Exail, a leading high-tech manufacturer of photonic components, optical fibres and laser systems, used this year’s Photonics West as the launch point for its latest, cutting-edge Low Vπ LiNbO3 Spectral Broadening Phase Modulator, designed especially for the rigorous demands of extremely high-power laser applications involving coherent beam combination (CBC) and spectral beam combination (SBC).
Key optical features of the new device include an annealed proton exchange process, very low insertion loss (<3dB), high optical power handling (up to 300mW at 1,060nm), and extremely stable performance. In addition, its low Vπ of only 2V at 50kHz minimises RF and power consumption. It is also available at other wavelengths (O-band, C-band, 2µm windows).
“After many years of work we have developed a phase modulator with an ultra-low Vπ value (up to 16GHz), offering stability over time, temperature and vibration, all while minimising power consumption,” Yves Deiss, sales manager for Exail, told Electro Optics at the firm’s booth. “While low Vπ modulators have been known to industry for a number of years, they have always been associated with low stability. Thanks to our recent R&D efforts resulting in multiple improvements to the technology, we can confidently say that we now offer the best phase modulator on the market for high-power laser applications.”
The phase modulator’s high optical power handling, combined with its exceptional durability, makes it ideally suited for a wide range of outdoor civil, scientific and defence high-power laser applications.
“Stability and efficiency were crucial factors in the design of this latest device, addressing challenges related to energy consumption,” Deiss explained. “The new Low Vπ LiNbO3 Phase Modulator stands out as a distinctive optical modulation solution, reshaping industry standards for stability, efficiency, and versatility. It marks an exceptional step forward in optical modulation, delivering outstanding results and specifications.”
Facilitating coherent and spectral beam combination
The new technology excels in coherent beam combination (CBC) laser applications, where a single source with fine linewidth (on the order of kHz) can be leveraged through multiple amplifications and an array of precise phase modulators to generate several high-power beams. The spatial and temporal properties of each beam are maintained due to the modulators dynamically correcting the distortions of the optical paths. By permanently maintaining constructive interferences, this guarantees maximum power efficiency when the multiple beams are then recombined to form a single, extremely powerful beam.
Exail's phase modulators can be deployed in CBC setups for directed energy applications and dynamic beam shaping
CBC is one of the key techniques used to achieve the exceptionally high power levels of Directed Energy Laser (DEL), a key target market for Exail and a prime defence-based application example of the low Vπ phase modulators. DEL continue to develop at a rapid pace, with a variety of research projects and successful demonstrations continually taking place across the US, Europe and the rest of the world.
CBC is also gaining interest in achieving dynamic beam shaping for high-power laser materials processing applications. “This could be an interesting market with a lot of potential for this technology”, said Deiss. “Being able to adjust between different beam shapes, simply by altering the coherence, will allow manufacturers to experiment with different laser parameters and achieve more efficient, thicker laser cuts at greater speeds. It’s a very versatile technology.”
The Low Vπ LiNbO3 Phase Modulator can also be used for spectral beam combination (SBC), another method for achieving extremely high laser power. Different beams with distinct wavelengths are superimposed via adaptive optics to achieve a uniform intensity distribution and an optical signal with power proportional to the number of beams combined. Here, the phase modulator widens the width of the laser line in order to suppress non-linear Brillouin effects in the optical fibre.
The new Low Vπ LiNbO3 Phase Modulator arranged in a spectral beam combining setup
SBC applications also include DEL and laser materials processing, with other applications such as long-range illumination and sensing also under development.
From fusion to frequency combs
In addition to DEL and laser materials processing, Exail also sees high-energy physics and nuclear fusion being target application areas for the new Low Vπ LiNbO3 Phase Modulator.
“Institutes such as the NIF at LLNL generate extremely high intensity laser beams from fibre sources for use across their numerous fields of research, and so need to broaden the spectrum in order to minimise non-linear effects,” said Nicolas Grossard, Product Manager at Exail. “Considering the successful announcement of fusion ignition at NIF in December 2022, and the advancements that have taken place in the field since then, this could one day be a very exciting market for low Vπ phase modulators in the future.”
However, while the NIF has demonstrated a yield of approximately 3.9MJ fusion energy using 2.1MJ of laser energy, approximately 500MJ of energy was still required to power the laser itself, and so fully net-positive nuclear fusion could still be years away from being reality. However, this doesn’t make the application any less exciting for Exail, as Grossard noted: “the race is on to be the first to demonstrate nuclear fusion as a reliable source of near-limitless energy, and so we can expect lots of work to take place globally in this field over the coming years.”
The new phase modulators can also be used to generate frequency combs, Grossard continued, which could open up application fields such as spectroscopy, timing, metrology and lidar (e.g. for autonomous vehicle guidance). “While the main market for this device will be directed energy applications, we expect scientific applications, such as high-energy physics and those involving frequency combs, to develop more over time.”
Learn more about Low Vπ Phase Modulators
To demonstrate the capabilities of the newly launched Low Vπ LiNbO3 Phase Modulator, as well other cutting-edge technologies enabling high power laser applications, Exail is hosting the ‘Photonics Users Conference’ in Saint-Germain-en-Laye, France, on 28 May.
This one-day event, featuring speakers from Amplitude, Civan, Ekspla, Hilase, LLNL, NKT, ORC, STFC, Thales and more, will offer two dedicated sessions: “High energy and directed energy lasers”, and “Scientific and pulsed lasers”.
Interested parties can register at: www.exail.com/events/2024-laser-users-conference
