We present a design and output characteristics of an optically quantum-well-pumped semiconductor laser for single- and dual-wavelength emission which has a resonant disk structure for two wavelengths that lie 36.7nm apart. The smaller resonance wavelength is intended for the pump wavelength of 940 nm. Laser emission, however, can either take place at the short and/or at the long resonance wavelength. A switch between the emission wavelengths is performed by moving the gain peak towards the desired wavelength. For instance, while the heat-sink of the laser is kept at -15°C the laser will only emit a wavelength of 957.0 nm, a change of the heat-sink temperature to 50°C does result in an emission at the other resonance wavelength located at 997.5 nm. In both cases slope efficiencies above 50% and output powers beyond 10W are possible. Limiting factor is the available pump power. A simultaneous emission at 960.8 and 997.5nm is observed for heat-sink temperatures between 21.3 and 27.1°C. The intra-cavity performed sum-frequency generation (SFG) of the dual-wavelength laser leads to an emission at 489.7 nm.
We present a VECSEL based on a gain sample design which utilizes only a single-layer dielectric Al2O3 coating for dispersion management. The gain structure generated pulse durations down to 193 fs in combination with a surface-recombination SESAM, with an average power of 400 mW at 1.6 GHz setting a new peak power record for sub-200 fs mode-locked VECSELs. The pulses obtained were, however, 2x transform-limited and a further FROG measurement of a similar laser is presented revealing a linear chirp and cubic spectral phase.
We present optically pumped semiconductor disk lasers (OPSDLs) emitting in the 900–1100nm band which are frequency doubled to access the visible spectrum. In particular, we focus on presenting the design, fabrication, and specific characteristics. Fundamental outputs exceeding 20W and visible radiation with powers of 5–10W are achieved. The blue and green emission at wavelengths around 450–470 and 520–540nm yield advantageous gamuts for display applications and can be utilized for stereo projection. Moreover, other accessible wavelengths in this spectral region, e.g. 493 nm, and the good beam quality of these devices enable optical ion trapping experiments.
The design of optically pumped semiconductor disk lasers is discussed with emphasis on the optimization for
high power conversion e_ciencies. Main topics are the compensation of strain in the epitaxial layer sequence,
the realization of a low-absorption Bragg reector which has a high reectivity for pump and laser wavelength
and a low thermal resistance, and the e_ect of a surface coating reducing optical losses inside the semiconductor
disk. As an alternative concept, quantum-well pumping may be more e_cient because of the reduced quantum
defect. E_cient intra-cavity second-harmonic generation can be obtain in folded cavity setups.
A novel type of all-optical pressure sensor has been developed. In this context, a vertical-cavity surface-emitting
laser (VCSEL) has been modified in its design to provide simultaneous light emission from both facets. One
beam serves as measuring signal while the other establishes a reference; and both paths lie on the same optical
axis. The VCSELs are based on active InGaAs quantum wells for laser output close to 960 nm wavelength where
the GaAs substrate is transparent. From both top and bottom facet, single-polarization and single-mode beams
are observed, having a power ratio of 1:2 to 1:4. In this paper we give insight into this new sensing application
for VCSELs, describe the laser fabrication and the static operation characteristics as well as the noise properties
which have paramount importance for high performance of the sensor.
With regard to the sensor application in acoustics, the focus of the noise measurements is put on the low-frequency,
i.e. kHz, regime. While laser diode noise performance is readily available for the MHz to GHz
frequency range, only very limited data exists in the Hz to kHz domain. The relative intensity noise of both
beams is measured and compared and the mutual correlation properties are investigated. The frequency noise
The layer structure of the gain element in an optically pumped semiconductor disk laser (OP-SDL) was designed for
wide tunability. This was achieved by a parametric optimization of the structure, which in effect balanced the spectrally
varying influence of the gain of the quantum wells, the longitudinal distribution of the standing wave lasing field in the
structure, and the degree of resonance in the subcavity formed between the distributed Bragg reflector at the bottom and
the air-semiconductor interface at the top. The quality measure in the optimization was the spectral reflectance of the
gain element for light incident from the external cavity at low power. This unsaturated reflectance was compared to its
target function, which was constant at a specified value larger than unity over a wide, prescribed wavelength range. The
fabricated gain element was used in a linear OP-SDL with a rotatable intra-cavity birefringent filter for wavelength
tuning. The design principles for achieving wide tunability were experimentally validated by the strong agreement
between measurements and simulations of the spectral threshold pump intensity. Furthermore, tuning experiments at
high pump powers were performed showing that the lasing wavelength could be tuned from 967 nm to 1010 nm with a
maximum output power of 2.6 W.