J. M. Yarborough

Room temperature continuous wave milliwatt terahertz source

We present a continuous wave terahertz source based on intracavity difference frequency generation within a dual color vertical external cavity surface emitting laser. Using a nonlinear crystal with a surface emitting phase matching scheme allows for high conversion efficiencies. Due to the tunability of the dual mode spacing, the entire spectral range of the terahertz gap can be covered. The terahertz output scales quadratically with the intracavity intensity, potentially allowing for terahertz intensities in the range of 10s of milliwatts and beyond.

High-Power Optically Pumped Semiconductor Laser at 1040 nm

We demonstrate near-diffraction limited (M 2 ¿ 1.5) output up to 23.8 W with optical-to-optical efficiency 27% and slope efficiency 32.4% and 40.7 W of multimode output from an optically pumped semiconductor laser at 1040 nm. Temperature-dependent photoluminescence measurements confirm accurate epitaxial growth according to the design thereby enhancing the effective gain.

Continuous-wave all-solid-state 244 nm deep-ultraviolet laser source by fourth-harmonic generation of an optically pumped semiconductor laser using CsLiB6O10 in an external resonator

We report an all-solid-state laser system that generates over 200 mW cw at 244 nm. An optically pumped semiconductor laser is internally frequency doubled to 488 nm. The 488 nm output is coupled to an external resonator, where it is converted to 244 nm using a CsLiB(6)O(10) (CLBO) crystal. The output power is limited by the available power at 488 nm, and no noticeable degradation in output power was observed over a period of several hours.

Heat Management in High-Power Vertical-External-Cavity Surface-Emitting Lasers

The thermal properties of a high-power vertical-external-cavity surface-emitting laser (VECSEL) are studied experimentally, focusing on the generation, distribution, and removal of excess heat under extreme pumping conditions. Different heat-spreading and heat-transfer approaches are analyzed. The performance of the device is optimized yielding a maximum emitted power beyond 70 W from a single spot. Finally, the potential for power-scaling in VECSELs and its restrictions are examined.

Influence of the spatial pump distribution on the performance of high power vertical-external-cavity surface-emitting lasers

The performance of a 1040 nm vertical-external-cavity surface-emitting laser is studied as function of the size and shape of the pumped area. The input-output characteristics of the device are monitored while simultaneously tracking the temperature in the active region. It is shown that the pump spot shape plays a crucial role in optimizing the laser output. Improvements up to a factor of 5 are found for a super-Gaussian in comparison to the standard Gaussian shape. For the large pump-spot sizes needed for high output powers, it turns out that the power-scalability breaks down due to the suppressed lateral heat flow.

Record pulsed power demonstration of a 2 μm GaSb-based optically pumped semiconductor laser grown lattice-mismatched on an AlAs/GaAs Bragg mirror and substrate

An optically pumped semiconductor laser resonant periodic gain structure, grown lattice-mismatched on an AlAs/GaAs Bragg mirror, exhibits a peak pulsed power of 70 W when pumped with a pulsed 1064 nm neodymium doped yttrium aluminum garnet laser.

VECSEL Optimization Using Microscopic Many-Body Physics

Vertical external cavity surface-emitting lasers (VECSELs) are designed and analyzed using an approach based on fully microscopically computed material properties like gain and carrier recombination rates. Very good agreement between theoretical predictions and measured characteristics of the realized devices is demonstrated. The high accuracy of the theoretical models allows one to determine even small deviations between the nominal designs and actual realizations. The models are used to find optimization strategies. It is shown how the external efficiency can be strongly improved using surface coatings that reduce the pump reflection while retaining the gain-enhancing cavity effects at the lasing wavelength. It is shown how incomplete pump absorption can be detrimental to the device performance and how this problem can be reduced using optimized distributed Bragg reflectors and metallization layers. A combination of improved metallization and use of such a coating more than doubles the external efficiency and maximum power for a realized VECSEL operating at 1010 nm and the theory indicates that further significant improvements are possible.

340-W Peak Power From a GaSb 2-

A GaSb-based vertical external cavity laser at 2 μm was pumped by 100- to 160-ns pulses from a Nd : YAG laser at 1.064 μm operating at 1 kHz. It was shown that the output power scales with the pump spot diameter to the extent of our experiments. A peak output of over 340 W was obtained.

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Heterodyne detection is used to characterize the terahertz (THz) emission of a novel room-temperature continuous wave source based on difference frequency generation within the cavity of a dual-color vertical external cavity surface emitting laser. Employing the high intracavity intensities allows for the generation of mW powers in a wide frequency range within the terahertz spectrum. Experimental results of heterodyne detection are presented for the emission frequencies of 820 GHz and 1.9 THz using Schottky and hot electron bolometer mixers. Simultaneous emission of multiple narrow-line THz frequency components is observed.

m Optically Pumped Semiconductor Laser (OPSL) Grown Mismatched on GaAs

Many applications of vertical-external-cavity surface-emitting lasers (VECSELs) [1], such as intra-cavity frequency mixing rely on the high-power characteristics of the devices. Generally, overheating limits any lasers performance and, thus, efficient cooling concepts are crucial for the high-power output [2]. Here, we experimentally investigate the thermal properties of a high-power device, focusing on the generation, distribution and removal of excess heat under extreme pumping conditions. Different heat-spreading and heat-transfer approaches are analyzed. The performance of the device is optimized yielding a maximum emitted power beyond 70W from a single spot. Finally, the potential for power-scaling in VECSELs and its restrictions are examined. Details on the chip and the experimental setup are given in [3].