A. Isomaki

Femtosecond soliton mode-locked laser based on ytterbium-doped photonic bandgap fiber.

We demonstrate a solid-core ytterbium-doped photonic bandgap fiber laser passively mode-locked with a semiconductor saturable absorber. Gain and anomalous dispersion simultaneously provided by the photonic crystal fiber allow for a compact subpicosecond soliton oscillator. We also discuss the effect of higher-order dispersion in photonic bandgap fiber on laser performance.

All-fiber ytterbium soliton mode-locked laser with dispersion control by solid-core photonic bandgap fiber

We exploit an anomalous dispersion generated by a solid-core photonic bandgap fiber for dispersion compensation in an ytterbium fiber laser passively mode-locked with a semiconductor saturable absorber. The bandgap-guiding fiber, adequately compatible with standard fiber based on guiding via total internal reflection, allows for an environmentally robust all-fiber subpicosecond soliton oscillator at 1 mum.

Femtosecond Soliton Mode-Locked Laser Based on Ytterbium-Doped Photonic Bandgap Fiber

Here we report on the first demonstration of a mode-locked laser using an ytterbium-doped photonic bandgap (Yb-PBG) fiber as the gain medium and a dispersion compensator. We show that using semiconductor saturable absorber mirror together with the Yb-PBG fiber allows for self-starting mode-locked laser around 1-mum wavelength range

Impedance-detuned high-contrast vertical cavity semiconductor switch

We report an all-optical semiconductor gate optimized for high-contrast switching. Using a pump signal with an intensity of less than /spl sim/25 KW/cm/sup 2/, we demonstrate a 30-dB contrast ratio for 10-GHz pulses with energy of 0.05 pJ.

Semiconductor mirror for optical noise suppression and dynamic dispersion compensation

We report on a monolithic Gires-Tournois semiconductor interferometer used for both suppression of low-intensity spontaneous noise in a high-power fiber amplifier and to generate a tunable delay. The potential of the noise suppression technique was demonstrated using a two-stage amplifier system. Gain improvement by a factor of five illustrates the capability of semiconductor gates to greatly enhance energy extraction from optical amplifiers. We demonstrate also that controllable saturable absorption in an optically pumped multiple-quantum-well semiconductor reflector provides promising means for rapidly changing the group delay of the reflector and represents a new form of dynamic dispersion compensator.

Semiconductor mirror for dynamic dispersion compensation

We report on a monolithic Gires–Tournois semiconductor interferometer used to generate a tunable delay. Controllable saturable absorption in optically pumped multiple-quantum-well semiconductor reflector was shown to provide promising means for rapid changing the group delay of the reflector, and represents an attractive form of dynamic dispersion compensation.

Self-starting mode-locked fiber laser using biased semiconductor absorber mirror

We present an erbium-doped fiber laser mode-locked using a reverse-biased InGaAsP multiple quantum-well saturable absorber. We have examined the performance of a p-type-intrinsic-n-type (PIN) structured semiconductor absorber mirror both in starting the pulse operation and in pulse shaping. We have also found that applying a reverse bias is a useful means to suppress the Q-switching instability. By varying the reverse bias voltage applied to the absorber mirror, we could change the recovery time of the device owing to the electric-field-induced carrier sweep-out. Through the sweep-out process we were able to control the mode-locking start-up capability and the pulse duration of the fiber laser. In the experiment the mode-locked pulse duration could be reduced from 50 to 20 ps by application of an 80 kV/cm sweep-out field in the intrinsic region of the PIN absorber. The equivalent spectral broadening by a factor of 2.5 was observed as well.

Fiber laser mode-locked with a semiconductor saturable absorber etalon operating in transmission

We demonstrate a resonant semiconductor saturable absorber used in transmission for mode-locking of fiber lasers. The cavity-enhanced modulation depth corresponding to low-loss transmission state enables a robust self-starting mode-locking highly tolerant to cavity dispersion.

Optical limiting semiconductor saturable absorber mirror

In this paper, we demonstrate that generation of free carriers in the narrow bandgap layers of the semiconductor distributed Bragg reflector (DBR) can also be used for designing the SESAM with optical limiting function. This DBR can serve as a fast all-optical switching element. In conclusion, we have examined the possibility of using a nonlinear semiconductor mirror, whose reflectivity decreases with light intensity.

Design and performance of an impedance-detuned high-contrast vertical cavity semiconductor switch

In this paper, the purpose of this work was to design, fabricate and characterize a saturable absorber-based VCS optimized for switching optical signals that have sufficient energies to partly saturate the optical absorption. The optical switching capabilities have been also demonstrated by measuring the oscilloscope traces of the 10-GHz signal after reflection from the optical gate. The device can be used for a wide range of applications including all-optical switching and wavelength conversion.