We report a compact ultrafast solid-state laser source with a pulse repetition rate tunable in the range of 0.5 – 1.3 GHz. The optical cavity design allows a user to vary the repetition rate only by moving the mirrors. The Yb:KYW crystal-based laser emits 250 fs pulses at a central wavelength of 1040nm and the SESAM modelocking enables self-starting. An average power up to 150 mW is achieved using a stabilized single mode pump source at 981 nm, emitting up to 800 mW. In continuous wave mode, up to 270 mW were measured with an optical-to-optical efficiency of 33%.
We report output characteristics from the FC/APC connectorized photonics crystal hollow core fiber when is subjected to coiling down to 50 mm radius, bending, torsion etc. We achieved coupling efficiency up to 75%, output average power 2 W and 24 nJ pulse energy. With proper coupling the depolarization could be as low as 7%. Torsion of the photonic crystal patchcord destroys the polarization and other pulse properties.
There is a growing demand for ultrafast laser systems with high average power and repetition rate. We present two hybrid master oscillator power amplifier (MOPA) architectures employing variety of available technologies to achieve 100 W average power femtosecond pulses. We achieved 120 W 820 fs pulses using solid-state oscillator and fiber amplifiers and chirped pulse amplification (CPA) technique (10 μJ pulse energy at 10 MHz and 100 μJ at 400 kHz). In the second experiment, we achieved 160 W 800 fs pulses in a compact system without the standard CPA using solidstate oscillator and single crystal fiber amplifiers. As currently every component experiences some limitations, it is a challenge to choose the optimal architecture with associated components to achieve a desired combination of laser output parameters.
Single crystal fibers (SCF) represent an alternative technology for ultrashort pulse amplification to high average power in a simple architecture. SCF have an aspect ratio of a short rod fiber or a thin and long crystal and benefit several advantages from the both concepts. Relatively short interaction length and large signal beam diameter mitigate the nonlinear effects and allow direct amplification of femtosecond pulses avoiding the standard chirped pulse amplification (CPA) technique. In this paper, we demonstrate the amplification of femtosecond pulses up to 160 W of average power using a compact and simple two-stage SCF amplifier without CPA. High brightness pumping and a double-pass signal configuration of the first stage allowed us to reach the small signal gain value of 32.5 dB, i.e. almost 2000, which is the highest reported value. Additionally, we implemented for the first time the bidirectional pumping scheme in the second stage. With the total pump power of 300 W, we achieved the highest average power of femtosecond pulses and the highest extraction efficiency from the SCF, i.e. 160 W and 42 %, respectively. The pulse duration at the maximum output power was measured to be 800 fs assuming sech2 temporal shape. The amplification details and spectral, temporal and spatial characterization of the output beam will be presented.
Ti:sapphire oscillators are a proven technology to generate sub-100 fs (even sub-10 fs) pulses in the near infrared and are widely used in many high impact scientific fields. However, the need for a bulky, expensive and complex pump source, typically a frequency-doubled multi-watt neodymium or optically pumped semiconductor laser, represents the main obstacle to more widespread use. The recent development of blue diodes emitting over 1 W has opened up the possibility of directly diode-laser-pumped Ti:sapphire oscillators. Beside the lower cost and footprint, a direct diode pumping provides better reliability, higher efficiency and better pointing stability to name a few. The challenges that it poses are lower absorption of Ti:sapphire at available diode wavelengths and lower brightness compared to typical green pump lasers. For practical applications such as bio-medicine and nano-structuring, output powers in excess of 100 mW and sub-100 fs pulses are required. In this paper, we demonstrate a high average power directly blue-diode-laser-pumped Ti:sapphire oscillator without active cooling. The SESAM modelocking ensures reliable self-starting and robust operation. We will present two configurations emitting 460 mW in 82 fs pulses and 350 mW in 65 fs pulses, both operating at 92 MHz. The maximum obtained pulse energy reaches 5 nJ. A double-sided pumping scheme with two high power blue diode lasers was used for the output power scaling. The cavity design and the experimental results will be discussed in more details.
