Michal Lukowski

High-power tunable two-wavelength generation in a two chip co-linear T-cavity vertical external-cavity surface-emitting laser

We report the design and experimental results of a two chip co-linear T-cavity vertical external cavity surface emitting laser (VECSEL) capable of generating two continuously tunable orthogonally polarized lasing wavelengths. A polarizing beamsplitter is used to overlap two VECSEL cavities thus generating high-power intra-cavity two-wavelength generation ideal for type-II nonlinear frequency conversion. Nearly equal power at each wavelength with a combined dual-wavelength CW output power in excess of 13 W was observed. In a high Q cavity, the wavelength separation was tuned from 35 nm to 52 nm by using birefringent filters in regions where each wavelength lases independently of the other.

Widely Tunable High-Power Two-Color VECSELs for New Wavelength Generation

We report a collinear two-color vertical external cavity surface emitting laser (VECSEL), which with minimal changes is suitable for intracavity type I second harmonic generation (SHG), type II sum frequency generation (SFG), and type II difference frequency generation (DFG). The demonstrated two-chip cavity provides high-brightness, independently tunable two color, orthogonally polarized intracavity lasing modes. VECSEL chips with emission around 970 and 1185 nm allow the generation of a wide range of wavelengths in the visible and long-wavelength spectral range. The open cavity, collinear geometry, provided a platform for efficient SHG yellow output, SHG blue output, and SFG of green output in the same cavity while only changing the nonlinear crystals. In all cases for visible light generation, a lithium triborate nonlinear crystal is introduced in the cavity region where the fundamental beams are overlapped. Simultaneous SHG and SFG in the same cavity resulting in overlapped outputs consisting of two visible colors are also demonstrated. By using two VECSEL chips with similar gain peaks, intracavity terahertz generation by DFG is demonstrated for the first time in a T-cavity VECSEL geometry. A custom-made tilted periodically poled lithium niobate nonlinear crystal generated DFG signal around 1 THz.

589-nm single-frequency VECSEL for sodium guidestar applications

Here we report on the development and demonstration of a tunable high power single frequency Vertical External Cavity Surface Emitting Laser (VECSEL) operating at 589nm. A highly strained InGaAs/GaAs VECSEL designed to operate at ~ 1178nm is used in conjunction with an intracavity Birefringent Filter (BF) and low finesse Fabry-Perot (FP) etalon to achieve the single frequency operation at the fundamental wavelength. An internal non-linear optical element is then used to obtain the single frequency output at the desired wavelength of 589nm. Our results show outputs in excess of 4W at 589nm with a FWHM linewidth of the fundamental frequency to be less than 10MHz. We demonstrate the measurement of the sodium D1 and D2 lines by passing the output through a reference cell.

Tunable type II intracavity difference frequency generation at 5.4 μm in a two chip vertical external cavity surface emitting laser.

We report on the generation and experimental demonstration of intracavity type II difference frequency generation in a two chip InGaAs/GaAs vertical external cavity surface emitting laser. The presented two chip cavity provides two orthogonally polarized, independently tunable, high-intensity lasing modes with emissions around 970 and 1170 nm. A silver thiogallate nonlinear crystal is inserted in the common collinear folded region of the cavity to generate output in the mid-IR spectral band. The independent tunability of each fundamental color allows for more than 100 nm of tuning around a 5.4 μm difference frequency generated signal with a CW output power in excess of 5 mW.

Tunable type II intracavity sum-frequency generation in a two chip collinear vertical external cavity surface emitting laser

We report on the generation and experimental demonstration of intracavity type II sum-frequency generation (SFG) in a two chip InGaAs/GaAs vertical external cavity surface emitting laser cavity. The demonstrated two-chip cavity generates two orthogonally polarized, independently tunable, high-intensity intracavity lasing modes at different colors. Using a lithium triborate nonlinear crystal in the common collinear folded cavity region, high output power in the blue-green band is generated. Wavelength tuning with CW output powers in excess of 750 mW is demonstrated. By independent wavelength tuning of each fundamental color, tunable SFG output around 490 nm is reported.

