Ultrarövid fényimpulzusok terjedésének vizsgálata fotonikus kristály optikai szálakban és szálerősítőkben = Investigation of propagation of ultrashort laser pulses in photonic crystal fibers and fiber amplifiers

Megmutattuk, hogy lehetséges 6 fs-nál rövidebb kompresszált fényimpulzusok előállítása fotonikus kristály szálakban 1 nJ-nál kisebb impulzusenergiák esetében is. Szimulációs programunk segítségével számításokat végeztünk, hogy milyen impulzusparaméterek (energia, impulzushossz) mellett lehetséges az impulzusok alakhű átvitele nagymagátmérőjű, illetve légmagos fotonikus kristály szerkezetű optikai szálakon. Szimulációs eredményeinket mérésekkel (spektrum, autokorrelációs függvények) ellenőriztük és alkalmaztuk egy új tipusú, valós idejű, 3D kétfoton mikroszkóp kisérleti példányának elkészítésénél. Üreges fotonikus kristály szálakat terveztünk és alkalmaztunk Yb adadékolt szálerősítő csörpölt impulzusainak kompresszálására illetve nemlineáris hatásoktól mentes átvitelére. Módusszinkronizált, erősen csörpölt néhány pikoszekundumos impulzusokat előállító, telítődő abszorbenssel módusszinkronizált Yb szállézert építettünk, amelynek impulzusait rácsos kompresszor segítségével 200 fs-nál rövidebbre kompresszáltuk. Yb adalékolt szál és fotonikus kristály szerkezetű pumpa geometria alkalmazásával szálerősítőt építettünk, aminek segítségével az impulzusok energiáját 80 MHz-es ismétlődési frekvencia mellett az 1-10 nJ tartományba növeltük. | We have shown that it is possible to generate sub-6-fs pulses by compression of low energy (E<1 nJ) pulses in small core area photonic crystal fibers. We have made numerical simulations to investigate that what pulse parameters (energy, peak intensity, spectral widths) allow us to deliver femtosecond laser pulses without spectral and temporal distortion through specific large mode area (LMA) and hollow core (HC) photonic crystal fibers. The validity of our simulations was checked by corresponding measurements (spectrum, autocorrelation traces). The LMA and HC fibers were applied to build a random access 3D nonlinear microscope system. The HC fibers were designed and applied for compression and distortion free delivery of amplified pulses of a picosecond pulse Yb fiber laser/amplifier system. Mode-locked, all-normal-dispersion, all-fiber Yb laser was constructed delivering few ps long, strongly chirped pulses with specral width of ~10 nm at around 1030 nm. The output of the oscillator was compressed down to 200 fs using a grating pair compressor. Using a double clad Yb doped fiber and a photonic crystal pump geometry, the pulse energy was boosted up to the 1-10 nJ regime at a repetition rate of 80MHz

Carrier-envelope offset stable, coherently combined ytterbium-doped fiber CPA delivering 1 kW of average power

We present a carrier-envelope offset (CEO) stable ytterbium-doped fiber chirped-pulse amplification system employing the technology of coherent beam combining and delivering more than 1 kW of average power at a pulse repetition rate of 80 MHz. The CEO stability of the system is 220 mrad rms, characterized out-of-loop with an f -to-2f interferometer in a frequency offset range of 10 Hz to 20 MHz. The high-power amplification system boosts the average power of the CEO stable oscillator by five orders of magnitude while increasing the phase noise by only 100 mrad. No evidence of CEO noise deterioration due to coherent beam combining is found. Low-frequency CEO fluctuations at the chirped-pulse amplifier are suppressed by a “slow loop” feedback. To the best of our knowledge, this is the first demonstration of a coherently combined laser system delivering an outstanding average power and high CEO stability at the same time. © 2020 Optical Society of Americ

Generation of three-cycle multi-millijoule laser pulses at 318 W average power

The generation of three-cycle multi-millijoule pulses at 318W power is reported by compressing pulses of a Yb-fiber chirped pulse amplifier in a 6 m long stretched flexible hollow fiber. This technique brings high-power lasers to the few-cycle regime. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Energetic sub-2-cycle laser with 216 W average power

Few-cycle lasers are essential for many research areas such as attosecond physics that promise to address fundamental questions in science and technology. Therefore, further advancements are connected to significant progress in the underlying laser technology. Here, two-stage nonlinear compression of a 660 W femtosecond fiber laser system is utilized to achieve unprecedented average power levels of energetic ultrashort or even few-cycle laser pulses. In a first compression step, 408 W, 320 mu J, 30 fs pulses are achieved, which can be further compressed to 216 W, 170 mu J, 6.3 fs pulses in a second compression stage. To the best of our knowledge, this is the highest average power few-cycle laser system presented so far. It is expected to significantly advance the fields of high harmonic generation and attosecond science. (C) 2016 Optical Society of Americ

A fast algorithm to predict spectral broadening in CW bidirectionally pumped high-power Yb-doped fiber lasers

A detailed, fast-converging iterative numerical method has been developed to model continuous-wave bidirectionally pumped Yb-doped fiber lasers with output powers of several hundred watts. The analysis shows nonlinearity-induced broadening of the lasing spectrum, which also modifies power efficiency. Cavity dynamics is described by combining the effects of Kerr nonlinearities with power evolution equations and rate equations. The fast method to find steady-state solutions for cavity setups is based on setting the temporal phase evolution as a stochastic process with proper spectral filtering. Spectral properties of bidirectionally pumped lasers are calculated within few minutes using a commercial desktop computer, and very good agreement with experimental measurements is obtained for up to 922 W total pump and 708 W output power