronic came up with a new series of automatic/motorized laser beam expanders. The unique design of an integrated printed circuit board provides an integrated communication port, a memory-based calibration function, and a high accuracy of 10μm.

A Laser beam expander is made up of two groups of lenses: a divergent lens and a converging lens. The diverging lens expands the input beam and the converging lens then collimates the divergent beam to be parallel. Thus the input laser beam size can be increased.  The magnification of a laser beam expander is equal to the focal length ratio of the converging/collimating lens and the diverging lens.  There are two main types of beam expanders: Galilean and Keplerian. The main difference between these two types of laser beam expander is in the diverging lens: A Galilean type uses a negative lens as the diverging lens whereas a Keplerian type applies a positive lens as the diverging lens. For both types, the focal points position of the diverging and converging lens are coincident.

Digitalnotchfilter

Galilean beam expanders can be used for a majority of laser applications, including high-power laser applications such as laser marking, soldering, cutting, etc.

Manual/motorized zoomed laser beam expanders have variable magnification in a certain range. This flexibility in magnification makes the beam expanders useful for applications that need controllable focused beam size. We offer zoomed beam expanders (BXZ and BXZ-MOT series) with the following specifications:

Notch filter design considerations include wavelength range, attenuation depth, and bandwidth, which together determine their performance and suitability for an application.

There are several configurations of laser beam expanders and they can be grouped differently. For instance, the Keplerian and Galilean beam expander design is one way of classifying laser beam expanders. Let’s first look at the difference between these two designs before we delve into other configurations.

This type of filter is often used in fields such as spectroscopy, imaging systems, and fiber optic communications, especially where broadband background or stray light needs to be removed from the signal. Broadband notch filters are effective in increasing the system’s sensitivity to specific wavelengths, thereby improving signal quality and contrast.

In a fixed beam expander, lenses can only be tuned to adjust the divergence angle of the laser beam. Compared with a zoomed beam expander, the fixed magnification beam expander features a more compact size and lighter weight.

As shown in figure 1, the Galilean beam expander design makes use of a negative and a positive lens pair with their focal position coincident with each other and the total length between the lenses is the difference between the two focal lengths.