Photomechanical Sensing from Spectral Shifts in Graphene-Doped Polydimethylsiloxane Reflection Gratings

Based on laser power meter calibration requirements, through the purchase of standard equipment and field monitoring equipment developed, standard laser detector, optical path related equipment, such as construction of laser radiation power meter calibration test system, implementation of laser power meter of laboratory test and vehicle, large equipment form a complete set of laser power meter field test and field test of the radiated power of the laser equipment. Calibration system is introduced in detail the composition and working principle of the uncertainty of the system are analysed in detail, and through the system stability test, laser power, beam monitoring and correction device performance test, ate test for power meter calibration experiment data analysis, proved in this study, the laser power meter calibration method provided will enable calibration system, the expanded uncertainty of relative reached 2% (k = 2), which can realise wavelength of 532 and 1064 nm, power measuring the range of 0.1 mW–20 W laser power meter calibration.

Aimed at the requirements of laser equipment, a verification system of laser power meter is established. The system can realize the verification and calibration of laser power meter with wavelength of 532nm, 633nm, 1064nm and power measurement range of 0.1mW to 20W. The relative expanded uncertainty of the system reaches 2% (k=2). The composition and working principle of the system are described in detail. The test methods and measurement data are given for the main parameters of system performance test, such as power stability of laser, power monitoring ratio stability of laser power beam splitter monitoring and correcting device, correction factor of standard laser power meter. After the system test, the performance of the laser power meter verification system has been more perfectly examined.

For the LCLS-II instruments we are developing laser power meters as compact intensity monitors that can operate at soft and tender X-ray photon energies. There is a need to monitor the relative X-ray intensity at various locations along an X-ray FEL beamline in order to observe a possible decrease in the reflectivity of X-ray mirrors. In addition for experiments, it is valuable to know the absolute intensity at the sample. There are two types of laser power meters based on thermopile and pyroelectric sensors. The thermopile power meters measure an average temperature and are compatible with the high repetition rates of LCLS-II. Pyroelectric power meters provide a pulse-by-pulse response. Ultra-high vacuum compatibility is being tested by residual gas analysis. An in-house development beamtime is being conducted at the LCLS SXR instrument. Measurements using both thermopile and pyroelectric power meters will be conducted at a set of photon energies in the soft X-ray range. The detectors’ response will be compared with the gas monitor detector installed at the SXR instrument.

Radiation pressure has recently been shown to have practical application for multikilowatt continuous wave (CW) laser power measurement. One key advantage lies in its ability to measure without absorbing the laser beam. This enables a new measurement paradigm where laser power can be measured traceable to the SI without perturbing the beam. Combining this measurement scheme with a laser constitutes a “traceable source” where laser output power is traceable to the SI in real time. This greatly simplifies the calibration process for multikilowatt laser power meters and yields a path to high-accuracy laser-based material processing. Here, we discuss the state of the art of this approach by describing recent results from calibrations of laser power meters performed using a radiation-pressure-enabled traceable source at CW powers from 1 to 50 kW. We describe measurement results and uncertainty contributions with expanded uncertainties at or below 1.7% for powers above 10 kW. We also briefly discuss the status of development of a radiation-pressure-based technology designed to provide source traceability in the laser manufacturing environment.

Since the laser was invented, laser has been applied in many fields such as material processing, communication, measurement, biomedical engineering, defense industries and etc. Laser power is an important parameter in laser material processing, i.e. laser cutting, and laser drilling. However, the laser power is easily affected by the environment temperature, we tend to monitor the laser power status, ensuring there is an effective material processing. Besides, the response time of current laser power meters is too long, they cannot measure laser power accurately in a short time. To be more precisely, we can know the status of laser power and help us to achieve an effective material processing at the same time. To monitor the laser power, this study utilize a CMOS (Complementary metal-oxide-semiconductor) camera to develop an on-line laser power monitoring system. The CMOS camera captures images of incident laser beam after it is split and attenuated by beam splitter and neutral density filter. By comparing the average brightness of the beam spots and measurement results from laser power meter, laser power can be estimated. Under continuous measuring mode, the average measuring error is about 3%, and the response time is at least 3.6 second shorter than thermopile power meters; under trigger measuring mode which enables the CMOS camera to synchronize with intermittent laser output, the average measuring error is less than 3%, and the shortest response time is 20 millisecond.

