In this proceeding, we present the development of the Optical Ground Support Equipment (OGSE) used for payload-level testing of the Ariel space mission. Ariel is an ESA mission that will use the transit spectroscopy method to observe the atmospheres of nominally ~1000 exoplanets. Ariel is a 1 m class cryogenic (∼ 40 K) space telescope that will be placed in a halo orbit around the Earth-Sun L2 point. To detect atmospheric molecular absorption features, Ariel will produce medium-resolution spectra (R ≥ 15) using three spectroscopic channels covering 1.1 – 7.9 μm as well as having photometric channels covering 0.5 – 1.1 μm. To achieve Ariel’s science goals, the payload requires detailed calibration and performance verification. The payload-level performance verification of the Ariel payload will take place in 2026 in a 5-meter vacuum chamber at the Rutherford Appleton Laboratory’s Space Instruments Test Facility. The payload will be enclosed in a Cryogenic Test Rig (CTR) to provide a space-like (~35 K) thermal environment and is illuminated by the OGSE. The OGSE provides point as well as extended source illumination across Ariel’s full wavelength range. The OGSE design also includes a series of mechanisms and features to enable the various illumination conditions required to test Ariel. Here we report design updates to the OGSE after a preliminary design review (PDR). Since PDR, there have been substantial revisions to the OGSE architecture. In this proceeding, we describe the evolution of the OGSE architecture. The updated OGSE design will then be presented.
The future ARIEL Space Mission aims achieving a photometric precision down to the parts-per-million (ppm) level, over periods longer than ten hours. This required level of sensitivity is crucial to obtain valuable information about the properties of the exoplanet and its atmosphere. The Institute of Astrophysics and Space Sciences is responsible for the development of the visible and near-infrared (Vis-NIR) illumination sub-system, integrated in ARIEL’s Optical Ground Support Equipment (OGSE). This study presents an in-depth analysis of two main component of the Vis-NIR illumination sub-system: a Quartz Tungsten-Halogen (QTH) calibration light source and an extended Indium Gallium Arsenide (InGaAs) reference detector, tested under cryogenic conditions. It is shown that these two components are compliant with the ARIEL's requirements, allowing the mission to obtain spectroscopic and photometric time series with the stability needed to identify signal variations from 20 ppm to 100 ppm, over a 10-hour observation period.
Event-activated biological-inspired subwavelength (sub-λ) optical neural networks are of paramount importance for energy-efficient and high-bandwidth artificial intelligence (AI) systems. Despite the significant advances to build active optical artificial neurons using for example phase-change materials, lasers, photodetectors, and modulators, miniaturized integrated sources and detectors suited for few-photon spike-based operation and of interest for neuromorphic optical computing are still lacking. In this invited paper we outline the main challenges, opportunities, and recent results towards the development of interconnected neuromorphic nanoscale light-emitting diodes (nanoLEDs) as key-enabling artificial spiking neuron circuits in photonic neural networks. This method of spike generation in neuromorphic nanoLEDs paves the way for sub-λ incoherent neural circuits for fast and efficient asynchronous brain-inspired computation.
A fiber fed, wide beam collimator was developed as a tool to support the Assembly, Integration and Verification (AIV) tasks associated to the integration of the ESA-PLATO telescope unit (TOU) to the focal plane, for the 26 cameras that are going to be assembled at the Centre Spatial de Liége (CSL). This collimator will work as source for the alignment process at ambient temperature, providing a white light beam that must comply with a series of critical requirements, namely high spatial uniformity over an clear aperture of 150 mm (better than 85%), Wavefront Error associated to focus aberration at the level of λ/30 rms and high flux stability over time (2% in 24h). This paper will present the steps taken towards the development, manufacture and integration of this collimator, as well as the tests devised to evaluate requirements compliance.
In this work we present a technique to perform long and absolute distance measurements based on mode-locked diode lasers. Using a Michelson interferometer, it is possible to produce an optical cross-correlation between laser pulses of the reference arm with the pulses from the measurement arm, adjusting externally their degree of overlap either changing the pulse repetition frequency (PRF) or the position of the reference arm mirror for two (or more) fixed frequencies. The correlation of the travelling pulses for precision distance measurements relies on ultra-short pulse durations, as the uncertainty associated to the method is dependent on the laser pulse width as well as on a highly stable PRF.
Mode-locked Diode lasers are a very appealing technology for its inherent characteristics, associated to compactness, size and efficiency, constituting a positive trade-off with regard to other mode-locked laser sources. Nevertheless, main current drawback is the non-availability of frequency-stable laser diodes. The laser used is a monolithic mode-locked semiconductor quantum-dot (QD) laser. The laser PRF is locked to an external stabilized RF reference. In this work we will present some of the preliminary results and discuss the importance of the requirements related to laser PRF stability in the final metrology system accuracy.
