Compact Diode-pumped Solid-state Lasers Research Articles

Compact Diode-Pumped Solid-State Laser with Intracavity Pump-Enhanced DFG Emitting at ~3.5 Microns

We report a diode-pumped solid-state (DPSS) laser used for intracavity pump-enhanced difference frequency generation (DFG) to create a 3.5-micron laser. Using a 50 mm-long periodically poled lithium niobate (PPLN) crystal inside the cavity of an Nd:YVO4 solid-state laser at 1064 nm with 4.5 W pump power at 808 nm, and a 310 mW C-band signal at 1529 nm, up to 31 mW of mid-infrared output power at 3499 nm is obtained. The cavity requires no active stabilization and/or locking, and the entire cavity is <8 cm in length. The obtained output power corresponds to a black-box efficiency of 2.20%W−1, which is the highest value reported to date for continuous-wave DFG based on a bulk nonlinear optical crystal with no active stabilization. Potential future applications in free-space optical communication are also discussed.

Intracavity losses effect on mode-locking in a waveguide laser with graphene saturable absorber

A single-wavelength compact diode-pumped solid-state laser based on a single-mode waveguide with a diameter of 20 µm and graphene saturable absorber is presented in this work. The total reflection coefficient of the intracavity interferometer has a significant effect on the level of intracavity losses. By accurate controlling the intracavity losses a stable continuous wave passive mode-locking at wavelength of 1064 nm with a pulse repetition rate of 9.5 GHz was obtained.

First tests of laser ignition in Wankel engine

Laser ignition has been studied in powerful four-stroke engines, not only because of the fast payback, but also because of the more convenient diagnostics in a large scale setup. High-performance compact engines have not been studied, even though advantages of laser ignition could be much more pronounced for those because of harmful emission reduction and multi-fuel abilities. Compact piston engines are considered as an alternative for fuel elements and batteries for portable, automotive and unmanned aerial vehicles. These are characterized by a small combustion chamber comparable to the spark plug inter-electrode gap in axial direction, and its low ratio to bore size. However, for Wankel engines this problem exists at any scale. Laser ignition of lean fuel mixtures in such engines could significantly improve performance by reduced fuel consumption, thermal loads, and a cleaner exhaust. We have investigated the possibility of laser ignition in rotary-piston (Wankel) sub-kW scale model engine using different kinds of fuel mixtures: hydrogen, methane, propane, butane, gasoline, and ethanol based. A custom built compact diode-pumped solid state laser has been used to substitute the original glow plug, respectively. Laser ignition has been found possible and quite beneficial for both types of engines and different fuel mixtures; in terms of NOx emission reduction especially.

Focus on lasers, imaging, and microscopy

Focus on lasers, imaging, and microscopy

Scalable broadband OPCPA in Lithium Niobate with signal angular dispersion

Angular dispersion of the signal beam is proposed for efficient, scalable high-power few-cycle pulse generation in LiNbO3 by optical parametric chirped-pulse amplification (OPCPA) in the 1.4 to 2.1µm wavelength range. An optimized double-grating setup can provide the required angular dispersion. Calculations predict 16.8fs (3 cycles) pulses with 13TW peak power. Further scalability of the scheme towards the 100-TW power level is feasible by using efficient, cost-effective, compact diode-pumped solid-state lasers for pumping directly at 1µm, without second-harmonic generation.

Femtosecond diode-pumped solid-state laser with a repetition rate of 48 GHz

We report on a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungstate) laser with a repetition rate of 4.8 GHz and a pulse duration of 396 fs. Stable fundamental modelocking is achieved with a semiconductor saturable absorber mirror (SESAM). The average output power of this compact diode-pumped solid state laser is 1.9 W which corresponds to a peak power of 0.9 kW and the optical-to-optical efficiency is 36%. To the best of our knowledge, this is the femtosecond DPSSL with the highest repetition rate ever reported so far.

Diode-pumped miniature lasers using microstructured silicon carriers

A new versatile design concept for compact diode-pumped solid-state lasers based on a microstructured silicon carrier with etched V-grooves is presented. The carrier provides efficient thermal management as well as compact integration and alignment of all active and passive optical components. In initial experiments, an Nd:YAG laser delivered a continuous-wave output of 3 W.

Intracavity frequency doubling of a continuous-wave, diode-laser-pumped neodymium lanthanum scandium borate laser

Neodymium-doped lanthanum scandium borate [Nd:LaSc(3)(BO(3))(4)] is a new material for efficient and compact diode-pumped solid-state lasers. A simple plane-plane 3-mm-long resonator is formed by a coated Nd(10%):LaSc(3)(BO(3))(4) crystal and a coated potassium titanyl phosphate (KTP) crystal. The second-harmonic output power at 531 nm is 522 mW at 2.05-W incident pump power of the diode laser. The corresponding optical efficiency is 25%, and the conversion efficiency from the fundamental to the second harmonic is 55%. The wellknown chaotic power fluctuations of intracavity frequency-doubled lasers (green problem) are avoided by use of a short KTP crystal, between 0.5 and 2 mm in length.

Scalable concept for diode-pumped high-power solid-state lasers

A new, scalable concept for diode-pumped high-power solid-state lasers is presented. The basic idea of our approach is a very thin laser crystal disc with one face mounted on a heat sink. This allows very high pump power densities without high temperature rises within the crystal. Together with a flat-top pump-beam profile this geometry leads to an almost homogeneous and one-dimensional heat flux perpendicular to the surface. This design dramatically reduces thermal distortions compared to conventional cooling schemes and is particularly suited for quasi-three-level systems which need high pump power densities. Starting from the results obtained with a Ti:Sapphire-pumped Yb:YAG laser at various temperatures, the design was proved by operating a diode-pumped Yb:YAG laser with an output power of 4.4 W and a maximum slope efficiency of 68%. From these first results we predict an exctracted cw power of 100 W at 300 K (140 W at 200 K) with high beam quality from a single longitudinally pumped Yb: YAG crystal with an active volume of 2 mm3. Compact diode-pumped solid-state lasers in the kilowatt range seem to be possible by increasing the pump-beam diameter and/or by using several crystal discs.

Development of the nonlinear optical crystal CsTiOAsO 4 II. Crystal growth and characterization

We report here the crystal growth and characterization of the new nonlinear optical crystal CsTiOAsO 4 (CTA). We have studied the Cs 2O-TiO 2-As 2O 5 ternary and identified the phase field within which orthorhombic CTA can be crystallized. Large inclusion-free single crystals measuring up to 30×20×25 mm 3 can be readily grown using the Cs 5As 3O 10 self-flux. As grown CTA crystals have the same crystal facets as KTP, although they tend to be multidomain. We present here two techniques for removing these domains: by trivalent oxide dopings and by ferroelectric poling. The refractive indices, nonlinear optical coefficients, electro-optic coefficients and dielectric properties of single domain CTA crystals are reported. Compared to the crystal KTiOPO 4, the smaller birefringence of CTA makes it particularly suitable for frequency doubling fundamental wavelengths between 1.3 and 1.5 μm. Our results suggest that CTA should find practical applications in electrooptic and in frequency conversion applications, such as optical parametric oscillators and compact diode-pumped solid state lasers.