Toomas Kübarsepp

• DrTech
• Metrosert AS

A polarisation-insensitive transmission trap detector was constructed from two identical polarisation-dependent transmission trap detectors, each containing four 10 mm×10 mm silicon photodiodes. The performance of the 8-element polarisation-independent and coaxial input–output transmission trap detector has been characterised at laser wavelengths o...

A photodetector based on two large-area InGaAs-photodiodes in transmission-type trap configuration has been studied. The alignment of the photodiodes provides polarisation-independent performance of the photodetector. The responsivity and spatial uniformity of responsivity and transmittance of InGaAs-based transmission trap detector are reported at...

We have developed a transmission trap detector sensitive over a wide optical wavelength range. The developed device takes advantage of the smooth reflectance profile of silicon photodiodes. The detector is based on two 10 mm size photodiodes – a Si photodiode and an InGaAs photodiode. The constructed hybrid trap detector is sensitive at the wavelen...

The quantum yield in silicon has previously been assumed to be of significance only in the ultraviolet spectral range. Due to the low internal losses of induced-junction silicon photodiodes and their predictability it is possible for the first time to make more accurate estimation of the quantum yield. We report on measurement of quantum yield in i...

The room temperature dual-mode self-calibrating detector combines low-loss photodiodes with electrical substitution radiometry for determination of optical power. By using thermal detection as a built-in reference in the detector, the internal losses of the photodiode can be determined directly, without the need of an external reference. Computer s...

ABSRACT Systematic influences in a mass comparator can affect their performance with very great importance to ensure the reliability of using instruments and to ensure adequate uncertainty estimations. This work gave experience in the field of high accuracy mass measurements in handling standard level for high accuracy instruments and handling meas...

Background Silicon single-photon avalanche diodes (Si-SPADs) are the most used devices for measuring ultra-weak optical radiant fluxes in many quantum technology fields, such as quantum optics, quantum communication, quantum computing, etc. In all these fields, the detection efficiency is the main parameter, which has to be accurately known for ach...

A new method improving precision of the phase difference measurement performed by two Keysight 3458A multimeters is proposed. The method is based on external synchronization of the multimeters by a specially selected sampling interval reducing the effect of the finite resolution of an internal time base (jitter) on the performance of the multimeter...

p> Background: Over the last decade have seen a drastically increase of interest in the Single photon avalanche diode (SPAD) detectors applications at many variety of quantum experiments where the detection efficiency at single-photon level is required. The calibration of such detectors involves predominantly the determination of the detection effi...

The effects of chemical and electrical passivation in self-induced junction photodiodes have been studied. By employing experimental methods and simulations, it is shown that chemical passivation dominates over electrical passivation in this type of photodiodes.

In manufacturing system, 3D Coordinate Measuring Machines (CMM) are widely used for inspection services where the product should be subjected to the verification of design specifications. It is usually necessary to know the accuracy of 3D CMM equipment during the verification process of the product quality in mass production. To insure and increase...

We have developed and characterized a new kind of trap detector based on InGaAs photodiodes. The detector contains only two 10 mm diameter InGaAs photodiodes arranged in a transmission trap configuration with non-coaxial beam orientation. The detector has large active area, more than 9 mm in diameter, and a built-in linearity monitoring feature. On...

Silicon single-photon avalanche diodes (Si-SPADs) play an important role in a variety of quantum experiments where the detection at single-photon level is required. The calibration of such detectors involves predominantly the determination of the detection. For this purpose, a reproducible and close-to-ideal alignment of the SPADs to the incident b...

The Metrology for Industrial Quantum Communication Technologies project (MIQC) is a metrology framework that fosters development and market take-up of quantum communication technologies and is aimed at achieving maximum impact for the European industry in this area. MIQC is focused on quantum key distribution (QKD) technologies, the most advanced...

A follow-up initiative of development in the field of optical radiometry undertaken in the frame of European Metrology Research Programme (EMRP) is described. Amongst the other tasks, the new project NEWSTAR aims at accurate determination of ratio e/h of fundamental constants - elementary charge e and Planck's constant h. This is envisaged to achie...

In this study the influence of the digital resolution on the properties of a data sample is experimentally determined in mass measurements. A mass comparator with adjustable digital resolution interval, also known as the quantization step size, was used in well controlled repeatable conditions. The same measurement procedure with the resolution dif...