We describe a multi-stages single crystal fiber (SCF) amplifier for the amplification of femtosecond pulses with radial or azimuthal polarization in view of high speed material processing (surface structuring, drilling). We demonstrate a three stages diode-pumped Yb:YAG single crystal fiber amplifier to achieve femtosecond pulses at an average power of 85W at 20 MHz in radial and azimuthal polarization.
In this work, we discuss mode-locking results obtained with low-loss, ion-exchanged waveguide lasers. With Yb3+-doped phosphate glass waveguide lasers, a repetition rate of up to 15.2 GHz was achieved at a wavelength of 1047 nm with an average power of 27 mW and pulse duration of 811 fs. The gap between the waveguide and the SESAM introduced negative group velocity dispersion via the Gires Tournois Interferometer (GTI) effect which allowed the soliton mode-locking of the device. A novel quantum dot SESAM was used to mode-lock Er3+, Yb3+-doped phosphate glass waveguide lasers around 1500 nm. Picosecond pulses were achieved at a maximum repetition rate of 6.8 GHz and an average output power of 30 mW. The repetition rate was tuned by more than 1 MHz by varying the pump power.
We present timing jitter measurements of an actively stabilized SESAM modelocked VECSEL generating 4-ps pulses
with 2-GHz repetition rate and 20-mW average output power. The repetition rate was phase-locked to a reference source
using a piezo actuator. The timing phase noise power spectral density of the laser output was measured with an Agilent
E5052B Signal Source Analyzer. The resulting rms timing jitter integrated over an offset frequency range from 1 Hz to
1 MHz gives a timing jitter of below 80 fs, several times lower than previous modelocked VECSELs and comparable to
the noise performance of ion-doped solid-state-lasers.
We demonstrate a novel low-cost, low-noise, tunable, high-peak-power, ultrafast laser system based on a SESAMmodelocked,
solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse
compression. The spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The
spectral broadening and fiber parameters are chosen to insure low-noise and short pulse operation of the tunable output.
The long-term stable output pulses are tunable from 800 to 1200 nm, with a peak power up to 30 kW and pulse duration
down to 26 fs. We demonstrate the generation of an output beam with 30 fs pulsewidth and multiple colors in infrared.
In particular, we compressed selected spectral slices centered at 960 and 1100 nm suitable for imaging with green
fluorescent protein and red dyes. Such a multicolor, 30 fs laser is ideally suited for simultaneous multispectral
multiphoton imaging. This system is attractive for variety of applications including multiphoton (TPE, SHG, THG,
CARS) and multimodal microscopy, nanosurgery, and optical coherence tomography (OCT). Such system is simpler,
lower-cost, and much easier to use (fully turn-key) compared to a currently available solutions for near-infrared
ultrashort pulses, typically a Ti:sapphire laser-pumped OPO.
We demonstrate a novel low noise, tunable, high-peak-power, ultrafast laser system based on a SESAM-modelocked,
solid-state Yb tungstate laser plus spectral broadening via a microstructured fiber followed by pulse compression. The
spectral selection, tuning, and pulse compression are performed with a simple prism compressor. The spectral
broadening and fiber parameters are chosen to insure low-noise operation of the tunable output. The long-term stable
output pulses are tunable from 800 to 1200 nm, with a peak power up to 30 kW and pulse duration down to 26 fs. This
system is attractive for variety of applications including ultrafast spectroscopy, multiphoton (TPE, SHG, THG, CARS)
and multimodal microscopy, nanosurgery, nanostructuring, and optical coherence tomography (OCT). Such system is
simpler, lower-cost, and much easier to use (fully turn-key) compared to a currently available solutions for near-infrared
ultrashort pulses, typically a Ti:sapphire laser-pumped OPO.