In this work we present a study on three types of semiconductor mode-locked lasers as possible sources for a high precision absolute distance metrology measurement concept based on pulse repetition frequency (PRF) sweep. In this work, we evaluated one vertical emission laser and two transversal emission sources. The topology of the gain element is quantum-well, quantum-dot and quantum-dash, respectively. Only the vertical emission laser has optical pump, whilst the others operate with electric pumping. The quantum-dash laser does not have a saturable absorber in its configuration but relies on a dispersion compensating fiber for generating pulses. The bottleneck of vertical emission laser is his high power density pump (4.5W/165μm), increasing the vulnerability of damaging the gain element. The other lasers, i.e., the single (quantum-dash) and double section (quantum-dot) lasers present good results either in terms of applicability to the metrology system or in terms of robustness. Using RF injection on the gain element, both lasers show good PRF stabilization results (better than σy(10ms) = 10−9 ) which is a requirement for the mentioned metrology technique.
In this study we present a scheme for modelocked laser stabilization that narrows the RF linewidth and lowers the timing jitter. The aim of this scheme is to stabilize the pulse repetition frequency (PRF) to be used in an absolute long distance measurement technique. In the most of the stabilization schemes, PRF is kept constant, however in this scheme; the PRF is required to perform a sweep, while achieving a relative error in the order of 10-8 or better within the tuning range. The laser used is a symmetrical cladding single section InAs/InP quantum dash emitting at 1550 nm and with a pulse repetition frequency of 4.37 GHz The techniques proposed for stabilization are hybrid mode-locking and optical feed-back. In hybrid modelocking, the PRF is locked to the local oscillator (LO), lowering the RF linewidth and the jitter. By performing a frequency modulation of LO, the PRF is modulated. The optical feedback technique uses a fraction of the output radiation that is fed back into the laser cavity after a certain delay. If the delay line is correctly adjusted, this will reduce the timing jitter of laser. The progress in this technique is in the synchronization of the LO with the delay line, combining the benefits of both techniques. Performing a sweep in PRF, the synchronization circuit adjusts the delay line to match incoming pulses within the cavity. Preliminary results are showed.
Heterodyne laser interferometry has proved to be a valuable technique for high accuracy optical displacement metrology. In many applications in science and engineering, it is required a highly accurate measurement of multiple degrees of freedom of a critical device with regard to a mechanical system reference. An example is the primary calibration of standard accelerometers by interferometry. In this context, it is proposed a multi-channel system based on a heterodyne interferometer for simultaneous measurement of piston and wobble of the accelerometer top surface. The implemented system is based on a Michelson interferometer, with four parallel beams of equal intensity that enable simultaneous measurement of different points of the surface. The parallel approach reduces the complexity due the simultaneous use of common units (laser source, modulators and some optics), maintaining the high resolution associated with interferometric sources. In this paper we present a new metrology concept based on heterodyne interferometry that can allow the simultaneous measurement of a surface piston and wobble movement, detailing the physical model of the sensor, the prototype implementation and the performance characterized by the test result. The future steps towards an implementation in a primary standard accelerometer calibration setup are also described.
We present an absolute distance measurement concept based on pulse frequency repetition (PRF) sweep with a mode-locked laser diode. This technique requires a Michelson interferometer, a mode-locked laser source and a cross-correlation detector. The role of the cross-correlator is to analyze the state of superposition of a pair of pulses, one travelling over the reference arm of the interferometer, the other, corresponding to the measuring arm, travelling from the apparatus to the target and reflected back. Using two distinct laser pulse repetition frequency and knowing the cross-correlation peak position at reference arm of the interferometer for each frequency, it’s possible to obtain the length of the measuring arm, i.e., a distance measuring. The main techniques for performing pulse correlation are based in 2nd order effects over second harmonic crystal (SHG) or a two-photon absorption (TPA) process in a semiconductor junction. Both SHG and TPA methods require reasonably high pulse energies to achieve fair signal to noise ratios. The use Degree of Polarization (DOP) technique for cross-correlation detection allows the use of optical powers as low as -60 dBm. Such high sensitivity can be very convenient for low energy pulse sources such is the case of high frequency mode-locked laser diodes. The DOP technique can however limit the maximum measurement range, constrained by the loss of coherence of the laser source for longer distances. In this paper we present the first results of this measurement concept, based in the DOP correlator, discussing the main limitations of this technique for long distance measurements.
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