Laser beam diagnostics:
What if Star Wars had deployed the ISO 11146 standard for laser beam diagnostics? We can’t rewrite history, but we can still delve into M2 measurement for your laser. (Image courtesy of Lucasfilm)

 

How is laser beam quality measured?

 

Several parameters are very useful to assess laser beam quality and properties. Among them are: M-squared factor (M2), divergence (), width at waist (w0), Beam Parameter Product (BPP), waist location, astigmatism, asymmetry, which can be calculated with conventional M2 beam propagation analyzers.

 

To reconstruct these parameters, such systems generally implement a camera that is moved along the laser propagation axis (z), either manually or by means of a translation stage, to acquire intensity maps of the beam. ISO 11146 standard defines that at least 10 observation planes are mandatory, half of them within one Rayleigh length (zR), the other half beyond 2 Rayleigh lengths.

 

What are the limitations of traditional M2 analyzers?

 

– Limitations include the fact that the translation has to be aligned respect with laser beam propagation, which takes time and limits the throughput in production. This is particularly true if laser manufacturing requires iterative steps and M2 measurements.

– Beam caustics must also be adapted to the available range of the translation stage, in order to acquire observation planes in and out the Rayleigh lengths. This is done by carefully choosing lenses of appropriate focal. Such lenses bring added aberrations to measured beam depending on their intrinsic quality and, again, quality of alignment. In addition, lens coating must also match the spectral properties of the laser. Such implementation results in voluminous benches, whose length is sometimes contained by internally folding the laser beam several times with the use of multiple mirrors. These mirrors also represent additional optical elements external to the laser.

– Last, the complete acquisition cycle requires time to scan the -at least- ten positions defined by the ISO 11146 standard. Any variation of the laser during this time affects the reconstruction of the M2 factor, which limits their use in case of dynamics effects.

 

New approach to laser beam diagnostics proposed by Imagine Optic

 

Imagine Optic proposes a new approach to conventional M2 beam propagation analyzers: in this method, the complete electromagnetic field of the laser is acquired from a single shot measurement and, from it, allows to access to as many observation frames within and out the Rayleigh lengths defined by the ISO 11146 standard and to fit the parameter M2.

 

Advantages of the method

Laser beam diagnostics is performed by Imagine Optic CAM SQUARED sensor:

+ It allows fast live acquisition thanks to its single shot acquisition (us to ms), making it perfect for alignment and characterization of laser or OPA dynamic changes

+ It is easy to set up, like a beam profiler, because there is no need to use a translation stage anymore, nor to align it on the laser beam ( 40 Seconds Demo Video )

+ This makes it a compact solution, with small footprint in the lab or on the production bench, and easy to handle for after-sales support and on-site service.

Avoid the path of Kylo Ren and don’t let a bad M2 factor ruin your day when there are quick and easy solutions at hand to test the quality of your laser beam. We are happy to discuss how they suit your needs. Reach us at sales@imagine-optic.com or through the contact form.

Why is M2 factor important?

The parameter M2 or beam quality factor- describes laser beam quality, or how close it is from a perfect gaussian beam: in this case M2 will tend to 1 and correspond to a diffraction-limited beam. M2 factor therefore describe the ability a laser beam has to be perfectly focused, or collimated (greater values than 1 means the laser departs from an ideal gaussian beam).

As an example, a HeNe laser typically have M2 factor close to 1.1.

What is the Beam Parameter Product (BPP)?

The Beam Parameter Product is the product of the beam radius at the beam waist and beam divergence half-angle () measured in the far field. BPP can be used to inform on beam quality of a laser -the lower the BPP, the higher the beam quality- but it presents the disadvantage of being dependent of the wavelength.

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This version of WaveSuite is a landmark for metrology and Adaptive Optics software, bringing huge benefits to our clients and users and synchronizing the version numbering of the three softwares:
– Waveview 4.3, the bench mark in wavefront metrology
– Wavetune 4.3, for perfect loop control
– Wavekit 4.3, a versatile and comprehensive SDK in C, LabVIEW and Python.

