Time trends in the laser beam parameters
In this article you will learn:
Discover the Latest Trends in Laser Beam Parameters
Trends in the laser beam parameters refer to the changes or variations that occur in the laser beam over time. By monitoring the laser beam parameters over a period of time, it is possible to detect and analyze these trends, which can provide valuable information about the performance of the laser and the consistency of the process. Trends monitoring is a critical tool in laser preventive maintenance. For instance, observing the laser beam position over time allows detection of drift caused e.g. by optomechanics instabilities or by a thermal drift. On the other hand detection and quantitative monitoring of trends in the diffraction patterns allows estimation of risk of the laser corruption or allows planning maintenance actions in the right time allowing maximization of the beam availability.
Optimal Performance and Preventive Maintenance in laser beam
Some examples of trends in the laser beam parameters that can be detected by monitoring the laser beam include:
Power drift: This refers to a gradual decrease or increase in the laser power over time. Power drift can be caused by factors such as changes in the laser’s temperature or aging of the laser’s components. For example a laser diode.
Beam pointing stability: This refers to changes in the position or alignment of the laser beam over time. Beam pointing stability can be affected by factors such as vibrations or changes in the alignment of the laser’s optics.
Beam width: Beam width can fluctuate over time if the optical system gets misaligned or due to thermal effects. Detecting this trend is vital to many processes. One good example could be using femtosecond lasers in the medical procedure of cataract removal. In such an operation a human eye retina is cut by a femtosecond laser to allow removal of a natural lens. The size of a spot has a direct impact on the size of a scar forming after the procedure. This scar later scatters the light causing side effects. The relation is: the greater focal spot, the greater the risk of the side effects. Another interesting example could be CNC laser-equipped mills which cut diamonds. Obviously, no one would like to lose more of this precious material than needed. Also if the size of the spot is too big thermal effects might cause the diamond uncontrolled break. Thus monitoring of beam width is of great interest.
Example of changes in the beam width of a test laser monitored in the Huaris Laser Cloud is presented in the image below.
Mode quality: This refers to changes in the transverse mode of the laser beam over time. Mode quality can be affected by factors such as changes in the temperature or alignment of the laser’s optics.
Spectral properties: This refers to changes in the wavelength or bandwidth of the laser beam over time. Spectral properties can be affected by factors such as aging of the laser’s components or changes in the temperature. It is well known that thermal drift has to be addressed by a proper heat management in many lasers to secure stable wavelength generation.
Coherence: This refers to changes in the spatial and temporal coherence of the laser beam over time. Coherence can be affected by factors such as changes in the temperature or alignment of the laser’s optics.
By detecting and analyzing trends in the laser beam parameters, it is possible to identify potential problems with the laser or its optics and take corrective actions before they lead to a significant reduction in the process quality or a failure of the equipment. It also helps in understanding the laser beam’s overall behavior over time, which can be very useful in the process quality management and prediction of future maintenance needs.
Beam width measurements in the long run
Measuring the beam width of a laser over a long period of time can provide valuable information about the stability and performance of the laser, as well as the consistency of the process. There are several different methods and parameters that can be used to measure the beam width of a laser over a long period of time, such as:
Continuous monitoring: One approach is to continuously monitor the beam width using a beam profiler, a power meter, or other types of detectors. This can provide real-time data about the beam width and allow for the detection of any variations or changes that may occur.
Time-series measurements: Another approach is to take periodic measurements of the beam width at regular intervals, such as every hour or every day. This can provide a record of the beam width over time and allow for the detection of any trends or patterns that may occur.
Long-term data storage: It is important to store the data collected over the long run for further analysis, this data can be stored in a computer, a cloud server or other types of storage devices. This allows for the data to be analyzed later and provides a historical record of the beam width.
Statistical analysis: The data collected over the long run can be analyzed using statistical methods to identify any patterns or trends in the beam width. This can provide valuable information about the stability and performance of the laser over time.
It’s worth noting that the choice of method and the specific parameters used to measure the beam width will depend on the specific requirements of the application and the type of laser. Additionally, a well-calibrated and well-designed system is needed to accurately measure these parameters over a long period of time, without any drift or changes in the system.
