Light propagating in waveguides can be manipulated by a moving refractive index front. A linear Schrödinger equation can be used to describe the interaction of a slowly varying signal envelope with a front. In waveguides with weak dispersion usually spatial evolution of the pulse temporal profile is tracked. However, we show that for waveguides with strong dispersion it is beneficial to track temporal evolution of the pulse spatial profile. Simulation examples close to the band edge of a photonic crystal waveguide are presented.
The process of an optical signal undergoing a transition between two modes of a photonic structure is referred to as a photonic transition. We show that a signal wave interacting with a free carrier front in a slow light waveguide experiences indirect photonic transitions leading to transmission or reflection from the moving front. Theory and experimental results are presented. The front induced dynamic frequency conversion is also compared to the frequency shifting based on other nonlinear effects like cross-phase modulation and four wave mixing.
Ultrashort laser pulses from vertical-external-cavity surface-emitting lasers (VECSELs) have been receiving much attention in the semiconductor laser community since the first demonstration of sub-ps-pulsed devices more than a decade ago. Originally relying on semiconductor saturable-absorber mirrors for pulse formation, mode-locked operation has not only become accessible by using a variety of saturable absorbers, but also by using a saturable-absorber-free technique referred to as self-mode-locking (SML). Here, we highlight achievements in the field of SML-VECSELs with quantum-well and quantum-dot gain chips, and study the influence of a few VECSEL parameters on the assumed nonlinear lensing behavior in the system.
We present a serially-connected two-chip vertical-external-cavity surface-emitting laser design, which generates dual wavelength emission with a wavelength separation of 10 nm and over 600 W intracavity power. Intracavity type-I second-harmonic generation and sum-frequency generation have been performed in a LiNbO<sub>3</sub> crystal. By employing different chip-combinations as well as birefringent filters, the laser is able to generate high-power emission with two wavelengths, which exhibit the same polarization and a desirable wavelength separation. Furthermore, the dependence of the emission wavelength on the cavity angle on the VECSEL chip is highlighted, which provides an additional means of wavelength tuning in VECSELs.
Vertical-external-cavity surface-emitting lasers (VECSELs) have proved to be versatile lasers which allow for various emission schemes which on the one hand include remarkably high-power multi-mode or single-frequency continuouswave operation, and on the other hand two-color as well as mode-locked emission. Particularly, the combination of semiconductor gain medium and external cavity provides a unique access to high-brightness output, a high beam quality and wavelength flexibility. Moreover, the exploitation of intra-cavity frequency conversion further extends the achievable radiation wavelength, spanning a spectral range from the UV to the THz. In this work, recent advances in the field of VECSELs are summarized and the demonstration of self-mode-locking (SML) VECSELs with sub-ps pulses is highlighted. Thereby, we present studies which were not only performed for a quantum-well-based VECSEL, but also for a quantum-dot VECSEL.