30 W output of short pulse duration nanosecond green laser generated by a hybrid fiber-bulk MOPA system

We reported a 30 W average output power 532 nm green laser with 5 ns pulsed duration working at 80–100 kHz generated by a hybrid MOPA system. The hybrid MOPA system consisted of a fiber amplifier and two solid-state amplifiers producing 77 W 1064 nm at pulse repetition rates of 80–100 kHz. The IR-to-green optical conversion efficiency was 44.7% at the working point of 100 kHz. The beam quality of green laser was measured better than M ² < 1.6 in both orthogonal directions. Nanosecond 532 nm lasers with short pulsed duration could be practicable in silicon-based material processing in the Photovoltaic industry.     

30.6 W CW Tm3+ fiber laser of seed amplification

We use all fiber single-mode lasers as seed source, all fiber amplifiers and pump laser coupling amplifier has been experimentally investigated, respectively. The max output power of all fiber amplifier is 30.6 W, corresponding slope efficiency is 39.1%. The two setups, amplifier output laser spectrum finely holds the property of seed laser spectrum, the wavelength of output laser are both 1947.6 nm, the spectrum width is less than 2 nm as same as the wavelength of seed laser. We estimate the beam quality to be M ² = 2.42, clearly indicating nearly diffraction-limited beam propagation.     

High efficiency Tm fiber laser of seed amplification

We use all-fiber single-mode lasers as seed source, amplifiers and pump laser coupling amplifier has been experimentally investigated, respectively. The maximum output power is 10.4 W, with the slope efficiency of 54.4% when the seed laser power is 1 W, and the slope efficiency is 48.7% when the seed laser power is 2 W. The slope efficiency of this scheme is higher than that of the all-fiber amplifier. This can be explained by the loss of pump power at the splice dots. The wavelength of the fiber amplifier is 1947.6 nm, the same as the seed laser's, with a linewidth of 2 nm. We estimate the beam quality to be M² = 2.39, clearly indicating nearly diffraction-limited beam propagation.     

Experimental study of SBS suppression and coherence property of 1064 nm high power multi-tone fiber amplifier

Seeding high power fiber amplifier employing multi-tone fiber laser is an effective approach to suppress stimulated Brillouin scattering (SBS). In this paper, a two-stage 1064 nm high power fiber amplification system was set up. Single-, two- and three-tone fiber lasers were employed. SBS threshold powers and maximum output powers of the multi-tone cases are enhanced compared with the single-tone case. The multi-tone amplifiers also show comparable optical-to-optical efficiency to the single-tone amplifier. To demonstrate and validate coherence property of the two multi-tone fiber amplifiers, the output laser beams of the amplifiers were self-interfered in our self-made coherent beam combining system. The laser beams of the multi-tone cases showed good coherence property comparable to the single-tone case, which implied that the high power output laser light of the multi-tone fiber amplifiers could be used for coherent beam combining.     

Diode-pumped single-frequency-Nd:YGG-MOPA for water–vapor DIAL measurements: design, setup and performance

A diode-pumped Q-switched and injection-seeded single-frequency laser, generating tunable laser radiation at 935 nm, is presented. Using Nd:YGG (Y₃Ga₅O₁₂) as the active medium, the laser that was developed to serve as a transmitter for water–vapor lidar measurements. The configuration consists of a stable resonator in rod geometry that is injection seeded by a narrowband diode laser and stabilized by the ramp-and-fire technique. Energy scaling was done in a power amplifier in slab geometry. Both oscillator and amplifier crystal were diode pumped at 806 nm. More than 30 mJ pulse energy at 100 Hz repetition rate with a beam propagation factor of M²<1.4 and pulse duration of 52 ns in single-frequency mode were generated. To our knowledge this is the first direct generation of 935 nm Q-switched pulses from Nd:YGG suitable for water–vapor measurements. The reported results show great promise of this laser in applications where high efficiency and reduced complexity is indispensable, such as for spaceborne or airborne water–vapor lidar instruments.     

