As the largest and most complex system in the ultrafast laser family, petawatt lasers are far from the "Turn-key" level expected by users. Currently, the global petawatt laser market is still monopolized by two French companies, Amplitude Technologies and Thales Opotronics. The prosperity of the global scientific research market has provided a large number of orders to these two companies, but it has also posed great challenges to their business services and follow-up technical support.
Looking at the Chinese market alone, these two companies currently do not have a well-established after-sales service network. Rejecting complete statistics, Amplitude Technologies has only one technical staff in China who specializes in titanium sapphire systems. We have not heard of Thales having any titanium sapphire system technical service personnel stationed in China. This brings great inconvenience to customers, and this situation should not change much in the long term.
This means that in most cases, users of titanium sapphire amplification systems either have to wait "long and helplessly" for service from the original manufacturer, or operate and maintain the complex laser system on their own. What is gratifying is that the technology involved in petawatt lasers is relatively mature, and there are many peer systems around the world that can be used for reference. There are also corresponding third-party technical service companies in China. I believe that manufacturers can be "abandoned" completely.
Next, the author will introduce to you the "self-reliance" experience of the Diocles petawatt laser system at the University of Nebraska-Lincoln (hereinafter referred to as UNL), hoping to provide some reference for domestic colleagues. UNL's Diocles laser system is a relatively early commercial chirped pulse amplification laser system. The project leader of this laser system is Professor Donald Umstadter. After he switched jobs to UNL from the University of Michigan, he purchased a 100TW (3J/30fs) from Thales. The laser system subsequently added four pump sources with a total energy of 100J, and was independently upgraded to 1PW for electron acceleration in the laser wake field and ultrafast X-ray research based on inverse Tompton scattering.
Like most current laser systems, the laboratory was fed up with the "incompetent technical services" of laser manufacturers in the early days, which seriously affected the progress of scientific research tasks. Therefore, it is urgent to establish a capable laser team. After several years of hard work, a team of three doctors (all from China) specializing in ultra-powerful lasers, two laser engineers (graduated from a laser college) and an electrical engineer (graduated with a master's degree) was finally formed to run the laser system in an orderly manner. The failure rate of the laser system within one year is less than 5%. The laser system service hours are from 10 am to 6 pm on working days. The 100TW beamline operates at 10Hz and the 1PW beamline operates at 0.1Hz.
These operating parameters are insignificant for a small-energy kHz laser system, but they are already world-leading indicators for a petawatt laser system. Due to the stable operation of the laser system and sufficient experimental data collection, scientific researchers basically do not need to work overtime, and the relationship between the experimental team and the laser team is relatively harmonious. With the support of this laser system, experimental scientists have set multiple world records in the field of ultrafast X-ray research based on inverse Tompton scattering, and published a number of original results in top magazines such as PRL and Nature Photonics. Next, we will introduce the “self-reliance” experience of this laser system from several aspects.
1. Laser technicians are paid relatively well, have stable staffing and are highly motivated.
The use of scientific research funds in the United States is relatively flexible in terms of "manpower". Laboratory technicians are more pressured and tempted by the industry, so they must be given higher salaries to retain them stably. According to UNL's public salary data, the pre-tax salary of laser technicians is between US$50,000 and US$60,000, which is enough to ensure a well-off life in the middle of the United States.
In terms of staffing, these technical staff are part of the school’s fixed staffing and are more stable than postdoctoral fellows and assistant researchers. Take the two laser engineers at Diocles as an example. They graduated from a junior college in a laser school in the United States. Their job task is to preheat the laser system and adjust the optical path before 7 a.m., and then go home from get off work around 2 p.m.
to go fishing and drink beer. They are also responsible for regular maintenance of the pump source and water cooler, formulating SOPs for the operation of the laser system, and regularly reminding us "undisciplined" scientific researchers to pay attention to safety, etc. This frees scientific researchers from tedious chores, especially those laser and physics researchers who are "unwilling to do chores for a long time." For petawatt lasers, which have a high threshold, only these middle-level technicians are completely insufficient, because some advanced laser technologies, especially ultrafast laser technologies, are beyond their control.
Therefore, they need to be equipped with well-trained doctors specializing in ultrafast lasers, such as some difficult Trouble shooting, experimental optical path design, laser system upgrades, etc. Ideally, a petawatt laser system should be equipped with more than three full-time laser technicians with PhD degrees.
