Passively mode-locked 40-GHz Er:Yb:glass laser

A diode-pumped Er:Yb:glass miniature laser has been passively mode-locked to generate transform-limited 4.3-ps pulses with a 40-GHz repetition rate and 18-mW average powe

New regime of inverse saturable absorption for self-stabilizing passively mode-locked lasers

The reflectivity of a semiconductor saturable absorber mirror (SESAM) is generally expected to increase with increasing pulse energy. However, for higher pulse energies the reflectivity can decrease again; we call this a ‘roll-over' of the nonlinear reflectivity curve caused by inverse saturable absorption. We show for several SESAMs that the measured roll-over is consistent with two-photon absorption only for short (femtosecond) pulses, while a stronger (yet unidentified) kind of nonlinear absorption is dominant for longer (picosecond) pulses. These inverse saturable absorption effects have important technological consequences, e.g. for the Q-switching dynamics of passively mode-locked lasers. A simple equation using only measurable SESAM parameters and including inverse saturable absorption is derived for the Q-switched mode-locking threshold. We present various data and discuss the sometimes detrimental effects of this roll-over for femtosecond high repetition rate lasers, as well as the potentially very useful consequences for passively mode-locked multi-GHz lasers. We also discuss strategies to enhance or reduce this induced absorption by using different SESAM designs or semiconductor material

Relative timing jitter measurements with an indirect phase comparison method

We propose and demonstrate experimentally a method for the sensitive measurement of the relative timing jitter of two mode-locked lasers, which can be either free-running or timing-synchronized to a common reference oscillator. The method is based on the indirect comparison of the phases of two photodetector outputs, using a microwave oscillator, the noise of which does not affect the results, electronic mixers, and a sampling oscilloscope. We carefully analyze and experimentally demonstrate the potential of this method. Compared to phase detector methods, it has a broader scope of applications and a lower sensitivity to intensity noise. We also obtained data on the coupling of intensity to timing noise in photodetector

Semiconductor saturable absorber mirror structures with low saturation fluence

ISSN:0946-2171ISSN:1432-0649ISSN:0721-7269ISSN:0340-379