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The 1550 nm band semiconductor optical amplifier (SOA) has great potential for applications such as optical communication. Its wide-gain bandwidth is helpful in expanding the bandwidth resources of optical communication, thereby increasing total capacity transmitted over the fiber. Its relatively low cost and ease of integration also make it a high-performance amplifier of choice for LiDAR applications. In recent years, with the rapid development of quantum-well (QW) material systems, SOAs have gradually overcome the shortcomings of polarization sensitivity and high noise. The research on quantum-dot (QD) materials has further improved the noise characteristics and transmission loss of SOAs. The design of special waveguide structures—such as plate-coupled optical waveguide amplifiers and tapered amplifiers—has also increased the saturation output power of SOAs. The maximum gain of the SOA has been reported to be more than 21 dB. The maximum saturation output power has been reported to be more than 34.7 dBm. The maximum 3 dB gain bandwidth has been reported to be more than 120 nm, the lowest noise figure has been reported to be less than 4 dB, and the lowest polarization-dependent gain has been reported to be 0.1 dB. This study focuses on the improvement and enhancement of the main performance parameters of high-power SOAs in the 1550 nm band and introduces the performance parameters, the research progress of high-power SOAs in the 1550 nm band, and the development and application status of SOAs. Finally, the development trends and prospects of high-power SOAs in the 1550 nm band are summarized. [ABSTRACT FROM AUTHOR]

Laser-induced breakdown spectroscopy (LIBS) is becoming a more mature technology every year with new variants such as laser ablation molecular isotopic spectrometry, reheating by various discharge techniques, and multiple pulse excitation schemes, in which sometimes lasers of different pulse lengths are used. However, lasers with inherent parameters like pulse length and repetition rate are still almost exclusively employed. Recent years have witnessed the advent of novel high-repetition-rate laser concepts for machining processes, like welding, milling, and engraving. Here, a comprehensive study of single-pulse LIBS spectra of a single aluminum target is presented to showcase the applicability of flexible high duty-cycle master oscillator power amplifier (MOPA) lasers. Although traditional flashlamp-pumped Fabry–Pérot lasers only permit a variation in the pulse energy and are operated at very low duty-cycles, MOPA lasers add repetition rate and pulse length as variable parameters. A thorough analysis of the temporal plasma behavior revealed the emission dynamic to closely match the excitation laser pulse pattern. An aluminum sample’s spectral response was shown to be significantly impacted by variations in both rate and length. Although the spectral emission strength of the elemental lines of Al, Sr, and Ca all peaked at slightly different parameter settings, the strongest impact was found on the relative abundance of molecular AlO bands. Unlike in previous laser ablation molecular isotopic spectrometry (LAMIS) publications, the latter could be readily detected with a good intensity and well-resolved spectral features without any temporal gating of the detector. This finding, together with the fact that MOPA lasers are both inexpensive and dependable, makes for a promising combination for future studies including the detection of diatomic band structures.

A monolithically integrated dual-wavelength multimode interference coupler-based master oscillator power amplifier is presented. It consists of two shallowly etched, laterally separated ridge waveguide laser cavities as master oscillators with individual distributed Bragg reflector gratings as cavity mirrors. A deeply etched coupling section containing S-bend shaped waveguides and a multimode interference coupler is used to couple the laser emission of the master oscillators into a shallowly etched single waveguide serving as power amplifier. Changing the etch depth for the coupling section enables a compact device layout. In addition, increased radiation angles of modes not coupled into the power amplifier help to suppress beam steering, otherwise indicated by laterally separated far-field intensity distributions. The device provides 0.5 W of dual-wavelength emission around 830 nm in individual and common operation. As designed, both emission wavelengths are separated by 0.5 nm with spectral widths below 20 pm, limited by the spectral resolution of the spectrometer. Both peak wavelengths remain within spectral windows of 50 pm within the available power range. This enables full flexibility selecting operating points for applications such as shifted excitation Raman difference spectroscopy and the generation of THz emission by photomixing. The emission wavelengths can additionally be non-continuously tuned by applying a heater current to resistors implemented next to the distributed Bragg reflector gratings. As an example, selected spectral distances of 0.5 nm, 1.0 nm, 1.5 nm, and 2.0 nm are demonstrated. Near field widths of 5 μ m and far field angles of 17° result in beam propagation ratios of 1.4 (1/e ^2 ) in all operation modes and enable easy beam shaping or optical single-mode fiber coupling.

