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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.

In this letter, we discuss the technology of a thin-film coating made with electron beam evaporation on a single-mode fiber end facet. A dichroic mirror made of ZrO2 and SiO2 was found to provide the necessary selectivity for 980-nm pump and 1040-nm signal wavelengths and enabled us to build a short-cavity mode-locked ytterbium fiber laser. Combined with a photonic crystal fiber dispersion compensator, it allows the realization of a 572-fs soliton all-fiber laser with a fundamental repetition rate of 571 MHz.

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.

We demonstrate a dielectric thin-film Fabry-Peacuterot etalon operated as a dispersion compensator in a mode-locked fiber-laser cavity. The etalon generates anomalous dispersion near the low-loss spectral window and, consequently, the laser mode-locked by the semiconductor saturable absorber favors operation at anomalous dispersion regime without spectral filter. The etalon compensator is tunable, compact, easy to align, and suitable for picosecond and subpicosecond pulse operation

We show in this contribution that there is a surprising beneficial application of the noise amplification capability. Launching a pulse train with a weak sinusoidal amplitude modulation into the microstructure fiber, we observe up to 30-fold optical signal amplification of this modulation after the fiber.

Since the discovery of a wideband (220–300 nm) infrared photoluminescence in bismuth containing alumosilicate glass centered in a 1.1–1.25 µm wavelength band, researchers have focused on exploiting this luminescence in oxide silicate glasses of various compositions for laser purposes [1]. Interest in this effect is mainly associated with the possibility to create Bi-doped fiber amplifiers in the second telecommunications window and for accomodating the future increase of data traffic in telecommunications optical fiber networks. The possibility of building femtosecond fiber lasers in a novel wavelength range is an added positive perspective. It is known that luminescence depends on the simultaneous presence of Bi with Al (or Ta) in the glass matrix, yet, the nature of the active optical center in Bi-doped glasses is still unclear [2]. The properties of host material and co-doping strongly affect the gain broadening and are instrumentalized for designing the optical amplifiers as well as tunable or mode-locked laser systems. Using other active atoms, earlier studies on fiber laser have shown that the character of the laser transition may vary across the gain bandwidth [3, 4]. In particular, it has been shown that transient effects, such as relaxation oscillations, can depend on the operation wavelength. However, unlike the conventional active fiber laser materials such as Er, Yb, Tm and Nd, bismuth is not a rare earth element, and its dynamical behavior may therefore vary significantly.

Owing to their good beam quality and high output power, near-infrared semiconductor disk lasers provide an attractive opportunity for visible light generation via frequency conversion. The typical cavity arrangement of a semiconductor disk laser, consisting of a semiconductor multiple quantum well gain mirror and one or more external mirror, offers a convenient configuration for intracavity frequency doubling. Recent progress in the disk laser development has led to demonstrations of multi-watt green-blue-yellow sources. These achievements have been enabled by the possibility to integrate high performance InGaAs/GaAs gain media and Al(Ga)As/GaAs Bragg reflectors operating in the 940-1160 nm wavelength range. In order to achieve ~620 nm red emission, a laser emitting near the fundamental wavelength of 1240 nm is needed. To achieve this spectral range we have developed GaInNAs/GaAs gain mirrors and we have achieved 1 W of output power at 617 nm by frequency doubling in a BBO crystal. This is to our knowledge the highest power reported to date for intracavity doubled disk laser based on dilute nitride gain material.

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.

Recent studies discover important parameters of thulium doped fiber. Particularly, the dependence of the emission efficiency on the doping level and transition cross section have been determined. Adding holmium as a co-dopant was shown to increase the pump absorption and to extend the thulium gain spectrum to longer wavelengths. The properties of host material and co-doping affect strongly the gain broadening and are used as an instrumental in designing the optical amplifiers, tunable and mode-locked laser systems.

We have demonstrated an ytterbium fiber laser that is compact and easy to align. Overall anomalous group-velocity dispersion was obtained by using a cavity with a thin-film etalon compensator. A self-starting passive mode-locking was ensured with semiconductor saturable absorber mirror providing a short pulse operation. The TFE is able to induce the necessary amount of anomalous dispersion with operation bandwidth sufficient to support picosecond soliton pulses. Without additional spectral filters, the operation wavelength becomes spontaneously locked to the low-loss - high anomalous dispersion region of the etalon.

We have successfully demonstrated a simple and cost effective scheme for all-optical packet contention resolution by means of a PEDC comprised of a saturable absorber-based VCSG and a SOA. An extinction ratio of 15 dB for the PEDC output signal was measured with 1.5 ns using time and 2.5 ns falling time. Major benefits of our solution are polarization independence, transparency to the input packet wavelength, compactness, reduced number of active devices and low power operation

Supercontinuum white-light generation in optical fibers is a process that is known for its extreme sensitivity toward fluctuations of the input pulses, giving rise to a strong amplification of input noise. Such noise amplification has been recognized as a detrimental effect that prevents compression of the broad white-light spectra into a few-cycle pulse. Here, we show that the same effect can be exploited to amplify and recover faint modulation signals to an extent that seems impossible with any electronic method. We experimentally demonstrate the deterministic amplification of faint amplitude modulation signals by up to 60 dB. As we show from numerical simulations, this amplification process arises from the interaction dynamics between solitons and dispersive radiation in the fiber. The resulting all-optic signal restoration provides a new photonic building block that enables signal processing at virtually unlimited processing speeds.

