M. Moser

Compact Nd:YVO/sub 4/ lasers with pulse repetition rates up to 160 GHz

We present a comprehensive study on multigigahertz repetition rate Nd:YVO/sub 4/ lasers, passively mode-locked with semiconductor saturable absorber mirrors. A brief review of Q-switching instabilities with special emphasis on high repetition rate is given. We then present basic design guidelines, and experimentally show that one can push the pulse repetition rate of a Nd: YVO/sub 4/ laser up to 157 GHz, reaching the fundamental limit to the repetition rate which is given by the pulse duration and thus by the amplification bandwidth. We also demonstrate an air-cooled diode-pumped 10-GHz Nd: YVO/sub 4/ laser with 2.1-W average output power and 13% electrical-to-optical efficiency, showing the potential of solid-state lasers generating multiwatt, multigigahertz pulse trains with high efficiency.

Diode-pumped passively mode-locked 1.3- μm Nd:YVO4 and Nd:YLF lasers by use of semiconductor saturable absorbers

We report on self-starting passively mode-locked diode-pumped 1.3-microm lasers obtained by use of semiconductor saturable absorbers. We achieved pulses as short as 4.6 ps in Nd:YVO(4) and 5.7 ps in Nd:YLF with average output powers of 50 and 130 mW, respectively.

Narrow-linewidth vertical-cavity surface-emitting lasers for oxygen detection.

The use of vertical-cavity surface-emitting lasers (VCSELs) for optical detection of atmospheric oxygen is described. The VCSELs were custom designed for single-mode emission in the 763-nm wavelength range, with low noise and narrow optical linewidth. Using standard wavelength modulation spectroscopy and a second-harmonic detection scheme with a 1-m air path, we determined an oxygen concentration resolution of 0.2%. Because of its small size, low power dissipation, and good tunability characteristics, the VCSEL promises to be an attractive light source for use in compact, low-cost optical sensor microsystems for trace gas detection.

Polarization competition and noise properties of VCSELs

Abstract A detailed experimental characterization of the dynamics of Vertical Cavity Surface Emitting Lasers (VCSELs) is presented. Evidence of strong anticorrelations between the different states of linear polarization of the field is given. As a consequence, it is shown that the noise of the single states of polarization is much higher than the total intensity noise. The dynamics of the polarizations is studied, showing that the statistics of the fluctuations is non-Gaussian in the competition regime.

Scaling of the antiresonant Fabry–Perot saturable absorber design toward a thin saturable absorber

We demonstrate and discuss the scaling of the antiresonant Fabry-Perot saturable absorber toward a novel antiref lection-coated thin saturable absorber. With a Ti:sapphire laser we obtained self-starting Kerr-lens mode-locked pulses as short as 19 fs. With the higher modulation depth of the thin saturable absorber we obtained soliton mode-locked self-starting 34-fs pulses over the full cavity stability regime with a significantly shorter mode-locking buildup time. The pulse duration was limited only by the semiconductor Bragg mirror.

A GaAs/AlGaAs-based refractometer platform for integrated optical sensing applications

Abstract We present a new type of integrated optical refractometer, based on a Mach-Zehnder interferometer using III–V semiconductor and TiO2 on SiO2 waveguides. We report on the design, optimized for high sensitivity in immunoassay sensing applications, and the fabrication of this sensor chip. Using a test liquid system of ethanol in water, we demonstrate a refractive-index resolution of 1× 10−5 for this refractometer. This device is a basic building block of a novel, monolithically integrated optical sensing circuit, which can be used for example in chemical or immunological sensing applications.

Lineshape of a vertical cavity surface emitting laser

We report on the experimental study of the lineshape of an air-post GaAs/AlGaAs Vertical-Cavity Surface-Emitting Laser (VCSEL). The signal is obtained by heterodyne with a narrow linewidth extended-cavity laser. This technique allows to fully take into account the entire spectrum of frequency fluctuations. In this way we can distinguish a Lorentzian and a Gaussian contributions to the lineshape, obtaining a clear picture of the dependence of the emission spectrum on the pump current. The study also includes the effects on the laser lineshape of the secondary transverse modes fluctuations.

High performance deep red AlAsAlGaAs top-emitting VCSELs grown by MOVPE at high growth rates

Abstract Top-emitting Alas AlGaAs vertical cavity surface emitting lasers emitting at 765 nm with minimum threshold currents of 0.6 mA and threshold voltages of 1.9 V have been grown by MOVPE. In order to keep the growth time low, we investigated the possibility to grow these structures at growth rates of 5 μm/h. Special attention was paid to the homogeneity that can be achieved over a 2″ wafer under these growth conditions. Spatially resolved reflectivity measurements on GaAs AlAs distributed Bragg reflectors showed, that the growth rate varies less than 0.3% in the center of the wafer and decreases by 1% at the wafer edge.

Memory effect for polarization of pump light in optically pumped vertical-cavity semiconductor lasers

We report that the polarization of the emission of an optically pumped vertical-cavity surface-emitting laser (VCSEL) is sensitive to the polarization state of the pump light. By measuring this memory effect for circularly polarized pump light, we determine the normalized relaxation rate of the carrier spin, /spl Gamma//sub s/, which is a vital parameter in current theoretical models of VCSEL polarization. We find /spl Gamma//sub s/=300/spl plusmn/150, a value which is significantly larger than previously estimated. We also observe a memory effect for the orientation of linearly polarized pump light. This signals that, apart from the carrier spin, the VCSEL polarization is also determined by the carrier momentum.

High density VCSEL arrays

Summary form only given. Top and bottom emitting 1D and 2D VCSEL arrays offer new perspectives in optical and electrical packaging and are therefore of high interest for future short haul parallel optical links, board-to-board and on-board high-speed optical interconnects. Results of short-wavelength multi-transverse mode VCSEL arrays demonstrating excellent uniformity, low threshold current, high modulation efficiency and multi-gigabit performance are presented.