Articles

Oscillators

• Ti:sapphire laser synchronised with femtosecond Yb pump laser via nonlinear pulse coupling in Ti:sapphire active medium

Tricolor
The Tricolor multi-channel femtosecond system has three inherently synchronized output channels with low relative jitter <1 fs.
Wavelength	1050 / 525 / 800 nm
Average power	1 W / 300 mW / 300 mW
Pulse duration	200 / 200 / 100 fs
Repetition rate	80 MHz
Jitter between channels	<1 fs
N.V. Didenko, A. V. Konyashchenko, D. A. Konyashchenko, P. V. Kostryukov, I. I. Kuritsyn, A. P. Lutsenko, A. O. Mavritskiy
A laser system utilising the method of synchronous pumping of a Ti : sapphire laser by a high-power femtosecond Yb³⁺-doped laser is described. The pulse repetition rate of the Ti : sapphire laser is successfully locked to the repetition rate of the Yb laser for more than 6 hours without the use of any additional electronics. The measured timing jitter is shown to be less than 1 fs. A simple qualitative model addressing the synchronisation mechanism utilising the cross-phase modulation of oscillation and pump pulses within a Ti : sapphire active medium is proposed. Output parameters of the Ti : sapphire laser as functions of its cavity length are discussed in terms of this model. A laser system utilising the method of synchronous pumping of a Ti : sapphire laser by a high-power femtosecond Yb³⁺-doped laser is described. The pulse repetition rate of the Ti : sapphire laser is successfully locked to the repetition rate of the Yb laser for more than 6 hours without the use of any additional electronics. The measured timing jitter is shown to be less than 1 fs. A simple qualitative model addressing the synchronisation mechanism utilising the cross-phase modulation of oscillation and pump pulses within a Ti : sapphire active medium is proposed. Output parameters of the Ti : sapphire laser as functions of its cavity length are discussed in terms of this model.
Keywords: synchronous pumping, femtosecond pumping, Ti:sapphire laser, cross-phase modulation.
http://iopscience.iop.org/article/10.1070/QEL16246/meta
• Femtosecond Er3+ fiber laser for application in an optical clock

EFO-COMB
Femtosecond mode-locked Er-doped PM fiber laser with 4 PM fiber-coupled outputs including an Er-fiber amplifier for supercontinuum generation, as well as an f-2f interferometer with sync and locking electronics.
Spectral range	520-2200 nm
Comb spacing (Frep)	125 MHz
Tuning range of offset frequency Fceo	>100 MHz
Stability	5*10^-13 in 1 s
M. A. Gubin, A. N. Kireev, A. V. Tausenev, A. V. Konyashchenko, P. G. Kryukov, D. A. Tyurikov, A. S. Shelkovikov The main elements needed for the realization of a compact femtosecond methane optical clock are developed and studied. A femtosecond laser system on an Er3+ fiber (λ = 1.55 μm) contains an oscillator, an amplifier, and a fiber with a relatively high nonlinearity in which the supercontinuum radiation is generated in the range 1–2 μm. In the supercontinuum spectrum, the fragments separated by an interval that is close to the methane-optical reference frequency (λ = 3.39 μm) exhibit an increase in intensity. The supercontinuum radiation is converted into the difference frequency in a nonlinear crystal to the range of the methane-reference frequency (λ = 3.3–3.5 μm), so that the frequency components of the transformed spectrum have sufficient intensities for the subsequent frequency-phase stabilization with respect to the methane reference. A system that stabilizes the pulse repetition rate of the femtosecond Er3+laser is also employed. Thus, the repetition rate of the ultrashort pulses of the femtosecond fiber laser is locked to the methane reference. The pulse repetition rate is compared with the standard second. Thus, the scheme of an optical clock is realized.
https://link.springer.com/article/10.1134/S1054660X07110023
• Efficient source of femtosecond pulses and its use for broadband supercontinuum generation

