Booster Amplifier Research Articles

Generation of high-contrast, 30 fs, 15 PW laser pulses from chirped-pulse amplification Ti:sapphire laser

High-contrast, 30 fs, 1.5 PW laser pulses are generated from a chirped-pulse amplification (CPA) Ti:sapphire laser system at 0.1 Hz repetition rate. The maximum output energy of 60.2 J is obtained, at a pump energy of 120 J, from a booster amplifier that is pumped by four frenquency-doubled Nd:glass laser systems. During amplification, parasitic lasing is suppressed by index matching fluid with absorption dye and the careful manipulation of the time delay between the seed and pump pulses. An amplified pulse passes through a pulse compressor consisting of four gold-coated gratings. After compression, the measured pulse duration is 30 fs, and the output energy is 44.5 J, yielding a peak power of about 1.5 PW. The output energy of 44.5 J and output power of 1.5-PW are the highest values ever achieved from the femtosecond CPA Ti:sapphire laser system. To maintain a sufficiently high temporal contrast, a saturable absorber is installed in the front-end system with two ultrafast Pockels cells in order to minimize the amplified spontaneous emission (ASE) and pre-pulse intensity. An adaptive optics system is implemented for PW laser pulses and a focused intensity of about 1 × 10(22) W/cm(2) can be obtained when an f/3 optic is used.

Thermal effects in kilowatt all-fiber MOPA

Thermal effects and output power characteristics of kilowatt all-fiber master-oscillator power amplifier (MOPA) are investigated. Proper designs for cooling apparatus are proposed and demonstrated experimentally, for the purpose of minimizing splice heating which is critical for the reliability of high power operation. By using these optimized methods, a thermal damage-free, highly efficient ytterbium-doped double-clad fiber MOPA operating at 1080 nm with 1.17 kW output was obtained. The maximum surface temperature at the pump light launching end splice of the booster amplifier was 345 K, and the temperature rise for this key splice was 0.052 K/W.

Tunable high power fiber laser using an AWG as the tuning element

In this paper, a design of a High Power Tunable Fiber Laser (HP-TFL) in C-band region from 1536.7 to 1548.6 nm is set forth with Erbium Doped Fibers (EDFs) being used as a seeding signal and a booster amplifier. With a 1 × 16 channels Arrayed Waveguide Grating (AWG), this setup is capable of generating 16 different wavelengths with an average output power of 20.7 dBm.

01 Hz 10 PW Ti:sapphire laser

We report on the generation of 1.0 PW, 30 fs laser pulses at a 0.1 Hz repetition rate from a chirped-pulse amplification Ti:sapphire laser system. The energy of the laser pulses is amplified up to 47 J in a final three-pass booster amplifier having 96 J pump energy. To the best of our knowledge, this is the first petawatt Ti:sapphire laser system at a 0.1 Hz repetition rate. The shot-to-shot energy fluctuation of the laser pulses is as low as 0.53% in rms value, and the laser pulses have homogeneous flattop spatial beam profiles.

High-energy, kHz-repetition-rate, ps cryogenic Yb:YAG chirped-pulse amplifier

We demonstrate amplification of picosecond laser pulses to 40?mJ at a 2?kHz pulse repetition frequency (PRF) from a two-stage cryogenic chirped-pulse Yb:YAG amplifier, composed of a regenerative amplifier (RGA) and a two-pass booster amplifier. The RGA produces 8.2mJ of energy at 2kHz PRF and 13.2mJ at 1kHz PRF with excellent energy stability (approximately 0.3% rms) and beam quality (M(2)<1.1). Pulse stretching and compression are achieved by using a chirped fiber Bragg grating and a multilayer dielectric grating pair, respectively. Compressed 15?ps pulses from the RGA are obtained with a throughput efficiency of approximately 80% (approximately 6.5 mJ for 2kHz). The booster amplifier further amplifies the pulses to 40mJ at 2kHz PRF, and approximately 32 mJ, approximately 15 ps pulses are expected after compression. The amplifier chain seeded from a femtosecond Yb-fiber laser enables the optical self-synchronization between signal and pump in optical parametric chirped-pulse amplifier applications.

