Shao Yang

Nonlinearity Measurements of High-Power Laser Detectors at NIST

We briefly explain the fundamentals of detector nonlinearity applicable to both electrical and optical nonlinearity measurements. We specifically discuss the attenuation method for optical nonlinearity measurement that the NIST system is based upon, and we review the possible sources of nonlinearity inherent to thermal detectors used with high-power lasers. We also describe, in detail, the NIST nonlinearity measurement system, in which detector responsivity can be measured at wavelengths of 1.06 µm and 10.6 µm, over a power range from 1 W to 1000 W. We present the data processing method used and show measurement results depicting both positive and negative nonlinear behavior. The expanded uncertainty of a typical NIST high-power laser detector calibration including nonlinearity characterization is about 1.3 %.

Optical fiber power meters: a round robin test of uncertainty

The proliferation of optical fiber systems has spawned a variety of optical power meters. These meters are important to the analysis and maintenance of fiber communication systems. One obvious attendant concern is with the uncertainty of the meter readings. In this paper, we give the results of an interlaboratory test conducted to circumscribe and define the extent of the problem. The test yielded 46 data points from 11 participants collected over a period of ∼9 months. The results indicate that the variation in power meter readings taken in different laboratories is unreasonably large. The variance improved when measurements taken with very small detectors were excluded from the data base. This suggests that errors are being made in the collection of power in typical laboratory environments.

Nonlinearity of high-power optical fiber power meters at 1480 nm.

We describe a calibration system that measures the nonlinearity of optical fiber power meters (OFPMs) at a maximum power of 0.6 W and a minimum power of 0.2 mW at 1480 nm. The system is based on the triplet superposition method. This system measures the nonlinearity of OFPMs by using correction factors at different powers; the system is an important tool for characterizing OFPMs at high powers in the S band. The measurement uncertainties, typically better than 0.2%, k = 2, associated with the high-power nonlinearity system are also described.

Measurements of detector nonlinearity at 193 nm

We have developed a measurement system based on a correlation method to characterize the nonlinearity of a detectors response over a large range of laser pulse energy. The system consists of an excimer-laser source, beam-shaping optics, a beam splitter, a monitor detector, a set of optical filters, and the detector under test. Detector nonlinearities as large as 10% or greater over an entire measurement range at an excimer-laser wavelength of 193 nm are observed. The measurement range of the current system is approximately 300 nJ to 50 mJ of laser pulse energy at the detector under test. The typical expanded measurement uncertainty of nonlinearity is 0.6% (k = 2).

193-nm detector nonlinearity measurement system at NIST

To meet the semiconductor industry’s demands for accurate measurements on excimer lasers, we have developed a system using the correlation method to measure the nonlinear response of pulse energy detectors of excimer laser at 193 nm. The response of the detector under test to incident laser pulse energy is compared to the corresponding response of a linear monitor detector. This method solves the difficulties caused by large pulse-to-pulse instability of the excimer laser and delivers measurement results with an expanded uncertainty (k=2) of 0.8 %.

Optical high-power nonlinearity comparison between the National Institute of Standards and Technology and the National Metrology Institute of Japan at 1480 nm

We compare the results of measurements of the nonlinearity of high-power optical fiber powermeters (OFPMs) by two national metrology institutes (NMIs): the National Institute of Standards and Technology (NIST-USA) and the National Metrology Institute of Japan/National Institute of Advanced Industrial Science and Technology (NMIJ/AIST-Japan) at a wavelength of 1480 nm. The nonlinearity and range discontinuity of a commercial OFPM were measured from 1 mW to 500 mW by use of a superposition method (both laboratories) and from 1 mW to 250 mW by use of a comparison method (NMIJ only). Measurement results showed largest differences of less than 1.6 parts in 10(3), which is within the combined expanded (k = 2) uncertainty for both laboratories.

Bilateral optical fiber power meter linearity comparison between NMIJ and NIST

Optical fiber power meter (OFPM) linearity standards of NMIJ (Japan) and NIST (USA) are compared using a commercial OFPM as a transfer standard at 1310 nm and 1550 nm over a power range [-60 dBm, 0 dBm]. At both wavelengths the comparison indicates an agreement between the two laboratories within the combined uncertainty. At 1550 nm the uncertainties are larger, which is attributed to unstable operation of the transfer standard at this wavelength.