High-power femtosecond mid-infrared (MIR) lasers are of vast importance to both fundamental research and applications. We report a high-power femtosecond master oscillator power amplifier laser system consisting of a single-mode Er:ZBLAN fiber mode-locked oscillator and pre-amplifier followed by a large-mode-area Er:ZBLAN fiber main amplifier. The main amplifier is actively cooled and bidirectionally pumped at 976 nm, generating a slope efficiency of 26.9%. Pulses of 8.12 W, 148 fs at 2.8 µm with a repetition rate of 69.65 MHz are achieved. To the best of our knowledge, this is the highest average power ever achieved from a femtosecond MIR laser source. Such a compact ultrafast laser system is promising for a wide range of applications, such as medical surgery and material processing. [ABSTRACT FROM AUTHOR]

This paper reports on the theoretical end experimental investigation of the output characteristics of a multisection master-oscillator power-amplifier (MOPA). It consists of a master oscillator (MO) composed by a gain section surrounded by two DBR sections monolithically integrated with a power amplifier (PA). We use a traveling wave equation model to calculate the optical output power in dependence on the current injected into the PA. The experimental results can be well explained with our theoretical analysis. For a finite front facet reflectivity of the PA the system is acting as a compound cavity.

• First demonstration of an all-polarization-maintaining continuous-wave fiber master oscillator power amplifier (MOPA) system at ∼1540 nm. • Experimental results closely followed simulation results based on Erbium-Ytterbium co-doped fiber (EYDF) design. • Achieved >20 W output power, ∼1.4 kHz linewidth, excellent power stability (<0.2 % RMS), and low intensity noise (−110 dBc/Hz). We have developed both theoretically and experimentally an all polarization-maintaining fiber-based master oscillator power amplifier (MOPA) system, which allows for amplifying the single-frequency continuous-wave (CW) fiber laser to >20 W without compromising the laser intensity noise (−110 dBc/Hz@ relaxation oscillation peak) at the specific wavelength of ∼1540 nm. The experimental results agree well with the simulated results. To the best of our knowledge, this is the first demonstration of a ∼1540-nm single-frequency all fiber laser and reaching such a high-power level. The amplified laser features a narrow linewidth of ∼1.4 kHz and a spectral side-mode-suppression ratio of >38 dB, even as the laser wavelength is tuned from 1538.216 nm to 1540.616 nm. It is believed to be the narrowest laser linewidth realized in the <1550-nm wavelength band of an Erbium-Ytterbium co-doped fiber MOPA system. The all polarization-maintaining configuration of the MOPA ensures the amplified laser linearly polarized with the polarization extinction ratio of >22 dB and power root mean square fluctuations of <0.2 %@1h. This high-performance single-frequency fiber laser is expected to be an ideal pump source in the spin-exchange relaxation-free (SERF)-based atomic sensors after second harmonic generation. [ABSTRACT FROM AUTHOR]

The 1550 nm band semiconductor optical amplifier (SOA) has great potential for applications such as optical communication. Its wide-gain bandwidth is helpful in expanding the bandwidth resources of optical communication, thereby increasing total capacity transmitted over the fiber. Its relatively low cost and ease of integration also make it a high-performance amplifier of choice for LiDAR applications. In recent years, with the rapid development of quantum-well (QW) material systems, SOAs have gradually overcome the shortcomings of polarization sensitivity and high noise. The research on quantum-dot (QD) materials has further improved the noise characteristics and transmission loss of SOAs. The design of special waveguide structures—such as plate-coupled optical waveguide amplifiers and tapered amplifiers—has also increased the saturation output power of SOAs. The maximum gain of the SOA has been reported to be more than 21 dB. The maximum saturation output power has been reported to be more than 34.7 dBm. The maximum 3 dB gain bandwidth has been reported to be more than 120 nm, the lowest noise figure has been reported to be less than 4 dB, and the lowest polarization-dependent gain has been reported to be 0.1 dB. This study focuses on the improvement and enhancement of the main performance parameters of high-power SOAs in the 1550 nm band and introduces the performance parameters, the research progress of high-power SOAs in the 1550 nm band, and the development and application status of SOAs. Finally, the development trends and prospects of high-power SOAs in the 1550 nm band are summarized.

We developed a three-stage, amplifying, tunable diode laser system that comprises a master laser in a Littrow configuration, frequency-stabilized by dichroic atomic vapour laser lock, acousto-optic frequency shifter, injection-locked slave laser, and tapered amplifier. The slave amplifies the injected frequency-shifted master beam while suppressing (within 0.5 %) the strong dependence of its intensity on the acousto-optic frequency shifter carrier frequency, thus acting as a strongly saturated optical limiting amplifier with constant output power. The resulting beam is then amplified in a tapered amplifier. The system provides an output power above 700 mW at a wavelength of 780 nm, with a time-averaged linewidth of 0.6 MHz, and a frequency drift below 2 MHz/h. Dichroic atomic vapour laser lock enables frequency stabilization in the range of 400 MHz around D2 lines of rubidium. The mode-hop-free tuning range amounts to 2 GHz. Determined by the acousto-optic frequency shifter model used, the fine-tuning range (precision of few tens kHz) spans 70 MHz. A description of the system was presented and its performance was tested. The basic components have been designed in our laboratory. [ABSTRACT FROM AUTHOR]

