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Extreme lasers capable of short, high-energy pulses are probing the frontiers of science and advancing practical technology. The utility of such lasers increases with their average power delivery, which enables faster data acquisition, higher flux of laser-driven particle and radiation sources and more efficient material processing. However, the same extreme energies and electric field strengths of these lasers are currently preventing their direct and high accuracy measurement for these experimental applications. To overcome this limitation, we use the momentum of the laser pulses as a measurement proxy for their energy. When light reflects from an ideal mirror, its momentum is transferred to the mirror, but its energy is reflected. We demonstrate here a force-sensing mirror configuration to measure laser pulse energies up to 100 J/pulse (10 ns duration, 10 Hz repetition rate) from a kilowatt-level average power multi-slab laser operated at the HiLASE facility of the Czech Academy of Sciences. We combine a radiation-pressure power meter with a charge integrator photodiode to form what we refer to as a Radiation Pressure Energy Meter. To our knowledge, this is the first demonstration of a high-accuracy, non-absorbing, SI traceable primary standard measurement of both single and average pulse energies of a 1-kW-average-power pulsed laser source. With this, we demonstrate a practical method for in-situ calibration of the traditional thermal instruments (pyroelectric detectors) currently used for indirect measurements of energy and power of such extreme lasers.

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.

To increase access, most U.S. museums provide free admission opportunities, either through episodic free days or other means. Although studies document the effects of museums transitioning from pai...

We introduce a micromachined force scale for laser power measurement by means of radiation pressure sensing. With this technique, the measured laser light is not absorbed and can be utilized while being measured. We employ silicon micromachining technology to construct a miniature force scale, opening the potential to its use for fast in-line laser process monitoring. Here, we describe the mechanical sensing principle and conversion to an electrical signal. We further outline an electrostatic force substitution process for nulling of the radiation pressure force on the sensor mirror. Finally, we look at the performance of a proof-of-concept device in open-loop operation (without the nulling electrostatic force) subjected to a modulated laser at 250 W and find its response time is less than 20 ms with noise floor dominated by electronics at 2.5 W/ $\surd $ Hz.

We present the first measurements of kilowatt laser power with an uncertainty less than 1 %. These represent progress toward the most accurate measurements of laser power above 1 kW at 1070 nm wavelength and establish a more precise link between force metrology and laser power metrology. Radiation pressure, or photon momentum, is a relatively new method of non-destructively measuring laser power. We demonstrate how a multiple reflection optical system amplifies the pressure of a kilowatt class laser incoherently to improve the signal to noise ratio in a radiation pressure-based measurement. With 14 incoherent reflections of the laser, we measure a total uncertainty of 0.26 % for an input power of 10 kW and 0.46 % for an input power of 1 kW at the 95 % confidence level. These measurements of absolute power are traceable to the SI kilogram and mark a state-of-the-art improvement in measurement precision by a factor of four.

Implementing computer-based decision support can improve physician compliance for prescription of impact-resistant lenses (IRLs) in functionally monocular patients. One of the compliance-limiting factors remains performing a refraction for qualifying patients. There are an estimated 2.4 million eye injuries in the US annually, approximately 90% of which can be prevented by the use of protective eyewear.1 The American Academy of Ophthalmology (AAO) Preferred Practice Patterns for Amblyopia recommends that individuals with unilateral vision impairment with vision of 20/50 in the amblyopic eye should wear protective eyewear full time, even if they do not require optical correction.2 At Dean McGee Eye Institute (DMEI) the preferred practice is to recommend protective eyewear for all functionally monocular individuals (best-corrected vision of 20/50 with qualifying diagnoses and > 2 lines of interocular difference in visual acuity [Table 1 and 2 at www.aaojournal.org ]). We embarked on large-scale quality improvement (QI) initiative for all providers at the DMEI/University for Oklahoma Department of Ophthalmology over a seven-year period.

We have demonstrated operation of a new photon momentum radiometer for measuring laser power levels above 1 kW by use of radiation pressure. The ‘axial’ design allows the input and output laser beams to remain collinear and the force sensing can be carried out with any analytical balance having a vertical sensing direction and sufficient readability (sensitivity). The design also provides for a parasitic fast photodiode power measurement that is calibrated in situ by the slower radiation pressure-based power measurement. This permits a short-time-constant measurement limited primarily by the photodiode bandwidth, rather than the response time of the force balance. Uncertainty contributions yield a relative expanded uncertainty of 2.1% for (1–2) kW and 1.2% above 2 kW (for laboratory environmental conditions). We perform a direct comparison between this new power meter and the existing primary standard radiation pressure power meter. We find the two techniques agree with an average inequivalence of 0.12% for continuous wave (CW) optical powers from (1–10.8) kW. This disagreement is well-explained by the quadrature-summed uncertainties of the two techniques.

Photon momentum radiometers measure the force imparted by a reflected laser beam to determine the laser’s optical power. This requires high-accuracy calibration of the force sensors using milligram and microgram mass artifacts. Calibrated test masses can therefore be used to provide traceability of these radiometers to the International System of Units, but low-noise calibration at these mass levels is difficult. Here, we present the improvement in calibration capability that we have gained from implementing a robotic mass delivery system. We quantify this in terms of the specific nuances of force measurements as implemented for laser power metrology.