EFOA-UB
Turn-key compact pulsed fiber white-light generator with fiber-coupled output.
Spectral coverage	1100-2000 nm
Average output power	>150 mW
Repetition rate	50...70 MHz
Anton V. Tausenev, P. G. Kryukov, M. M. Bubnov, M. E. Likhachev, E. Yu. Romanova, M. V. Yashkov, V. F. Khopin and M. Yu. Salganskii A femtosecond Er3+-doped fibre laser system is developed and studied. The system contains a master oscillator operating in the pulse stretching regime, an amplifier of chirped pulses, and a device for pulse compression. The laser emits 1.55-μm, 100-fs, 90-mW pulses with a pulse repetition rate of 25 MHz. The setup was used for supercontinuum generation in an optical fibre heavily doped with GeO2. The width of the generated supercontinuum was close to an octave.
http://iopscience.iop.org/article/10.1070/QE2005v035n07ABEH006586
• Self-mode-locking in erbium-doped fibre lasers with saturable polymer film absorbers containing single-wall carbon nanotubes synthesised by the arc discharge method

EFO
Mode-locked femtosecond fiber lasers based on Er-doped active fibers. Include models with simple oscillators, as well as models with one or several additional preamplifiers.
Wavelength	1560±10 nm
Pulse duration	50 fs to 5 ps
Average power	10 mW to 5 W
Repetition rate	65...100 MHz (fixed)
Anton V. Tausenev, Elena D. Obraztsova, A. S. Lobach, A. I. Chernov, Vitalii I. Konov, Aleksandr V. Konyashchenko, P. G. Kryukov and Evgenii M Dianov We studied the ring and linear schemes of erbium-doped fibre lasers in which passive mode locking was achieved with the help of saturable absorbers made of high-optical quality films based on cellulose derivatives with dispersed single-wall carbon nanotubes. The films were prepared by the original method with the use of nanotubes synthesised by the arc discharge method. The films exhibit nonlinear absorption at a wavelength of 1.5 μm. Pulses in the form of optical solitons of duration 1.17 ps at a avelength of 1.56 μm were generated in the ring scheme of the erbium laser. The average output power was 1.1 mW at a pulse repetition rate of 20.5 MHz upon pumping by the 980-nm, 25-mW radiation from a laser diode. The pulse duration in the linear scheme was reduced to 466 fs for the output power up to 4 mW and a pulse repetition rate of 28.5 MHz. The specific feature of these lasers is a low pump threshold in the regime of generation of ultrashort pulses.
http://iopscience.iop.org/article/10.1070/QE2007v037n03ABEH013520
• Fabrication of superconducting nanowire single-photon detectors by nonlinear femtosecond optical lithography

TEMA
Yb-doped solid-state ultrafast laser with high average power output around 1 um and short femtosecond pulse duration.
Wavelength	1050 nm
Pulse duration	70...150 fs
Average power	up to 12 W
Repetition rate	80 MHz
N. V. Minaev, M. A. Tarkhov, D. S. Dudova, P. S. Timashev, B. N. Chichkov and V. N. Bagratashvili This paper describes a new approach to the fabrication of superconducting nanowire single-photon detectors from ultrathin NbN films on SiO₂ substrates. The technology is based on nonlinear femtosecond optical lithography and includes direct formation of the sensitive element of the detector (the meander) through femtosecond laser exposure of the polymethyl methacrylate resist at a wavelength of 525 nm and subsequent removal of NbN using plasma-chemical etching. The nonlinear femtosecond optical lithography method allows the formation of planar structures with a spatial resolution of ~50 nm. These structures were used to fabricate single-photon superconducting detectors with quantum efficiency no worse than 8% at a wavelength of 1310 nm and dark count rate of 10 s⁻¹ at liquid helium temperature. Keywords: optical lithography, nanostructures, single-photon detector, femtosecond lithography
http://iopscience.iop.org/article/10.1088/1612-202X/aa8bd1/meta
• Highly effective 525 nm femtosecond laser crosslinking of collagen and strengthening of a human donor cornea

