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The photonics-based Rb standard was being realized using the low phase noise Er-doped mode-locked femtosecond fiber laser, extended cavity diode laser, dielectric resonator and Sagnac interferometer. The locked voltage controlled oscillator (VCO) was connected to the reference input of the phase-locked dielectric oscillator and consequently, ultra-low phase noise 6.834 GHz MW signal, which was locked to the fiber laser, was obtained. The measured phase noise reaches -200 dBc/Hz for an offset frequency of 10 MHz. The achievd frequency stability of the photonic-based Rb atomic clock is 3x10-12@1 s and decreased to 2.5x10-13@400 s and 7.1x10-13@104 s.

We report on a mode-locked laser design using Yb-doped fiber lasers for low-noise frequency-comb generation. The frequency comb covers the spectral range from $700$ to $1400$ nm. Although this range is more practical for many measurements than that produced by the more commonly used Er-fiber lasers, it has been addressed in only a handful of reports, mainly due to the difficulty of generating a fully coherent supercontinuum at $1\;\mu$m. We overcome this difficulty by a tailored design of the mode-locking dynamics that succeeds in generating energetic 33 fs-long pulses without even using higher-order dispersion compensation, while ensuring that the laser operates with net zero cavity dispersion for low-noise supercontinuum generation. After locking to a Cs atomic clock, this frequency comb is used for absolute-frequency measurements of a Nd:YAG-I$_2$ laser to verify its accuracy by comparison with results from the International Committee for Weights and Measures. After this verification, it is further used to measure the absolute frequency of a 543-nm two-mode stabilized He-Ne laser, which is routinely used for length measurements in our institute, thus verifying its practical utility in metrology applications. The entire setup is built with readily available components for easy duplication by other researchers.

Phase noise measurement is a method for measuring short term stability of signal sources. There are commercial phase noise measurement systems on the market and manufacturers may use different measurement methods on their products. In this paper, the bilateral phase noise comparison results are presented. Same type of phase noise measurement system was used by each laboratory. Travelling standard of comparison has phase noise characteristics comparable to reference signal source of phase noise measurement system so three oscillator comparison method was used. The comparison was carried out at 10 MHz, 100 MHz, 1 GHz, 5 GHz, 10 GHz and 20 GHz carrier frequencies for 1 Hz, 10 Hz, 105 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, 10 MHz (except 10 MHz carrier) offset frequencies. Since each signal source which were used in the comparison has special low noise mode, 10 MHz Low-Noise, 100 MHz Low-Noise and 250 MHz Low-Noise carrier frequencies were also added to comparison. For carrier frequencies higher than 1.6 GHz, there are two options for phase noise measurements. The first one is to use low noise downconverter module and second one is to use second phase detector which has frequency range up to 26.5 GHz. To compare each method, normal and downconverter measurements were performed at 5 GHz, 10 GHz and 20 GHz carrier frequencies. While very close comparison results can be achieved for most of carrier and offset frequencies, relatively big differences were measured for others. All results are presented with calculated uncertainty values. The calculated uncertainty values vary from 2.31 dB up to 6.70 dB.

The redefinition of the kilogram in terms of Planck constant came into effect on 20 May 2019. The National Metrology Institute of Turkey (UME) realised the new definition by means of the oscillating magnet Kibble balance. The novel dynamical measurement procedure developed for Kibble balance in Turkey has the advantage of being less sensitive to environmental disturbances compared to the traditional Kibble balance experiments. Precise displacement measurements are performed either with Michelson or Fabry-Perot interferometers in worldwide Kibble balances. Moreover, most of them operate in a global vacuum. A commercial Michelson interferometer has been used in UME’s Kibble balance experiment. In this article, we determine the contribution of ultra-small oscillations to the Planck constant by taking simultaneous displacement measurements on two back-to-back mirrors attached to the piezoelectric transducer, undergoing an oscillatory motion with the Michelson and Fabry-Perot interferometers. The following novel measurement procedure makes such measurements possible in a regular laboratory environment. Otherwise, the experiment needs to be performed in a global vacuum. This is why we were required to investigate the resolution performances of these devices in laboratory conditions. As the expected relative uncertainty in the redefinition of kilogram is above the resolution uncertainties of both interferometers, we may conclude that a commercial Michelson interferometer will serve our purposes in our route to the redefinition of a kilogram by means of local vacuum.