The market offers a relatively wide range of laser power meters for high power applications, but when it comes to verifying measurements, a lot of know-how is required. Even the comparison of national standards between different countries in some cases has given evidence for discrepancies. For high power measurements, a major drawback has been that the primary standards of all the national calibration institutes are cryogenic radiometers, which are built for low power applications, while industrial applications often require lasers in the 0.1 - 12 kW range, thus creating the need for transfer standards from low to high power range. Primes GmbH currently is setting up a calibration laboratory for high power cw laser power meters in cooperation with the German institute for standards, the PTB, which will allow to trace high power laser measurements back to national standards and extend the measurement range substantially. Certified calibration services will be open to all users and manufacturers of laser power meters for high power applications.

For the LCLS-II X-ray instruments, we have developed laser power meters as compact X-ray power monitors. A calibration of the responsivity of the power meters was carried out against a silicon photodiode with synchrotron radiation and a gas monitor detector with FEL X-rays. A manipulator with two power meters was installed in various locations at the LCLS. In the LCLS front end, the power meters were compared with the gas detectors, which are calibrated by the electron energy loss method. The agreement between the power meters and the gas detectors was better than 20% at 1500 eV with the pulse energy measured by the gas detectors higher than that from the power meters. In the AMO instrument, the power meters evaluated the improvement in beamline transmission caused by the oxygen plasma cleaning of the Kirkpatrick-Baez mirrors. Measurements were also conducted one and two years later to observe the effect of further contamination of the optical surfaces. Finally at the SXR instrument, the power meters determined the pulse energy at the sample for a beamtime, where the X-ray intensity was an important parameter.

For the LCLS-II X-ray instruments, laser power meters are being developed as compact X-ray power diagnostics to operate at soft and tender X-ray photon energies. These diagnostics can be installed at various locations along an X-ray free-electron laser (FEL) beamline in order to monitor the transmission of X-ray optics along the beam path. In addition, the power meters will be used to determine the absolute X-ray power at the endstations. Here, thermopile power meters, which measure average power, and have been chosen primarily for their compatibility with the high repetition rates at LCLS-II, are evaluated. A number of characteristics in the soft X-ray range are presented including linearity, calibrations conducted with a photodiode and a gas monitor detector as well as ultra-high-vacuum compatibility tests using residual gas analysis. The application of these power meters for LCLS-II and other X-ray FEL sources is discussed.

We report the design of a cost effective, highly sensitive cw laser power meter with a large dynamic range based on a photodiode. The power meter consists of a photodiode, a current to voltage converter circuit, an offset balancing circuit, a microcontroller, an analog to digital converter, reed relays, and an alphanumeric liquid crystal display. The power meter can record absolute laser power levels as low as 1 pW. The dynamic range measured with a cw laser at a wavelength of 532 nm is 8x10(10). The high sensitivity and large dynamic range are achieved by the implementation of an analog background balancing circuit and autoranging.

Low cost and facile fabrication of broadband laser power meter based on reduced graphene oxide film

An uncooled photon detector is fabricated for the mid-wave infrared (MWIR) wavelength of 4.21 μm by doping an n-type 4H-SiC substrate with gallium using a laser doping technique. The dopant creates a p-type energy level of 0.3 eV, which is the energy of a photon corresponding to the MWIR wavelength 4.21 μm. This energy level was confirmed by optical absorption spectroscopy. The detection mechanism involves photoexcitation of carriers by the photons of this wavelength absorbed in the semiconductor. The resulting changes in the carrier densities at different energy levels modify the refractive index and, therefore, the reflectance of the semiconductor. This change in the reflectance constitutes the optical response of the detector, which can be probed remotely with a laser beam such as a He-Ne laser and the power of the reflected probe beam can be measured with a conventional laser power meter. The noise mechanisms in the probe laser, silicon carbide MWIR detector, and laser power meter affect the performance of the detector in regards to aspects such as the responsivity, noise equivalent temperature difference (NETD), and detectivity. For the MWIR wavelengths of 4.21 and 4.63 μm, the experimental detectivity of the optical photodetector of this study was found to be 1.07×10(10) cm·Hz(1/2)/W, while the theoretical value was 1.11×10(10) cm·Hz(1/2)/W. The values of NETD are 404 and 15.5 mK based on experimental data for an MWIR radiation source with a temperature of 25°C and theoretical calculations, respectively.