Optimization of erbium-doped fiber MOPA laser

An erbium-doped fiber laser (EDFL) constructed in a master oscillator and power amplifier (MOPA) configuration is analyzed. The pump powers for the fiber cavity laser and the booster amplifier stages are managed properly to achieve maximal pump conversion efficiency. Our design achieves a pump conversion efficiency of 91.4%, corresponding to a quantum efficiency of 96.6%, for a 1565.8 nm MOPA laser pumped by a total power of 300 mW at 1480 nm. The optimized MOPA laser shows a 25% enhancement in the pump conversion efficiency, compared to a non-MOPA fiber laser. A side lobe suppression ratio of 48 dB for the optimized MOPA laser is observed.

All-fiber eye-safe pulsed laser with Er-Yb Co-doped multi-stage amplifier

We report an all-fiber pulsed laser with multistage fiber amplifier which was suitable for high power eye-safe free space optical communications. Tapered structure has been utilized between booster and final amplifiers, which could increase the power coupling from the former fiber into the core of the latter fiber, and the beam quality of the output laser could be improved simultaneously. A maximum output power over 6 W has been achieved from the master-oscillator-power-amplifier system. With the multi-stage configuration and forward pumping, the optical signal to noise ratio was measured to be better than 50 dB.

Power scaling of resonantly cladding-pumped, Yb-free, Er-doped LMA fiber lasers

The results of the recent major efforts in power scaling of resonantly cladding-pumped Yb-free Er fiber lasers are presented. Commercially available Yb-free Er-doped large mode area Er60-20/125 (LMA) DC fibers were tested in two regimes: (i), as a booster amplifier in a single-frequency (SF) MOPA configuration and, (ii), in a Bragg grating (FBG) based narrowband fiber laser configuration. We obtained ∼28.5 W of output power at 1590 nm, the highest power reported so far out of Yb-free Er-doped LMA fiber with resonant cladding pumping. The achieved optical-to-optical conversion slope efficiency of ∼56.6% is also believed to be the highest efficiency ever reported from Yb-free Er-doped fiber laser with resonant cladding pumping.

Design of a Femtosecond Ti:sapphire Laser for Generation and Temporal Optimization of 0.5-PW Laser Pulses at a 0.1-Hz Repetition Rate

A chirped-pulse amplification Ti:sapphire laser system has been designed using a 10-Hz 100-TW Ti:sapphire laser to generate 0.1-Hz 0.5-PW laser pulses and optimize their temporal qualities such as temporal contrast and pulse duration. A high-energy booster amplifier to be added is expected to produce an energy above 30 J through the parasitic lasing suppression and the efficient amplification. To improve the temporal contrast of the laser pulses, a high-contrast 1-kHz amplifier system is used as a front-end. A grating stretcher which makes the laser pulse have 1-ns duration is used to prevent optical damages due to high pulse energy during amplification. A grating compressor has been designed with group delay analysis to obtain the recompressed pulse duration close to the transform-limited pulse duration. The final laser pulses are expected to have energy above 20 J and duration below 40 fs.

Optically amplified passive optical networks: a power budget analysis

Passive optical networks (PONs) are being aggressively pursued as a means of delivering access network solutions. The cost benefits resulting from a reduction in the number of interfaces between nodes has enabled increasing deployment of a PON delivering fiber to the home and fiber to the curb. However, in many cases, the need for high split ratios or an extended-reach requires amplification to overcome additional losses. Erbium-doped amplifiers have a limited use in PONs since the operational wavelengths typically include backhaul at 1.3 μm. Semiconductor optical amplifiers (SOAs) offer a cost-effective solution with a migration path toward integration; deployment options include its use as a preamplifier, booster, or midspan amplifier. We present a theoretical treatment that analyzes the amplified system operational requirements and justifies this analysis through the experiment. The analysis considers for the first time to our knowledge the dc offset that is introduced into the receiver as a result of the significant amplified spontaneous emission powers present in amplified PONs, where filter widths are typically 20 nm or greater.