We have detected and analysed narrow high-contrast coherent population trapping (CPT) resonances, which are induced in absorption of a weak monochromatic probe light beam by counterpropagating two-frequency pump radiation in a cell with rarefied caesium vapour. The experimental investigations have been performed by the example of nonclosed three level Λ-systems formed by spectral components of the D2 line of caesium atoms. The applied method allows one to analyse features of the CPT phenomenon directly at a given low long-lived level of the selected Λ-system even in sufficiently complicated spectra of atomic gases with large Doppler broadening. We have established that CPT resonances in transmission of the probe beam exhibit not only a higher contrast but also a much lesser width in comparison with well- known CPT resonances in transmission of the corresponding two-frequency pump radiation. The results obtained can be used in selective photophysics, photochemistry and ultra-high resolution atomic (molecular) spectroscopy.

This Bilateral Comparison of gauge blocks calibration by interferometry was held in 2017. The gauge blocks measured in the comparison, are short (2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 10 mm, 50 mm, 80 mm and 100 mm) and long gauge blocks (200 mm, 500 mm and 600 mm). The blocks were inspected and illustrated prior and after the comparison according to the stability. The degree of equivalence is calculated for each of the gauge blocks and the results show that there is a degree of equivalence within 1. The latest comparison, which UME had participated, is EURAMET.L-K1.2011, calibration of short and long gage blocks by interferometry. Since GULFMET is a new RMO, this comparison can provide a link to the EURAMET key comparison. KEY WORDS FOR SEARCH Gauge blocks, length measurement, interferometry, comparison Main text To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

We experimentally investigated the influence of dielectric supports used on RE102 radiated emission tests of the MIL-STD-461F EMC standard for table-top and conductive surface mounted Equipment Under Test (EUT). A variety of dielectric materials which are commonly selected as supports under EUT cables in RE102 tests were investigated by using an actual RE102 test setup in a semi anechoic chamber. Each investigated material yielded different effects on REI02 test results in comparison to the case without support, in other words, with the air support.

We experimentally investigated the resonance interaction of laser, microwave, and radio frequency (RF) fields with Cesium (Cs-133) atomic gas. The observed Zeeman components produced by means of an external static magnetic field on the double radiooptical resonance (DROR) were used as a frequency-adjustable RF field detection sensor based on the laser spectroscopy technique. The change in the RF interaction frequency of Zeeman components with the increasing level of the static magnetic field was investigated and linear dependence of the RF interaction frequency of the Zeeman components on the external static magnetic field was observed. In addition, the change in the amplitude of the Zeeman components with the level of RF fields was investigated and an approximately linear relation in certain regions was detected. We also studied the relation of the Zeeman component amplitudes with laser and microwave powers. Finally, a new approach to Helmholtz coil calibrations by using this atomic sensor is discussed.

Six European National Measurement Institutes (NMIs) have joined forces within the European Metrology Research Programme funded project NANOTRACE to develop the next generation of optical interferometers having a target uncertainty of 10 pm. These are needed for NMIs to provide improved traceable dimensional metrology that can be disseminated to the wider nanotechnology community, thereby supporting the growth in nanotechnology. Several approaches were followed in order to develop the interferometers. This paper briefly describes the different interferometers developed by the various partners and presents the results of a comparison of performance of the optical interferometers using an x-ray interferometer to generate traceable reference displacements.

This work describes the observed effects in the polarization resonance of the 5S1/2–5D5/2 atomic transitions of 87Rb atoms induced by both Faraday effects and coherent light induced anisotropy of the atoms when immersed in different levels of constant magnetic field intensities. Specifically, linear collision broadening and frequency shift of the polarization resonance, as a function of Rb atomic gas density, were measured in a temperature controlled magnetically shielded cell. From the results, density-dependent line broadening and line frequency shift were observed with the coefficients of (3.53 ± 0.09) × 10−10 and (−1.66 ± 0.09) × 10−10 cm3 Hz, respectively. Additionally, fluorescence and polarization signals illustrated an amplitude dependency on atomic density.

The absolute frequency of the f-component for the UME laser was measured with the BIPM femtosecond laser comb to be (473 612 353 602.0 ± 1.1) kHz during 3 March to 8 March, 2003 and with the UME comb to be (473 612 353 600.6 ± 1.1) kHz from 20 June to 25 June, 2005. After appropriate correction for power and modulation shifts a subkilohertz agreement between the two measurements was found. Moreover, the relative frequency stability for different UME–BIPM laser pairs is investigated using standard heterodyne techniques and Allan variance statistics.

We have detected and analysed interesting features of sub-Doppler resonances, which are induced in absorption of the weak monochromatic probe light beam (with the scanned frequency) by the counterpropagating two-frequency pumping radiation implementing the phenomenon of the coherent population trapping (CPT) on resonant.-systems of atomic levels. Our experimental investigations have been carried out on example of spectral components of the Doppler broadened D-2 line of cesium atoms. Obtained results may be used for optimization of laser frequencies stabilization on atomic transitions.

