Katrin Paschke

600 mW optical output power at 488 nm by use of a high-power hybrid laser diode system and a periodically poled MgO:LiNbO3 bulk crystal

600 mW second-harmonic blue light at 488 nm has been generated by use of a master-oscillator power amplifier diode laser system as a pump source with a maximum optical output power of 4 W in continuous-wave operation. For frequency doubling, a periodically poled MgO:LiNbO3 bulk crystal was used in a single-pass configuration. A conversion efficiency of 15% and an overall wall-plug efficiency of 4% were achieved.

Diode-pumped gigahertz femtosecond Yb:KGW laser with a peak power of 3.9 kW

We present a diode-pumped Yb:KGW laser with a repetition rate of 1 GHz and a pulse duration of 281 fs at a wavelength of 1041 nm. A high brightness distributed Bragg reflector tapered diode laser is used as a pump source. Stable soliton modelocking is achieved with a semiconductor saturable absorber mirror (SESAM). The obtained average output power is 1.1 W and corresponds to a peak power of 3.9 kW and a pulse energy of 1.1 nJ. With harmonic modelocking we could increase the pulse repetition rate up to 4 GHz with an average power of 900 mW and a pulse duration of 290 fs. This Yb:KGW laser has a high potential for stable frequency comb generation.

High-Power DBR-Tapered Laser at 980 nm for Single-Path Second Harmonic Generation

We present experimental results about edge-emitting distributed-Bragg-reflector-tapered diode lasers emitting at 980 nm. The investigated lasers show an output power of up to 12 W with a conversion efficiency of about 45%. The lasers also exhibit a small vertical divergence <15deg full-width at half maximum (FWHM), a nearly diffraction-limited beam quality, and a narrow spectral linewidth with FWHM smaller than 12 pm. These properties allow efficient single-pass second harmonic generation with power levels of more than 1 W at 488 nm.

20W continuous wave reliable operation of 980nm broad-area single emitter diode lasers with an aperture of 96μm

High power broad area diode lasers provide the optical energy for all high performance solid state and fiber laser systems. The maximum achievable power density from such systems is limited at source by the performance of the diode lasers. A crucial metric is the reliable continuous wave optical output power from a single broad area laser diode, typically for stripe widths in the 90-100 μm range, which is especially important for users relying on fibered multi-mode pumps. We present the results of a study investigating the reliable power limits of such 980nm sources. We find that 96μm stripe single emitters lasers at 20°C operate under continuous wave power of 20W per emitter for over 4000 hours (to date) without failure, with 60μm stripe devices operating reliably at 10W per stripe. Maximum power testing under 10Hz, 200μs QCW drive conditions shows that 96μm stripes reach 30W and 60μm stripes 21W per emitter, significantly above the reliable operation point. Results are also presented on step-stress-studies, where the current is step-wise increased until failure is observed, in order to clarify the remaining reliability limits. Finally, we detail the barriers to increased peak power and discuss how these can be overcome.

Diode-pumped mode-locked Yb:LuScO(3) single crystal laser with 74 fs pulse duration.

The mode locking of the mixed sesquioxide single crystal Yb:LuScO(3) is demonstrated. This crystal is locally disordered and has the broadest emission spectrum of all sesquioxides known so far. Pulse durations as short as 111 and 74 fs were obtained using the semiconductor saturable absorber mirror and Kerr-lens mode locking, respectively. The latter regime was reached using a two-section distributed Bragg-reflector tapered diode laser as a pump source.

Femtosecond diode-pumped solid-state laser with a repetition rate of 4.8 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 high power operation of a femtosecond laser inscribed Yb:YAG waveguide laser [Invited]

Waveguides were written into single crystalline Yb(7%):YAG with a femtosecond laser. Laser oscillation of the waveguides without external mirrors at an output coupling transmission of 99% was demonstrated. The laser performance of the waveguide lasers, pumped with various light sources, was examined. With an optically pumped semiconductor laser (OPS) as pump source a slope efficiency of 51% regarding incident pump power and a maximum output power of 1.76 W could be achieved. By using a high brightness DBR tapered diode laser as pump source the possible miniaturization of the waveguide laser device was demonstrated. With this pump source even 2.35 W of output power from the waveguide laser was achieved. The beam quality at highest output power turned out to be excellent with an M2-factor of less than 1.3.

Beam Properties of 980-nm Tapered Lasers With Separate Contacts: Experiments and Simulations

The beam properties of 980-nm tapered lasers with separate current drives for the ridge waveguide and tapered sections are analyzed by means of a comparison between simulations and experimental results. The simulations are performed with a new model for this type of tapered lasers, providing a good qualitative agreement with experiments. The observed improvement in the beam quality by a stronger pumping of the ridge waveguide section with respect to the tapered section is attributed to the reduction of the backward field intensity. The simulations show that this improvement, far from being a general rule, depends on the details of the device geometry.

96 mW longitudinal single mode red-emitting distributed Bragg reflector ridge waveguide laser with tenth order surface gratings

Red-emitting ridge waveguide lasers with integrated tenth order surface distributed Bragg reflector gratings were developed. The grating was implemented by the use of a BCl3-Ar-plasma, while the shape of the grating trench was controlled by additional He-backside cooling of the wafer. The devices exhibit longitudinal single mode operation up to 96 mW at 635.3 nm with a side mode suppression ratio of 18 dB and a good beam quality of M2<3. The spectrum is free of mode hops for a span of more than 55 pm.

Properties of ion-implanted high-power angled-grating distributed-feedback lasers

An improvement of the linearity of the light-current characteristics and the beam quality of high-power /spl alpha/-distributed feedback lasers is achieved by an ion implantation of the regions outside the contact stripe. The linear part of the light-current characteristics of 4-mm-long devices emitting at 1060 nm is extended to P=1.8 W output power. The times-diffraction-limit factor M/sup 2/ remains constant, equal to 1.7 over the whole power range. Simulations of the electro-optical behavior reveal that the improvement is achieved by a suppression of optical field components which propagate inside the cavity perpendicular to the facets.