Igor Vayshenker

High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films

We report on MoSi SNSPDs which achieved high system detection efficiency (87.1 ± 0.5% at 1542 nm) at 0.7 K and we demonstrate that these detectors can also be operated with saturated internal efficiency at a temperature of 2.3 K in a Gifford-McMahon cryocooler. We measured a minimum system jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.3 ± 0.1%. The performance of MoSi SNSPDs at 2.3 K is similar to the performance of WSi SNSPDs at < 1 K. The higher operating temperature of MoSi SNSPDs makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation.

Comparison of reference standards for measurements of optical-fibre power

National reference standards for determining optical-fibre power maintained by the National Institute of Standards and Technology (NIST, USA) and the All-Russian Research Institute for Optophysical Measurements (VNIIOFI, Russian Federation) were compared at wavelengths near 1300 nm and 1550 nm at a power level of 0.5 mW. Instruments from both laboratories are based on thermal detectors capable of electrical calibration. The comparisons indicate relative differences of 2 parts in 103 or less, which is easily within the combined uncertainty of the two laboratories.

Automated measurement of nonlinearity of optical fiber power meters

We have developed a system for measuring the nonlinearity of optical power meters or detectors over a dynamic range of more than 60 dB at telecommunications wavelengths. This system uses optical fiber components and is designed to accommodate common optical power meters and optical detectors. It is based on the triplet superposition method. The system also measures the range discontinuity between neighboring power ranges or scale settings of the optical power meter. We have developed an algorithm to treat both the nonlinearity and the range discontinuity in a logically consistent manner. Measurements with this system yield correction factors for powers in all ranges. The measurement system is capable of producing results which have standard deviations as low as 0.02%. With slight modification the system can operate over a 90 dB dynamic range at telecommunications wavelengths. This measurement system provides accurate determination of optical power meter or detector nonlinearity; the characterized detectors then can be used for such applications as absolute power and attenuation measurements.

Intramural Comparison of NIST Laser and Optical Fiber Power Calibrations

The responsivity of two optical detectors was determined by the method of direct substitution in four different NIST measurement facilities. The measurements were intended to demonstrate the determination of absolute responsivity as provided by NIST calibration services at laser and optical-communication wavelengths; nominally 633 nm, 850 nm, 1060 nm, 1310 nm, and 1550 nm. The optical detectors have been designated as checks standards for the purpose of routine intramural comparison of our calibration services and to meet requirements of the NIST quality system, based on ISO 17025. The check standards are two optical-trap detectors, one based on silicon and the other on indium gallium arsenide photodiodes. The four measurement services are based on: (1) the laser optimized cryogenic radiometer (LOCR) and free field collimated laser light; (2) the C-series isoperibol calorimeter and free-field collimated laser light; (3) the electrically calibrated pyroelectric radiometer and fiber-coupled laser light; (4) the pyroelectric wedge trap detector, which measures light from a lamp source and monochromator. The results indicate that the responsivity of the check standards, as determined independently using the four services, agree to within the published expanded uncertainty ranging from approximately 0.02 % to 1.24 %.

Planar electrical-substitution carbon nanotube cryogenic radiometer*

We have developed a fully-lithographic electrical-substitution planar bolometric-radiometer (PBR) that employs multiwall vertically-aligned carbon nanotubes (VACNT) as the absorber and thermistor, micro-machined Si as the weak thermal link and thin-film Mo as the electrical heater. The near-unity absorption of the VACNT over a broad wavelength range permits a planar geometry, compatible with lithographic fabrication. We present performance results on a PBR with an absorption of 0.999 35 at 1550 nm, a thermal conductance of 456 µW K−1 at 4 K and a time constant (1/e) of 7.7 ms. A single measurement of approximately 100 µW optical power at 1550 nm achieved in less than 100 s yields an expanded uncertainty of 0.14% (k = 2). We also observe an elevated superconducting transition temperature of 3.884 K for the Mo heater, which opens the possibility of future devices incorporating more sensitive thermistors and superconducting thin-film wiring.

Optical detector nonlinearity: a comparison of five methods

We derived a set of unified equations for five methods to evaluate nonlinearity of power meters and detectors. We performed computer simulations of these methods. The simulations assist in design of a measurement system to meet a target accuracy. Measurements verified the simulations.<<ETX>>

Silicon Wedge-Trap Detector for Optical Fibre Power Measurements

We have designed and built an optical fibre power detector based on a large-area silicon PIN photodiode and a concave mirror in a wedge-trap configuration. The detector was designed as a high-accuracy transfer standard for near IR (835-865 nm) optical fibre power measurements with multimode fibre-ribbon cables in a manufacturing-production environment. Additional requirements were that the detector be insensitive to the input beam geometry, and able to accommodate different optical fibre connector types, collimated laser light, and highly diverging light from optical fibres. Four identical copies of the detector were evaluated at the NIST Laser Sources and Detectors Group calibration facility and one was tested in the manufacturing environment. The spatial and angular responsivity was highly uniform and varied less than 1% for angles of incidence ranging from to . Absolute spectral responsivity measurements, for collimated and diverging light input wavelengths ranging from 672-852 nm, showed quantum efficiencies as high as 99%. Linearity measurements from a few nanowatts to a few milliwatts indicated a nonlinearity of only 0.05%.

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.

Optical-Fiber Power Meter Comparison between NIST and PTB

We describe the results of a comparison of reference standards between the National Institute of Standards and Technology (NIST-USA) and Korea Research Institute of Standards and Science (KRISS-R.O. Korea) for optical fiber-based power measurements at wavelengths of 1302 nm and 1546 nm. We compare the laboratories’ reference standards by means of a temperature-controlled optical trap detector. Measurement results showed the largest difference of less than 2.5 parts in 103, which is within the combined standard (k=1) uncertainty for the two laboratories’ reference standards.

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.