2. The self-developed ultrafast laser system realizes "feedback" for petawatt laser maintenance and operation.
In addition to having commercial laser systems, Diocles Laser Laboratory has been seeking to develop independent laser systems. The first is to improve the design flaws of the current laser system, and the second is to provide technicians with a platform for laser technology research and development and to publish papers, laying a foundation for continuing to engage in scientific research. The management of personnel and projects of a petawatt laser system is no less than that of a small enterprise. Since most of the staff have doctorates, in addition to salary, satisfying this group's sense of career fulfillment is a very important issue. For example, most Ph.D. personnel are not satisfied with simple light path adjustment, daily maintenance and other tasks, because in the long run their career development is limited and their sense of accomplishment is not strong. The development of scientific laser systems meets the career development needs of this group.
3. Maintain, update and transform the pump source.
The most prone to problems in petawatt laser systems is the green light pump source, because its energy is generally large and prone to component damage and other failures. For example, aging of a small O-ring can paralyze a laser, thus affecting the operation of the entire laser chain. There are a total of 19 green light pump sources and one backup pump source in the Diocles laser system. The operating data of each unit is recorded, and regular maintenance and better aging of components (mainly O-rings and flash lamps) occur. Although damage accidents occasionally occur, the overall failure rate is low.
4. The core components of the system that are easily damaged must be adequately stocked and replaced quickly after damage.
The entire chain of petawatt lasers contains thousands of optical components and control equipment. Due to the serial design, if each one fails, the laser system will stop operating. Therefore, after scientifically analyzing the cause of the damage and eliminating hidden dangers, rapid replacement of damaged components will greatly improve operating efficiency. The Diocles system backs up all the lenses, crystals and gratings required by the system. After replacement, the ordering process is started immediately to ensure backup at all times. Of course, the laser engineer will issue a damage report as soon as possible and keep a good file.
5. System consumables are always available from multiple alternative manufacturers, and optical components are 100% free from original factory restrictions.
Under normal circumstances, laser system users will rely more on the accessories provided by the original laser system manufacturer. However, if they encounter an incompetent manufacturer, the efficiency will be low and the price will generally be much more expensive than the market price. Diocles Laser Laboratory generally looks for more than two device suppliers for core components to get rid of the restrictions on original manufacturers.
6. Encourage technicians to disassemble and assemble laser systems to gain experience.
It is impossible to truly own a complex laser system without disassembling it from scratch. The laboratory encourages everyone to be "brave and careful" in dismantling the laser system, and mark it before disassembly to ensure recovery. From the seed source, pump source (including power supply), amplifier to compressor, the technicians have disassembled and assembled it several times and accumulated rich experience. It can be said with confidence that Diocles' laser technicians have a deeper understanding of the laser system than the manufacturer's general technical engineers, and there is no need for in-depth communication with the manufacturer in the long run.
7. Build multiple control feedback systems to improve system time and space quality
For strong-field physics experiments that rely on petawatt lasers, peak power density is the most important indicator. Therefore, in addition to sufficient energy, the pulse width must be narrow, the signal-to-noise ratio must be high, the focused spot must be small, and the near-field quality of the spot must be high. Commercial pulse shapers and spatial adaptive optics systems can ensure the improvement of space-time quality. Diocles Laser Laboratory does not hesitate to invest in improving laser quality.
Multiple sets of Dazzler and deformable mirror systems push the quality of time and space to the theoretical limit, which is one of the reasons why the experiment can be successful.
8. Automated control of experimental instruments to improve experimental operation efficiency
The Diocles Laser Laboratory is equipped with technical staff with rich LabView programming background, integrating the measurement of laser parameters and the control of experimental instruments into an overall interface. Every time the experimenter collects data, the corresponding laser parameters and other corresponding related data are synchronized and automatically stored, and quickly analyzed online. The period from data collection to article publication is greatly reduced.
9. Full-time project manager and ERP system
Professor Umstadter's successful experience is to manage the laboratory in the same way as a company. He is currently one of the few project leaders to implement ERP systems and full-time project managers in petawatt laser laboratories. The ERP system ensures that each project operates scientifically according to the logic of management. Project managers with rich management experience are responsible for coordinating the progress of all projects in the laboratory. They have greater rights to constrain laboratory personnel to comply with rules, but project managers do not participate in actual scientific research activities. It is best for the project manager to have a professional background in science and engineering as well as a business background. For example, the project manager of Diocles previously graduated with majors in biology and computer science, and later received an MBA degree.
To sum up, a petawatt laser system requires a highly motivated laser technical team, scientific and reasonable management methods and large financial support to operate efficiently. The Boliang Technology team has rich experience in the maintenance and operation of titanium sapphire petawatt lasers. They are familiar with the current laser systems of AT and Thales companies, and can provide all high-quality products and customized services for the entire chain of petawatt laser systems. We hope to work with experimental scientists to write a new chapter for China's petawatt laser devices!