High-power Diode-pumped Solid-state Lasers Research Articles

Accurate thermal stress induced birefringence measurement of laser crystal with cavity ring-down technique

One of the main sources of beam quality deterioration encountered in high-power diode-pumped solid-state lasers is the thermal stress induced birefringence. Cavity ring-down (CRD) technique is applied to the accurate measurement of thermal stress induced birefringence of laser crystal under pump diode laser illumination. Measurements of the pump laser illumination induced temperature profile and thermal stress induced birefringence retardance distribution in the laser crystal are performed and compared to numerical calculations to determine the absorption and thermal diffusivity of the laser crystal and further the relevant stress-optical constant. The experimental results demonstrated that CRD is a highly sensitive and accurate technique to measure the thermal stress induced birefringence and relevant stress-optical constant of laser crystals, which is helpful for the evaluation and optimization of the performance of high-power laser systems.

Cycloidal diffractive waveplates fabricated using a high-power diode-pumped solid-state laser operating at 532 nm

Diffractive waveplates (DWs) are highly efficient optical components realized by means of a polarization holography setup that makes use of UV/blue laser sources. It is more convenient to perform the holographic recording process with green lasers (e.g., continuous wave operating at 532 nm) because they offer compactness, efficiency, and high power. Unfortunately, the photo-alignment materials used for DW fabrication exhibit limited sensitivity at 532 nm. Herein, we report the realization of cycloidal diffractive waveplates (CDWs) by employing a polarization holographic setup using a high-power, diode-pumped solid-state laser operating at 532 nm. The enabling factor is the use of a photo-alignment material with a broad absorption band extending into the visible part of the spectrum. Samples are characterized in terms of morphological and optical properties. They exhibit a well-defined morphology along with very high diffraction efficiency (≈97%). The possibility to realize CDWs with larger apertures is underway, enabling the realization of a new generation of optical components for integration in modern applications.

High-power diode-pumped solid-state lasers

Diode-pumped solid-state laser technology is reviewed with an emphasis on laser materials and concepts important to high power systems with excellent beam quality. A first principal approach to power scaling is taken in order to summarize and compare the wide variety of laser architectures. Successful approaches are highlighted and directions for future work are discussed.

Self-compensation of thermal lens in high-power diode pumped solid-state lasers

We present a comprehensive model to describe the optic-thermal coupling in the diode pumped solid-state lasers (DPSSL). The thermal transition of particles at the upper laser level leads the heat-generation of laser crystals to depend on shape of the laser beam, while the laser field is also influenced by the temperature because of the thermal excitation of doped particles among various Stark levels. These effects, together with the usual thermal-optic effect that induces a fluctuation of the refraction index by an inhomogeneous temperature distribution, cause a complicated coupling between the laser field and the temperature field. We show that the optic-thermal coupling plays an important role in high-power DPSSL with larger size beam. That effect may yield a self-compensation for the thermal lens and improve the beam quality.

Thermal lens study of energy transfer in Yb^3+/Tm^3+-co-doped glasses

Energy transfer (ET) and heat generation processes in Yb(3+)/Tm(3+)-co-doped low-silica calcium-aluminosilicate glasses were investigated using thermal lens and photoluminescence measurements. Stepwise ET processes from Yb(3+) to Tm(3+), with excitation at 0.976 mum, produced efficient emission in the mid-infrared range at around 1.8 mum, with high fluorescence quantum efficiency (~0.50) and relatively low thermal loading (</=0.42). An equation was deduced for the description of the thermal lens results which provided the absolute value of the ET efficiency and optimal Tm3+ concentration that result in population of the 1.8 mum Tm(3+) emitting level. These results suggest that the studied co-doped system would be a promising candidate for the construction of high-power diode-pumped solid-state lasers in the mid-infrared range, which are especially important for the purpose of medical procedures.