We report on the generation of 42 fs pulses at 1 mu m in a completely fiber-integrated format, which are, to the best of our knowledge, the shortest from all-fiber-integrated Yb-doped fiber lasers to date. The ring fiber cavity incorporates anomalous-dispersion, solid-core photonic crystal fiber with low birefringence, which acts as a broadband, in-fiber Lyot filter to facilitate mode locking. The oscillator operates in the stretched-pulse regime under slight normal net cavity dispersion. The cavity generates 4.7 ps long pulses with a spectral bandwidth of 58.2 nm, which are dechirped to 42 fs via a grating pair compressor outside of the cavity. Relative intensity noise (RIN) of the laser is characterized, with the integrated RIN found to be 0.026% in the 3 Hz-250 kHz frequency range. (C) 2013 Optical Society of America

A differential Fabry–Perot interferometer (DFPI) was applied for the detection of ultra-small angles in the level of nanoradian (nrad) precision. During application, down to 1 nrad angular steps were generated using the available high precision small angle generator (HPSAG) and these steps were detected using the frequency stabilised lasers as an alternative and outperforming method to conventional angle interferometers. The use of the DFPI provided the displacement measurements (further angular displacements through optical configuration) with picometre sensitivity free from linearity errors. A coefficient of 1.436 964 × 10−9 arcsec Hz−1 (about 7 × 10−6 nrad Hz−1) for the DFPI was calculated using the generated–measured traceable angular values of the HPSAG and various angular steps were measured by the DFPI using this coefficient. The tests were carried out up to the range of 0.5 arcsec (2500 nrad) in angular steps down to 1 nrad. The work is in progress under the SIB58 Angles project and aims to reduce the noise level of the HPSAG with further statistical process and later to extend the measurement range of the DFPI readings with the same optical configuration, rather than using different beam spacing configuration in the DFPI.

We have detected and analyzed narrow, high contrast coherent population trapping resonances, which appear in transmission of the probe monochromatic light beam under action of the counterpropagating two-frequency laser radiation, on example of the nonclosed three level {\Lambda}-system formed by spectral components of the Doppler broadened D2 line of cesium atoms (in the cell with the rarefied Cs vapor). These nontrivial resonances are determined directly by the trapped atomic population on the definite lower level of the {\Lambda}-system and may be used in atomic frequency standards, sensitive magnetometers and in ultrahigh resolution laser spectroscopy of atoms and molecules., Comment: 4

We have detected and analyzed narrow, high contrast coherent population trapping (CPT) resonances, which appear in transmission of the probe monochromatic light beam under action of the counter propagating two frequency laser radiation, on example of the nonclosed three level Lambda-system formed by spectral components of the Doppler broadened D-2 line of cesium atoms. Given resonances may be used in atomic frequency standards, sensitive magnetometers and in ultrahigh resolution laser spectroscopy of atoms and molecules.

Loop-antenna calibration is discussed in this tutorial. Loop antennas are especially used in low-frequency radiated-emission (RE) and radiated-susceptibility (RS) measurements and tests. These are important in commercial systems, but critical in military systems. The standards used for this purpose are reviewed, and comparisons among them are made. Results are presented with commercial as well as home-made loop antennas.

200-1000 mm lengths measured with 50-200 nm uncertainty using developed Koster’s interferometer and three frequency stabilized lasers. Absolute frequency of used stabilized He-Ne/I2, Nd:YAG/I2, ECDL/Cs are measured using Ti:Sa fs Comb.

Date of Conference: 13–16 February 2011 Conference name: Advanced Solid-State Photonics 2011 Development of an all-normal-dispersion Yb-doped fiber laser-based frequency comb is reported. Repetition-frequency stabilization to the cesium standard, amplitude and phase noise measurements indicate low-noise performance. © 2011 Optical Society of America.

We experimentally investigated the resonance interaction of laser and microwave fields with Cs-133 atomic gas in farfield and free-space conditions. The observed double radiooptical resonance (DROR) on the D-2 line of Cs atoms was used as a novel-type field sensor, based on the laser spectroscopy technique, for the detection and investigation of the time-varying magnetic field. The effects of the Cs cell length, both laser and microwave powers, and their polarizations to the changing amplitude of the DROR signal were investigated. Almost linear dependencies of the DROR signal amplitude with both laser and microwave powers have been observed. The splitting of DROR signal under a constant magnetic field was detected. The time response of the sensor system was investigated under pulsed microwave. The amplitude fluctuation of the microwave magnetic field was measured using the DROR signal and the isotropic probe simultaneously. The stability of amplitude fluctuations of the microwave field with time was analyzed by using Allan variance statistics.