Wavelength tuning of VECSELs by cavity geometry

In this paper we report on the wavelength tuning of a VECSEL by changing the cavity geometry. The development and demonstration of a tunable high power single frequency Vertical External Cavity Surface Emitting Lasers (VECSEL) operating at various wavelengths from the UV to the IR region of the spectrum have been reported in many papers. However, it is important to understand that in many instances a precise lasing wavelength is required for proper operation. For example, VECSELs have been designed to specifically interact with the sodium spectral lines. If the VECSEL growth is not adequate, it may not be possible to reach the desired wavelength in a traditional cavity where the intracavity mode interacts with the VECSEL chip at normal incidence. Here we notice that if a fold angle is introduced at the VECSEL chip, a spectral blue shift occurs, and extended tunability may be possible. Therefore, by altering the cavity geometry it may be possible to further optimize a VECSEL design to obtain maximum output power at a desired wavelength.

Generation of high-power spatially structured beams using vertical external cavity surface emitting lasers

In this paper, we demonstrate the generation of high-power and spatially structured beams using vertical external cavity surface emitting lasers (VECSEL). At the fundamental wavelength, an intracavity mode-control element is first employed to generate a range of Hermite-Gaussian (HG) modes in a linear cavity. The same HG modes are then excited and frequency doubled in a V-cavity geometry to generate a rich variety of high-power spatially structured beams. The results compare well with our numerical modeling.

High power two-color orbital angular momentum beam generation using vertical external cavity surface emitting lasers

We report the design and experimental results for a two-chip T-cavity vertical external cavity surface emitting laser utilized for two-color collinear generation of Hermite-Gaussian and Laguerre-Gaussian (LG) transverse modes. A combination of intracavity mode-control elements and an external astigmatic mode converter was used to achieve high power LG modes. By incorporating intracavity birefringent filters in each arm of the T-cavity, wide wavelength tuning in excess of 12 nm of each mode is demonstrated. Output power exceeding 1.5 W is measured for all the modes.

Over 10 Watt, collinear blue and green vertical external cavity surface emitting laser

A high power, two color, collinear, blue and green vertical external cavity surface emitting laser (VECSEL) is demonstrated. Two different InGaAs/GaAs VECSEL chips operating with gain centers near 970 nm and 1070 nm are used to make two separate V-folded laser cavities. Two critically phase-matched intracavity lithium triborate nonlinear crystals are used to generate blue and green outputs which are then combined in a polarizing beam splitter. This results in a single beam which contains over 10 watts of combined blue and green output power. This concept can be expanded upon by adding a red output for the creation of a high power, white laser source.

High-power tunable two-color VECSEL for on-demand wavelength generation

High power, tunable two color lasers are highly suitable for the new wavelengths generation thanks to various nonlinear conversion phenomena. Vertical external cavity surface emitting lasers (VECSELs) are of special interest due to the access to the high intracavity circulating power and wavelength control. We report a novel VECSEL cavity design, which can deliver high power, tunable two color emission. The VECSEL setup is based on a two-chip T-shape cavity configuration which utilizes a polarizing beam splitter to combine two VECSEL cavities. This allows for two-color orthogonally polarized high-power collinear outputs. The two color emission of this kind is ideal for type II nonlinear frequency conversion. A high-Q folded T-cavity is utilized to achieve the combined beams circulating power in excess of 175 W. Intracavity birefringent filters are used to facilitate tunability and wavelength separation between two colors. A configuration of this type is used for high power intracavity type II sum frequency generation, which resulted in tunable blue emission with above 750 mW output, and in the second case a tunable green emission with more than 1.4 W output was obtained. A signal around 1 THz was achieved through type II difference frequency generation in tilted periodically poled lithium niobate. Lastly, a silver thiogallate was utilized to generate mid-IR wavelength around 5.36 μm through type II difference frequency generation.