Recently, particle size and analysis technology are used for various industry filed and become very important. Because small particle can affect to manufacture process and product yield. Especially. As design rule of semiconductor device is miniaturizing to 10 nm class. Because of this, very fine particle which size is below 100 nm can affect to the wafer as shown Fig. 1. In addition to this, after chemical mechanical polishing (CMP) process many defects can occur by fine particles in CMP slurry which are remain on the wafer. In this reason, we need a technology which is measure the particle property of slurry in CMP process.In this study, particle detecting technology has been investigated which is can detect a particle in the CMP slurry for wafer polishing. In this experiment, single particle sizing system (SPOS) is used for particle detecting in CMP slurry. The SPOS system is a single particle detecting system which system is the principle of measuring scattering light generated by particles. It can get a high resolution from detecting a small size particle also analysis of particle property such as size, shape and so on.Fig, 2 shows a schematic of the experiment set-up and result, which experiment was consisting of five devices that is He-Ne laser, laser power meter, tubing pump and lens system. The experimental principle is firstly preparing the solution which contain particles to flow the quartz tube. Second, prepare the focusing and collecting lens system. Third, aligning the laser to the quartz tube where the solution flows and turning it on will cause the laser light to hit the particles present in the solution, which will measure the scattered light with a laser power meter. Figure 1

Laser drilling is an energy dependent process in which energy consumption is linearly proportional to the thickness of the material being drilled. Thus, providing linear output power from the laser can provide considerable advantages in the repair of devices such as TFT-LCD pixels. Unfortunately, the non-linear energy characteristics of lasers require compensation to achieve linear power output. Conventional compensation schemes use laser power meters that require repeatedly switching the laser system off and on again. This study developed a software-based energy compensation method to provide optimized energy output and continuous linear laser energy. This software solution enables the measurement of laser energy in a fixed period and its manipulation using a compensation table, which eliminates the need for a laser power meter and enables the system to remain in operation during laser power calibration. The proposed method provides linear output in which the linear energy proportion (R2) reaches 0.9988 and provides a very stable power source. We applied this method to repair bright pixels in LCD panels, achieving a success rate of 86 %. In addition, the proposed method eliminates the need to remove the LCD casing from the fabrication module, thereby increasing the efficiency of production.

Overly-crowded optical set-ups and safety enclosures often make it difficult to insert a regular laser power detector. To provide a measurement solution that offers simpler handling than the usual detector-cable-meter combination, Gentec-EO developed a series of compact laser power meters that are operated remotely and wirelessly. In this product demonstration, we will show how to display and acquire laser power measurement on a smartphone, at up to 30 m away from the wireless detector. The 4 simple steps to obtain a wireless measurement will be shown: 1. Start the BLU app 2. Connect the device 3. Zero the sensor 4. Turn on your laser In the video, we also provide expert tips on how to handle the detector and best practices that will help you make the most accurate laser power measurements, remotely. INCREDIBLE PERFORMANCE Each detector of the all-in-one BLU series offers the same outstanding performance as any Gentec-EO power meter, from a few microwatts to multiple kilowatts. FLEXIBILITY This module is offered with most Gentec-EO laser power detectors, for both the general-use thermopile sensors (UP series) and all our high-power detectors (HP series). HOW TO ORDER The best way to select a BLU power meter is to start by identifying which power detector is best suited for your application. Contact your local sales representative at https://www.gentec-eo.com/contact-us or get a recommendation instantly by filling out the 3 Product Finder questions on our website: https://www.gentec-eo.com/products?type=smart Visit our webpage for more information about the BLU series: https://www.gentec-eo.com/products/blu

With the development of high-power laser technology, accurate measurement of laser power has been a difficult task. The light pressure weighing method (LPWM) can replace the calorimetric laser power meter as a standard measurement device in the high power range due to its fast response, high accuracy, and direct traceability to mass. When the laser power is less than 1 kW, the accurate measurement of light pressure requires a weighing sensor with a higher level of resolution, and multiple environmental disturbances will significantly affect the measurements. We present a high-precision LPWM power meter based on a W-shaped dual-reflection structure and a 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{g}$ </tex-math></inline-formula> resolution weighing sensor, corresponding to a laser power measurement resolution of 0.78 W. Simulation of air parameters near the sensing mirror shows that the laser causes different air pressure changes at the top and bottom of the sensing mirror, and monitoring of temperature, relative humidity and laser power all show linear trends. By using the segmented compensation strategy, we successfully achieve more stable measurements and significantly improve the level of measurement repeatability. The expanded uncertainty after compensation is better than 2% for laser power above 150 W and better than 1% for power above 500 W. This article makes it possible to quickly and accurately measure laser power from 150 W to 1 kW in conventional environments and is also expected to replace calorimetry as the standard device in the sub-kilowatt range.