Nonlinear magneto-optical resonances on the hyperfine transitions belonging to the D2 line of rubidium were changed from bright to dark resonances by changing the laser power density of the single exciting laser field or by changing the vapor temperature in the cell. In one set of experiments atoms were excited by linearly polarized light from an extended cavity diode laser with polarization vector perpendicular to the light's propagation direction and magnetic field, and laser induced fluorescence (LIF) was observed along the direction of the magnetic field, which was scanned. A low-contrast bright resonance was observed at low laser power densities when the laser was tuned to the Fg = 2 −→ Fe = 3 transition of 87 Rb and near to the Fg = 3 −→ Fe = 4 transition of 85 Rb. The bright resonance became dark as the laser power density was increased above 0.6mW/cm 2 or 0.8 mW/cm 2 , respectively. When the Fg = 2 −→ Fe = 3 transition of 87 Rb was excited with circularly polarized light in a second set of experiments, a bright resonance was observed, which became dark when the temperature was increased to around 50 o C. The experimental observations at room temperature could be reproduced with good agreement by calculations based on a theoretical model, although the theoretical model was not able to describe measurements at elevated temperatures, where reabsorption was thought to play a decisive role. The model was derived from the optical Bloch equations and included all nearby hyperfine components, averaging over the Doppler profile, mixing of magnetic sublevels in the external magnetic field, and a treatment of the coherence properties of the exciting radiation field.

This Letter reports on the realization of a highly coherent light source at 193 nm. By frequency-quadrupling an amplified diode laser, over 15 mW of laser emission could be generated using the nonlinear crystal potassium fluoro-beryllo-borate. The high stability of the setup was proven in an 80 h-measurement, and the impact of the crystal transmission on the output power was thoroughly studied. This laser source is an ideal tool for photoemission spectroscopy and reaches the power level to replace excimer lasers in metrological applications.

We report on the realization of a continuous-wave light source based on nonlinear interaction in KBBF at a wavelength of 191 nm. More than 1.3 mW of deep-ultraviolet power was generated in a mechanically robust setup pumped by an amplified grating stabilized diode laser. Mode hop-free tuning over 40 GHz at 191 nm could be demonstrated.

We present a mask-aligner lithographic system operated with a frequency-quadrupled continuous-wave diode laser emitting at 193 nm. For this purpose, a 772 nm diode laser is amplified by a tapered amplifier in the master-oscillator power-amplifier configuration. The emission wavelength is upconverted twice, using LBO and KBBF nonlinear crystals in second-harmonic generation enhancement cavities. An optical output power of 10 mW is achieved. As uniform exposure field illumination is crucial in mask-aligner lithography, beam shaping is realized with optical elements made from fused silica and CaF featuring a diffractive non-imaging homogenizer. A tandem setup of shaped random diffusers, one static and one rotating, is used to control speckle formation. We demonstrate first experimental soft contact and proximity prints for a field size of 1 cm with a standard binary photomask and proximity prints with a two-level phase mask, both printed into 120 nm layers of photoresist on unstructured silicon substrates.

We present a resonantly frequency-doubled tapered amplified semiconductor laser system emitting up to 2.6 W blue light at 400 nm. The output power is stable on both short and long timescales with 0.12% RMS relative intensity noise, and less than 0.15%/h relative power loss over 16 hours of free running continuous operation. Furthermore, the output power can be actively stabilized, and the alignment of the input beams of the tapered amplifier chip, the frequency doubling cavity and -in case of fiber output -the fiber can be optimized automatically using computer-controlled mirrors.