Efficient optical amplifier using a low-concentration erbium-dopedfiber

A gain coefficient of 3.8 dB/mW was achieved for an erbium-doped fiber amplifier pumped by a 1.48 μm laser diode. The main reasons for the improvement are high NA (0.23) and low concentration (43 p.p.m.). Pump-to-signal energy conversion efficiency was 18% at 3 dB gain compression. A decrease in saturation power with increasing erbium concentration was also demonstrated. In high-concentration fiber, fluorescence at 0.98 μm due to cooperative upconversion was detected. These results indicate that several kilometers of distributed fiber amplifier with high gain and high output saturation power could be possible, because the absorption coefficient at 1.48 μm is still two orders higher than the background loss in the 43 p.p.m. fiber     

Er3+-doped fiber amplifier pumped by 0.98 μm laserdiodes

The performance of an Er³⁺-doped fiber amplifier pumped by 0.98 μm InGaAs laser diodes (LDs) is reported. By using a fiber with low Er³⁺ content and optimizing the fiber length, a maximum signal gain of 37.8 dB at 30-mW pump power was realized at a signal wavelength of 1.536 μm. A maximum gain coefficient of 1.9 dB/mW at 14 mW pump power was achieved. It was found that the fiber amplifier pumped by the 0.98-μm LDs is twice as efficient as that pumped by 1.48-μm LDs, from the viewpoint of both required fiber length and the attained gain     

Theoretical characterization of Raman oscillation with intracavitypumping of fiber lasers

Theoretical results relating to the generation of continuous-wave (CW) output from fiber lasers that are internally pumped with light generated from the stimulated Raman effect are presented. This investigation establishes the important fiber and resonator parameters, such as the fiber length and glass composition, dopant concentration, and pump power required to realize this new form of fiber laser arrangement. Three examples are studied: the Ho³⁺-doped silica fiber laser that is pumped at a wavelength of 1.15 μm, the Er ³⁺-doped silica fiber laser which is pumped at 1.48 μm and, the Tm³⁺-doped silica fiber laser which Is pumped at 1.625 μm. These three examples cover first Stokes pumping, second Stokes pumping, and first Stokes pumping with direct dopant absorption of the pump light, respectively. The simulations involve the use of simple numerical models comprising the spatially dependent field propagation equations (under the slowly varying field approximation) and the rate equations for the population densities. It is established that intracavity Raman pumping of fiber lasers with first Stokes radiation is efficient when the losses at the pump, Stokes and laser wavelengths are kept low (<10 dB/km). It is also established that second Stokes pumping is, even with direct absorption of the pump light, theoretically quite efficient and, as a result, the Er³⁺-doped silica fiber laser which is pumped with second Stokes radiation at 1.48 μm may provide the best demonstration of intracavity Raman pumping     

Multipass diode-pumped Nd:YAG optical amplifiers at 1.06 μm and1.32 μm

We have built two versions of a diode-pumped Nd:YAG amplifier using a compact multipass confocal geometry with a fiber-coupled input. This confocal geometry provided efficient power and high gain in a volume of approximately 100 cm³. When pumped with a commercially mature 2 W 809 nm laser diode, the 1.06 μm version produced 460 mW and a small signal gain of 51 dB. The 1.32 μm version produced 170 mW and a small signal gain of 29 dB. Such an efficient amplifier, especially at 1.32 μm would be useful as a power booster in fiber optic telecommunications     

Upconversion pumped thulium-doped fluoride fiber amplifier andlaser operating at 1.47 μm

A 1.064-μm band upconversion pumped Tm³⁺-doped fluoride fiber amplifier and a laser both operating at 1.47 μm are investigated in detail. The two devices are based on the ³F ₄→³H₄ transition in a trivalent thulium ion, which is a self-terminating system. When pumped at 1.064 μm, the amplifier has a gain of over 10 dB from 1.44 to 1.51 μm and a low-noise characteristic. Also, the fiber laser generates a high-output power of over 100 mW with a slope efficiency of 59% at around 1.47 μm. These levels of performance will be important for optical communication systems     

Compensation of Raman-induced crosstalk using a lumpedgermanosilicate fiber Raman amplifier in the 1.571-1.591-μm region

A new method to equalize power imbalance caused by Raman-induced crosstalk among optical channels is proposed using a lumped germanosilicate fiber Raman amplifier. Evolution of optical channels through the Raman amplifier was simulated using Raman frequency modeling, which theoretically predicted simultaneous amplification and power equalization. Experimentally, a gain band with negative slope in the range of 1.571-1.591 μm was achieved in a lumped Raman amplifier pumped by a broad-band laser diode centered at 1.467 μm. We demonstrated compensation of the Raman-induced crosstalk of 5 dB accumulated along 330 km of conventional single-mode fiber     

