Within the DLR project COMPASSO, optical clock and link technologies will be evaluated in space on the Bartolomeo platform attached to the Columbus module of the ISS. The system utilizes two iodine-based frequency references, a frequency comb, an optical laser communication and ranging terminal and a GNSS disciplined microwave reference. While COMPASSO is specifically dedicated to test optical technologies relevant for future satellite navigation (i.e. Galileo), the technologies are also crucial for future missions related to Earth observation and science. The optical frequency reference is based on modulation transfer spectroscopy (MTS) of molecular iodine near a wavelength of 532 nm. An extended cavity diode laser (ECDL) at a wavelength of 1064 nm is used as light source, together with fiber-optical components for beam preparation and manipulation. The laser light is frequency-doubled and sent to a mechanically and thermally highly stable free-beam spectroscopy board which includes a 20 cm long iodine cell in four-pass configuration. The iodine reference development is lead by the DLR-Institute of Quantum Technologies and includes further DLR institutes, space industry and research institutions. Phase B of the project will be finalized soon and an Engineering Model of the iodine reference, which represents the flight models in form, fit and function, will be realized by mid 2023. The launch of the COMPASSO payload is planned for 2025. Additional presentation content can be accessed on the supplemental content page.
We investigate the optical performance of anti-reflective coatings subject to high temperatures and the presence of iodine gas to determine the most suitable technological process for iodine-filled absorption cell production. Two unwanted effects need to be avoided or mitigated. One is the settling of iodine gas in the coating structure, which reduces the transmittance of the cell windows. The other is the thermally induced spectral shift which limits the effect of the antireflective coating. We investigate the thermal resistance of TiO2 and Ta2O5 based coatings produced by electron beam evaporation (e-beam) and plasma ion-assisted deposition (PIAD). We prepared sets of quartz samples subject to a range of temperatures and the presence of iodine gas. We show that the choice of the coating technique and annealing procedure can mitigate the aforementioned effects.
We present an experimental study of the method using a spatial light modulator for correction of the wavefront reflected from the optically rough surface. This method is based on the detection of the mutual phase differences between different regions of the wavefront that correspond to the constructive interference. We study the capabilities of this method from the metrological point of view for the ground glass samples characterized by several different levels of roughness. The resulting wavefront correction is tested in dependence on the measurement parameters settings and is verified by analyzing two specific patterns generated by the spatial light modulator.
We investigate motion of particle pairs optically bound in tractor beam. The tractor beam can exert a negative force on a scatterer, in contrast to the pushing force associated with radiation pressure, which can pull the scatterer towards the light source. The particle movements can be enhanced by long-range interaction between illuminated objects, called optical binding. We study optical binding of two micro-particles in various geometrical configurations and investigate their motional behaviour in tractor beam. We demonstrate that motion of two optically bound objects strongly depends on their mutual distance and spatial orientation. Such configuration-dependent optical forces add an extra flexibility to our ability to control matter with light. Understanding these interactions opens the door to new applications involving the sorting or delivery of colloidal self-organized structures.
We report on the results of the common collaborative project of applied research where the Institute of Scfientific Instruments (ISI) of the Academy of Sciences of the Czech Republic and a company Meopta – optika joined their effort in development of high-precision interferometric systems for dimensional metrology and nanometrology. This research exploits previous results in the field of laser standards of optical frequencies and the methodology of interferometric metrology of length together with detection systems of interference signals and their processing at the ISI and the production technology of precise optical components at Meopta – optika. Within this project we developed a compact, solid-state frequency stabilized laser referenced to iodine transitions and technology of iodine cells for laser frequency stabilization. A fundamental setup of the laser interferometer has been arranged and tested. The company Meopta – optika contributes with development of new technology for processing and polishing of high-precision flat-surface optical components.
We report on the results of the common collaborative project of applied research where the Institute of Scientific Instruments (ISI) of the Academy of Sciences of the Czech Republic and a company Meopta - optika joined their effort in development of high-precision interferometric systems for dimensional metrology and nanometrology. This research exploits previous results in the field of laser standards of optical frequencies and the methodology of interferometric metrology of length together with detection systems of interference signals and their processing at the ISI and the production technology of precise optical components at Meopta – optika.
The main aim of the project is a design of a complex interferometric measuring system in a form of a prototype serving as a master for further production. It concept is a modular family of components configurable for various arrangements primarily for multi-axis measurements in nanotechnology and surface inspection. Within this project we developed a compact, solid-state frequency stabilized laser referenced to iodine transitions and technology of iodine cells for laser frequency stabilization. A fundamental setup of the laser interferometer has been arranged and tested. The company Meopta – optika contributes with development of new technology together with a design of a machine for processing and polishing of high-precision flat-surface optical components.