The accurate method for angle measurements of a complicated geometrical object has been elaborated by using Moving Bridge TESA MICRO-HITE 3D Coordinate Measuring Machine (CMM). This type of 3D CMM allow high accuracy measurements of complicated geometric objects with resolution 0.0001 mm. The measurements were conducted for machined mechanical part...

The predictable quantum efficient detector (PQED) is intended to become a new primary standard for radiant power measurements in the wavelength range from 400 nm to 800 nm. Characterization results of custom-made single induced junction photodiodes as they are used in the PQED and of assembled PQEDs are presented. The single photodiodes were tested...

The design and construction of a predictable quantum efficient detector (PQED), suggested to be capable of measuring optical power with a relative uncertainty of 1 ppm (ppm = parts per million), is presented. The structure and working principle of induced junction silicon photodiodes are described combined with the design of the PQED. The detector...

The method for inhomogeneity investigation of measurement standards for electrical conductivity has been studied in the conductivity range from 2 MS/m to 14 MS/m. For this purpose a planar spiral coil has been developed and characterized. The impedance values of the coil are measured in the air and with a conducting plate above the coil at discrete...

A practical method for the quantification of systematic errors of large-scale automatic comparators is presented. This method is based on a comparison of the performance of two different comparators. First, the differences of 16 equal partial loads of 1 kg are measured with a high-resolution mass comparator featuring insignificant bias and 1 kg max...

This paper presents an overview of the establishment of the national measurement standard for temperature at METROSERT - the national metrology institute in Estonia. The temperature scale and traceability arrangements are realized in the temperature range from -40 degrees C to + 300 degrees C by means of a group of calibrated standard platinum resi...

The spectral responsivity of a predictable quantum efficient detector (PQED) is calculated based on the responsivity of an ideal quantum detector and taking into account reflection losses from the surface of the photodiode and internal charge-carrier gains/losses inside the diode. The internal quantum deficiency (IQD) is obtained from simulations w...

The accurate method for electrical conductivity measurements has been established. In the realization of the method Van der Pauw' DC-measurement technique is applied. The measurements were conducted for five metal plates whose electrical conductivity nominal values are in the range from 2 MS/m to 14 MS/m. The limiting factors of the accuracy in DC-...

The internal quantum efficiency of silicon photodiodes can be made very close to unity [1-3]. This has raised interest to use induced-junction photodiodes [4] as absolute radiometric detector standards with measurement uncertainty in the parts-per-million (ppm) range [5,6]. The design and construction of a Predictable Quantum Efficient Detector (PQ...

The Predictable Quantum Efficient Detector (PQED) is intended to improve optical power measurements in the wavelength range from 450 nm to 900 nm. Characterization results for two produced batches of photodiodes that will be used in the PQED are presented. These results will be used to develop a model to predict the response of the PQED to optical...

The throughput performance of a ten-element transmission trap detector has been investigated at the laser wavelength 647.1 nm. The input beam of 1/e2 diameter 1.9 mm was studied at the output of the device in both s and p polarization states. The beam diameter was measured to change by less than 0.1 mm after undergoing ten internal reflections with...

Realization of the national mass scale for the optimal coverage of the industrial need for the mass calibrations at the Estonian national metrology institute, AS Metrosert, is described. The cost effective technical solutions to meet the calibration requirements of the advised OIML class E1 weights have been established. The traceability to the Int...

The properties of what is, to the best of our knowledge, the first ten-element polarization-dependent transmission trap detector consisting of silicon photodiodes are described. The responsivity and the transmittance of the photodetector were measured at laser wavelengths of 476.2 and 647.1 nm . In particular, the effect of the polarization state o...

Four high-accuracy LCR meters have been compared with the use of Metrosert and MIKES impedance standards. Specifications of LCR meters have been verified at frequency of 1 kHz for the resistance range from 1 Ω to 100 kΩ, for the capacitances in the range from 100 pF to 1 μF and for 100 mH inductor. The performance of LCR meters have been compared a...

The capabilities in measurements of direct voltage and electrical resistance have been improved in Estonia. The Volt and Ohm standards are based on electronic voltage standards and standard resistors, respectively. The reference standards are traceable to Josephson voltage (JVS) and quantized Hall (QHR) effect resistance standards by means of the a...

