Lasse Orsila

Picosecond SESAM-based ytterbium mode-locked fiber lasers

Using semiconductor saturable absorber mirrors and a grating-pair dispersion compensator, we obtain reliable self-starting mode locking of a ytterbium (Yb) fiber laser tunable over 125 nm. The 980-1105-nm tuning range is achieved by optimization of nonlinear reflection and bandgap characteristics of the multiple-quantum-well saturable absorber and by proper engineering of the laser cavity. A short-length Yb-doped double-clad amplifier seeded with mode-locked Yb-fiber laser produces picosecond pulses with energy of 30 nJ (700 mW of average power). A compact version of the fiber laser was built using a Gires-Tournois compensator and short length (1-cm long) of highly doped Yb fiber. Using a novel semiconductor saturable abserver mirror based on GaInNAs structure, self-started 1.5-ps pulse mode-locked operation was obtained at 1023 nm with a repetition rate of 95 MHz. A mode-locked Yb-doped fiber laser was also developed without using any dispersion compensation technique. Overall group-velocity dispersion was minimized by using highly doped Yb fiber in a compact amplifying loop cavity. Self-started mode-locked operation was obtained in 980-1030-nm wavelength range with a fundamental repetition rate of 140 MHz. Without using dispersion compensation, the lasers produced pulses in a range from 15 to 26 ps.

High power frequency doubled GaInNAs semiconductor disk laser emitting at 615 nm

We report on an optically-pumped intracavity frequency doubled GaInNAs/GaAs -based semiconductor disk laser emitting around 615 nm. The laser operates at fundamental wavelength of 1230 nm and incorporates a BBO crystal for light conversion to the red wavelength. Maximum output power of 172 mW at 615 nm was achieved from a single output. Combined power from two outputs was 320 mW. The wavelength of visible emission could be tuned by 4.5 nm using a thin glass etalon inside the cavity.

Harmonically mode-locked VECSELs for multi-GHz pulse train generation

We report on optically-pumped vertical-external-cavity surface-emitting lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The results present first systematic study of multiple pulse formation in passively mode-locked VECSELs.

Mode-locked VECSEL emitting 5 ps pulses at 675 nm

A picosecond GaInP/AlGaInP/GaAs vertical external-cavity surface-emitting laser (VECSEL) at 675 nm is reported. The laser is mode-locked with a GaInP/AlGaInP/GaAs saturable absorber mirror and emitted ~5.1 ps pulses at a 973 MHz repetition rate and an average power of 45 mW. To our knowledge, this is the first demonstration of a passively mode-locked VECSEL emitting fundamental laser radiation at the visible part of the spectrum.

Mode-locked ytterbium fiber lasers

A compact fiber laser is demonstrated with use of a Gires-Tournois compensator and a short length (2-4 cm-long) of highly doped ytterbium (Yb) fiber providing net anomalous group-velocity dispersion. With use of a novel semiconductor saturable absorber mirror based on GaInNAs structure, self-started 1.5-ps-pulse mode-locked operation was obtained at 1023 nm with a repetition rate of 95 MHz. A mode-locked Yb-doped fiber laser was developed without the use of any dispersion compensation technique. Overall group-velocity dispersion was minimized by using a short length of highly doped Yb fiber in a compact amplifying loop cavity. Self-started mode-locked operation was obtained in 980-1030-nm wavelength range with a fundamental repetition rate of 140 MHz.

Intracavity Sum-Frequency Generation in Dual-Wavelength Semiconductor Disk Laser

We report on intracavity sum-frequency generation in a semiconductor disk laser operating simultaneously at the wavelengths of 986 and 1043 nm. An LBO crystal was used for nonlinear frequency conversion of the infrared radiation into the aquamarine sum-wavelength of 507 nm. Total converted power of 130 mW was obtained. The results suggest that a similar concept could be applied for difference-frequency generation to create a compact mid- infrared emitter operating at room temperature.

Simultaneous Dual-Wavelength Conversion With Multiresonant Saturable Absorption Vertical-Cavity Semiconductor Gate

We experimentally demonstrate the use of a multiresonant, all-optical vertical-cavity semiconductor gate for simultaneously converting the wavelength of an optical data signal into two signals with different wavelengths. The operation of the gate is based on saturable absorption effect in multiple quantum-well structures. The repetition rate of the converted signal is limited by the recovery time of the saturable absorber. The device is compact, passive, polarization-independent, and enables wavelength conversion with a high extinction ratio of more than 10 dB and maximum optical signal-to-noise ratio penalty lower than 3 dB.

Red and UV generation using frequency-converted GaInNAs-based semiconductor disk laser

We report on the intracavity frequency-doubling of a GaInNAs/GaAs disk laser. The laser operated at 1220 nm and delivered 4.6 W of power at ∼610 nm. The red emission was further frequency-doubled to 305 nm.

All-Optical Packet Envelope Detection Using a Slow Semiconductor Saturable Absorber Gate and a Semiconductor Optical Amplifier

We propose a simple and effective scheme for all-optical packet envelope detection (AO-PED), exploiting a slow saturable absorber-based vertical cavity semiconductor gate and a semiconductor optical amplifier. A high extinction ratio of 15 dB was measured for the recovered envelope signal. The scheme is suitable for photonic integration, and is transparent to the packet polarization state and data rate. It also shows relatively low sensitivity to the input packet wavelength compared to previous all-optical schemes. AO-PED is experimentally demonstrated at 12.5 and 40 Gb/s; the recovered envelope was used to drive a 1 2 all-optical switch for low-priority packets deflection in case of contention occurring between time-slotted synchronous packets. The deflected packets could be routed to a buffering stage or to a different path, depending on network topology, allowing thus contention resolution without packet loss. Error-free bit-error rate (BER) was achieved for packet payload data at the switch output.

Three- and four-level transition dynamics in Yb-fiber laser

The behavior of transient oscillations has been studied experimentally for the first time in a broadly tunable ytterbium fiber laser. Spectroscopic study of the relaxation frequency allows one to distinguish three- and four-level transitions and provides a useful tool for controlling the dynamics of pulsed lasers. Particularly, the relaxation oscillation frequency depends on the occupation of the terminal level of the laser transition and clearly shows that the laser transition becomes four-level at the long-wavelength tail of the gain spectrum of ytterbium fiber (lambda > 1060 nm). The wavelength dependence of relaxation oscillations can be used to determine the parameters of the gain material such as transition crosssection.