Sergey Vasilyev

Demonstration of high self-Raman laser performance of a diode-pumped SrMoO4:Nd3+ crystal.

Passively Q-switched self-Raman laser oscillations in the SrMoO4:Nd3+ crystal optically pumped by a laser diode (LD) at 804 nm are demonstrated for the first time to our knowledge. Output parameters of LD-pumped SrMoO4:Nd3+ laser were investigated in free-running, passively Q-switched, and self-Raman regimes of laser operation, over a wide range of pulse repetition rates (8.5-85 kHz). A pulse energy of 21 microJ was measured in the self-Raman regime at 1163 nm (first Stokes) wavelength, which is 6 times higher than that for the GdVO4:Nd3+ self-Raman laser of similar design.

Broadly tunable single-frequency cw mid-infrared source with milliwatt-level output based on difference-frequency generation in orientation-patterned GaAs

A narrow-linewidth mid-IR source based on difference-frequency generation of an amplified 1.5 microm diode laser and a cw Tm-doped fiber laser in orientation-patterned (OP) GaAs has been developed and evaluated for spectroscopic applications. The source can be tuned to any frequency in the 7.6-8.2 microm range with an output power of 0.5 mW. The measured characteristics of the OP-GaAs sample demonstrate a high quality of the material.

The space optical clocks project: Development of high-performance transportable and breadboard optical clocks and advanced subsystems

The use of ultra-precise optical clocks in space (“master clocks”) will allow for a range of new applications in the fields of fundamental physics (tests of Einsteins theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission, improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE-2010-1 project no. 263500 (SOC2) (2011–2015) aims at two “engineering confidence“, accurate transportable lattice optical clock demonstrators having relative frequency instability below 1×10−15 at 1 s integration time and relative inaccuracy below 5×10−17. This goal performance is about 2 and 1 orders better in instability and inaccuracy, respectively, than todays best transportable clocks. The devices will be based on trapped neutral ytterbium and strontium atoms. One device will be a breadboard. The two systems will be validated in laboratory environments and their performance will be established by comparison with laboratory optical clocks and primary frequency standards. In order to achieve the goals, SOC2 will develop the necessary laser systems - adapted in terms of power, linewidth, frequency stability, long-term reliability, and accuracy. Novel solutions with reduced space, power and mass requirements will be implemented. Some of the laser systems will be developed towards particularly high compactness and robustness levels. Also, the project will validate crucial laser components in relevant environments. In this paper we present the project and the results achieved during the first year.

Spectrally narrow, long-term stable optical frequency reference based on a Eu3+:Y2SiO5 crystal at cryogenic temperature.

Using an ultrastable continuous-wave laser at 580 nm we performed spectral hole burning of Eu(3+):Y(2)SiO(5) at a very high spectral resolution. The essential parameters determining the usefulness as a macroscopic frequency reference, linewidth, temperature sensitivity, and long-term stability, were characterized using a H-maser stabilized frequency comb. Spectral holes with a linewidth as low as 6 kHz were observed and the upper limit of the drift of the hole frequency was determined to be 5±3 mHz/s. We discuss the necessary requirements for achieving ultrahigh stability in laser frequency stabilization to these spectral holes.

Robust frequency stabilization of multiple spectroscopy lasers with large and tunable offset frequencies

We have demonstrated a compact, robust device for simultaneous absolute frequency stabilization of three diode lasers whose carrier frequencies can be chosen freely relative to the reference. A rigid ULE multicavity block is employed, and, for each laser, the sideband locking technique is applied. A small lock error, computer control of frequency offset, wide range of frequency offset, simple construction, and robust operation are the useful features of the system. One concrete application is as a stabilization unit for the cooling and trapping lasers of a neutral-atom lattice clock. The device significantly supports and improves the clocks operation. The laser with the most stringent requirements imposed by this application is stabilized to a line width of 70 Hz, and a residual frequency drift less than 0.5 Hz/s. The carrier optical frequency can be tuned over 350 MHz while in lock.

Towards Neutral-atom Space Optical Clocks (SOC2): Development of high-performance transportable and breadboard optical clocks and advanced subsystems

The use of ultra-precise optical clocks in space (“master clocks”) will allow for a range of new applications covering the fields of fundamental physics (tests of Einsteins theory of General Relativity, time and frequency metrology by means of the comparison of distant terrestrial clocks), geophysics (mapping of the gravitational potential of Earth), and astronomy (providing local oscillators for radio ranging and interferometry in space). Within the ELIPS-3 program of ESA, the “Space Optical Clocks” (SOC) project aims to install and to operate an optical lattice clock on the ISS towards the end of this decade, as a natural follow-on to the ACES mission (which is based on a cesium microwave clock), improving its performance by at least one order of magnitude. The payload is planned to include an optical lattice clock, as well as a frequency comb, a microwave link, and an optical link for comparisons of the ISS clock with ground clocks located in several countries and continents. Undertaking a necessary step towards optical clocks in space, the EU-FP7-SPACE2010-1 project no. 263500 (SOC2) (2011-2015) will develop two “engineering confidence“, accurate transportable lattice optical clock demonstrators having relative frequency instability below 1×10 -15 at 1s integration time and relative inaccuracy below 5×10 -17 . This goal performance is about 2 and 1 orders better in instability and inaccuracy, respectively, than today’s best transportable clocks. The devices will be based on trapped neutral ytterbium and strontium atoms. One device will be a breadboard. The two systems will be validated in laboratory environments and their performance will be established by comparison with laboratory optical clocks and primary frequency standards. In order to achieve the goals, SOC2 will develop the necessary laser systems adapted in terms of power, linewidth, frequency stability, long-term reliability, and accuracy. Novel solutions with reduced space, power and mass requirements will be implemented. Some of the laser systems will be developed towards particularly high compactness and robustness levels. Also, the project will validate crucial laser components in relevant environments. This paper will give an overview of the project and of the results achieved during theProject ReCover aims at developing beyond state-of-the-art service capabilities to support fighting deforestation and forest degradation in the tropical region. The service capabilities mean provision of a monitoring system of forest cover, forest cover changes, and biomass including a robust accuracy assessment. This paper presents the forest monitoring concept and the first results on Recover study sites. ReCover contributes to the efforts to reduce the errors in the estimates of the terrestrial carbon balance that result from uncertain rates of tropical deforestation. It develops methods for the REDD (Reducing Emissions from Deforestation and Forest Degradation) process by developing and implementing satellite image based methods for the monitoring of tropical forests. The REDD will be a major driver for the development of more effective and more reliable procedures for the monitoring of tropical forests. Many developing countries lack human resources and funding for detailed forest inventories. This paper reports the achievements of the first year of ReCover and the results of services in Mexico, Guyana, Democratic Republic of Congo, and Fiji. Altogether 42 products were delivered to the users of Recover. The accuracy in forest and non-forest classification was from 85 % to 91 % with one exception (76 %).