We numerically investigate the modulation dynamics in an integrated three-section MOPA using a voltage driven traveling-wave model. The three-section device includes a distributed feedback laser, a modulation section, and a high power tapered amplifier. Both small and large modulation signals are considered, as well as binary data with pseudorandom sequences. The results indicate that dynamic responses of the modulation and amplification sections produce counteracting effects, giving rise in some cases to a reduced chirp, a faster step response, and a decrease of the patterning effects in comparison with the behavior of a single amplifier. In addition to the speed of the carrier response, two dynamical effects are relevant: the reverse current dynamics in the modulation section and the gain saturation dynamics in the amplifier section. [ABSTRACT FROM AUTHOR]

A compact, micro integrated, diode laser-based dual-wavelength master oscillator power amplifier at 785 nm is presented. Laser emission from a Y-branch distributed Bragg reflector laser is coupled into a tilted ridge waveguide amplifier on a $5\times 25$ mm2 micro optical bench. At 25°C and 20 mW pump power, an optical output power of 0.5 W is obtained. The corresponding emission wavelengths are 784.62 and 785.24 nm, resulting in a spectral distance of 10 cm $^{-1}$. The measured spectral bandwidths and side mode suppression ratios are 0.02 nm (0.3 cm $^{-1}$) and 30 dB, respectively. At both wavelengths beam propagation parameters of 1.3 ($\text{M}{^{2}}_{4\boldsymbol \sigma }$) are obtained. This allows for efficient dual-wavelength single-mode fiber coupling. In addition, the device does not show any effects from optical feedback. It neither shows a lateral spatial tilt of the far field intensity distributions for the two wavelengths, previously reported for single Y-branch diode lasers. Based on these parameters, the device is suitable for demanding applications such as shifted excitation Raman difference spectroscopy or confocal Raman microscopy. [ABSTRACT FROM AUTHOR]

• L-band dissipative soliton NALM laser • Ultrafast L-band MOPA system with watt-level output power. • Gneration of L-band fs noise-like pulses in the amplifier. • A broad mid-infrared supercontinuum from 0.87 μm to 3.75 μm. Here, we propose a high power dissipative soliton (DS) laser with a central wavelength of ∼1612 nm. The whole laser system includes the mode-locking oscillator and the corresponding master oscillator power amplifier (MOPA). The mode-locking oscillator is a nonlinear amplifier loop mirror (NALM) cavity, which has a net normal dispersion enabling the generation of nJ-level DS pulses. To further enhance the output power of the 1.6 μm DS pulses, the specially-designed MOPA system consisting of multiple-stage single-pass amplifier is constructed, which can amplify the output power to watt level and meanwhile keeps a high suppression ratio to C-band amplified spontaneous emission (ASE). This high power 1.6 μm DS laser will have further applications in biomedical research and material processing. In the amplifier, we observe the automatic evolution of the DS pulses into the noise-like (NL) pulses under high pumping strength. At the maximum pump power, the MOPA system delivers the NL pulses with an output power of over 2 W. The narrowest spike duration is ∼70 fs (fs). This 1.6 μm fs-scale NL laser is a good pump source for generating the mid-infrared supercontinuum without short wavelength region loss. To demonstrate the superiority of this NL laser, a broad supercontinuum from ∼0.87 μm to ∼3.75 μm waveband is achieved with a piece of highly germanium-doped (Ge-doped) fiber. [ABSTRACT FROM AUTHOR]

We present experimental results on the emission characteristics of a 1.5-μm distributed feedback (DFB) tapered master oscillator power amplifier (MOPA) in a wide range of steady-state injection conditions, showing different dynamical behaviors. A detailed analysis of the optical and radio-frequency spectra has allowed the identification of three different emission regimes: i) stable amplified DFB emission, but with wavelength jumps when sweeping the injection currents; ii) multimode Fabry-Perot (FP) operation of the complete MOPA cavity; and iii) self-pulsed operation at frequencies between 5 and 8 GHz. The quasi-periodic occurrence of these emission regimes as a function of the injected currents is interpreted in terms of a thermally tuned competition between the modes of the master oscillator and the compound cavity modes. The physical origin of the wavelength jumps and of the alternation between regimes is discussed.