PMD Tolerance of 10 Gbps Modulated Signals due to SOA-Induced Chirp in SOA Booster Amplifiers

We investigated how the polarization-mode dispersion (PMD) tolerance was degraded by semiconductor optical amplifier (SOA)-induced chirp for the 10 Gb/s nonreturn-to-zero (NRZ), duobinary NRZ, return-to-zero (RZ), and carrier-suppressed RZ (CS-RZ) modulation formats. The power penalty was calculated as a measure of the system performance due to PMD for a given SOA-induced chirp. Considering only first-order PMD, all modulation formats have a similar PMD tolerance regardless of SOA-induced chirp. On the other hand, when both first- and second-order PMD are considered, the PMD tolerance of all modulation formats with the exception of the CS-RZ modulation format are degraded by SOA-induced chirp. Among all modulation formats considered here, the NRZ modulation format has the PMD tolerance with the highest sensitivity to SOA-induced chirp. When the peak-to-peak chirp induced by SOAs is $0.28{\AA}$ , its PMD tolerance is degraded up to 4 dB for a differential group delay (DGD) of 50 ps. However, the PMD tolerance of the CS-RZ modulation format is largely unaffected by SOA-induced chirp.

The TIL commissioning and performance

The TIL serves for both technological platforms for SG-III construction and physical experiments to study and understand target physics toward ignition and plasma burning [2]. The TIL has been designed to produce 10kJ blue light. Its eight-beam are stacked 4 high by 2 wide, The clear optical aperture is 30cm×30cm The cavity and booster amplifiers have 9 and 6 glass slabs respectively, with thickness of 3.8cm. The cavity is a four-pass amplification stage with the seed pulse injected through its cavity spatial filter, while the booster a single pass amplification stage. The commissioning experiments have successfully been conducted to test the output and control abilities of the system. A single beam line of TIL produced 3-ns pulse of 1645 Joule blue light at the target, which demonstrated that the TIL can deliver ten-thousand-joule blue light to the target. Beam qualities have been investigated jointly with the laser chain simulations using the SG-99 code. The wavefront distortions of the beams will be improved by deformable mirrors.

Channel pre‐emphasis equalization for a 270 km 40 × 40 GBIT/S WDM system

AbstractOptical channel pre‐emphasis equalization is experimentally researched for a 270 km 40 × 40 Gbit/s WDM transmission system with three EDFAs concatenated as booster amplifier. The channel imbalance of the overall system changes with different sets of power launched into EDFAs. Appropriately choosing the power input to concatenated EDFAs can make the output spectrum of 40‐channel signal be equalized to the most extent. The merit of benefit can be around 5.5 dB by this pre‐emphasis equalization. The requirement for the gain equalizer is therefore greatly released although still necessary. To take the channel imbalance of transmitter signal into account, the gain imbalance of the overall system almost matches the power imbalance of 40 channels, but the significant difference lies at some channels. Finally, the pump power into Raman amplifier is also optimized, and another 1.3‐dB improvement of channel balance can be further achieved. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1632–1634, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23450

High-energy, diode-pumped, nanosecond Yb:YAG MOPA system

Diode-pumped nanosecond multi-pass laser amplification to the joule level using an Yb:YAG slab crystal has been demonstrated. A maximum output pulse energy of 2.9 J at an optical-to-optical efficiency of 10% has been achieved. The seed pulses with a pulse duration of 6.4 ns were generated in a Q-switched Yb:YAG laser and amplified up to a pulse energy of 200mJ in a multi-pass booster amplifier. A maximum average output power of 15W at a repetition rate of 10 Hz has been measured. We also present a relay imaging semi-stable cavity for multi-pass amplification and a diode-pumping scheme employing horizontally stacked high-power laser diodes.