Er-doped superfluorescent fiber laser pumped by 1.48 μm laserdiode

Output power of 4 mW at an 80-mW pump power is reported for an Er-doped superfluorescent fiber laser pumped by a 1.48 μm laser diode. A stable spectrum profile of 2-nm bandwidth (FWHM) is observed at output powers above 1 mW. The degree of polarization was observed, and it was found that more than 99.8% of the light was unpolarized within the limit of experimental error     

Cladding-pumped fiber laser

Laser emission at 1.06 μm, pump light absorption, laser threshold, slope efficiency, and alignment tolerance as a function of the fiber length have been measured for a cladding-pumped double-clad Nd:glass fiber laser. The fiber laser was pumped with a laser diode emitting at 810 nm. It produced an output power of 15.9 mW at an absorbed pump power of 55.1 mW. This corresponds to an optical-optical conversion efficiency of 38.8%     

Frequency-tunable optically pumped carbon monoxide laser

Single-line frequency-tunable lasing was observed in an optically pumped, repetitively pulsed, room-temperature CO laser for the first time. The R(0) and R(7) ro-vibrational transitions in the (2,0) overtone of CO at 2.3 μm were optically pumped with a high-energy optical parametric oscillator. Single-line lasing was observed on (2,1) P(2)-P(17) transitions and R(0)-R(11) transitions (covering wavelengths within the range 4.6-4.9 μm) when using a diffraction grating as the spectrally selective reflector of the laser resonator. The observed CO laser pulse lengths were ~10^-7 s with peak power up to 10⁴ W. The influence of CO pressure, the addition of buffer gas (He, Ar), Q-factor of the laser resonator, and the pump pulse energy on CO laser pulse temporal characteristics and output energy spectral distribution was studied experimentally     

Efficient integrated Nd3+ fiber laser

An efficient, integrated, low-threshold, tunable, laser-diode pumped Nd³⁺ fiber laser has been fabricated. The integrated fiber laser incorporated two highly reflecting intracore Bragg reflectors, which were formed holographically by transversely exposing the core to a UV two-beam interference pattern. When the fiber laser was diode pumped, a maximum output of 2.3 mW was observed at 1.088 μm, and a slope efficiency of 41% was measured     

A 170 J electron beam pumped XeF(C→A) laser

A pulse output energy of 170 J has been achieved from an XeF(C→A) laser system, pumped by a pair of counterpropagating, three-meter-long electron beams. This represents a record for all types of pumping, for this excimer system. Energy was extracted from a volume of ~100 L, using a free-running stable oscillator. No evidence of laser oscillations on the competing XeF(B→X) transition was observed. Within the extraction volume the laser gas was pumped at a rate of 140 kW/cm³ (time average value), for a period of 1.7 μs. The optical cavity was folded, giving a gain length of 6 m. The optical pulse duration was 0.8 μs (full width at half maximum), and the observed flux buildup time of ~1 μs was consistent with modeling and a measurement of the net gain. The specific output energy was 1.7 J/L which is comparable to that achieved in previous, small scale experiments at somewhat higher pump rate. The results confirm the volumetric scalability of the electron beam pumped XeF(C→A) laser system to high output energy per pulse, and the feasibility of operating this system at a low electron beam pump rate which relaxes constraints on the design of the electron gun and pulse power subsystems in a high output energy device. Means for extending the laser pulse duration and increasing the output energy of the specific test device are discussed. An output energy of ~1000 J is projected for an optimized gas cell width, for full size resonator mirrors, and with injection     

1.3-μm Pr-doped In-Ga-based fluoride fiber amplifiers pumped bygrating-fiber-pigtailed 0.98-μm-band laser diodes with a detunedwavelength of 1 μm

At most efficient pump wavelength, a praseodymium-doped In-Ga-based fluoride fiber is directly pumped by four 0.98-μm-band laser diodes. These lasing wavelengths are detuned from 0.98 to 1 μm by external selective optical feedback from fiber grating reflectors. Maximum signal output power of +13.5 dBm is obtained at 1.296 μm. Four-wavelength multiplexed signals at 1.296-1.311 μm are amplified with a deviation of gain less than 1.9 dB. By using the amplifier as a power booster, data of 2.5 Gb/s is successfully transmitted more than 100 km     

Efficient cladding-pumped Tm-doped silica fibre laser with highpower singlemode output at 2 μm

