Multistage Yb-doped fiber amplifier generating megawatt peak-power, subnanosecond pulses

A Q-switched microchip laser generating 1064 nm wavelength, subnanosecond pulses at a 13.4 kHz repetition rate was used to seed a dual-stage amplifier featuring a 40 microm core Yb-doped photonic-crystal fiber (PCF) as the power amplifier. From this source, we obtained diffraction-limited (M2 = 1.05), approximately 450 ps pulses of energy > 0.7 mJ, peak power in excess of 1.5 MW, and an average power of approximately 9.5 W. By further amplifying the PCF output in a multimode 140 microm core Yb-doped fiber, we generated a peak power in excess of 4.5 MW, the highest obtained in a fiber source to our knowledge.     

High-efficiency,high-repetition-rate,temperature-tuning optical parametric oscillator based on periodically poled MgO-doped lithium niobate

We report a compact and viable source of high-efficiency, high-repetition-rate, temperature-tuning, mid-IR optical parametric oscillator (OPO) based on periodically poled MgO-doped lithium niobate (PPMgOLN) pumped by a homemade high power AOM Q-switched Nd:YVO₄ laser centered at 1.064 μm. With an optimal plane-concave resonator configuration, average output power of 5.7 W at 2.73 μm was obtained when the pump power was 25 W at the repetition rate of 80 kHz. The conversion efficiency from the 1.064 μm laser to the 2.73 μm laser was 22.8%. Temperature tuning of the OPO yielded a signal wavelength range from 1.67 to 1.75 μm and an idler wavelength in the range of 2.72 to 2.92 μm.     

Mid-infrared ZnGeP2 parametric oscillator directly pumped by a pulsed 2 microm Tm-doped fiber laser

We have demonstrated what we believe to be the first mid-infrared optical parametric oscillator (OPO) pumped directly by a pulsed Tm-doped fiber laser. The Tm-fiber pump laser produces 30 ns pulses with a repetition rate of 30 kHz at a wavelength of 2 microm. The ZnGeP2 (ZGP) OPO produces 20 ns mid-IR pulses in the 3.4-3.9 microm and 4.1-4.7 microm spectral regions simultaneously. More than 658 mW of mid-IR output power has been generated with a total OPO slope efficiency greater than 35%.     

High-power femtosecond fiber-feedback optical parametric oscillator based on periodically poled stoichiometric LiTaO3

We demonstrate a synchronously pumped high-gain optical parametric oscillator with feedback through a fiber, using a passively mode-locked Yb:YAG thin-disk laser as a pump source. We obtain as much as 19-W average signal power at a wavelength of 1.45 microm in 840-fs pulses and 7.8 W of idler power at 3.57 microm. The repetition rate of the pulses is 56 MHz, and the transverse beam quality of the generated signal is M2 < 1.6.     

Observation of thermal-induced optical guiding and bistability in a mid-IR continuous-wave, singly resonant optical parametric oscillator

We report the observation of thermal-induced optical guiding and bistability in a mid-IR cw, singly resonant optical parametric oscillator (SRO) at approximately 3.2 microm. The SRO employs a MgO:PPLN crystal as the gain medium and a 1-nm-linewidth Yb-fiber laser at 1.064 microm as the pump source. As soon as the pump power reaches the thermal guiding threshold at 16.5 W, the SRO shows a step increase in the parametric efficiency by a factor of 2.5. At 25 W pump power, the SRO generated 5.3 and 1.2 W at 1.58 and 3.23 microm, respectively, with single-longitudinal-mode performance for the 3.23 microm radiation.     

High-power diode-cladding-pumped Tm-doped silica fiber laser

The operation of a diode-pumped Tm-doped silica fiber laser that uses the cladding-pumping arrangement to produce high-power cw output at wavelengths near 2 microm is reported. We obtained a maximum output power of 5.4 W at a slope efficiency of 31% with respect to the launched pump power at a total optical-to-optical efficiency of 22%. The fiber-laser output wavelength was tuned between 1.880 and 2.033 microm by adjustment of the fiber length, with >4W of power obtainable from 1.94 to 2.01 microm. Self-pulsations detected in the output from the double-clad fiber laser may indicate the presence of ion-clustering effects.     

High-average-power mid-infrared ZnGeP2 optical parametric oscillator with a wavelength-dependent polarization rotator

A wavelength-dependent polarization rotator is used to transform the orthogonal polarizations of the signal and idler of a near-degenerate type II KTP optical parametric oscillator (OPO) into a common polarization state. This common polarization allows a single ZnGeP2 OPO to fully utilize the 2 microm signal and idler KTP OPO outputs in a mid-IR conversion. The simple design of the wavelength-dependent polarization rotator yields a compact source that simultaneously generates four mid-JR wavelengths collinearly with a total mid-IR average power of 5.5 W at a >15 kHz pulse repetition rate.     