Amplification of a <Emphasis Type="Italic">Q</Emphasis>-Switched Ho:GdVO<Subscript>4</Subscript> Oscillator in Thulium-Doped Large-Mode-Area Fiber

We report a high peak power, narrow linewidth, stable pulsed Ho:GdVO₄ amplifier based on thuliumdoped fiber, which produces 6.65 W average output power at 2,048 nm and 56.8 kW peak power with 11.7 ns pulse width at 10 kHz repetition rate. We use a simple Q-switched Ho:GdVO₄ laser as a seed laser and a thulium-doped fiber pumped by a 792 nm laser diode as an amplifier. The fiber amplifier provided 6.5 dB gain to the input signal. The spectral linewidth of the Ho:GdVO₄ amplifier remains < 0.5 nm with an M² beam quality of 1.36.     

High-repetition-rate high-beam-quality 43 W ultraviolet laser with extra-cavity third harmonic generation

High-power, high-repetition-rate extra-cavity third harmonic generation of 355 nm with high beam quality has been developed. The acoustic-optical Q-switched Nd:YVO₄ MOPA laser including 2- and 4-stage amplifiers was used as the IR source. With the extra-cavity frequency conversion of LBO crystals, 30.2 W TEM₀₀-mode 355 nm UV laser was obtained with a 2-stage amplifier MOPA laser, and the optical-to-optical (1064 nm to 355 nm) conversion efficiency was up to 30%. Enhanced 43 W TEM₀₀ UV laser at 60 kHz was achieved with a 4-stage amplifier MOPA IR laser, and pulse duration was 10.7 ns corresponding to the peak power as high as 67 kW, with single pulse energy of 0.72 mJ. The optical–optical efficiencies from IR and diodes to UV were 28% and 10% respectively.     

High efficiency, dual-wavelength fibre Raman pump laser for U-band fibre Raman amplifiers

A dual-wavelength, continuous wave, high efficiency fibre Raman ring laser for pumping U-band (1625–1675 nm) fibre Raman amplifiers is demonstrated. Two fibre Bragg gratings were used as wavelength-selective elements resulting in lasing lines at 1529.7 and 1558.7 nm with respective maximum powers of 209.0 and 390.9 mW. A simple U-band Raman amplifier was constructed to test the dual-wavelength pump laser and on:off gain with a peak of 7.3 dB and a 3-dB bandwidth of 73 nm was obtained.     

Laser-diode-pumped Yb:YAG laser as a new pump source and its application to an Er3+, Yb3+-codoped high-output-power fiber amplifier

We propose a laser-diode-pumped Yb:YAG laser as a novel practical fiber amplifier pump source, and describe its first successful application of high-output-power operation (850 mW=+29.3 dB m) of an Er³⁺,Yb³⁺-codoped fiber amplifier at 1.55 μm. We have developed both bulk and microchip Yb:YAG lasers and obtained 3.3 W and 2.7 W, respectively, in the cw mode at room temperature. Laser-diode-pumped Yb:YAG lasers are shown to have a potential applicability to such fiber amplifiers as Pr³⁺-doped amplifiers and Tm³⁺-doped amplifiers, as well as Er³⁺,Yb³⁺-codoped fiber amplifiers. Received: 12 August 1999 / Revised version: 3 September 1999 / Published online: 20 October 1999     

Powerful, diffraction-limited semiconductor laser using photorefractive beam coupling

We use semiconductor laser amplifiers and a photorefractive crystal to generate a high-power, diffraction-limited laser beam at 860 nm. Using a single flared amplifier, we obtain 1.09 W in a diffraction-limited beam from 2.2 W of pump power. Using an array of flared amplifiers, we also demonstrate efficient beam coupling, showing that this technique is easily extended to semiconductor amplifier arrays.     

全固态kHz啁啾脉冲飞秒激光放大器

要建造大功率超强激光系统,必须将nJ量级的种子进行放大,以得到mJ量级以及更高能量的激光输出.为达到这个目的,必须使种子能量指数增加,再生腔放大器是实现这一目的的良好途径;同时,为了得到更稳定的激光输出,须采用高重复频率的泵浦源.为此,设计了一种kHz重复频率激光泵浦的再生放大器,使用15 mJ的527 nm的绿光泵浦,得到了约2.3 mJ的800 nm放大激光输出,同时,对其输出激光的光谱特性进行了测量,将带宽为40 nm的种子注入后,得到了光谱带宽约为30 nm激光输出.     