TEMA
Yb-doped solid-state ultrafast laser with high average power output around 1 um and short femtosecond pulse duration.
Wavelength	1050 nm
Pulse duration	70...150 fs
Average power	up to 12 W
Repetition rate	80 MHz
B.S. Shavkuta, M.Y. Gerasimov, N.V. Minaev, D.S. Kuznetsova, V.V. Dudenkova, I.A. Mushkova, B.E. Malyugin, S.L. Kotova, P.S. Timashev, S.V. Kostenev
A two-photon laser femtosecond crosslinking process at the wavelength of 525 nm was studied in a human donor cornea in the presence of riboflavin using two-photon optical microscopy and nanoindentation. It was shown that such an approach results in efficient crosslinking of the corneal collagen and a significant (three-fold) increase in the Young's modulus of the corneal structure. Application of a femtosecond laser with the wavelength of 525 nm allows a drastic enhancement of efficiency in the presence of riboflavin on human corneas and a 50-fold reduction of the laser treatment duration in comparison with the use of a femtosecond laser with the wavelength of 760 nm. We relate this effect to a significant growth in the coefficient of two-photon absorption due to the laser wavelength falling within the edge of the photoinitiator (riboflavin) absorption band. Our studies on a donor human cornea demonstrate the good potential for the clinical application of a femtosecond laser with the wavelength of 525 nm for increasing the cornea rigidity using the two-photon laser femtosecond crosslinking technique. Keywords: 525 nm femtosecond laser, human cornea, two-photon collagen crosslinking, keratoconus, riboflavin, micromechanical properties
http://iopscience.iop.org/article/10.1088/1612-202X/aa963b/meta

Amplifiers

• An atom probe tomography prototype with laser evaporation

TETA
Femtosecond Yb-doped diode-pumped solid-state amplifier system with an integrated fiber seed oscillator is ideally suitable for industrial applications such as micromachining, as well as for scientific research activities.
Average power	up to 20 W
Central wavelength	1030 nm
Pulse energy	up to 2 mJ
Repetition rate	up to 1 MHz
Pulse duration	<270 fs
S.V. Rogozhkin, A.A. Aleev, A.A. Lukyanchuk, A.S. Shutov, O.A. Raznitsyn, S.E. Kirillov The results of development, creation, and tests of an atom-probe prototype with femtosecond laser evaporation and a position-sensitive microchannel detector with delay lines for the tomographic (3D) analysis of chemical composition of materials are presented. The atom-probe tomography is based on the principle of atom-by-atom “disassembling” of materials and projection magnification, which was previously used in field-ion microscopy, as well as the time-of-flight mass spectrometry that is applied to each evaporated ion. The prototype characteristics (mass resolution, spatial resolution, and data-collection efficiency) were demonstrated in study of tungsten.
https://link.springer.com/article/10.1134/S002044121702021X
• Multiterawatt Hybrid (Solid/Gas) Femtosecond Systems in the Visible (Chapter 6 from High Energy and Short Pulse Lasers)

REUS
A family of regenerative and multipass ultrafast solid-state titanium-sapphire laser amplifiers. The systems produce ultra-short pulses in microjoule and millijoule pulse energy range.
Central wavelength	800±20 nm (fixed)
Pulse energy	from 50 uJ to 40 mJ
Pulse repetition rate	up to 10 kHz
Pulse duration	from 30 to 120 fs
Leonid D. Mikheev and Valery F. Losev (2016). Multiterawatt Hybrid (Solid/Gas) Femtosecond Systems in the Visible, High Energy and Short Pulse Lasers, Dr. Richard Viskup (Ed.), InTech, DOI: 10.5772/63972. A novel hybrid (solid/gas) approach to the development of femtosecond high‐intensity laser systems operating in the visible is presented in this chapter. Behind this approach is a combination of a solid‐state front end relying on widespread and highly developed techniques for femtosecond pulse generation in the near infrared with a photochemically driven boosting amplifier operating in the visible spectral range. Historical background of developing photochemically pumped gas lasers on broad bandwidth electronic transitions in molecules and physical principles of their operation are briefly summarized as well. The architecture and the design issues of the hybrid femtosecond systems relying on the amplification of the second harmonic of Ti:sapphire front ends in the photodissociation XeF(C‐A) power‐boosting amplifiers driven by the VUV radiation from electron‐beam‐to‐VUV‐flash converters are described, as well as breakthrough results of proof‐of‐principle experiments demonstrating a high potential of the hybrid approach. Wavelength scaling of laser‐matter interaction is shortly discussed to demonstrate advantages of shorter driver wavelengths for some applications with main emphasis placed on recombination‐pumped soft X‐ray lasers.
https://www.intechopen.com/books/high-energy-and-short-pulse-lasers/multiterawatt-hybrid-solid-gas-femtosecond-systems-in-the-visible
• Femtosecond Laser Simulation Facility for SEE IC Testing