An experimental setup for characterization of thermal imagers has been designed and constructed. The setup comprises a climatic chamber and a temperature-controlled flat blackbody target that allow testing of thermal imagers in the ambient temperature range from −13°C to +23 °C and at target temperatures from −15°C to +120°C. The setup has been tes...

Planar spiral coils are used in the present paper to estimate electrical conductivity of a conducting plate by eddy current method. Formulas for the change in impedance are derived from the corresponding formulas for air-cored cylindrical coils in the limit where the height of the coil approaches zero. The difference between experimental and theore...

Thermal imagers are often used under ambient conditions, which differ significantly from the calibration conditions. In this paper a method for characterization of thermal imagers under various ambient conditions is described in the ambient temperature range from -10 °C to +23 °C. A flat-plate blackbody source attached to a climatic chamber has bee...

The realization of the mass scale in Estonia is basing on the 1 kg group standard traceable via PTB to the international prototype kilogram. Starting from year 2000, realization of the mass scale by subdivision and multiplication is carried out in the range from 1 mg to 50 kg. Stability and reproducibility of reference weights, both the 1 kg group...

According to the international practice a link between measurement results and the International System of Units (SI) should be demonstrated. The National Metrology Institute of Estonia (METROSERT) has participated in the EUROMET comparison project no. 714 results of which are linked to the SI definition of Kelvin in accordance with the CIPM Recomm...

The national standard of volt in Estonia is based on the ten solid-state references and consists of maintenance and transfer modules. Traceability of the dc voltage standards is obtained by annual calibration of 4 Zener units fitted in the transfer module. The calculated expanded uncertainty is less than 10 muV, taking into account the component du...

An automated system for measurements of standard resistors has been developed. The system is based on high-accuracy direct current comparator bridge, range extender and current source. The setup is used for comparison, characterization and calibration of standard resistors in the range from 1 Omega to 10 kOmega with relative uncertainties below (1....

The uncertainty of a primary spectral irradiance scale based on filter radiometers (FRs) is studied by analysing the propagation of uncertainties and covariances through a spectral interpolation process, when a modified Planck's radiation law is fitted to the measurement data. The advantage of performing the uncertainty analysis in optimizing the s...

A method of measuring the absolute spectral irradiance of quartz-halogen-tungsten lamps is described, based on the known responsivity of a filter radiometer, the components of which are separately characterized. The characterization is described for the wide wavelength range essential for deriving the spectrum of a lamp, from 260 nm to 950 nm. Nove...

The spectral irradiance of lamp standards can be stabilized within a limited spectral range using a suitable selective detector to control the irradiance of the lamps. The capability of one commercial lamp facility incorporating a computer-controlled power supply was tested in an international comparison. A set of three lamps and the detector-stabi...

The results of a comparison of spectral irradiance scales between the National Institute of Standards and Technology (NIST, USA), and the Metrology Research Institute, Helsinki University of Technology (HUT, Finland), are presented. The comparison was carried out by measuring irradiances of two sets of 1 kW FEL-type lamps in the spectral range 290...

A method developed at the Helsinki University of Technology (HUT) for calibrating standard lamps of spectral irradiance in UV-A and UV-B regions is presented. The method is based on a compact filter radiometer that is characterized absolutely to measure spectral irradiance. The filter radiometer can be brought to laboratories where accurate calibra...

We improve the methods used to interpolate the responsivity of unbiased silicon photodetectors in the near-ultraviolet region. This improvement is achieved by the derivation of an interpolation function for the quantum yield of silicon and by consideration of this function in the interpolation of the internal quantum efficiency of photodiodes. The...

An automated instrument based on the beam-addition technique has been developed for measurement of the linearity of photodetectors. The system is designed for absolute characterization of a transfer standard photodetector, against which the linearity of other detectors can be measured. The measurement set-up has been made as simple as possible. A d...

Nonlinearities of the responsivity of various types of silicon photodetectors have been studied. These detectors are based on photodiodes with two sizes of the active area (10 × 10 mm² and 18 × 18 mm²). The detector configurations investigated include single photodiodes, two reflection trap detectors, and a transmission trap detector. For all devic...

A six-element polarization-independent transmission trap detector with coaxial input and output beams has been constructed and full characterized. The measured optical parameters are compared with their values, predicted by Fresnel equations. Measured transmittances are in agreement with the predicted values within 2 × 10⁻⁵ in the wavelength region...