We present a voltage driven traveling-wave model for the simulation of an integrated three-section master oscillator power amplifier. The model considers the applied voltage to each active section as an input parameter and calculates the longitudinal profiles of the local current and carrier densities. The model reproduces the experimental evidence of either a positive current when the section is acting as an amplifier or a negative current when it is acting as a photodiode in the photovoltaic mode. We validate the model by comparing with experimental results obtained both, under static operation for a variety of biasing conditions and under direct modulation. [ABSTRACT FROM AUTHOR]

Watt-class visible laser light with a high luminance can be created with high-power GaAs-based lasers either directly in the red spectral region or using single-pass second harmonic generation (SHG) for the colors in the blue-yellow spectral region. The concepts and results of red- and near infrared-emitting distributed Bragg reflector tapered lasers and master oscillator power amplifier systems as well as their application for SHG bench-top experiments and miniaturized modules are presented. Examples of these high-luminance light sources aiming at different applications such as flying spot display or holographic 3D cinema are discussed in more detail. The semiconductor material allows an easy adaptation of the wavelength allowing techniques such as six-primary color 3D projection or color space enhancement by adding a fourth yellow color. [ABSTRACT FROM AUTHOR]

• Wavelength tunable dissipative soliton resonance is realized in an all polarization maintaining Yb-doped fiber laser. • Based on a pulse picker, the repetition rate of pulses can be changed from 100 kHz to 3.6 MHz. • A record pulse peak power of 1.91 MW at 100 kHz for pulse width of 55 ps is achieved after amplification and compression. High peak power dissipative soliton resonance (DSR) with tunable wavelength and flexible repetition rate is experimentally achieved based on an all polarization maintaining master oscillator power amplifier fiber laser. The figure-of-eight oscillator outputs DSR pulse at a fundamental repetition rate of 3.6 MHz with square-shaped temporal pulse duration of 600 ps. By adjusting the intracavity fiber filter, the center wavelength of the DSR pulse can be continuously changed from 1017 to 1042 nm. These wavelength and temporal duration tunable pulses are then coupled into an all-fiber pulse picker to gain another tuning freedom of repetition rate from 100 kHz to 3.6 MHz. Seeded by the flexible pulse, an two-stage all-fiber amplifier is used to boost the average power to 20 W with the polarization extinction ratio of 18.2 dB. After compression, a record pulse peak power of 1.91 MW is achieved at the repetition rate of 100 kHz with pulse duration of 55 ps. [ABSTRACT FROM AUTHOR]

We report a compact, all fiber, 150 ps fiber master oscillator power amplifier operating at 1064 nm that has the ability of producing a maximum average output power of 2.16 W with peak power as high as 10 kW. The output from the master oscillator power amplifier is spliced with a highly nonlinear photonic crystal fiber, generating a supercontinuum with an average power of 250 mW at repetition rate of 1 MHz and spectrum bandwidth spanning from 600 to 1700 nm. The developed supercontinuum system is used to detect the presence of heavy metal contaminants in water by a simple light transmittance method to ensure that the water is free from heavy metal contaminants and safe for consumption. The supercontinuum laser source was shone onto a water sample with a detector placed at another end in order to measure the transmitted supercontinuum light. By measuring the amount of light attenuated at particular wavelength, the concentration of heavy metal contaminants present in the water sample could be determined. [ABSTRACT FROM AUTHOR]

The suitability of a three-section master oscillator power amplifier for pseudorandom lidar is investigated by means of the experimental characterization and analysis of its emission characteristics under modulation. The proposed architecture consists of a distributed feedback laser, a modulation section, and a tapered semiconductor optical amplifier. The modulation section acts as an absorber or amplifier when driven at zero or positive bias. Under pseudorandom modulation at 25 Mb/s, a high optical modulation amplitude and extinction ratio were achieved. The characterization of the emission spectra under modulation revealed typical features of frequency modulation due to the carrier-induced refractive index changes. [ABSTRACT FROM PUBLISHER]

We present a micro-integrated laser module based on an amplified diode laser and second harmonic generation which is a promising candidate for a green light source in next-generation 3D holographic displays. The light emitted by the amplified laser has a wavelength of 1064 nm, reaches a power up to 8.2 W and has a long coherence length of >400 m. For second harmonic generation, we tested two geometries of periodically poled lithium niobate crystals in single pass: a bulk crystal and a planar waveguide crystal. With the planar waveguide crystal, we achieve an output power >900 mW and a coherence length >20 m at a wavelength of 532 nm. [ABSTRACT FROM AUTHOR]

Red-emitting lasers for display applications require high output powers and a high visibility. We demonstrate diode lasers and modules in the red spectral range based on AlGaInP with optical output powers up to 1 W and a nearly diffraction limited beam. These high-luminance light sources based on tapered lasers are well suited for laser TVs and projectors for virtual reality simulators based on the flying spot technology. Additionally, we developed diode lasers with internal distributed Bragg reflector (DBR) surface gratings. These DBR tapered lasers and master-oscillator power-amplifiers based on DBR ridge-waveguide lasers and tapered amplifiers feature high power, single mode emission with coherence lengths up to several meters, which are suitable for the next-generation 3D displays based on holography. [ABSTRACT FROM AUTHOR]