주파수영역 광 간섭 단층촬영 시스템을 위한 파장가변 광원 및 신호처리계의 구현

주파수영역 광 간섭 단층촬영 시스템을 위한 파장가변 광원과 주파수 보정(calibration)을 위한 신호처리계를 구현하였다. 제작된 레이저의 평균출력을 부스터(booster) 반도체 광 증폭기를 이용하여 14 mW까지 증폭시키고, 레이저 스펙트럼의 편이(shift)를 보상하였다. 패브리-페롯 에탈론(Fabry-Perot etalon)과 디지털 신호처리(digital signal processing)로 신호처리계를 제작함으로서 파장가변광원의 속도가변에 따른 비트주파수(beat frequency)의 넓어짐을 보정하였다. 제작된 광 간섭 단층촬영 시스템은 종방향 주사속도 154.4 kHz, 측정깊이 0.95 mm, 종방향 분해능 <TEX>$12{\pm}0.37{\mu}m$</TEX>의 특성을 가진다. We demonstrate the wavelength swept source and signal processing for the frequency domain optical coherence tomography. The laser output performance is improved by using a semiconductor optical amplifier with a booster amplifier. The laser generates 14 mW of average power of which wavelength shift in the lasing spectral shape is compensated. Adopting a Fabry-Perot etalon and digital signal processing, the broadening of the beat frequency due to the variance of wavelength-sweep-velocity is calibrated. The optical coherence tomography system shows 154.4 kHz of axial scanning speed, 0.95mm of depth range, and <TEX>$12{\pm}0.37{\mu}m$</TEX> of axial resolution.

Design and demonstration of a high-energy booster amplifier for a high-repetition rate petawatt class laser system

We have successfully developed a high-energy, high-repetition rate Ti:sapphire laser system that delivers 33 J before compression at 0.1 Hz. The final booster amplifier is based on a 100 mm diameter Ti:sapphire crystal pumped with 72 J of energy in six beams delivered by three frequency-doubled high-repetition rate Nd:glass lasers. This system is, to the best of our knowledge, the first demonstrated petawatt class laser system running at a high repetition rate.

High-Performance Semiconductor Optical Amplifier Modules at 1300 nm

Semiconductor-based optical amplifiers (SOAs) offer solutions to a variety of amplification requirements covering operational wavelengths ranging from 600 to 1600 nm. This letter reports on the design and performance of buried heterostructure SOA modules exhibiting state-of-the-art performance within the 1300-nm operational window. The first, a high-gain variant, is optimized for preamplification applications while the second is designed for use as a booster amplifier. Record low noise figure performances for packaged devices are reported

Semiconductor optical amplifier based swept wavelength source at 1060 nm using a scanning Fabry–Perot filter and an YDFA-based booster amplifier

We demonstrate a tuneable laser operating in the 1–1.1μm wavelength region with a tuning range of 43nm (FWHM), an output power of 19mW and coherence length of 14mm. The source is based on a master laser consisting of a cavity tuned ring configuration with a fibre Fabry–Perot filter used as a tuning element and a semiconductor amplifier as gain medium. The output of the master laser is subsequently power boosted using an Ytterbium doped fibre amplifier (YDFA). In addition to providing a power boost, we demonstrate that by tailoring the gain spectrum of the YDFA it is possible to increase the FWHM scanning range by 7nm compared to that of the master laser.

Linear and nonlinear crosstalk suppression for DWDM RZ-DPSK transmitter using a saturated SOA as power booster amplifier

Saturated semiconductor optical amplifiers (SOAs) can be used as booster amplifiers for dense wavelength-division-multiplexing (DWDM) return-to-zero differential phase-shift keying (RZ-DPSK) transmitters. By introducing time interleaving (TI), both linear crosstalk induced by WDM components and nonlinear crosstalk induced by SOA nonlinearities are suppressed. Receiver sensitivities for four-channel DWDM RZ-DPSK signals with 100- and 50-GHz channel spacing were improved 2.2 and 4.2 dB, respectively, by applying proper TI between adjacent channels. A 1-dB gain enhancement was also achieved.

Optimisation of a two colour pumped Tm3+-doped ZBLAN fibre amplifier at 1.49 µm

The authors have constructed a 4 metre length thulium-doped ZBLAN fibre amplifier optically pumped at 0.8 µm by a tuneable Ti∶Sapphire and at 1.06 µm by an Nd3+∶YAG laser. The authors obtained 12.5 dB for small-signal gain at 60 mW for the two pumps' optical power. The behaviour of the amplifier has been analysed with the optical power of the signal approaching the saturation condition (−5 dBm) and at different wavelengths for the Ti∶Sapphire pump laser. A model was developed for the optimisation of the amplifier for signal power below the saturation intensity at wavelengths between 1.49 and 1.53 µm (S-band). This shows an empirical quadratic dependence of the Nd3+∶YAG power with respect to the Ti∶Sapphire power in order to obtain the maximum photon conversion efficiency making the optimised amplifier employable as a booster amplifier in the supporting telecommunication band.