Recent development of optically-pumped semiconductor laser (OPSL) technology provide a Ti:sapphire pump source
reducing cost and complexity while maintaining a high standard of performance and reliability. In this paper we report
on the performance of a compact (930 x 330 x 170 mm³), cavity-dumped ultrafast Ti:Sapphire laser oscillator pumped by
an OPSL and using negative dispersion mirrors. The system generates broadband pulses of more than 45nJ pulse energy
from single shot to 2 MHz repetition rate. At higher repetition rates the pulse energy decreases as it is typical for cavity
dumped laser systems, but with 10 nJ at 27 MHz (division ratio of 1:2) the pulse energy is at the level of the Mantis in
standard configuration (8 nJ). FWHM spectrum of the Mantis is specified >70nm and bandwidth over 100nm could be
achieved by fine adjustment of the dispersion with intracavity wedges. Compressed pulse duration down to 12.5fs was
measured. The system is based on the standard Coherent Mantis laser with a cavity dumper extension, making the
footprint only 350 mm longer. It can be user configured either as standard oscillator or as a cavity dumped oscillator.
Ultrashort pulse (USP) Ti:Sapphire oscillators are constantly improving in cost, performance, and reliability. These
improvements have been driven in part by improvements in the CW lasers used to pump the Ti:Sapphire gain medium.
Recent development of optically-pumped semiconductor (OPS) lasers heralds a USP pump source that reduces cost and
complexity while maintaining a high standard of performance and reliability. OPS lasers offer significant advantages
with respect to traditional diode-pumped solid state (DPSS) lasers in regards to wavelength flexibility, broad pump
tolerance, efficient spectral and spatial brightness conversion and high power scaling. In this paper, we report the
performance of different types of ultrashort pulse Ti:Sapphire oscillators pumped by OPS lasers: broad bandwidth
(approximately 100 nm) negative dispersion mirror based, broad bandwidth (approximately 100 nm) prism based, and
narrower bandwidth (approximately 10 nm) tunable prism based oscillator. We analyze the impact of multimode spatial
mode operation of the OPS pump laser on the mode quality, bandwidth and intensity noise of the USP oscillator output.
We compare the performance of USP oscillators pumped by multiple transverse mode OPS lasers with traditional single
transverse mode Nd:YVO4 DPSS lasers. We demonstrate excellent regenerative amplifier seeding with the OPS
pumped Ti:Sapphire oscillator.
A novel device designed for pulse shaping, characterization and phase compensation in ultrafast laser systems is
described. The pulse shaper exhibits low transmission loss and is widely applicable to lasers with spectral bandwidth
from 10 nm to over 400 nm. Pulse characterization and phase compensation is fully computer controlled in a closed loop
via MIIPS method. This system is designed to enhance performance of ultrafast oscillators and ultrafast amplifiers
including terawatt lasers and cryogenically cooled amplifier systems. Seed laser spectral amplitude shaping results in
increased bandwidth while preserving the output power in ultrafast regenerative amplifiers. Subsequent phase
compensation enables the robust delivery of output pulses within couple of percent of transform limit. Such system
could find numerous applications including MPE microscopy, CARS, and more general coherent control experiments.
Cryogenic cooling of Ti:Sapphire is a well known technique for improving its thermal performance. In particular the
improvement in thermal conductivity, temperature dependence of the index of refraction and thermal expansion around
77 K dramatically reduces the thermal lensing. This allows a significant increase in the possible pump power, while
keeping a very good beam quality over a wider range of operation. As an example we demonstrate a single-stage
regenerative amplifier that is capable of delivering compressed output powers of 7.5 W and 11.9 W at 1 and 5 kHz,
respectively, as well as a multi-pass amplifier delivering 13.2 W at 1 kHz.
The gain dynamics of a semiconductor optical amplifier (SOA) are studied for the amplification of long, short and multiwavelength pulses from an external cavity semiconductor mode-locked laser. Nonlinear effects such as carrier heating and cooling, four wave mixing, and self phase modulation are observed, and it is shown how the inherent chirp of semiconductor mode-locked laser pulses helps to avoid these nonlinear effects.
A novel dispersion-managed breathing-mode mode-locked semiconductor ring laser is studied. The working regime and pulse evolution at the key cavity points are experimentally characterized and numerically simulated. Linearly chirped, asymmetric exponential pulses are generated, suitable for external amplification and compression. The pulses are externally compressed to duration as short as 274 fs, which is within 10% of the bandwidth limit. The close agreement between the simulated and the measured results verifies our ability to control the physical mechanisms involved in pulse formation and shaping within the ring cavity.
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