Summary from only given. We demonstrate for the first time that a dispersive saturable absorption mirror (D-SAM) with positive group velocity dispersion (GVD) can be used for implementing a short cavity stretched-pulse fiber laser without employing dispersion compensating fiber. Changing the amount of negative dispersion, accomplished by the wavelength tuning, allows for direct comparison of pulse energy extraction in the soliton supporting dispersion regime and in stretched pulse mode-locking regime.

We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture, that exploits the optical saturation of absorption in semiconductor quantum wells. The modulation section of the modulator, which is composed of quantum wells placed within a Fabry–Perot cavity, is optically controlled by an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer and grown in a single epitaxial step. The modulation section and the in-plane laser share the same medium; therefore, efficient coupling between the control beam and the signal beam is achieved. The device was successfully used for active mode locking of an erbium-doped fiber laser.

Measurement of nonlinear optical reflectivity of saturable absorber devices is discussed. A setup is described that enables absolute accuracy of reflectivity measurements better than 0.3%. A repeatability within 0.02% is shown for saturable absorbers with few-percent modulation depth. The setup incorporates an in situ knife-edge characterization of beam diameters, making absolute reflectivity estimations and determination of saturation fluences significantly more reliable. Additionally, several measures are discussed to substantially improve the reliability of the reflectivity measurements. At its core, the scheme exploits the limits of state-of-the-art digital lock-in technology but also greatly benefits from a fiber-based master-oscillator power-amplifier source, the use of an integrating sphere, and simultaneous comparison with a linear reflectivity standard.

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.

A 1234 nm GalnNAs/GaAs optically-pumped semiconductor disk laser utilising an intracavity BBO (beta barium borate) crystal for nonlinear frequency conversion is reported. 1 W of power at 617 nm has been achieved.

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.

An optically pumped semiconductor vertical external cavity surface emitting laser, with high output power and excellent beam quality operating at a wavelength near 1.05 mm, is reported. A transparent diamond heat spreader was used for thermal management of the laser.The gain structure grown by molecular beam epitaxy includes 13 compressively strained InGaAs quantum wells. Maximum output power of 4 W with diffraction-limited beam (M21.15) was achieved using a 2% output coupler and incident pump power of 20 W. It is shown that power scalability is feasible with the presented laser geometry.

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 (lambda1060 nm). The wavelength dependence of relaxation oscillations can be used to determine the parameters of the gain material such as transition crosssection.

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.

We demonstrate a vertical-cavity intensity modulator exploiting optical pumping of a semiconductor saturable absorber mirror. The device reflection is modulated by means of a control beam generated by a laser integrated within the modulator structure.

We present a surface-normal semiconductor intensity modulator based on optically pumped saturable absorber mirror. The modulation section consists of quantum wells placed within a Fabry-Perot cavity. A laser integrated monolithically within the modulator structure generates the control beam used to pump the absorber. Since the modulation section and the in-plane laser share the same medium, an efficient coupling between the control beam and the signal beam is achieved. The modulator provides an efficient light modulation mechanism that is sufficient to actively mode-lock an Er-doped fiber laser.

This paper presents results of experiments made in attempts to investigate the nonlinear and dispersive properties of resonant semiconductor saturable absorber mirrors. We show that resonant nonlinear reflectors are versatile devices for controlling the properties of mode-locked fiber lasers and that can be used as tunable dispersion compensators.

We report on intracavity frequency-doubling and sum-frequency generation in optically-pumped semiconductor disk lasers. High power second-harmonic red emission from a GaInNAs-based disk laser and aquamarine sum-frequency emission from a dual-wavelength semiconductor disk laser were obtained.

The regime of harmonic mode-locking in semiconductor disk lasers, studied both numerically and experimentally, is shown to be an inherent attribute of these lasers; the number of pulses circulating in the cavity progressively increases with pump power. Saturation and fast recovery of the gain ensure efficient pulse ordering mechanism resulting in strong suppression of cavity fundamentals.

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.

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.

We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture that exploits saturation of absorption in semiconductor quantum wells pumped optically. The modulation section, composed of quantum wells placed within a Fabry-Perot cavity, is exposed to an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer. Since the modulation section and the in-plane laser share the same medium, an efficient coupling between the control beam and the signal beam is achieved. Design guidelines and device performance are presented. We demonstrate that the modulator provides an efficient light modulation mechanism that is sufficient to actively mode-lock an erbium-doped fiber laser.