In the quest for a new SI traceable power measurement, we performed measurements of the radiation pressure of a radio-frequency (RF) electromagnetic field. There are several groups around the world investigating methods to perform more direct SI traceable measurements of RF power (where RF is defined to range from 100s of MHz to THz). A measurement of radiation pressure offers the possibility for a power measurement traceable to the kilogram and to Planck's constant through the redefined SI. Towards this goal, we demonstrate the ability to measure the radiation pressure/force carried in a field at 2.45 GHz and 15 GHz using two different devices.

Recently, many research studies have been carried out on the efficiency of light-shelf daylighting systems, especially comparing performance improvements and the limitations of reflective surfaces and their lighting performance. In this study, a crystal face reflective surface is proposed. The objective of the study is to evaluate the lighting performance of a crystal face light-shelf through a performance study. The performance study was carried out in a full scale test-bed in order to calculate the light distribution and energy consumption utilizing the standard indoor illumination as an index. The conclusions of the performance study are as follows. 1) The optimal angle of incidence for daylighting for both the operable flat type light-shelf and the crystal face light-shelf are taken in the natural environment on the dates of the winter and summer solstices, as well as the autumn and spring equinoxes. 2) The application and installation of the crystal face light-shelf can produce a 29.9%~34.3% increase of light distribution within the indoor space. However, the increase of light distribution can also lead to a decrease in the uniformity ratio, a design challenge that should be considered when applying a crystal face light-shelf. 3) It is possible to achieve a 7.98%~13.3% greater reduction in energy consumption when applying a crystal face light-shelf than when applying a flat type light-shelf. The increase in the number of crystal faces should concur with the analysis of the energy reduction. A limitation of the study is that only one predetermined pattern was performance tested for a crystal face light-shelf. In order to carry out further research on crystal face light-shelves, additional performance studies are needed based on alternative patterns and designs.

We describe a non-traditional optical power meter which measures radiation pressure to accurately determine a laser's optical power output. This approach traces its calibration of the optical watt to the kilogram. Our power meter is designed for high-accuracy and portability with the capability of multi-kilowatt measurements whose upper power limit is constrained only by the mirror quality. We provide detailed uncertainty evaluation and validate experimentally an average expanded relative uncertainty of 0.016 from 1 kW to 10 kW. Radiation pressure as a power measurement tool is unique to the extent that it does not rely on absorption of the light to produce a high-accuracy result. This permits fast measurements, simplifies power scalability, and allows high-accuracy measurements to be made during use of the laser for other applications.

We present a novel measurement scheme and instrumentation for quantifying laser power by means of photon momentum. The optical design is optimized such that the incoming laser beam is minimally perturbed and is available for other purposes along the incoming beam axis. Additionally, the geometry of the instrument gives access to the small but measurable transmittance between two passive mirrors that face the force sensor. The force sensor is based on a commercially available weighing instrument (“scale”) that has a temporal response of approximately 5 s and a readability of approximately 1 μg (∼2 W). Our measurement results demonstrate beam profile and power for 500 W, but the mirror and mass (or force) calibration are suitable for very high power up to 50 kW and beyond. The optics are based on commercially available, off-the-shelf mirrors optimized for the angle of incidence and maximum reflectance at the wavelength of 1070 nm. The size of the complete instrument has an input aperture of O75 mm, but this constraint is only a matter of optimizing the beam path and box geometry.

Human aldo-keto reductase family 1 member C3 (AKR1C3) was initially identified as an enzyme in reducing 5α-dihydrotestosterone (5α-DHT) to 5α-androstane-3α, 17β-diol (3α-diol) and oxidizing 3α-diol to androsterone. It was subsequently demonstrated to possess ketosteroid reductase activity in metabolizing other steroids including estrogen and progesterone, 11-ketoprostaglandin reductase activity in metabolizing prostaglandins, and dihydrodiol dehydrogenase x (DDx) activity in metabolizing xenobiotics. AKR1C3 was demonstrated in sex hormone-dependent tissues including testis, breast, endometrium, and prostate; in sex hormone-independent tissues including kidney and urothelium. Our previous study described the expression of AKR1C3 in squamous cell carcinoma and adenocarcinoma but not in small cell carcinoma. In this report, we studied the expression of AKR1C3 in normal tissue, adenocarcinomas (43 cases) and neuroendocrine (NE) tumors (40 cases) arising from the aerodigestive tract and pancreas. We demonstrated wide expression of AKR1C3 in superficially located mucosal cells, but not in NE cells. AKR1C3-positive immunoreactivity was detected in 38 cases (88.4%) of adenocarcinoma, but only in 7 cases (17.5%) of NE tumors in all cases. All NE tumors arising from the pancreas and appendix and most tumors from the colon and lung were negative. The highest ratio of positive AKR1C3 in NE tumors was found in tumors arising from the small intestine (50%). These results raise the question of AKR1C3’s role in the biology of normal mucosal epithelia and tumors. In addition, AKR1C3 may be a useful adjunct marker for the exclusion of the NE phenotype in diagnostic pathology.