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Illustration of the experiment's principle (DM, dispersive mirror; CM, concave mirror; ROC, radius of curvature; OC, output coupler).
Source publication
We demonstrate a compact extreme ultraviolet (XUV) source based on high-harmonic generation (HHG) driven directly inside the cavity of a mode-locked thin-disk laser oscillator. The laser is directly diode-pumped at a power of only 51 W and operates at a wavelength of 1034 nm and a 17.35 MHz repetition rate. We drive HHG in a high-pressure xenon gas...
Citations
... It also shows the historical progression of the intra-oscillator approach. The dashed connecting line follows the development of our system, starting from the first demonstration in 2017 [29]. A similar system has been demonstrated by the group of Midorikawa closely after in the same year [30,31]. ...
Resonant enhancement inside an optical cavity has been a wide-spread approach to increase efficiency of nonlinear optical conversion processes while reducing the demands on the driving laser power. This concept has been particularly important for high harmonic generation XUV sources, where passive femtosecond enhancement cavities allowed significant increase in repetition rates required for applications in photoelectron spectroscopy, XUV frequency comb spectroscopy, including the recent endeavor of thorium nuclear clock development. In addition to passive cavities, it has been shown that comparable driving conditions can be achieved inside mode-locked thin-disk laser oscillators, offering a simplified single-stage alternative. This approach is less sensitive to losses thanks to the presence of gain inside the cavity and should thus allow higher conversion efficiencies through tolerating higher intensity in the gas target. Here, we show that the intra-oscillator approach can indeed surpass the much more mature technology of passive enhancement cavities in terms of XUV flux, even reaching comparable values to single-pass sources based on chirped-pulse fiber amplifier lasers. Our system operates at 17 MHz repetition rate generating photon energies between 60 eV and 100 eV. Importantly, this covers the highly attractive wavelength for the silicon industry of 13.5 nm at which our source delivers 60 nW of outcoupled average power per harmonic order.
... It also shows the historical progression of the intra-oscillator approach. The dashed connecting line follows the development of our system, starting from the first demonstration in 2017 [26]. A similar system has been demonstrated by the group of Midorikawa closely after in the same year [27,28]. ...
Resonant enhancement inside an optical cavity has been a wide-spread approach to increase efficiency of nonlinear optical conversion processes while reducing the demands on the driving laser power. This concept has been particularly important for high harmonic generation XUV sources, where passive femtosecond enhancement cavities allowed significant increase in repetition rates required for applications in photoelectron spectroscopy, XUV frequency comb spectroscopy, including the recent endeavor of thorium nuclear clock development. In addition to passive cavities, it has been shown that comparable driving conditions can be achieved inside mode-locked thin-disk laser oscillators, offering a simplified single-stage alternative. This approach is less sensitive to losses thanks to the presence of gain inside the cavity and should thus allow higher conversion efficiencies through tolerating higher intensity in the gas target. Here, we show that the intra-oscillator approach can indeed surpass the much more mature technology of passive enhancement cavities in terms of XUV flux, even reaching comparable values to single-pass sources based on chirped-pulse fiber amplifier lasers. Our system operates at 17 MHz repetition rate generating photon energies between 60 eV and 100 eV. Importantly, this covers the highly attractive wavelength for the silicon industry of 13.5 nm at which our source delivers 60 nW of outcoupled average power per harmonic order.
... It also shows the historical progression of the intra-oscillator approach. The dashed connecting line follows the development of our system, starting from the first demonstration in 2017 [26]. A similar system has been demonstrated by the group of Midorikawa closely after in the same year [27,28]. ...
Resonant enhancement inside an optical cavity has been a wide-spread approach to increase efficiency of nonlinear optical conversion processes while reducing the demands on the driving laser power. This concept has been particularly important for high harmonic generation XUV sources, where passive femtosecond enhancement cavities allowed significant increase in repetition rates required for applications in photoelectron spectroscopy, XUV frequency comb spectroscopy, including the recent endeavor of thorium nuclear clock development. In addition to passive cavities, it has been shown that comparable driving conditions can be achieved inside mode-locked thin-disk laser oscillators, offering a simplified single-stage alternative. This approach is less sensitive to losses thanks to the presence of gain inside the cavity and should thus allow higher conversion efficiencies through tolerating higher intensity in the gas target. Here, we show that the intra-oscillator approach can indeed surpass the much more mature technology of passive enhancement cavities in terms of XUV flux, even reaching comparable values to single-pass sources based on chirped-pulse fiber amplifier lasers. Our system operates at 17 MHz repetition rate generating photon energies between 60 eV and 100 eV. Importantly, this covers the highly attractive wavelength for the silicon industry of 13.5 nm at which our source delivers 60 nW of outcoupled average power per harmonic order.