Trends of the laser power in longer time
Measuring the laser power over a long period of time can provide valuable information about the stability and performance of the laser, as well as the consistency of the process. There are several different methods and parameters that can be used to measure the laser power over a long period of time, such as:
Continuous monitoring: One approach is to continuously monitor the laser power using a power meter or other types of detectors. This can provide real-time data about the laser power and allow for the detection of any variations or changes that may occur.
Time-series measurements: Another approach is to take periodic measurements of the laser power at regular intervals, such as every hour or every day. This can provide a record of the laser power over time and allow for the detection of any trends or patterns that may occur.
Long-term data storage: It is important to store the data collected over the long run for further analysis, this data can be stored in a computer, a cloud server or other types of storage devices. This allows for the data to be analyzed later and provides a historical record of the laser power.
Statistical analysis: The data collected over the long run can be analyzed using statistical methods to identify any patterns or trends in the laser power. This can provide valuable information about the stability and performance of the laser over time.
Comparison to specifications: By comparing the measured laser power to the laser’s specifications, it’s possible to detect any variations or changes that may occur and take corrective actions before they lead to a significant reduction in the process quality or a failure of the equipment.
It’s worth noting that the choice of method and the specific parameters used to measure the laser power will depend on the specific requirements of the application and the type of laser, and also the power measurement system should be calibrated and stable over time to provide accurate measurements. Additionally, the environment and temperature can affect the power measurements, so it’s important to consider these factors when monitoring the laser power over a long period of time.
Diffraction patterns in the laser beam profile
Diffraction patterns refer to the patterns that are formed when a laser beam passes through an aperture. These patterns are a result of the diffraction of light, which is a fundamental, non-avoidable physical phenomenon.
When a laser beam is passed through an aperture or reflected by a mirror, the diffraction of light causes the beam to spread out and form a pattern of light and dark regions. These regions are known as diffraction orders, and the intensity of the light in each region is determined by the size of the aperture and the wavelength of the light. The shape of the pattern is also affected by the distribution of the intensity on the laser beam and by the shape of the aperture.
Example diffracted beam is shown in the picture below. In this case it is linear diffraction on the Gaussian beam presented in the Huaris profiling software local application.
The most commonly observed diffraction patterns in laser beam profile are:
Airy disk: This is the central bright spot formed by the diffraction of light within the beam waist. The size of the Airy disk is determined by the wavelength of the light and the numerical aperture (NA) of the lens or mirror system.
Airy rings: These are the series of concentric bright and dark regions that surround the Airy disk. The intensity of the light in each ring is determined by the size of the aperture and the wavelength of the light.
Diffraction spikes: These are the bright lines that extend outward from the Airy disk. They are caused by the diffraction of light at the edges of the aperture or mirror.
Diffraction on the edges of optical elements: These are diffraction effects occurring when the laser beam is deflected and/or reflected on the edge of an optical element. E.g. it could be a lens or a mirror. Typically this phenomenon can be observed when the optical setup gets misaligned.
Diffraction on dust: This is a situation when the laser beam travels through the dirty optical elements. The particles of dust will cause tiny interference patterns and will damage the beam quality. If the intensity of the laser beam is high the dust may also absorb the light making it easier to damage the optical element that it sits on.
Diffraction on rough surfaces: If the surface of a mirror or of the lens is not smooth then it may also cause the diffraction of the laser beam.
The diffraction patterns can be observed in the laser beam profile by using a beam profiler or other types of detectors that can measure the intensity distribution of the beam. Understanding these diffraction patterns can be useful in assessing the quality of the laser beam, and can also be used to optimize the laser beam for specific applications.
It’s worth noting that diffraction patterns are dependent on the optical system and the wavelength of the laser, and can also be affected by other factors such as aberrations or the presence of dirt or dust on the optics.
Huaris Laser Cloud uses AI to:
- Detect the presence of diffraction patterns
- Specify the type of diffraction
- Estimate the surface area of a diffraction pattern
The patterns are observed in Huaris in the long term and the user obtains notification when they are detected and when the trend in their area is observed.
Another key feature of the Huaris Cloud is the possibility to monitor all key laser beam parameters measured with the beam profiler in the long term.
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