The first benefit is the end of the 4 GB RAM limit, allowing virtually unlimited image buffers and/or up to 4x phase point measurement at full speed. All applications’ performance will benefit from this breakthrough, especially those involving high-frequency/high-resolution sampling.

The second major benefit is to processing speed, with computing speed up 3x allowing for quicker calculations of wavefronts, intensity, PSF, MTF, and most importantly the LIFT algorithms that power our new HASO LIFT series with 272 x 200 and 680 x 500 phase point sampling.

Last but not least, the M2 function returns, thanks to these memory and speed improvements with better than laser beam simulations.

WaveSuite4.3 is the version currently being delivered with new wavefront sensors, optical metrology systems and deformable mirrors. It will soon be available as an upgrade for compatible hardware. If you would like more information, please get in touch with us at sales@imagine-optic.com.

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If you’re first interested in finding out more about our line of Wavefront Sensors and Deformable Mirrors or AO solutions, you can reach us at sales@imagine-optic.com or through the contact form (red enveloppe on the side).

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The most powerful laser in the world has reached 10 PetaWatts with a 0.9 Strehl ratio, and the help of Imagine Optic’s AO Laser solutions. In the last two decades, adaptive optics (AO) has dramatically improved the performance of Ultra-High Intensity Laser (UHIL) by mastering wavefront aberrations to deliver optimal focus for cutting-edge scientific applications. The latest generation of UHIL is now based on lasers delivering more peak and mean power than previous technology, and rely more than ever on adaptive optics.

The HPLS (High Power Laser System) manufactured by Thales belongs to the latest generation of UHIL and was comissioned at ELI-NP (Extreme Light Infrastructure Nuclear Physics) in Romania. It embeds a new generation of AO solutions combining highly accurate and robust wavefront sensors, and fast and precise deformable mirrors, namely our ILAO star DM controled through our WaveTune software.

The HPLS presents two beamlines which deliver each a main beam of 10 PW peak power at 1 shot per minute, and 2 other intermediate outputs at 100 TW, 10 Hz and 1 PW, 1 Hz. Each of these 6 outputs rely on Imagine Optics’ ILAO* deformable mirror and Wavetune software to optimize and stabilize these ultraintense beams along 2 main objectives:
– Focusability, with a 0.9 Strehl ratio capability.
– Compressor’s gratings protection, thanks to the correction of aberrations of the laser beam prior to compression in order to avoid potential hot spots.

Feel free to reach us if you would like more info on our work for UHIL. You can also check out our recent webinar “A practical tour of Adaptive Optics” for more on AO.

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Our third webinar and live demo completes our on ongoing series on wavefront metrology and correction.

You can (re)watch our 3rd webinar, a practical tour of adaptive optics, wavefront sensing and correction. Our CSO Xavier Levecq, and our CTO Guillaume Dovillaire addressed fundamental topics on adaptive optics (AO), covered a variety of applications, and showcased telescope optimization using AO.

The 2 setups, featuring our MIRAO 52E deformable mirror and HASO4 First and HAOS4 FAST wavefront sensors, help them showcase, among other things :
• The main principles of AO, how it works and why it can dramatically improve optical applications (1st demo).
• How do industrial and research applications take advantage of adaptive optics.
• What makes high speed AO a game-changer to mastering atmospheric turbulences, as an example (2nd demo).

If you’re interested in finding out more about our line of Wavefront Sensors and Adaptive Optics Solutions, you can reach us at sales@imagine-optic.com or through the contact form (red enveloppe on the side).

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The ultimate Adaptive Optics optimization is just one click away.

WaveTune 4.1.10 Conjugation Helper is a game-changer in the optimization of Adaptive Optics setting as it simplifies the WFS/DM alignment to a one-click process.

Adaptive Optics are key to optimizing the optical quality of any instrument or set-up. Obviously both the performance of the wavefront sensor (WFS) and deformable mirror (DM) are fundamental in obtaining the best corrections, but the quality of the WFS-DM conjugation is also a major additional factor to get the best out of adaptive optics.