基于光纤激光器的中红外差频多波长激光产生

针对由YDFL和EDFL作为基频光源的QPM-DFG激光系统,利用PPMgLN晶体的色散关系及其温度特性,有效拓宽了QPM波长接受带宽.模拟结果表明,当采用1550和1060 nm波段的EDFL和YDFL分别作为DFG的信号和抽运光源时,对于相同的中红外波段,满足QPM条件所允许的抽运光波长变化范围远大于信号光波长变化范围.当固定信号光波长为1560 nm时,对于给定的晶体温度,1060 nm波段抽运光的QPM接受带宽超过17 nm,对应于中红外差频光带宽可约180 nm.采用多波长YDFL作为抽运源,单 关键词： 差频产生 准相位匹配 多波长中红外 光纤激光器     

Efficient mid-IR spectral generation via spontaneous fifth-order cascaded-Raman amplification in silica fibers

Spontaneous cascaded Raman amplification is demonstrated as a practical and efficient means of power transfer from telecommunications wavelengths to mid-IR wavelength bands through use of conventional silica fibers and amplifiers. We show that silica fibers possessing normal dispersion over all near-IR and mid-IR wavelengths can facilitate 37% and 16% efficient Raman power conversion from 1.53 microm to 2.15 and 2.41 microm wavelength bands, respectively, using nanosecond pulses from an all-fiber laser source. In contrast to supercontinuum-based techniques for long-wavelength generation, the high levels of Raman gain generated at these wavelength bands could produce useful optical amplification necessary for the development of numerous mid-IR laser sources.     

10-W-level diode-pumped compact 2.78 microm ZBLAN fiber laser

We report on >9W transverse-fundamental-mode CW output near 3 mum from a 4m heavily erbium-doped ZBLAN double-clad fiber laser pumped by a collimated 100 W 975 nm laser diode array. The pump threshold of the fiber laser was about 1W, and the slope efficiency was 21.3%. The peak wavelength of free running was about 2708 nm at low pump power and moved to around 2785 nm at high pump power. Output of 9W was obtained when the launched pump power was 42.8W. The output, however, fluctuated intensively like a pulsed laser, and the operation broke down with optical damage of the pumping end facet when the pump was increased beyond 42.8 W. Therefore, alleviation of the operation fluctuation, heat management, and strengthening the pumping fiber are crucial considerations for the stable operation of 10-W-level mid-IR ZBLAN fiber lasers.     

Wavelength-agile mid-infrared (5-10 microm) generation using a galvano-controlled KTiOPO4 optical parametric oscillator

A wavelength-agile mid-infrared (IR) ZnGeP2 (ZGP) optical parametric oscillator (OPO) using a galvano-controlled double-crystal KTiOPO4 (KTP) OPO was demonstrated. The mid-IR wavelength was tuned by varying the KTP OPO pump wavelength while the ZGP crystal angle remained fixed. Rapid tuning of the KTP OPO was achieved by changing the crystal angle by using the galvano scanner. Our mid-IR source can jump to a different wavelength without scanning through the intermediate wavelengths while also permitting continuous-wavelength scanning. The mid-IR source can be tuned from approximately 5to10 microm at a phase-matching angle of 51 degrees , while the pump wavelength is controlled in the 1.95-2.2 microm range.     

Broadly tunable single-frequency cw mid-infrared source with milliwatt-level output based on difference-frequency generation in orientation-patterned GaAs

A narrow-linewidth mid-IR source based on difference-frequency generation of an amplified 1.5 microm diode laser and a cw Tm-doped fiber laser in orientation-patterned (OP) GaAs has been developed and evaluated for spectroscopic applications. The source can be tuned to any frequency in the 7.6-8.2 microm range with an output power of 0.5 mW. The measured characteristics of the OP-GaAs sample demonstrate a high quality of the material.     

中红外超连续谱在氟化物光纤中的产生

为获得高功率全光纤中红外超连续谱,采用自制的掺Er锁模光纤激光器作为种子源,激光经过两级放大至1.67W,泵浦氟化物光纤,获得光谱覆盖1000~2400nm的超连续光谱;光谱宽度随着泵浦功率的增加而展宽,当输出功率达到1.21W时,转换效率为72%,并且产生的超连续谱被强烈的调制,在多个波长点处谱功率密度调制到0mW/nm,但调制波长与泵浦功率无关。     

高重复频率、单模纳秒脉冲全光纤激光器

报道了一种基于主振荡放大技术的全光纤脉冲激光器.种子激光器使用直接调制的单纵模半导体激光器,其输出波长为1 063.8 nm,重复频率100 kHz~10 MHz连续可调谐,光纤放大器采用了多级放大器级联的方法.在重复频率100 kHz、脉冲宽度5 ns时,激光器获得了平均功率为1.2 W,峰值功率为2.4 kW的单横模激光脉冲输出.     