Red picosecond pulses generated by frequency doubling a Raman amplified widely tunable 1.3 microm fiber ring laser

We generated 0.66 microm picosecond pulses by second-harmonic generation of the Raman amplified output of a 1.3 microm actively mode-locked fiber ring laser in a periodically poled potassium titanyl phosphate (PPKTP) waveguide. The ring laser produced 9 ps pulses at a 20 GHz repetition frequency, was tunable over 1284-1330 nm, and was based on a semiconductor optical amplifier and a Mach-Zehnder amplitude modulator. The Raman amplifier served both to amplify the ring laser and to compress the pulses as solitons. The spectral flexibility of the amplifiers and the modulator should enable similar configurations to be made at other wavelengths and facilitate efficient frequency doubling in waveguides to other visible wavelengths.     

Remotely Pumped Hybrid Amplifiers for Extended Bidirectional Passive Optical Networks

In this contribution, we optimize design parameters of hybrid optical amplifiers utilizing distributed Raman amplification in transmission fiber and gain of discrete, remotely pumped erbium-doped fiber amplifier (EDFA) for wideband, bidirectional operation in metropolitan area networks (MAN). The design is based on an application of a numerical model, which takes into account pump-to-pump and signal-to-signal interactions and generation of amplified spontaneous emission in the Raman amplifier and solves the standard rate-propagation equations in an erbium-doped fiber (EDF). We predict 12 dB gain across 72 nm of optical bandwidth with gain ripple better than 10%. The recently proposed serial topology of EDFA is considered; this enables the wideband, bidirectional operation of a hybrid amplifier with only two pump laser diodes emitting in the 1430 and 1480 nm bands.     

Modeling of a two-color, two-stage, ultrafast Yb-doped fiber amplifier

We have modeled a two-stage, Yb-doped fiber amplifier system to amplify two-color ultrafast laser pulses in near-infrared. The first and second stages namely preamplifier and power amplifier are single-clad, single-mode and double-clad, single-mode Yb-doped fibers respectively. From numerical simulations of the modeled fiber amplifiers, the optimal lengths of the two fibers to have equal power at two colors centered at 1035 nm and 1105 nm are in agreement with our experimental results. Numerical simulations have also been performed to demonstrate the impact of using a flat-top, two-color seed spectrum on the system performance.     

Nd:YVO₄ amplifier for ultrafast low-power lasers

An Nd:YVO₄ amplifier consisting of two modules end pumped at 808?nm at 30?W total absorbed power has been designed for efficient, diffraction-limited amplification of ultrafast pulses from low-power seeders. We investigated amplification with a 50?mW, 7?ps Nd:YVO₄ oscillator, a 2?mW, 15?ps Yb fiber laser, and a 30?mW, 300?fs Nd:glass laser. Output power as high as 9.5?W with 8?ps pulses was achieved with the 250?MHz vanadate seeder, whereas the 20?MHz fiber laser was amplified to 6?W. The femtosecond seeder allowed extracting Fourier-limited 4?ps pulses at 7?W output power. To our knowledge, these are the shortest pulses from any Nd:YVO₄ laser device with at least 7?W output power. This suggests a novel approach to exploit the gain bandwidth of vanadate amplifiers with high output power levels. Such amplifier technology promises to offer an interesting alternative to high-power thin disk oscillators at few picoseconds duration, as well as to regenerative amplifiers with low-repetition-rate fiber seeders.     

