HIGH ACCURACY FILTER TRANSMISSION MEASUREMENT FOR DETERMINATION OF THE DETECTION EFFICIENCY CALIBRATION OF Si-SPAD DETECTORS

Transcription

1 10th International DM Baltic Conference "INDUSTRIL ENGINEERING" 1-13 May 015, Tallinn, Estonia HIGH CCURCY FILTER TRNSMISSION MESUREMENT FOR DETERMINTION OF THE DETECTION EFFICIENCY CLIBRTION OF Si-SPD DETECTORS Dhoska, K.; Hofer, H.; López, M.; Rodiek, B.; Kübarsepp, T. & Kück, S. bstract: high accracy filter transmission measrement for the determination of the detection efficiency of a Si-SPD detector has been carried ot sing an integrating sphere with attached detector. The measrement method and the improvement of total measrement ncertainty of the Si-SPD detection efficiency calibration are described in this paper. Key words: Si-SPD detector, integrating sphere, filter transmission measrement, detection efficiency. 1. INTRODUCTION Over the last decade, silicon single-photon avalanche diodes (Si-SPDs) have become increasingly important in different application fields sch as qantm operations, vision systems, astrophysics telecommnications, biology and medicine. Sch a variety of sage fields of Si-SPDs is based on their high detection efficiency at few photon levels in a wide spectral range; from the visible to the near infrared. The detection efficiency is typically measred by sending few photons onto the detector at a known repetition rate and recording the nmber of detection events [ 1 ]. Typically a strong attenated laser or incandescent lamp is sed as a light sorce. Ths, in order to achieve reliable measrements for the detection efficiency calibration, the Physikalisch-Technische Bndesanstalt (PTB), the national metrology institte of Germany, established recently a compact setp for Si- SPD calibration that ses traceable transfer standards and a measrement procedre based on filter transmission techniqe, see Fig. 1 and ref. [, 3 ]. However, the previos calibration reslts of the Si-SPD detection efficiency have shown that one of the major ncertainty contribtions in the measrement ncertainty bdget comes from the netral density filter transmission measrement [ 3 ]. For this reason, a high accracy filter transmission measrement is reqired to improve the measrement ncertainty of the Si-SPD detection efficiency. The novelty of this research work is that instead of sing a single silicon detector (Si- Diode), an integrating sphere is employed for the filter transmission measrement. The integrating sphere is a device sed for collecting and spatially integrated radiant flx [ 4 ]. The systematic errors that may be introdced de to speclar reflections between the Si-Diode and the objective sed dring the filter transmission measrement are practically eliminated by sing the integrating sphere. Fig. 1. Schematic view of the calibration setp for Si-SPDs [, 3 ].

2 . MESUREMENT METHOD ND SETUP For the determination of the Si-SPD detection efficiency applying this techniqe, the transmission of the filters is reqired to calclate the optical power impinging on the Si-SPD detector. However, since a very low filter transmission is needed, which is not possible to be measred directly with an analoge detector, a two step measrement procedre for the filter transmission determination is reqired. This is carried ot as follows: in a first step, the filter transmission is measred individally for each filter (T F, T F3 ) by sing high accracy translation position stages and the integrating sphere with attached detector as a light sensor. In a second step, the filter transmission of the two filters is measred as a filter package ( T Combined ); i.e. both filters are simltaneosly placed in the beam path. From these three measrements a deviation between individal filters and total filter combination can be calclated, that is, TF TF 3 Dev = 1. (1) This deviation can be taken as an overall ncertainty contribtion of the filter transmission measrement for the determination of the detection efficiency of Si-SPD detectors, as described in [ 3 ]. The measrement setp for the filter transmission measrement and the determination of the qantm detection of Si-SPD detector is shown in Fig.. tnable laser sorce with a wavelength range from 766 nm to 781nm is sed. The laser beam is focsed throgh a microscope objective PO M-PLN 0x with an 0.4 nmerical apertre and a working distance of 0 mm. We have sed netral density filter NG9 D.6 for Filter and netral density filter NG9 D 3.0 for testing the measrement procedre. Fig.. Top view pictre of the setp for the determination of the detection efficiency calibration of Si-SPD detector by sing integrating sphere with attached detector. n gilent VEE program has been developed for the realization of atomated measrements. t each wavelength, in the range from 766 nm to 781nm with steps of nm, were realized 100 measrements. In the measrement procedre, Filter and Filter 3 are moved in x-direction of the translation stage. The position repetition of the translation stages is 5 µm, which avoid errors de to the spatial nonhomogeneity of the filter transmission. The translation range of the stages is 80 mm. The measrement program is composed of 4 modles. In modle 1 the optical power of the laser is measred with the integrating sphere withot any filter. The mean vale of the measrement obtained with modle 1 is sed as a reference vale

3 for calclation of the filter transmission in relation to the reslts obtained in the next measrement modles. fterwards, the measrement modle only Filter is moved in the beam path (x = 37 mm). Modle 3 contines with the measrement of the individal filter transmission by moving Filter to position x = 0 mm and Filter 3 to position x = 37 mm. Finally, modle 4 completes the measrement procedre by measring the total transmission of the filter combination, i.e. Filter and Filter 3 are positioned in the beam path (position x = 37 mm) simltaneosly. 3. MESUREMENT RESULTS The smmary of the filter transmission measrement reslts with their deviations for different wavelengths are shown in Table 1 and dispersions of the deviations are depicted in Fig. 3. The deviation between the transmission measrement of the single and combined filters is 0.05 % for the whole measred wavelength range. Nr λ (nm) Filter Filter 3 Combined Filters Deviation (%) Table 1: Smmary of the filter transmission measrement reslts and deviations calclated by eqation (1). Fig. 3. Deviation of the filter transmission measrements calclated by eqation (1) for different wavelengths. 4. DETECTION EFFICIENCY UNCERTINTY The mathematical model for determination of the detection efficiency of the Si-SPD accompanied with all possible contribtion factors for evalation of the measrement ncertainty is given by [ 3 ], hc 3 Q1Q 4 h = s Si F filt, () l Q Q 1 3