... High-power ultrafast lasers in the near-infrared (NIR) wavelength region have important applications in diverse fields, such as industrial material processing [1,2], lithography technology [3][4][5], medicine [6,7], and aerospace [8]. Furthermore, such lasers with high peak power are excellent driving sources for high-harmonic generation (HHG) [9][10][11][12], which produces ultrafast pulses in the wavelength region of extreme and vacuum ultraviolet. In addition, ultrashort terahertz (THz) [13,14] and wideband femtosecond mid-infrared (MIR) pulses [6,[15][16][17] can also be generated via nonlinear frequency conversion driven by high peak power lasers. ...
... An alternate solution is to directly undertake the conversion process within the NIR femtosecond laser oscillator [9], taking full advantage of the very high intra-cavity peak power within the cavity. However, when this is done in a linear standing-wave cavity, the forward and backward propagating NIR pulses will each generate its own MIR or high-harmonic beam, splitting the total converted output power into two parts and leading to potential wastage of the converted power. ...
... The pulse duration has been shortened down to ∼100 fs [26,27] or even less [28,29]. Until now standing-wave thin-disk oscillators have been successfully used for intra-cavity HHG [9,30]. In addition, highpower few-cycle THz pulses were generated efficiently inside a standing-wave femtosecond thin-disk oscillator recently, showing great advantage of thin-disk oscillators in the THz generation via the intra-cavity nonlinear frequency conversion [31]. ...
High-power femtosecond pulses delivered at a high-repetition rate will aid machining throughput and improve signal-to-noise ratios for sensitive measurements. Here we demonstrate a Kerr-lens mode-locked femtosecond Yb:YAG ring-cavity thin-disk oscillator with a multi-pass scheme for the laser beam. With four passes through the thin disk, 175-fs pulses were delivered from the oscillator at an average power of 71.5 W and a repetition rate of 65.3 MHz. The corresponding intra-cavity peak power of 110 MW is ample for intra-cavity nonlinear conversion into more exotic wavelength ranges. With six passes, the average output power reached 101.3 W. To the best of our knowledge, this is the highest average output power of any mode-locked ring laser. These results confirm the viability of using multi-pass configuration on a thin-disk ring oscillator for high-throughput femtosecond applications.
... The concept of HHG inside a TDL oscillator has been pioneered by our group since the last decade [9]. In this work we show the latest progress of our system when we reached a sufficiently high peak intensity inside the laser to drive HHG in neon. ...
Thin-disk laser oscillators can nowadays reach few tens of femtosecond pulses at gigawatt-level intracavity powers and megahertz-repetition rates becoming increasingly more powerful sources for intra-oscillator high harmonic generation (HHG). Currently, we can generate high harmonics in neon reaching photon energies of 70 eV, which we expect to increase toward 100 eV in the near future. In parallel, the achievable average and peak output powers of these oscillators in the range of 100 W and 100 MW, respectively, make these sources very promising to drive HHG in single-pass configuration after nonlinear pulse compression. Starting from transform-limited 30 to 50-fs soliton output soliton pulses of TDL oscillators, we will likely see these lasers approaching a single-cycle regime becoming highly attractive sources for attosecond science.
... With the Kerr-lens mode locking (KLM) scheme, the ringcavity pulses generation was first demonstrated in a Yb:YAG thin-disk oscillator with a pulse duration of 440 fs and intracavity peak power beyond 100 MW at a repetition rate of 15 MHz [22]. Afterward, 255-fs pulses at a 17-MHz repetition rate were generated in a Yb:Lu 2 O 3 thin-disk oscillator with an intra-cavity peak power of ∼60 MW by using a semiconductor saturable absorption mirror (SESAM), and it generated XUV light down to 60.8 nm [23]. In 2020, a KLM ring-cavity Yb:YAG thindisk oscillator was developed generating 610-fs pulses at the repetition rate of 3 MHz with an intra-cavity peak power of 870 MW, which enabled HHG at the wavelength of 24 nm [24]. ...