Lasers from nine national metrology institutes (NMIs) were compared as part of the CCL-K11 ongoing key comparison, initiated by the 13th meeting of the Comite Consultative des Longeurs (CCL) in 2007. The absolute frequency of the f component of the R(127) 11–5 transition of molecular iodine was measured for these lasers following the technical protocol for CCL-K11. The results of these measurements are compiled in the present report. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Experimental research is carried out into the features of sub-Doppler absorption resonances caused by optical pumping and transit relaxation of Cs atoms in a thin 120-mu m cell (with rarefied Cs vapor) for ring-shaped laser beams. Such resonances are analyzed both in the transmission of the single running beam and at the interaction of counterpropagating beams for different degrees of their spatial overlapping in the cell.

In this work, the mechanical design, optical setup and temperature measurement system of a Kosters interferometer are described for the length measurements of long gauge blocks. The temperature variation of 9 mK at 15 degrees C and 2 mK at 20 degrees C was measured inside the interferometric chamber using the six air and four surface thermistors. The temperature stability is analysed by using standard deviation and Allan variance statistics.

In this work, a derivative of spectrum of polarization resonances in 5S{sub 1/2}-5D{sub 5/2} transitions of Rb atoms at different values of longitudinal magnetic field, which occurs due to the Faraday effect, was observed in a temperature controlled and magnetically shielded cell. The amplitude and spectral shape of Faraday resonances were investigated as a function of external magnetic field and the experimental results are described by a simple theoretical model.

An international comparison of the UME and BIPM He-Ne/I2 lasers was carried out. The frequency difference between the lasers was determined by the matrix method. Furthermore, the absolute frequency of the f-component for the UME laser was measured with the BIPM femtosecond laser comb to be (473 612 353 602.0 plusmn 2.2) kHz

In this work, we present electromagnetic compatibility (EMC) facilities at National Metrology Institute (UME) in Turkey. At UME for EMC test and measurements, 10 meter open area test site (OATS), 10 meter anechoic chamber and four screened rooms were constructed. OATS with a normalized site attenuation (NSA) value less than /spl plusmn/1 dB is used for antenna calibration and radiated emission measurements. Test and measurements setups for realization of testing in accordance with Mil-Std-46 IE, EN commercial standards, and telecommunication (ETSI) standards included specific absorption rate (SAR) and automotive standards are under developing in anechoic chamber and screened rooms. Anechoic chamber has capability as used semi or fully and four screened rooms have frequency capability between 9 kHz and 40 GHz and electric field strength value up to 200 V/m. is used, for testing at anechoic chamber and four screened rooms.

Electromagnetic radiations from GSM (global service for mobile communication) base stations were measured in the far-field region by using directional antennas (biconical-log/hybrid, horn antenna) and isotropic electric field probes and detected signals were analyzed by using low-resolution bandwidth (30 Hz) spectrum analyzer and field probe meter respectively. Electric fields of the electromagnetic radiations were measured in x, y and z orthogonal directions with vertical and horizontal polarizations. Amplitude fluctuation of electromagnetic radiation of GSM base station were detected at long time interval (more than 8 hours) and analyzed using standard deviation and Allan variance statistics. The results and uncertainties of the electric field measurements by biconical-log/hybrid antenna, horn antenna and electric field probe were compared. The measured electric field values of GSM base stations were compared to the value of reference levels for general public exposure to time-varying electric fields limits of ICNRP guidelines.

X-ray interferometry is emerging as an important tool for dimensional nanometrology both for sub-nanometre measurement and displacement. It has been used to verify the performance of the next generation of displacement measuring optical interferometers within the European Metrology Research Programme project NANOTRACE. Within this project a more detailed set of comparison measurements between the x-ray interferometer and a dual channel Fabry-Perot optical interferometer (DFPI) have been made to demonstrate the capabilities of both instruments for picometre displacement metrology. The results show good agreement between the two instruments, although some minor differences of less than 5 pm have been observed.

