Klaus Petermann

Large single-mode rib waveguides in GeSi-Si and Si-on-SiO/sub 2/

Mode-matching and beam-propagation methods are used to analyze single-mode operation of optical GeSi-Si and Si-SiO/sub 2/ semiconductor rib waveguides. The waveguide dimensions that allow only the fundamental HE/sub 00/ or EH/sub 00/ mode to propagate have been determined. For both material systems, it is found that the rib can be several microns wide and several microns high, thus allowing efficient coupling to single-mode fibers. Numerical examples are given for monomode guiding group-IV materials, but the results apply to III-V rib waveguides. It is shown that single-mode rib guides with large cross sections are feasible as long as the waveguide is at least several millimeters long. >

External optical feedback phenomena in semiconductor lasers

The phenomena occurring in semiconductor lasers due to weak external optical feedback are reviewed, including mode hopping and related mode-hopping noise, linewidth narrowing and broadening, and the transition to the coherence collapse regime. Guidelines are given for designing semiconductor lasers, both edge emitters and VCSELs, with high endurance against external optical feedback. >

Small signal analysis for dispersive optical fiber communication systems

A small signal analysis for analyzing the conversion between intensity and phase modulation or noise in a dispersive fiber is given. Using this theory the small signal response of laser diodes with respect to intensity and phase modulation in dispersive optical fibers is derived. Guidelines are also given for considerably reducing the intensity noise if a fiber with a suitable dispersion is used. All analytical calculations are compared with numerical simulations and good agreement is achieved. >

Four-wave mixing in semiconductor optical amplifiers for frequency conversion and fast optical switching

Four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) is an important tool for frequency conversion and fast optical switching in all-optical communication networks. We review the main applications of SOAs as nonlinear optical components. Concentrating on FWM, we define general parameters that are of relevance for signal processing applications. We show, how basic experiments and general simulation procedures can be used to determine optimum operating conditions for the intended applications. Besides a comprehensive investigation of FWM among continuous waves, we present new experimental results on FWM with picosecond optical pulses. A comparison of both reveals a different behavior and demonstrates that new optimization criteria and advanced theoretical models have to be applied for the case of short optical pulses. Moreover, we discuss the possibility to extract the dynamical SOA parameters from our experiments.

Femtosecond thin-disk laser with 141 W of average power

We present a semiconductor saturable absorber mirror mode-locked thin disk laser based on Yb:Lu(2)O(3) with an average power of 141 W and an optical-to-optical efficiency of more than 40%. The ideal soliton pulses have an FWHM duration of 738 fs, an energy of 2.4 microJ, and a corresponding peak power of 2.8 MW. The repetition rate was 60 MHz and the beam was close to the diffraction limit with a measured M(2) below 1.2.

Comparison of NRZ- and RZ-modulation format for 40-Gb/s TDM standard-fiber systems

Nonreturn-to-zero (NRZ) and return-to-zero (RZ) signal transmission in dispersion-managed high-speed time-division multiplexed (TDM) systems operating at 1.55 /spl mu/m over the already installed standard-fiber network are compared by numerical simulations. It is shown that for upgrading the existing network to 40 Gb/s, the RZ-modulation format is superior compared to conventional NRZ-modulation. Standard fiber transmission distances of about 1200 km and 400 km are shown to be feasible within the RZ- and NRZ-format, respectively.

Highly efficient Yb:YAG channel waveguide laser written with a femtosecond-laser

Using a femtosecond Ti:Sapphire laser, micro-tracks of material damage were written into Yb:YAG crystals. Waveguiding was achieved in a channel between pairs of tracks with guiding losses of 1.3 dB/cm at a wavelength of 1063 nm, due to a stress induced change of the refractive index. Pumped at a wavelength of 941 nm, highly efficient laser oscillation in a Yb:YAG channel waveguide at a wavelength of 1030 nm was demonstrated. An output power of 0.8 W at 1.2 W of launched pump power was achieved, resulting in a record slope efficiency of 75%.

0.1 dB/cm waveguide losses in single-mode SOI rib waveguides

Waveguide losses as low as 0.1 dB/cm at a wavelength of /spl lambda/=1.3 /spl mu/m have been achieved in SOI rib waveguides fabricated by wet chemical etching. The single-mode waveguides have a large cross section yielding field mismatch losses to a standard single-mode fiber of only 0.17 dB/facet (both polarizations). Polarization independent fiber-chip-fiber insertion losses of 0.9 dB (best 0.5 dB) at a chip length of 60 mm have been measured.

High melting sesquioxides: crystal growth, spectroscopy, and laser experiments

Abstract Due to their high thermal conductivity the sesquioxides Sc2O3, Y2O3, and Lu2O3 are interesting host materials for high power laser applications. Furthermore the strong crystal field of these host lattices is especially favourable for quasi-four-level systems such as the trivalent ytterbium ion. Several lanthanide-doped yttria, scandia, and lutetia crystals and a large boule with monocrystalline areas of a few cm3 in volume have been prepared at our institute by the Bridgman method. The grown crystals exhibit promising features for laser operation. Here, we report on the spectroscopic characterization and first diode-pumped laser experiments with ytterbium-doped lutetia.

Broadly tunable high-power Yb:Lu 2 O 3 thin disk laser with 80% slope efficiency

We report on efficient laser operation of high quality crystalline Yb(3+):Lu(2)O(3) in thin disk configuration. Using doping concentrations between 1 at.% to 3 at.% and disk thicknesses between 0.08mm and 0.45mm the optimum crystal parameters have been determined. Pumped at 976 nm the laser operates at 1034 nm and 1080 nm. With a 0.25mm thick 3 at.% Yb:Lu(2)O(3) disk 32.6W of output power at 45.3W incident pump power with a slope efficiency of 80% and a resulting optical-to-optical efficiency of 72% have been realized. These are the highest values in terms of slope efficiency as well as optical-to-optical efficiency for an Yb-doped thin disk laser reported so far. Using an 1mm birefringent filter continuous tuning from 987 nm to 1127 nm with more than 10Wof output power over a tuning range of 90 nm has been achieved.