Quasi-self-imaging planar waveguide lasers with high-power single-mode output

We describe high-power planar waveguide laser which can achieve single-mode output from a multi-mode structure. The planar waveguide is constructed with incomplete self-imaging properties, by which the coupling loss of each guided mode can be discriminated. Thermal lens effects are evaluated for single-mode operation of such high-power diode-pumped solid-state lasers.

Compact scalable diode-pumped Nd:YAG ceramic slab laser

We describe our preliminary studies of the use of neodymium-doped slab-shaped ceramic YAG media in the construction of compact, rugged, high-power diode-pumped solid-state lasers. A maximum extraction of more than 160 W at a 20% slope efficiency level, with a narrow transverse direction beam-parameter product of the order of 4 mm mrad(-1) is experimentally obtained from an extremely simple and compact (overall dimensions 160 mm x 100 mm x 60 mm) laser head in a quasi-continuous-wave regime. Experimental data together with finite-elements method simulations indicate that power extraction can be scaled up at least to 900 W cw with this laser head geometry.

Diamond Cooling of High-Power Diode-Pumped Solid-State Lasers

We have demonstrated the feasibility of cooling high-power solid-state lasers with diamond windows, whose thermal conductivity is about two orders of magnitude higher than that of sapphire. An output power of 200 W was achieved from a single Nd:YVO/sub 4/ slab in a zigzag configuration when pumped with 600-W diodes at 808 nm. The maximum output power previously reported in the literature using conventional cooling schemes is only about 100 W. A 2.3/spl times/4/spl times/24 mm/sup 3/ slab was pumped from its broad side (4/spl times/24 mm/sup 2/) through a 0.3-mm-thick optical diamond window placed in close contact with the lasing crystal. The diamond window, held in a water-cooled copper housing, acted as a heat conductor. The other broad side of the crystal was cooled directly by its water-cooled copper housing. Since pumping and cooling were along the same axis, a Cartesian thermal gradient was achieved, while the zigzag scheme was used to minimize thermal lensing. By using a BBO Q-switch, 70-W average power was obtained at 20 kHz with a pulse width of 19 ns and with a beam quality of 3 and 12 times the diffraction limit in the zigzag and transverse directions, respectively. The output of a two-head configuration was 295 W. In addition, a cavity was designed to achieve increased beam quality and 133 W was accomplished with a beam quality of 2 and 7.5 times diffraction-limited on the zigzag and nonzigzag axes, respectively. Operating this cavity with an RTP Q-switch produced 114 W with a beam quality of 1.5 and 9.5 on the respective two axes.

Solid-State High-Energy Laser Weapons

Recent advances in semiconductor and solid-state lasers are being applied in the realm of laser weaponry. High-power diode-pumped solid-state lasers bring with them tough questions about the dangers of eye injury, both to soldiers and noncombatants.

Self-adjusting compensating thermal lens to balance the thermally induced lens in solid-state lasers

The thermal lens is a critical issue, particularly in high-power diode-pumped solid-state laser rods. A self-adjusting scheme for compensation of the thermally induced lens is presented. The requirements for such an element and its influence on the resonator are discussed. With an appropriate compensating element and a suitable resonator design, constant beam parameters are expected to be achieved over a pump range of several kilowatts.

Recent Progress in High-Power Diode-Pumped Solid-State Lasers.

Recent Progress in High-Power Diode-Pumped Solid-State Lasers.

752 nm wing-pumped Cr:LiSrAlF/sub 6/ laser

The authors have demonstrated a LiSrAlF/sub 6/:Cr/sup 3+/ (Cr:LiSrAlF/sub 6/) laser pumped at 752 nm in the longwave wing of the /sup 4/A/sub 2/ to /sup 4/T/sub 2/ pump band. Measured optical, laser, and thermal properties of LiSrAlF/sub 6/-LiSrCrF/sub 6/ solid solutions indicate that efficient laser pumping can be achieved in the 750-780 nm region, and that AlGaAs laser diode arrays may be used to make efficient high-power diode-pumped tunable solid-state lasers. >

High-power transverse diode-pumped solid-state lasers

High-power transverse diode-pumped solid-state lasers