In this contribution we present a technology for thin film optical coating deposition and laser induced damage threshold (LIDT) testing of coatings available at the Institute of Scientific Instruments. We use our e-beam evaporation coating system equipped with plasma ion assisted deposition to produce various optical coatings and a LIDT test station to test them. The station allows for testing at room temperature as well as cryogenic conditions.
In this contribution we present a technology for deposition and testing of interference coatings for optical components
designed to operate as in power pulsed lasers. We have designed and are in the process of building a testing apparatus
which serves as an addition to our existing optical coating production facility. This allows us to prepare a coating which
can then tested and the results might be used to optimize it. The test samples are placed in a vacuum chamber, cooled
down to approximately 120K and illuminated by a pulsed laser to determine laser damage threshold of the coatings under
conditions similar to real life operation. Optical microscopy and spectrophotometer measurements are going to be used
for coating investigation after the conducted experiments.
We present a measuring technique for displacement and position sensing over a limited range with detection of standingwave pattern inside of a passive Fabry-Perot cavity. The concept considers locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Sensing of the interference maxima and minima within the cavity along the beam axis has been tested and proven with a low loss photoresistive photodetector based on a thin polycrystalline silicon layer.
We present a measuring technique for displacement and position sensing over a limited range with detection of standingwave pattern inside of a passive Fabry-Perot cavity. The concept considers locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Fixing the length of the cavity to e.g. a highly stable mechanical reference allows to stabilize wavelength of the laser in air and thus to eliminate especially the faster fluctuations of refractive index of air due to air flow and inhomogeneities. Sensing of the interference maxima and minima within the cavity along the beam axis has been tested and proven with a low loss photoresistive photodetector based on a thin polycrystalline silicon layer. Reduction of losses was achieved thanks to a design as an optimized set of interference layers acting as an antireflection coating. The principle is demonstrated on an experimental setup.
We present an overview of approaches to the design of nanometrology coordinates measuring setup with a focus on
methodology of nanometrology interferometric techniques and associated problems. The design and development of a
nanopositioning system with interferometric multiaxis monitoring and control involved for scanning probe microscopy
techniques (primarily atomic force microscopy, AFM) for detection of the sample profile is presented. Coordinate
position sensing allows upgrading the imaging microscope techniques up to quantified measuring. Especially imaging
techniques in the micro- and nanoworld overcoming the barrier of resolution given by the wavelength of visible light are
a suitable basis for design of measuring systems with the best resolution possible. The practical measurement results of
active compensation system for positioning angle errors suppression are presented as well as the analysis of overall
achievable parameters. The system is being developed in cooperation with the Czech metrology institute and it is
intended to operate as a national nanometrology standard combining local probe microscopy techniques and sample
position control with traceability to the primary standard of length.
We present an interferometric technique based on differential interferometry setup for measurement in the subnanometer
scale in atmospheric conditions. One of the important limiting factors in any optical measurement are fluctuations of the
refractive index of air representing a source of uncertainty traditionally compensated when the index is evaluated
indirectly from the physical parameters of the atmosphere. Our proposal is based on the concept of overdetermined
interferometric setup where a reference length is derived from a mechanical frame made from a material with very low
thermal coefficient on the 1*E-8 level. The technique allows to track the variations of the refractive index of air on-line
directly in the line of the measuring beam and to compensate for the fluctuations. The optical setup consists of three
interferometers sharing the same beam path where two measure differentially the displacement while the third evaluates the changes in the measuring range acting as a tracking refractometer. The principle is demonstrated on an experimental setup and a set of measurements describing the performance is presented.
In scanning probe microscopy laser interferometers are usually used for measuring the position of the probe tip with a
metrological traceability. As the most of the AFM setups are designed to work under standard atmospheric conditions
the changes of the refractive index of air have an influence to measured values of the length with 1.0exp(-4) relatively.
In order to achieve better accuracies the refractive index of air has to be monitored continuously and its instantaneous
value has to be used for compensating the lengths measured by all of the interferometric axes. In the presented work we
developed a new concept of an electronic unit which is able to monitor the refractive index of air on basis of
measurement of ambient atmospheric conditions: temperature, humidity, pressure of the air and the CO2 concentration. The data processing is based on Ciddor equation for calculating the refractive index of air. The important advantage of the unit is a very low power consumption of the electronics so the unit causes only negligible temperature effects to the
measured environment. The accuracy of the indirect measuring method employed by the unit was verified. We tested
the accuracy in comparison with a direct method of measuring refractive index of air based on an evacuatable cell
placed at the measuring arm of a laser interferometer. An experimental setup used for verification is presented together with a set of measurements describing the performance. The resulting accuracy of the electronic unit falls to the 4.1 exp(-7) relatively.