Lasers from three national metrological institutes (NMIs) have been measured following the protocol of the BIPM.L-K11 ongoing key comparison initiated by the Comit? Consultative des Longueurs (CCL) 11th meeting in 2003. The absolute frequency of the f component of the R(127) 11-5 transition at 633 nm was measured for two of these lasers in their home institutes, AIST/NMIJ and UME, while the b5 component of the R(106) 28-0 transition at 543 nm was measured on a standard from NIM at the BIPM. The results of these measurements are compiled in the present paper. The comparison reports, as communicated by each participant, are included as Appendices. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Summary form only given. An intense research effort has been channelled into improving mode-locked Yb-fiber oscillators in recent years. Despite efforts in all-normal dispersion oscillators, dispersion management is evidently necessary to reach pulse durations below 50 fs. This is implemented most commonly with bulk optical components in Yb-doped fiber lasers. Increased robustness remains a valuable trait, for which all-fiber-integration is highly desirable. Photonic crystal fibers (PCF) with anomalous dispersion have small mode field diameters, enhancing nonlinear effects and usually are birefringent. The first mode-locked laser to incorporate a PCF was reported in 2002 [1]. However, mode-locking was not self-starting owing to the residual birefringence of the PCF Since then, a number of dispersion-managed Yb-doped fiber lasers using PCFs and all-fiber-integrated lasers have been reported. After 10 years, no all-fiber-integrated Yb-fiber laser has been demonstrated to support pulses below 60 fs [2]. Here, we present an all-fiber-integrated, dispersion-managed Yb-doped oscillator incorporating a segment of PCF. The oscillator is self-starting and generates pulses with a spectral bandwidth of 58.2 nm, compressible externally to 42 fs. The pulse evolution had to be carefully designed to achieve this performance: the residual birefringence that prevented self-starting operation of the first fiber laser with PCF [1] is actively employed to construct an intra-cavity Lyot filter to ease initiation of mode-locking [3]. The filtering effect has been characterized using a Sagnac loop seeded by a broadband amplified emissions source (Fig. 1(a)). Numerical simulations were performed to investigate the mode-locking dynamics (Fig. 1(b)). The pulse duration and spectral bandwidth decrease in the first half of the gain fiber, then grow essentially self-similarly. Initial compression in the PCF is followed by stretching, accompanying with spectral broadening and narrowing. The pulse energy is reduced to ~78 pJ in the PCF to prevent excessive nonlinear effects. This requires an intra-cavity gain of 60 to reach the maximum pulse energy of 4.7 nJ. While the overall evolution is consistent with stretched-pulse operation, influence of self-similar evolution in the gain fiber is observed due to the strong nonlinearity, which counteracts gain narrowing.In conclusion, we have demonstrated an all-fiber-integrated Yb-doped laser with an anomalous-dispersion PCF. The compressed pulse duration is 42 fs, which is the shortest, to the best of our knowledge, from an all-fiber oscillator at 1 μm. These results have been achieved 10 years after the first mode-locked oscillator with PCF was demonstrated, which was plagued with non-self-starting operation and limited long-term stability primarily due to the residual birefringence of the PCF. Here, the birefringence of the PCF is exploited to function as a fiber-integrated Lyot filter for stable and self-starting mode-locking. Nonlinear effects and spectral shaping throughout the cavity is carefully managed to avoid multiple pulsing.

Date of Conference: 16-21 May 2010 Conference Name: Conference on Lasers and Electro-Optics, CLEO-QELS 2010 Repetition-frequency stabilization of a Yb-doped fiber laser to the Cesium standard is reported. Laser amplitude and phase noise is characterized. Performance is limited to 2x10-14 at 100000 averaging time by intrinsic stability of the Cs-standard.

Date of Conference: 12-16 May 2013 Conference Name: Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference, CLEO EUROPE/IQEC 2013 Despite the prevalence of fiber frequency combs around 1.5 μm, few fully stabilized frequency combs have been demonstrated around 1.0 μm, despite the generally superior performance of Yb-fiber lasers compared to Er-fiber lasers. Short pulses are to generate coherent supercontinuum using anomalous dispersion regime of microstructured fibers. Near-zero cavity dispersion is highly desirable for low-noise frequency comb performance. Here, we report a Yb-doped fiber laser that operates at net-zero group-velocity dispersion and produces pulses that can be compressed externally to 33-fs. The frequency comb generated by this system is repetition-and carrier-envelope-phase-locked to Cs atomic clocks. The laser oscillator design is based on a novel algorithmic methodology, which allows us to design cavities to meet specific requirements; in this case, there was the need to generate as short pulses as possible, while having several nJ of pulse energy and the cavity at strictly zero total dispersion.

Date of Conference: 1-6 May 2011 Development of an all-normal-dispersion Yb-doped fiber laser-based frequency comb is reported. Repetition-frequency stabilization to the cesium standard, amplitude and phase noise measurements indicate low-noise performance. ©2011 Optical Society of America.