All-fiber clad-pumped Tm3+-doped fiber amplifier using high power fiber combiner

The diode laser (LD) clad-pumped 1947.6 nm continuous wave (CW) Tm³⁺-doped fiber amplifier is reported using the master oscillation power amplifier (MOPA) method. The injected seed laser is provided by an all-fiber LD-clad-pumped Tm³⁺-doped single-mode fiber laser, which has a nearly 2.4 W maximal output power and 0.1 nm ultra-narrow linewidth based on the intracore reflection FBG. Using the 25/400 μm double-clad LMA Tm³⁺-doped fiber as the gain fiber, the output maximal output power is 30.6 W from the fiber amplifier, with a slope efficiency of 39.1% respected to the LD total output power. A high power multi-mode fiber combiner is used to couple high power LD light into the gain fiber. The output wavelength is also located at 1947.6 nm, with the slightly expanded laser linewidth of 0.2 nm.     

Iodine photodissociation laser SOFIA with MOPO-HF as?a?solid-state oscillator

The hybrid iodine photodissociation laser SOFIA has been constructed. The pulse feeding the amplifier chain is the idler wave of an optical parametric oscillator (OPO) tuned to the atomic iodine transition at 1315 nm. This solid-state oscillator enables ps-synchronization to other laser systems. A homemade automatic stabilization of the OPO idler wave as to wavelength and pointing ensures long-term stable operation of the whole system. The active medium of the SOFIA amplifiers is a mixture of C₃F₇I and He. The SOFIA pulses are frequency-tripled in two KD*P crystals and then serve as the driver in a two-stage optical parametric amplification scheme in which chirped broadband Ti:sapphire laser pulses are amplified (OPCPA).     

A hybrid OPCPA/Nd:phosphate glass multi-terawatt laser system for seeding of a petawatt laser

To enhance radiographic abilities on its Z-Accelerator, Sandia National Laboratories is incorporating a petawatt laser system into the existing Z-Backlighter laser facility. As part of this work, a short-pulse laser has been constructed to seed the larger Beamlet type Nd:phosphate glass slab amplifiers. This seed laser consists of an optical parametric chirped pulse amplification (OPCPA) system joined to a Nd:phosphate glass rod amplifier system in order to achieve multi-Joule sub-picosecond operation. The rod amplifier system has been modeled using the Miró code which shows good agreement with the experimental results. This system can achieve focal intensities up to 10¹⁸ W/cm² at a repetition rate of once every 20 min and has been applied to produce k-alpha X-rays in copper.     

Broadband photoluminescence from pulsed laser deposited Er2O3 films

Photoluminescence (PL) with the bandwidth of 45 nm (1523-1568 nm at the level of 3 dB) was observed in amorphous Er₂O₃ films grown on to the quartz substrate by pulsed laser ablation of erbium oxide stoichiometric target. Optical transmission spectrum has been fitted to Swanepoel formula to determine the dispersion of refractive index and to extract resonance absorption peaks at 980 and 1535 nm. The maximum gain coefficient of 800 dB/cm at 1535 nm was estimated using McCumber theory and experimental spectrum of the resonance absorption. In 5.7 mm-long waveguide amplifier a theory predicts the spectral gain of 20 dB with 1.4 dB peak-to-peak flatness in the bandwidth of 31 nm (1532-1563 nm) when 73% of Er³⁺ ions are excited from the ground state to the ⁴I_13/2 laser level. Strong broadband PL at room temperature and inherently flat spectral gain promise Er₂O₃ films for ultra-short high-gain optical waveguide amplifiers and integrated light circuits.     

Compact all-solid-state continuous-wave single-frequency UV source with frequency stabilization for laser cooling of Be<Superscript>+</Superscript> ions

A compact setup for generation, frequency stabilization, and precision tuning of UV laser radiation at 313 nm was developed. The source is based on frequency quintupling of a C-band telecom laser at 1565 nm, amplified in a fiber amplifier. The maximum output power of the source at 313 nm is 100 mW. An additional feature of the source is the high-power output at the fundamental and the intermediate second- and third-harmonic wavelengths. The source was tested by demonstration of laser cooling of Be⁺ ions in an ion-trap apparatus. The output of the source at the third-harmonic wavelength (522 nm) was used for stabilization of the laser frequency to molecular iodine transitions. Sub-Doppler spectroscopy and frequency measurements of hyperfine transitions in molecular iodine were carried out in the range relevant for the Be⁺ laser cooling application.