In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the Eropean plan to build a new generation of large research facilities selected by the the Eropean Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material or the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of hear need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consistion of a vacuum chamber an a cooling system. The samples were placed into the vacuum chamber which was evacuated and them the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.
We present a concept combining traditional displacement incremental interferometry with a tracking refractometer following the fluctuations of the refractive index of air. This concept is represented by an interferometric system of three Michelson-type interferometers where two are arranged in a counter-measuring configuration and the third one is set to measure the changes of the fixed length, here the measuring range of the overall displacement. In this configuration the two counter-measuring interferometers have identical beam paths with proportional parts of the overall one. The fixed interferometer with its geometrical length of the measuring beam linked to a mechanical reference made of a high thermal-stability material (Zerodur) operates as a tracking refractometer monitoring the atmospheric refractive index directly in the beam path of the displacement measuring interferometers. This principle has been demonstrated experimentally through a set of measurements in a temperature controlled environment under slowly changing refractive index of air in comparison with its indirect measurement through Edlen formula. With locking of the laser optical frequency to fixed value of the overall optical length the concept can operate as an interferometric system with compensation of the fluctuations of the refractive index of air.
In this contribution we present a technology for deposition and testing of interference coatings for optical components designed to operate in power pulsed lasers. The aim of the technology is to prepare components for high power laser facilities such as ELI (Extreme Light Infrastructure) or HiLASE. ELI is a part of the European plan to build a new generation of large research facilities selected by the European Strategy Forum for Research Infrastructures (ESFRI). These facilities rely on the use of diode pumped solid state lasers (DPSSL). The choice of the material for the lasers' optical components is critical. Some of the most important properties include the ability to be antireflection and high reflection coated to reduce the energy losses and increase the overall efficiency. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. The conducted experiments served as preliminary tests of laser damage threshold measurement methodology that we plan to use in the future. We designed a special apparatus consisting of a vacuum chamber and a cooling system. The samples were placed into the vacuum chamber which was evacuated and then the samples were cooled down to approximately 120K and illuminated by a pulsed laser. Pulse duration was in the nanosecond region. Multiple test sites on the sample's surface were used for different laser pulse energies. We used optical and electron microscopy and spectrophotometer measurements for coating investigation after the conducted experiments.
In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research facility) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of the material for the lasers' active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG and Yb:CaF2 samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress from temperature shocks, etc. Coated samples were placed into cryogenic environment in order to simulate conditions similar to those in real life operation. Optical microscopy was used for coating investigation after the conducted experiments.
We present techniques oriented to improvement of precision in incremental interferometric measurements of displacements over a limited displacement range. The wavelength of the coherent laser source is here directly stabilized to a mechanical reference and not to a reference of any optical frequency. This may represent a reduction of uncertainty linking the laser wavelength not to indirectly evaluated refractive index but to the setup mechanics which cannot be completely eliminated. Here we suggest an approach where the traditional interferometers are replaced by a passive Fabry-Perot cavity with position sensing using an intracavity transparent photodetector.
In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of material for the lasers active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG, Yb:CaF2 and Yb:KGW samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress resulting from temperature shocks, etc. Coated samples were placed in a specially designed cryogenic apparatus in order to simulate conditions similar to those in real life operation. Optical microscopy and spectrophotometer measurements were used for coating investigation after the conducted experiments.
In construction of highly mechanically stable measuring devices like AFM microscopes or nano-comparators the use of low expansion materials is very necessary. We can find Zerodur ceramics or ULE glasses used as a frame or basement of these devices. The expansion coefficient of such low-expansion materials is lower than 0.01 x 10-6 m•K-1. For example in case of a frame or basement 20 cm long it leads to a dilatation approximately 4 nm per 1 K. For calculation of the total uncertainty of the mentioned measuring devices the knowledge of the thermal expansion coefficient of the frame or basement is necessary. In this work we present a method, where small distance changes are transformed into rf-frequency signal. The frequency of this signal is detected by a counter which measures the value of the frequency with respect to an ultra-stable time-base. This method uses a Fabry-Perot cavity as a distance measuring tool. The spacer of the optical resonator is made from the investigated low-expansion material. It is placed into a vacuum chamber where the inside temperature is controlled. A selected mode of the femtosecond frequency of the femtosecond comb which represent the distance changes of the optical resonator. The frequency is measured by the rf-counter which is synchronized by a time-base signal from an atomic clock. The first results show the resolution of the method in the 0.1 nm order. Therefore the method has a potential in characterisation of materials in the nanoworld.
In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of material for the lasers active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG, Yb:CaF2 samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress resulting from temperature shocks, etc. Coated samples were placed into cryogenic environment in order to simulate conditions similar to those in real life operation. Optical microscopy was used for coating investigation after the conducted experiments.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.