Continuous-wave operation of a double-clad Tm-doped silica fibre laser at 2 μm pumped by two beam-shaped diode bars, yielded an output power of 14 W in a singlemode (M²<1.1)beam for 36.5 W of launched pump power at 787 nm. The slope efficiency with respect to launched diode power was ~46%     

Theoretical and experimental investigations of small-signal gainfor a diode-pumped Q-switched Cr:LiSAF laser

We present a theoretical model proving that up-conversion and thermal quenching of fluorescence strongly limit small-signal gain in a CW pumped Cr:LiSAF laser. We have a good agreement with experimental measurements of small-signal gain obtained with a new simple method. We have then optimized the gain in a Cr:LiSAF laser pumped by two 400-mW red diodes. The highest gain, 1.11 at 600 mW of absorbed pump power, is obtained if the pump spot is circularized inside the crystal and if the Cr:LiSAF is pumped on both sides. In Q-switched operation, this laser produces tunable pulses (up to 6.5 μJ at 10 kHz) between 800 and 900 nm     

光泵CH3F和D2O远红外脉冲激光器

本文叙述了无镜远红外激光器的结构及其实验结果。用可调谐TEA CO_2激光器作为泵浦源,其输出能量在9P(20),9R(22)线上均可达1J左右。用CO_29P(20)线泵浦CH_3F分子,获得了能量为0.5mJ,波长为496μm的激光输出;用9R(22)线泵浦D_2O分子,获得了能量为1mJ,波长为385μm的激光输出。输出能量和波长是分别用热电堆和Fabry-Perot干涉仪测量的。     

Mid-infrared fluoride fiber lasers in multiple cascade operation

CW fiber laser cascades in an Er³⁺-doped fluorozirconate fiber operating simultaneously at 2.7 μm/1.55 μm or at 3.45 μm/2.7 μm/1.55 μm pumped around 650 nm are reported. Output powers of nearly 20 mW at 1.55 μm and 1.2 mW around 2.7 μm were obtained with a nonoptimized experimental setup for the 2.7 μm/1.55 μm cascade. At 1.55 μm a laser efficiency of 5% was achieved. By varying the parameters of the experimental setup, additional effective simultaneous laser action at 3.45 μm was demonstrated     

28.3 dB gain 1.3 μm-band Pr-doped fluoride fiber amplifiermodule pumped by 1.017 μm InGaAs-LD's

A praseodymium (Pr)-doped fluoride fiber amplifier (PDFA) module that is pumped by strained quantum-well InGaAs laser diodes (LDs) is described. The amplifier module, consisting of a four LD pump configuration and a high NA Pr-doped fluoride fiber with low scattering loss, exhibits a maximum signal gain of 28.3 dB and a saturation output power of 6 dBm at a signal wavelength of 1.30 μm. It is shown to be the most promising module for the 1.3-μm-band optical amplifier     

Modulation instability and soliton-Raman generation inP2O5 doped silica fiber

Generation of high-repetition-rate modulation instability pulse trains and high- energy soliton-Raman pulses of ≃60 fs durations, in a single-mode P₂O₅-doped silica fiber, is reported. The 7 mol.% concentration P₂O₅ fiber was pumped in a single pass arrangement by a Q-switched and mode-locked Nd:YAG laser operated at 1.319 μm. Operating in the region of zero second-order dispersion, modulation instability Stokes sideband seeded resonantly cascade stimulated Raman scattering associated with Si-O-Si and P=0 vibration modes of the fiber. As a result, broad bandwidth and widely tunable 1.36-1.80 μm femtosecond pulses were obtained     

Er3+-Yb3+ and Er3+ doped fiberlasers

Single-mode fiber lasers operating at ~1.57 μm are described. Output powers of >2 mW are reported for laser diode pumped operation. Direct comparison is made between fiber lasers using sensitized erbium (Er³⁺ and Yb³⁺) and erbium on its own. The performance of Er³⁺-Yb³⁺ fiber lasers is analyzed in more detail as a function of fiber length. Both CW and Q-switched operations are studied and the results obtained demonstrate that practical sources at 1.5 μm are available from diode pumped Er³⁺ -Yb³⁺ systems     

Fabrication and properties of polymer optical fibers containingNd-chelate

Graded-index poly(methyl methacrylate) optical fibers (GI POF) containing a Nd-chelate have been fabricated. The absorption spectrum of the fiber exhibited several strong bands in the visible and infrared regions. We have observed infrared fluorescence (0.90, 1.06, and 1.3 μm) of the Nd³⁺ ion of the fiber at room temperature when it was pumped with an Ar⁺-pumped dye laser at 580 nm