B. Eppich

200 mW at 488 nm From a ppMgO:LN Ridge Waveguide by Frequency Doubling of a Laser Diode Module

We report on second-harmonic generation in a single-pass bench top configuration using a MgO-doped periodically poled LiNbO3 ridge waveguide (RW) and a hybrid integrated master oscillator power amplifier laser module at 976 nm. A coupling efficiency into the crystal RW of 66% was realized and 200 mW of continuous-wave radiation at 488 nm at room temperature were reached. A conversion efficiency of 43% with regard to the coupled near-infrared radiation was obtained. The experimental results agreed well with simulations including material inhomogeneities, higher optical absorption, and thermal effects.

17-W Near-Diffraction-Limited 970-nm Output From a Tapered Semiconductor Optical Amplifier

High power, high beam quality and narrow, stable spectra are achieved simultaneously using a truncated-tapered optical amplifier in a master-oscillator power amplifier-system. We compare the influence of lateral geometric design on amplifier performance, by using devices with super large optical waveguide (4.8 μm) and relative low confinement factor (Γ = 1%) . We find that the use of an amplifier with a larger active region results in both high power and high beam quality. An abandonment of cavity spoiling grooves leads to strongly improved beam characteristics.

Miniaturized Tunable External Cavity Diode Laser with Single-Mode Operation and a Narrow Linewidth at 633 nm

A miniaturized, standalone tunable semiconductor laser module operating at a wavelength of 633 nm with a footprint as small as 10 mm × 5 mm is presented. The module is based on an external cavity diode laser system with no moving parts and features a frequency tuning range of 25 GHz with a spectral linewidth of approximately 10 MHz. An output power of 10 mW within a nearly diffraction-limited beam is demonstrated. The electrical power consumption, including thermal management, is around 0.7 W.

940-nm Broad Area Diode Lasers Optimized for High Pulse-Power Fiber Coupled Applications

Diode lasers with 400- μm stripe widths measured in pulsed-current mode are shown to reach peak (saturation) powers of 60 W for 1-ms pulses (60 mJ) and 189 W for 300-ns pulses ( ~ 55 μJ). Use of laterally structured contact and etched index guides at the stripe edges enables these devices to sustain stable lateral near- and far-field profiles to the highest bias, with a lateral beam parameter product of . Optical calculations are presented for an example system where arrays of these single emitters are incoherently coupled into a fiber with 1-mm core and numerical aperture of 0.22, extrapolating 5 kW in fiber for 1 ms (5 J) and 18 kW in fiber for 300-ns pulses ( ~ 5 mJ). Such sources would be well suited for pumping Yb:YAG crystals for applications needing high beam quality, or as direct sources.

Prediction of Single-Mode Fiber Coupling Efficiencies of a Tapered Diode Laser From Measured Wigner Distribution Functions

In this letter, we demonstrate how the coupling efficiency of a tapered diode laser (TPL) into a single-mode fiber under specified conditions can be predicted from measured Wigner distribution functions (WDFs). The WDFs were measured with a simple setup similar to the method of measuring the beam propagation ratio M2 as specified in the ISO standard 11146. We used the measured WDFs to predict the coupling efficiencies of the beam into a single-mode fiber by using a predefined and well-known optical system. We then realized the fiber coupling and compared the measured coupling efficiencies to the predicted values. For this comparison we used the beam of a distributed Bragg reflector TPL which emits a fairly complex and structured beam. The predictions fitted the experimental result with relative deviations below 10%.

Modal Behavior, Spatial Coherence, and Beam Quality of a High-Power Gain-Guided Laser Array

In this paper, we investigate the modal behavior and the spatial coherence properties of a gain-guided laser array emitting an optical output power of more than 50 W in quasi-continuous-wave operation at a wavelength of 1070 nm and above. The lateral near- and far-field intensity profiles and the Wigner distribution function were measured from low to high output power. The array modes were calculated by solving the waveguide equation taking into account the power-dependent temperature distribution and were also experimentally determined by a modal decomposition of the cross spectral density. The analysis revealed that, at a low power, a single array mode lases, whereas at high power, multiple single stripe modes dominate the lasing due to the thermally induced index rise under the stripes.

High-Brightness 980-nm Tapered Laser— Optimization of the Laser Rear Facet

We present experimental results on a gain-guided tapered diode laser with rear facet coating variation from 98% down to 5% reflectivity. We show that in comparison to the common high reflection coating, a lower back facet reflectivity is suitable to suppress the propagation of modes outside of the ridge waveguide and the tapered section by keeping the output power at nearly the same level. Therefore, we can improve the spatial as well as the spectral beam quality.

Increasing the luminance of a red emitting laser light source by spectral beam combining

Summary form only given. Current diode laser based projections systems suffer from low output power and hence poor visibility, especially of the red laser sources. An additional constraint for flying-spot projection is that the light source should feature an almost diffraction limited beam and a low speckle contrast. This can be achieved with tapered lasers (TPL) [1], but the output power is limited to about 1 W. One possible way to further increase the luminance is spectral beam combining of multiple emitters. We developed high power TPL with internal distributed-Bragg-reflector (DBR) gratings in the red spectral range near 635 nm [2]. The variable period length (Λ1 - Λ10) of the DBR allowed the processing of a bar of ten diode lasers with increasing, successive wavelengths (λ1 - λ10). Figure 1 shows on the left the light-current-voltage characteristics of such a DBR-TPL-BAR as a function of temperature. The right side shows the spectrum at about 1.6 W (I = 12 A, T = -20°C) showing the emission of all ten individual lasers. The cooling was required due to the combination of the low T0 value of about 30 K and the mutual heating of the laser chips on the bar.