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Tutorial
Power and Energy Meters: From Sensors to Displays
By Burt Mooney, Ophir-Spiricon Inc.
From the time the first laser was built, physicists probably thought, “That’s great! Now how do we measure it?” Thus laser power and energy meters were born.
Since lasers are good sources of concentrated heat, it was probably assumed that heat sensing methods would best be employed for measurement. The simplest device to measure heat is a thermocouple. A simple device to measure light is a photodiode. So, some enterprising engineer designed and built such a device. Then they needed an instrument to display the results and give rapid feedback in order to tweak, align, or adjust the laser for maximum output. Early displays were basically analog meters that had a needle on a dial that went from left to right as the laser power went up.
Current Technology of Laser Beam Profile Measurements
by Carlos B. Roundy, Ph.D.
There are many applications of lasers in which the beam profile is of critical importance. When
the beam profile is important, it is usually necessary to measure it to insure that the proper profile exists.
For some lasers and applications this may only be necessary during the design or fabrication phase of the laser. In other cases it is necessary to monitor the laser profile continuously during the laser operation. For example scientific applications of lasers often push the laser to its operational limits and continuous or periodic measurement of the beam profile is necessary to insure that the laser is still operating as expected. Some industrial laser applications require periodic beam profile monitoring to eliminate scrap produced when the laser degrades. In other applications, such as some medical uses of lasers, the practitioner has no capability to tune the laser, and the manufacturers measure the beam profile in design to ensure that the laser provides reliable performance at all times. However, there are medical uses of lasers, such as photo-refractive keratotomy, PRK, wherein periodic checking of the beam profile can considerably enhance the reliability of the operation. PRK is an example of laser beam shaping which is a process whereby the irradiance of the laser beam is changed along its cross section.
In order for this laser beam shaping to be effective, it is necessary to be able to measure the degree to which the irradiance pattern or beam profile has been modified by the shaping medium.
This paper describes the general state of the art of laser beam profile analysis. 1-14 It introduces the general need for beam profile analysis, methods for measuring the laser beam profile, a description of instrumentation that is used in beam profile measurement, a discussion of the information that can be obtained simply by viewing the beam profile, and finally, how quantitative measurements are made on laser beam profiles, and the significance of those quantitative measurements.
the beam profile is important, it is usually necessary to measure it to insure that the proper profile exists.
For some lasers and applications this may only be necessary during the design or fabrication phase of the laser. In other cases it is necessary to monitor the laser profile continuously during the laser operation. For example scientific applications of lasers often push the laser to its operational limits and continuous or periodic measurement of the beam profile is necessary to insure that the laser is still operating as expected. Some industrial laser applications require periodic beam profile monitoring to eliminate scrap produced when the laser degrades. In other applications, such as some medical uses of lasers, the practitioner has no capability to tune the laser, and the manufacturers measure the beam profile in design to ensure that the laser provides reliable performance at all times. However, there are medical uses of lasers, such as photo-refractive keratotomy, PRK, wherein periodic checking of the beam profile can considerably enhance the reliability of the operation. PRK is an example of laser beam shaping which is a process whereby the irradiance of the laser beam is changed along its cross section.
In order for this laser beam shaping to be effective, it is necessary to be able to measure the degree to which the irradiance pattern or beam profile has been modified by the shaping medium.
This paper describes the general state of the art of laser beam profile analysis. 1-14 It introduces the general need for beam profile analysis, methods for measuring the laser beam profile, a description of instrumentation that is used in beam profile measurement, a discussion of the information that can be obtained simply by viewing the beam profile, and finally, how quantitative measurements are made on laser beam profiles, and the significance of those quantitative measurements.
Hartmann Wavefront Analyzer
The Hartmann sensor was invented a century ago to perform optical metrology. Subsequently these ensors have been adapted to a wide variety of applications including adaptive optics, ophthalmology, and laser wavefront characterization. In this document we will explain the operation of the Spiricon Hartmann Wavefront Analyzer (HWA), analyze the device limitations, and compare it to other similar technologies.
What is M2
M2, or Beam Propagation Ratio, is a value that indicates how close a laser id to being a single mode TEM00 beam. This in turn relates to how small a spot a laser can be focused.
