Dr. Huabao Cao Profile

Dr. Huabao Cao

at ELI-ALPS Research Institute

SPIE Involvement:

Author

Publications (5)

Proceedings Article | 13 May 2019 Presentation

Development status and operation experiences of the few cycle high average power lasers of ELI-ALPS (Conference Presentation)

Károly Osvay, Ádám Börzsönyi, Huabao Cao, Eric Cormier, János Csontos, Péter Jójárt, Mikhail Kalashnikov, Balint Kiss, Rodrigo López-Martens, Szabolcs Tóth, Zoltan Varallyay

Proceedings Volume 11034, 110340L (2019) https://doi.org/10.1117/12.2523057

KEYWORDS: Pulsed laser operation, Laser development, Hydrogen fluoride lasers, Laser sources, Particles, Terahertz radiation, Mid-IR, Aluminium phosphide, Laser engineering

Read Abstract +

Most of the laser sources of ELI-ALPS are operating in the 100 W average power regime, while the peak power and the repetition rate range from 0.1 TW at 100 kHz up to PW at 10 Hz. The pulse duration lasts typically a few optical cycle, feeding six attosecond beamlines, two particle and two THz beamlines, as well as many end stations associated with the beamlines [1]. The first 100 kHz repetition rate lasers have been installed by end 2017, and became available for experiments from the beginning of 2018. The Mid-InfraRed laser (MIR) provides 150 µJ, 40 fs pulses at 3.1µm [2]. The first High-Repetition rate laser (HR1) has been operating in long pulse mode (1.5 mJ, 40 fs pulses at 1030 nm). The short pulse operation mode (1mJ, <7fs) will be completed by March 2019. The second High-repetition Rate laser (HR2) offering 5 mJ and sub-7 fs pulses, will be commissioned by mid 2019. The kHz repetition rate SYLOS laser [3] has been completed its second development phase for providing >5 TW peak power pulses at sub-7 fs pulse duration. The system is available to run four beamlines from April 2019. In the meanwhile, parallel to its operation, the final upgrade stage will be developed, reaching an energy of >100 mJ by mid 2020. In order to serve the four beamlines efficiently, a so called SYLOS experimental alignment laser has been implemented. The laser “mimicking” the SYLOS laser at lower repetition rate, providing the similar beam size, peak intensity, and duration (3.8TW, 12 fs) at 10Hz repetition rate is available from end 2018. The High Field Petawatt (HF PW) laser of ALPS has been designed to operate at 10 Hz repetition rate with a pulse duration shorter than 17 fs. The system is under installation, 10 Hz operation at 0.4PW level will be reached by mid 2019, while the full 10Hz operation will be demonstrated by Fall 2020. We also carry on experiments towards the elimination of bottlenecks of high repetition rate sub-10fs operation of the 100Hz branch of the HF laser. The MIR and HR1 lasers have successfully served almost ten commissioning user experiments with external collaborators, investigating phenomena like electron migration in water, K-shell excited elections, etc., altogether for 51 operational weeks in 2018. Next year we expect to extend the commissioning experiments for the SYLOS laser as well as at least two attosecond and THz beamlines. The challenge of the laser R&D to design and implement such lasers was taken by the industry (EKSPLA, Light Conversion (both Lithuania), Fastlite, Amplitude Technologies (both France), AFS GmbH (Germany)), academia, and ELI-ALPS, resulting in a change of paradigm in laser engineering, leading to novel state of the art research grade lasers just in a few years. [1] S. Kuhn et al., Mol. Opt. Phys. 50 (2017) 132002 [2] R.Budrinas et al., Opt.Exp. 25 (2017) 5797 [3] N.Thiere et al., Opt.Exp. 26 (2018) 26907

Proceedings Article | 13 May 2019 Presentation

KW-class thin-slab amplifiers based on Ti:sapphire (Conference Presentation)