4 where η is the detection efficiency of the SPD; i.e. the measrand vale, h is the Planck constant, c is the speed of light, λ is the wavelength, 1,, 3 are the signal amplification factors, Q 1, Q, Q 3 are the ratios of the signal of the Si-diode attached to the integrating sphere and the monitor detector signal, Q 4 is the ratio of the conter and the monitor detector signal, s Si is the spectral responsivity of the integrating sphere with the attached Sidiode, and F filt is the factor taking into accont the se of two filters. The estimation of ncertainty of the detection efficiency measrement is carried ot following the gide to the expression of ncertainty in measrement (GUM) [ 5 ]. Based on the propagation law of ncertainty and ncertainty of inpt qantities, we can evalate the combined ncertainty as [ 3 ]: ( h) c c c = 1 h c 3 l Q 9 Q 3 10 Q 4 3 s Int. Sph 1 F Filt Q1, (3) where the (i) are the standard ncertainties of the inpt qantities and c i are the sensitivity coefficients which are calclated from the partial derivatives of all inpt qantities. In continity on the improvement of the total measrement ncertainty we will not focs to the estimation of all possible contribtor factors bt only at the factor of the se of two filters as one of the major contribtion. The deviation between combined and individal filters measrements will inflence in the correction factor. The expression of the deviation between two measrements is estimated from eqation (1) and correction factor by eqation (4): FFilt = =, (4) TIndividal TF TF 3 where T F, T F3 are the filters transmission of each individal filter and T combined is the filter transmission of combined filter. These reslts have shown that the largest deviation 0.05 % comes from the transmission measrements carried ot at l=774 nm. This deviation is sed, for simplicity, for the estimation of the ncertainty of the correction factor F Filt for each wavelength. Ths, the standard ncertainty of the correction factor that ses two filters is estimated: TIndividal Tcombined 4 F Filt = = (5) Tcombined 3 The ncertainty contribtion of the factor which ses two filters is obtained: 4 c ( FFilt ) = c1 F =. 10, (6) Filt where sensitivity coefficient is c 1 = The final reslt has shown that ncertainty contribtion is 8.1 %. Referring to the previos estimated reslts we have improved one of the major ncertainty contribtions by significantly redcing measrement ncertainty from 54.8 % [ 3 ] to 8.1 %. The new contribtion vale of the factor sing two filters is inclded into the ncertainty bdget and is sed to estimate the combined ncertainty c (η). Finally, the obtained detection efficiency of the Si- SPD detector is: η SPD = ± , η SPD = ± 0. %. 5. CONCLUSIONS In this paper, the accrate filter transmission measrement method and the improvement of its measrement ncertainty have been developed for the calibration of the detection efficiency of Si-SPD detector. The se of an integrating sphere instead of a single Si-Diode for the filter transmission measrement has significantly redced the measrement ncertainty contribtion of the filter factor from 54.8 % to 8.1 %. The relative standard ncertainty of the detection efficiency of the Si-SPD was improved from < 0.5 % to < 0.5 %. Ftre work will be focsed on redcing the ncertainty contribtion of the absolte spectral responsivity on the integrating

5 sphere as the last larger contribtion factor for the determination of detection efficiency of Si-SPD detectors. 6. REFERENCES 1. Ch. J. Chnnilall, I. P. Degiovanni, S. Kück, I. Müller and. G. Sinclair, Metrology of single-photon sorces and detectors: a review, Optical Engineering, 014, 53, S. Kück, H. Hofer, S. Peters, M. López, Detection Efficiency Calibration of Silicon Single-Photon valanche Diodes Traceable to a National Standard, In: Proceedings of NEWRD: 1th International Conference on New Developments and pplications in Optical Radiometry, (Park, S. and Ikonen, E., eds.) Espoo, Finland, 014, M. López, H. Hofer, S. Kück, Detection efficiency calibration of single-photon silicon avalanche photodiodes traceable sing doble attenator techniqe, Jornal of Modern Optics, 015, 6, S1-S7. 4. technical gide to integrating sphere theory and applications. al-gides/a-gide-to-integrating-spheretheory-and-applications.pdf. 5. ISO/IEC Gide 98:1995. Gide to the expression of ncertainty in measrement (GUM). International Organization for Standardization: Geneva. 7. DDITIONL DT BOUT UTHORS Klodian Dhoska, doctoral stdent, Department of Mechatronics, Tallinn University of Technology, Ehitajate tee 5, 19086, Estonia. klodian.dhoska@tt.ee Helmth Hofer, engineer, helmth.hofer@ptb.de Beatrice Rodiek, doctoral stdent, beatrice.rodiek@ptb.de Marco López, doctor, marco.lopez@ptb.de Toomas Kübarsepp, professor, Department of Mechatronics, Tallinn University of Technology, Ehitajate tee 5, 19086, Estonia. toomas.kbarsepp@tt.ee Stefan Kück, professor, stefan.keck@ptb.de 8. CKNOWLEDGEMENT This research work has been spported by Physikalisch-Technische Bndesanstalt in Branschweig, the national metrology institte of Germany and by the project Single-Photon Sorces for Qantm Technology (SIQUTE) of the Eropean Metrology Research Programme (EMRP). The EMRP is jointly fnded by the EMRP participating contries within EURMET and the Eropean Union.