Ultrafast ring-cavity thin-disk oscillators combine high output power with the flexibility of generating output either unidirectionally or bidirectionally. Here, we report a Kerr-lens mode-locked ring-cavity Yb:YAG thin-disk oscillator delivering unidirectional 89-fs pulses by inducing additional spectral broadening with nonlinear plates. This is the shortest pulse duration for a ring-cavity mode-locked thin-disk oscillator. Bidirectional mode-locking was also realized. These results lay the foundation for the more efficient generation of high-order harmonics at MHz repetition rates and high-power dual frequency combs.
... High power ultra-short pulse lasers have significant applications in nonlinear frequency conversion [1][2][3], novel manufacturing mechanisms [4,5] and ultrafast spectroscopy [6]. Architectures based on Ytterbium (Yb 3+ ) doped gain medium with high quantum efficiency have achieved impressive results with high-power ultra-short pulse lasers pumped by high-power semiconductor laser diodes(LD) [7][8][9][10], among which bulk Yb 3+ doped crystal lasers have attracted much attention due to low cost, compactness and high efficiency [11,12]. ...
... A schematic diagram of experimental setup is illustrated in Fig. 1. Two N g -cut Yb:KGW crystals with doping concentration of 3.0 at.% and dimension of 7(N g ) × 5(N p ) × 2(N m ) mm 3 were employed as gain medium. The laser polarization direction was parallel to the N m -axis and N p -axis of the two crystals, respectively. ...
We demonstrated a TEM00 mode orthogonal dual-slab Yb:KG(WO4)2(Yb:KGW) laser oscillator with high average power. Polarization anisotropy of thermal lenses was investigated and alleviating the astigmatism based on orthogonal dual-slab. In addition, the laser polarization was directly controlled by adjusting the net gain of the two crystals. The maximum output power was highly enhanced compared with single crystal due to effective thermal distribution. For an absorbed pump power of 52.4 W, this oscillator delivered an average power of 26.5 W, corresponding to an optical-to-optical conversion efficiency of 50.6%. Meanwhile, the ellipticity of the output laser was optimized to 0.940. Nearly diffraction-limited beam quality was measured to be $M_x^2$ M x 2 = 1.19 and $M_y^2$ M y 2 =1.18.
... High power ultra-short pulse lasers have significant applications in nonlinear frequency conversion [1][2][3], novel manufacturing mechanisms [4,5] and ultrafast spectroscopy [6]. ...
We demonstrated a TEM₀₀ mode orthogonal dual-slab Yb:KG(WO₄)₂(Yb:KGW) laser oscillator with high average power. Polarization anisotropy of thermal lenses was investigated and alleviating the astigmatism based on orthogonal dual-slab. In addition, the laser polarization was directly controlled by adjusting the net gain of the two crystals. The maximum output power was highly enhanced compared with single crystal due to effective thermal distribution. For an absorbed pump power of 52.4 W, this oscillator delivered an average power of 26.5 W, corresponding to an optical-to-optical conversion efficiency of 50.6%. Meanwhile, the ellipticity of the output laser was optimized to 0.940. Nearly diffraction-limited beam quality was measured to be M_x^2 =1.19 and M_y^2=1.18.
... Since the concept of thin-disk lasers was first presented in 1994 [1], ultrafast thin-disk lasers have become a promising laser source for a vast number of applications in micromachining [2], high-harmonic generation (HHG) [3][4][5], high-field science [6], and generation of mid-infrared pulses [7]. Ultrafast thin-disk lasers have more advantages in terms of thermal management than conventional bulk lasers, resulting in higher repetition rate, higher average power, higher pulse energy, as well as better beam quality [8][9][10]. ...
We experimentally demonstrate a 38-fs chirped-pulse amplified (CPA) Ti:sapphire laser system based on the power-scalable thin-disk scheme with an average output power of 1.45 W at a repetition rate of 1 kHz, corresponding to peak power of 38 GW. The beam profile close to the diffraction limit with a measured M² value of approximately 1.1 is obtained. It demonstrates the potential for an ultra-intense laser with high beam quality compared with the conventional bulk gain amplifier. To the best of our knowledge, this is the first reported Ti:sapphire regenerative amplifier based on the thin-disk approach reaching 1 kHz.
... The field enhancement within the cavity enables generating the required peak power even at up to several-hundred-megahertz repetition rate [1]. A simplified approach of fsEC is to drive the HHG directly within a high-power femtosecond laser oscillator [2]. Both these concepts typically use a collinear generation geometry, which requires optical elements to separate the generated XUV from the driving laser. ...