Roland Sándor Nagymihály, Huabao Cao, Vladimir Chvykov

Proceedings Volume 11033, 110330Q (2019) https://doi.org/10.1117/12.2520934

KEYWORDS: Amplifiers, Semiconductor lasers, Crystals, Laser crystals, Pulsed laser operation, Optical amplifiers, Oscillators, Ultrafast lasers, Laser systems engineering, Picosecond phenomena

Read Abstract +

The thin disk (TD) technique has been used in laser oscillators and amplifiers for almost three decades to increase the average power of ultrafast laser systems [1]. Different host materials have been tested mostly with Yb-doping, which resulted in a wide range of pulse durations from 1 ps to sub-100 fs in combination with high average power, good stability and reliability [2]. An even more industrial approach, the thin-slab laser geometry, uses slab-shaped gain media instead of disks, where the cooling is performed from both large surfaces of the crystal [3]. A great advantage of Yb-based TD and thin-slab systems is that the laser crystal can be pumped by continous wave laser diodes due to the long active lifetime of the gain medium. However, the small gain bandwidth supports only sub-ps pulse duration, if high energy pulses are required. Ti:Sapphire (Ti:Sa), on the other hand, offers a gain bandwidth that supports sub-20 fs pulse duration in combination with peak powers up to the petawatt regime without using any post compression techniques [4]. Amplification with the TD geometry has been already demonstrated to be efficient based combined with Ti:Sa, but only in the multi-J regime with a repetition rate of 10 Hz [5]. Scaling the TD geometry to mJ-class pulses leads to serious thermal issues in the gain medium due to the decreased cooled surface to volume ratio. Recently, laser diodes operating around 450 nm were also found to be a good pumping source for Ti:Sa amplifiers with repetition rates in the 100 kHz regime [6], while laser operation in Ti:Sa pumped by a stack of LEDs was also demonstrated and stated to be scalable for high pulse energies [7]. For this reason, thin-slab type amplification is suggested based on Ti:Sa to obtain mJ-class, kW level average power pulses in combination with sub-20 fs pulse duration. Numerical simulations were performed on the amplification and thermal performance for different pulse energies, repetition rates and so average powers. The results revealed the limitations of the thermal performance in the thin-slab geometry. Water-cooled amplifiers were found to be able to provide pulses with 2 kW average power with reasonably low temperature gradient in the crystal. Room temperature cooling enabled 0.3 J output energy and extraction efficiency greater than 50% with a repetition rate exceeding 10 kHz. An increase of one order of magnitude in the repetition rate is possible when cryogenic cooling is considered with 77 K coolant temperature. Laser diode pumping was also investigated in combination with 1 MHz repetition rate of the amplified pulses, where the wall-plug efficiency of the amplifier system is expected to be increased significantly compared to conventional solid-state laser pumping. Experimental demonstration of the thin-slab type Ti:Sa amplification is under work with repetition rates ranging from 2 to 10 kHz in combination with a pump average power of 50 W. References 1. J. Speiser, J. Opt. Soc. Am. B, 26, 26-35 (2009). 2. F. Druon et al, IEEE Phot. Journ. 3(2), 268-273 (2011). 3. P. Russbueldt et al, IEEE J. of Sel. Top. in Q. El. 21(1), 3100117 (2015). 4. Sergei Kühn et al, J. Phys. B: At. Mol. Opt. Phys. 50 132002 (2017). 5. V. Chvykov et al, Opt. Lett. 41(13), 3017-3020 (2016). 6. S. Backus et al, Opt. Expr. 25, 3666-3674 (2017). 7. P. Pichon et al, Optica 5(10), 1236-1239 (2018).