Why is this optical conjugation so important ?
– A good DM-WFS conjugation is required to get a relevant interaction matrix as well as the highest number of correction modes in the command matrix.
– With a good conjugation, the beam shape measured by the WFS becomes independent of the beam aberrations. The beam shape keeps perfectly stable during the correction process.
Without an adequate conjugation, a simple astigmatism will make the beam shape elliptical, and constantly change during correction : these effects will systematically prevent reaching the best correction.

Imagine Optic has developed the newly-released Conjugation Helper function as part of its WaveTune 4.1.10 upgrade. The Conjugation Helper acts is a one-click process that will display both the distance and direction to adjust the wavefront to in order to get the perfect conjugation. This delicate and time-consuming WFS/DM alignment is now just a simple, instantaneous click-through process, thanks to the Conjugation Helper function.

WaveTune 4.1.10 is the latest version of Imagine Optic’s acclaimed software, and is currently available and shipped with all our Wavefront Sensors and Deformable Mirrors.

UPDATE : watch this 4 min video where Xavier Levecq, CSO Imagine Optic, showcases:
– the Conjugation Helper module,
– how to make an optical conjugation measurement,
– how to perform adaptive optics calibration.

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The use of adaptive optics (AO) for IR wavefront control is essential to optimize the phase-matching conditions and therefore enhance the signal of the HHG. Furthermore, the vortex IR driver results in up-converted EUV with a wide range of orbital angular momentum orders, as reported by Laboratoire de Physique des Gaz et des Plasmas .

Wavefront sensing is critical in AO since its performance drives the correction efficiency or the correct application of a desired wavefront to the IR driver. Moreover, sensing EUV wavefront correctly gives insight into the plasma process as well as facilitates the alignment of the focal spot on the target. AO improves the performance of optical systems by reducing the effect of wavefront distortions with the goal of delivering the desired focal beam profile to the gas or solid media for the HHG process.

Hartmann wavefront sensing in the EUV range was first introduced by Imagine Optic more than 10 years ago, providing real-time, single-shot, achromatic EUV wavefront characterization with a an accuracy typically better than lambda/50. Imagine Optic provides all the AO components necessary to boost your HHG setup, on both sides of the plasma, including wavefront sensors in the IR and EUV range, deformable mirrors and AO software.

Examples of how our AO products have been used in HHG experiments are available in the new application note and the publication list.

If you’re interested in finding out more about our X-EUV line of Wavefront Sensors and Adaptive Optics hardware and software, you can reach us at sales@imagine-optic.com or through the contact form (red enveloppe on the side).

The post Maximize EUV-XUV photons through adaptive optics for HHG appeared first on Imagine Optic.

Adaptive Optics (AO) dramatically improve the performance of optical systems by mastering wavefront distortions to deliver optimal focus and quality imaging for both scientific and industrial applications.

The principle of an AO optimization for UHIL is that a deformable mirror combined with a wavefront sensor and the appropriate software addresses all the requirements for either closed or open loop setups, and correct wavefront defects that inevitably affect UHIL beams.

The first step in such settings consists in measuring the wavefront with a sensor that features high accuracy, linearity and dynamic range in order to determine optimal corrections. The appropriate software should then not only gather all the data needed for the diagnostic part but moreover enable for the configuration of the interactions matrix that controls the deformation of the mirror, and makes the whole system perform optimally.

From that point the AO loop – i.e. the wavefront sensor / software / deformable mirror combo – will ensure that the UHIL beam is permanently optimized and delivers (the right intensity with the right shape at the right place) high Strehl-ratio focal spot to the right plane. Imagine Optic has been helping UHIL teams all over the world for the past 10 years, and most recently equipped all 6 beamlines of ELI – NP project that is currently ongoing in Romania, and recently reached record power level of 10.3PW.

Whatever your UHIL setup, feel free to reach out to us, we can help you make the most of your experiment. As a partial view of our know-how and capabilities, here is an application note on the “full correction of a laser chain including final focusing optics”.

If you’re interested in finding out more about our UHIL Laser metrology and correction products, you can reach us at sales@imagine-optic.com or through the contact form (red enveloppe on the side).

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