REUS
A family of regenerative and multipass ultrafast solid-state titanium-sapphire laser amplifiers. The systems produce ultra-short pulses in microjoule and millijoule pulse energy range.
Central wavelength	800±20 nm (fixed)
Pulse energy	from 50 uJ to 40 mJ
Pulse repetition rate	up to 10 kHz
Pulse duration	from 30 to 120 fs
A. N. Egorov et al., "Femtosecond Laser Simulation Facility for SEE IC Testing," 2014 IEEE Radiation Effects Data Workshop (REDW), Paris, 2014, pp. 1-4. doi: 10.1109/REDW.2014.7004570 The new SEE laser simulation facility based on femtosecond laser source with tunable pulse duration is presented, and its most important features are discussed. The influence of laser pulse duration on simulation results is observed.
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=7004570&isnumber=7004502

Diagnostics

• Contrast degradation in a chirped-pulse amplifier due to generation of prepulses by postpulses

COMET
The device is used to measure contrast of femtosecond pulses and to determine pulse pedestal, pre- and post-pulses, as well as amplified spontaneous emission (ASE) in femtosecond amplifier systems.
Possible input wavelength range	700-1500 nm
Scan range	up to 4 ns
Dynamic range	10^10
Sensitivity	50-100 uJ
N.V. Didenko, A.V. Konyashchenko, A.P. Lutsenko, and S.Yu. Tenyakov Experiment and modeling show that the refractive index nonlinearity can significantly degrade the contrast of a chirped-pulse amplifier seeded with a pulse and a single postpulse. Multiple powerful non-equidistant pre- and postpulses are generated. For a Gaussian pulse and a hat-top beam, an incident postpulse of energy W results in a prepulse of energy 0.58B^2 W, where B is the nonlinear phase (B-integral) of the main pulse. Calculations show that level of satellites due to gain saturation is negligibly small. Experimental results for Ti:Sapphire regenerative and multipass amplifiers and prepulse generation in fused silica agree well with the theory.
https://doi.org/10.1364/OE.16.003178

Components

• Efficient amplification of a femtosecond Ti:sapphire laser with a ring regenerative amplifier

OG-B/F
Electro-optic pulse picker systems with fixed gate open time are used to select single pulses from a train of femtosecond pulses for numerous applications. The systems are also used for injection/ejection purposes in an ultrafast laser amplifier system, as well as for amplifier contrast improvement.
Possible operating wavelength range	200...2700 nm
Max. output rep. rate	up to 1 MHz
Rise time	down to 700 ps
Clear aperture	up to 20 mm
Contrast ratio	>1500:1
Wei Zhang, Hao Teng, Zhaohua Wang, Zhongwei Shen, and Zhiyi Wei, Appl. Opt. 52, 1517-1522 (2013).  A high-stability and high-efficiency ring Ti:sapphire regenerative amplifier is demonstrated based on a double-gating pulse picker at a repetition rate of 1 kHz. Pulse energy up to 5.7 mJ is obtained using a pump energy of 20.0 mJ at 527 nm, corresponding to a relatively high slope efficiency of 30.3%. After a grating compressor, the laser pulse is compressed to 37.2 fs with an energy of 4.1 mJ. The beam quality factors M2 are 1.4 and 1.3 in tangential and sagittal directions, respectively. The measured root mean square energy stability is better than 0.31% over an 11 h period.
https://doi.org/10.1364/AO.52.001517