Proceedings Article | 13 May 2019 Presentation

Energetic few-cycle pulses by polarization-encoding in Ti:sapphire: on the compression, carrier-envelope phase stability and decoding efficiency (Conference Presentation)

Roland Sándor Nagymihály, Huabao Cao, Vladimir Chvykov, Péter Jójárt, Viktor Zuba, Roland Flender, Oleg Antipov, Imre Seres, Ádám Börzsönyi, Nikita Khodakovskiy, Károly Osvay, Mikhail Kalashnikov

Proceedings Volume 11033, 1103304 (2019) https://doi.org/10.1117/12.2520928

KEYWORDS: Amplifiers, Crystals, Lithium, Lutetium, Laser spectroscopy, System on a chip, Americium, Ultrafast phenomena, Laser stabilization, Laser systems engineering

Read Abstract +

Ultrashort pulses with TW to multiple PW peak power are mostly generated by state-of-the-art Ti:Sapphire- (Ti:Sa) based chirped pulse amplification (CPA) systems [1,2]. The main reasons of using Ti:Sa crystals are the extremely large gain bandwidth and exceptional physical properties of the gain medium [3], the availability of the high energy pulsed pumping sources. Additionally, carrier-envelope phase (CEP) stabilization schemes can be easily implemented for Ti:Sa laser systems up to TW peak power [4]. Polarization-encoded CPA (PE-CPA) is a recently developed technique, which holds promise to support a gain bandwidth sufficient for compressed pulses in the few-cycle regime with Ti:Sa-based amplification [5,6]. The performance of the PE-CPA technique is however affected by the spectral amplitude and phase variations along both gain cross-sections. The population inversion induced refractive index changes (RICs) were measured within the main emission band of Ti:Sa. By using spectrally resolved interferometry (SRI), spectral phase changes of amplified pulses were measured in a Jamin-type arrangement. The spectral phase shift induced by inversion for both π- and σ-polarized pulses was extracted at different pump fluence values. At room temperature, a zero-phase shift was found with a sign change at the peak of the gain spectrum, while for σ-polarized pulses no such behavior was observed in the investigated spectral range. By decreasing the temperature of the crystal to 30 K, similar behavior was found, however, the zero-phase crossing was found to be shifted to around 760 nm. The electronic RICs are explained by the polarizability difference between excited and unexcited Ti3+ ions in the crystal. Compression of PE-amplified pulses is currently under investigation by numerical simulations and will be experimentally tested with a spectral bandwidth corresponding to sub-10 fs pulse duration. Carrier-envelope phase (CEP) fluctuations were also investigated in a PE amplifier stage by using the SRI technique. Temperature and inversion instabilities were found to be the major sources of CEP noise caused by the amplification process, accounting for 60 mrad of CEP noise in a four-pass amplifier stage with 1.2 J/cm2 absorbed pump fluence. CEP stability of the PE amplification was compared to the conventional process, which showed a sub-10 mrad noise increase in case of the PE amplifier under similar operating conditions. However, the degradation of the CEP stability in the PE amplifier compared to the conventional stage was found to be below 10 mrad within the same operational conditions [7]. References 1. Z. Gan, L. Yu, S. Li, C. Wang, X. Liang, Y. Liu, W. Li, Z. Guo, Z. Fan, X. Yuan, L. Xu, Z. Liu, Y. Xu, J. Lu, H. Lu, D. Yin, Y. Leng, R. Li, and Z. Xu, Opt. Express 25(5), 5169-5178 (2017). 2. A. Golinelli, X. Chen, E. Gontier, B. Bussière, O. Tcherbakoff, M. Natile, P. d’Oliveira, P.-M. Paul, and J.-F. Hergott, Opt. Letters 42(12), 2326-2329 (2017). 3. P. F. Moulton, “Spectroscopic and laser caracteristics of Ti:Al2O3,” J. Opt. Soc. Am. B 3(1), 125-133 (1986). 4. F. Lücking, V. Crozatier, N. Forget, A. Assion, and F. Krausz, Opt. Lett. 39(13), 3884–3887 (2014). 5. M. Kalashnikov, H. Cao, K. Osvay, and V. Chvykov, Opt. Letters 41(1), 25-28 (2016). 6. H. Cao, M. Kalashnikov, K. Osvay, N. Khodakovskiy, R. S. Nagymihaly, and V. Chvykov, Laser Phys. Lett. 15 045003 (2018). 7. R. S. Nagymihaly, H. Cao, P. Jojart, M. Kalashnikov, A. Borzsonyi, V. Chvykov, R. Flender, M. Kovacs, and K. Osvay, J. Opt. Soc. Am. B 35(4), A1-A5 (2018).