Robust, frequency-stable and accurate mid-IR laser spectrometer based on frequency comb metrology of quantum cascade lasers up-converted in orientation-patterned GaAs

Summary form only given. The mid-infrared (MIR) spectral range (λ > 4.5 μm) is of interest in both applied and fundamental spectroscopy, for diverse applications such as trace gas detection and molecular frequency metrology. Approaches currently pursued for enabling MIR spectroscopy with accurate frequency control are based on generating the desired radiation by down-conversion, either of frequency combs or of cw near-infrared (NIR) sources. Such downconverted sources, however, typically have low power per frequency interval.Upconversion of the MIR radiation to the NIR range in principle provides a way to take advantage of the frequency measurement capabilities of the standard Erbium-fiber frequency comb. In previous work, the spectral range λ <; 4.5 μm (Muecke et al. (2004), Borri et al (2010), Gatti et al (2011)) and λ U 9.1 μm (Amy-Klein et al. (2004, 2005), Mills et al. (2012)) were successfully covered, by using the standard nonlinear-optical material periodically poled lithium niobate and AgGaS2, respectively. In this work we present a simple and robust solution applicable to the whole spectral range 4.5 μm <; λ <; 12 μm, based on the use of quantum cascade lasers (QCL) as the source of spectroscopic radiation. Orientationpatterned gallium arsenide is used as the nonlinear material to generate the sum-frequency wave of a QCL with a standard high-power cw Erbium fiber laser (1.5 μm). The sum-frequency wave is further amplified by a semiconductor amplifier. Continuous measurements of this waves and the fiber lasers frequency by a standard Erbium fiber frequency comb provide signals allowing frequency control of the MIR laser. The proof of principle is performed with a quantum cascade laser at 5.4 μm, which is upconverted to 1.2 μm. Both the QCL and the cw fiber laser are stabilized to the frequency comb using feedback control. At the same time, the absolute QCL frequency is determined, with 100 kHz-level inaccuracy, relative to an atomic frequency reference. We achieved a frequency instability to sub-10 kHz level and also long-term stability (Fig. 1 left) and controlled frequency tuning (Fig. 1 right). The implementation of the method is robust and relatively simple. All components except the OP-GaAs crystal are standard, i.e. frequency comb, atomic reference, 1.5 μm cw high-power single-frequency fiber laser, semiconductor amplifier, detectors, etc. The whole system is nearly turn-key, requiring only short warm-up time, and operates frequency-stably over multiple hours. This is an important advantage for use of the apparatus as part of more complex experimental set-ups. With its current performance and its ease of use, this type of spectrometer could be used e.g. for photoacoustic spectroscopy, multipass-cell spectroscopy, integrated cavity output spectroscopy, or Lamb-dip spectroscopy.

Compact All-Solid-State Continuous-Wave Single-Frequency UV Source for Laser Cooling of Beryllium Ions

A compact setup for generation, absolute frequency stabilization, and precision tuning of the UV laser radiation at 313 nm was developed and tested. The maximum output power of the source is 100 mW.

A Widely Tunable CW Mid-Infrared Spectrometer Based on Difference Frequency Generation in Orientation-Patterned GaAs

A widely tunable difference frequency generation based mid-infrared spectrometer for the detection of sulfur dioxide (SO2), nitrous oxide (N2O), and methane (CH4) above 7 µm has been developed for industrial applications.

Demonstration of internal state laser cooling of molecular ions

One important prerequisite for high-precision spectroscopic measurements on cold molecules is the ability to control the translational as well as internal degrees of freedom of the molecules. For neutral molecules ultracold translational temperatures and recently also transfer to the internal ground state with up to 80% efficiency have been achieved [1]. For molecular ions of a variety of species, the motion can be cooled efficiently via sympathetic cooling by laser cooled atomic ions down to temperatures in the milliKelvin range [2]. Cooling of the internal degrees of freedom has so far not been possible in non-cryogenic environments since the sympathetic cooling does not affect the internal degrees of freedom and the black-body radiation will distribute the molecular population over several ro-vibrational states [3]. Here, we present an experiment which constitutes to the best of our knowledge the first demonstration of an all-optical internal state cooling scheme for molecular ions.