Volker Raab

External resonator design for high-power laser diodes that yields 400 mW of TEM 00 power

Normal diode lasers with average output powers of 1 W or more exhibit bad beam quality and therefore cannot be applied for high-precision applications or nonlinear optics. Therefore an external output coupling mirror was used in our experiments. Diffraction-limited operation was achieved, which yielded 400 mW of power and a factor-of-12 improvement in brightness. With this resonator type 1.1 W of average output power was also obtained, with a beam propagation factor of 2.6 in the slow axis; fast axis emission is always diffraction limited.

Tuning high-power laser diodes with as much as 0.38 W of power and M 2 = 1.2 over a range of 32 nm with 3-GHz bandwidth

Gain-guided diode lasers usually have emission wavelengths determined by the manufacturing process, with typically 0.5-1-nm bandwidth. Furthermore, their beam quality is rather poor. We show that external cavities allow for tunable narrow-bandwidth operation of gain-guided diode lasers. At the same time the beam quality is drastically improved; almost diffraction-limited light of more than 200 mW has been achieved over the whole tuning range from 910 to 942 nm with narrow bandwidth.

Tunable 6.8 W narrow bandwidth emission from a single-stripe continuous-wave broad-area laser diode in a simple external cavity

An antireflection-coated broad-area laser diode with an emitter size of 400 microm x 1 microm and a chip length of 1500 microm is operated in a simple external cavity. For wavelength stabilization and to narrow the bandwidth a diffraction grating in a Littrow configuration is used. At an injection current of 9 A up to 6.8 W of optical output power and a resulting slope efficiency of 0.8 W/A could be achieved. Further, the bandwidth could be narrowed to 100 pm (FWHM), and a tuning range of 40 nm around 976 nm was obtained.

Tunable diffraction-limited light at 488 nm by single-pass frequency doubling of a broad area diode laser

A laser system that is based on second-harmonic generation of a broad area laser diode and provides 23.2 mW of diffraction-limited light with narrow bandwidth is described. It is tunable from 487.4 to 489 nm. The broad area laser diode is frequency stabilized in an external cavity that yields 800 mW of diffraction-limited light. This infrared light is converted into the visible by use of a 1 cm periodically poled MgO:LiNbO(3) bulk crystal with a measured single-pass conversion efficiency of up to 3.6%/W x cm.

Phase-locked array of 25 broad-area lasers

We will report experimental results on the coherent laser operation of a bar of broad area lasers. The array is 1 cm wide and consists of 25 lasers of 200 micrometer width each. Under normal conditions the lasers possess no mutual coupling and, therefore, emit incoherently. The resulting beam quality is correspondingly very low and typically more than 2000-fold diffraction-limited. To coherently couple the emitters we operate them in an external cavity. Inside the cavity a multiplexing and mutual coupling is achieved by means of a 16 level diffractive optic (DO) designed as a 1:25 beam splitter. We show that a stable phase-locked laser mode can build up inside the resonator. Its pronounced central angular emission lobe possesses a beam quality of approximately 60 times diffraction limit. In a passive setup, in which the internal dynamics of the broad area lasers can be suppressed by use of a seeding laser of good beam quality (M2<2), the central emission lobe is better than five times diffraction-limited.

Direct Generation of 50 ps-Pulses from an External Cavity Diode Laser Yielding 200 mW Average Output Power

We present a broad area diode laser with a very simple external resonator which shows self-induced modelocking of about 10 longitudinal modes at a repetition rate of 1-3 GHz, resulting in short pulses.

ps-Pulse generation by self-induced modelocking of a high power broad area diode laser in an external resonator

Up to 250 mW of ps-pulses with a pulsewidth of 50 ps and a repetition rate of 1-3 GHz are generated by self-induced modelocking of a high-power diode-laser working in an external resonator.

Tunable cw-diode laser for 940 to 990 nm with over 700 mW of near-diffraction limited light

In this paper, the setup for the tunable cw-GaAs diode laser chip in an external cavity, which consists of stripe-array, a fast axis collimator, a grating, and a /spl lambda//2-plate, has been explained.

High Brightness High Brilliance Tunable Broad Area Diode Laser with 1 W of Near Diffraction Limited Light

An unstable external cavity diode laser is presented with an AR-coated stripe-array diode as gain medium which yields up to 1 W with a bandwidth below 3 MHz and M2< 2 over the tuning range 940 nm through 980 nm.

Spectral Beam Combining of 25 Diode Lasers to get 10 W cw emission

A diode laser bar is operated in an external cavity which spectrally multiplexes the emitters between 920 nm and 940 nm with a total output power of 10 W and a beam propagation factor M2< 14.