Proceedings Article | 9 June 2017 Presentation

Thin Disk Ti:Sapphire amplifiers for Joule-class ultrashort pulses with high repetition rate (Conference Presentation)

Roland Nagymihály, Huabao Cao, Mikhail Kalashnikov, Nikita Khodakovskiy, Lutz Ehrentraut, Károly Osvay, Vladimir Chvykov

Proceedings Volume 10238, 102380C (2017) https://doi.org/10.1117/12.2265290

KEYWORDS: Amplifiers, Laser systems engineering, Laser applications, Ultrafast phenomena, Crystals, Laser development, Laser crystals, Absorption, Numerical simulations, Femtosecond phenomena

Read Abstract +

High peak power CPA laser systems can deliver now few petawatt pulses [1]. Reaching the high energies with broad spectral bandwidth necessary for these pulses was possible by the use of large aperture Ti:Sa crystals as final amplifier media. Wide applications for these systems will be possible if the repetition rate could be increased. Therefore, thermal deposition in Ti:Sa amplifiers is a key issue, which has to be solved in case of high average power pumping. The thin disk (TD) laser technology, which is intensively developed nowadays by using new laser materials, is able to overcome thermal distortions and damages of laser crystals [2]. TD technique also has the potential to be used in systems with both high peak and average power. For this, the commonly used laser materials with low absorption and emission cross sections, also low heat conductivity, like Yb:YAG, need to be replaced by a gain medium that supports broad enough emission spectrum and high thermal conductivity to obtain few tens of fs pulses with high repetition rates. Parasitic effects during the amplification process however seriously limit the energy that can be extracted from the gain medium and also they distort the gain profile. Nevertheless, the application of the Extraction During Pumping (EDP) technique can mitigate the depopulation losses in the gain medium with high aspect ratio [3]. We proposed to use Ti:Sa in combination with TD and EDP techniques to reach high energies at high repetition rates, and we presented numerical simulations for different amplifier geometries and parameters of the amplification [4,5]. We present the results of the proof-of-principle experiment, where a EDP-TD Ti:Sa amplifier was tested for the first time. In our experiment, the final cryogenically cooled Ti:Sa amplifier in a 100 TW/10 Hz/28 fs laser system was replaced with the EDP-TD room temperature cooled arrangement. Amplified seed pulse energy of 2.6 J was reached only for 3 passes through TD with 0.5 J of input seed and 5 J of absorbed pump energy. We verified the excellent heat extraction capabilities of our amplifier module. Results of the scaling simulations on the base of this experiment for 100s of TW peak power laser systems operating at up to 100 Hz will be also presented. References 1. Y. Chu et al, Opt. Lett. 40, 5011-5014 (2015). 2. C. R. E. Baer et al, Opt. Exp. 20, 7054-7065 (2012). 3. V. Chvykov et al, Opt. Comm. 285, 2134-2136 (2012). 4. V. Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Exp. 24, 3721 (2016). 5. V.Chvykov, R. S. Nagymihaly, H. Cao, M. Kalashnikov, K. Osvay, Opt. Lett. 41,13, 3017 (2016).

Proceedings Article | 9 June 2017 Presentation

Active spectral pre-shaping with polarization encoded amplifiers (Conference Presentation)

Huabao Cao, Mikhail Kalashnikov, Károly Osvay, Nikita Khodakovskiy, Roland Sándor Nagymihály, Vladimir Chvykov

Proceedings Volume 10238, 1023809 (2017) https://doi.org/10.1117/12.2264702

KEYWORDS: Amplifiers, Polarization, Quartz, Sapphire lasers, Computer simulations, Modeling, Crystals, Energy efficiency, Computer programming, High power lasers

Read Abstract +

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years