High-power diode-pumped fiber laser operating at 3 μm

A high-power diode-cladding-pumped Ho3?-doped fluoride glass fiber laser operating in cascade mode is demonstrated. The ?I?→?I? and ?I?→?I? laser transitions produced 0.77 W at a measured slope efficiency of 12.4% and 0.24 W at a measured slope efficiency of 5.2%, respectively. Using a long fiber length, which forced a large threshold for the ?I?→?I? transition, a wavelength of 3.002 μm was measured at maximum output power, making this system the first watt-level fiber laser operating in the mid-IR.     

高重复频率、单模纳秒脉冲全光纤激光器

报道了一种基于主振荡放大技术的全光纤脉冲激光器.种子激光器使用直接调制的单纵模半导体激光器,其输出波长为1 063.8 nm,重复频率100 kHz～10 MHz连续可调谐,光纤放大器采用了多级放大器级联的方法.在重复频率100 kHz、脉冲宽度5 ns时,激光器获得了平均功率为1.2 W,峰值功率为2.4 kW的单横模激光脉冲输出.     

Generation of 287 W, 5.5 ps pulses at 78 MHz repetition rate from a cryogenically cooled Yb:YAG amplifier seeded by a fiber chirped-pulse amplification system

We generate linearly polarized, 287 W average-power, 5.5 ps pulses using a cryogenically cooled Yb:YAG amplifier at a repetition rate of 78 MHz. An optical-to-optical efficiency of 41% is obtained at 700 W pump power. A 6 W, 0.4 nm bandwidth picosecond seed source at 1029 nm wavelength is constructed using a chirped-pulse fiber amplification chain based on chirped volume Bragg gratings. The combination of a fiber amplifier system and a cryogenically cooled Yb:YAG amplifier results in good spatial beam quality at large average power. Low nonlinear phase accumulation as small as 5.1 x 10(-3) rad in the bulk Yb:YAG amplifier supports power scalability to a > 10 kW level without being affected by self-phase modulation. This amplification system is well suited for pumping high-power high-repetition-rate optical parametric chirped-pulse amplifiers.     

Mode-locked 1.93 microm thulium fiber laser with a carbon nanotube absorber

We report a ring-cavity thulium fiber laser mode locked with a single-wall carbon nanotube absorber used in transmission. A carboxymethyl cellulose polymer film with incorporated carbon nanotubes synthesized by the arc discharge method has an absorption coinciding with in the amplification bandwidth of a Tm-doped fiber. This laser is pumped by an erbium fiber laser at 1.57 microm wavelength and produces a 37 MHz train of mode-locked 1.32 ps pulses at 1.93 microm wavelength with an average output power of 3.4 mW.     

Single-transverse-mode 2.5-W holmium-doped fluoride fiber laser operating at 2.86 microm

A high-power tandem-pumped Ho3+, Pr3+-doped ZBLAN fiber laser is demonstrated. Using the free-running 1100-nm output from a diode-cladding-pumped Yb3+-doped silica fiber laser as the pump source, a maximum output power of 2.5 W was generated at a slope efficiency of 29% after the threshold of approximately 30 mW was reached. Saturation of the output is avoided with Pr3+ codoping, which allows single-transition output. The center wavelength of the output was 2.86 microm and the bandwidth at maximum power was approximately 15 nm.     

Efficient, high-power, ytterbium-fiber-laser-pumped picosecond optical parametric oscillator

We report a high-power picosecond optical parametric oscillator (OPO) synchronously pumped by a Yb fiber laser at 1.064 μm, providing 11.7 W of total average power in the near to mid-IR at 73% extraction efficiency. The OPO, based on a 50 mm MgO:PPLN crystal, is pumped by 20.8 ps pulses at 81.1 MHz and can simultaneously deliver 7.1 W of signal at 1.56 μm and 4.6 W of idler at 3.33 μm for 16 W of pump power. The oscillator has a threshold of 740 mW, with maximum signal power of 7.4 W at 1.47 μm and idler power of 4.9 W at 3.08 μm at slope efficiencies of 51% and 31%, respectively. Wavelength coverage across 1.43-1.63 μm (signal) and 4.16-3.06 μm (idler) is obtained, with a total power of ~11 W and an extraction efficiency of ~68%, with pump depletion of ~78% maintained over most of the tuning range. The signal and idler output have a single-mode spatial profile and a peak-to-peak power stability of ±1.8% and ±2.9% over 1 h at the highest power, respectively. A signal pulse duration of 17.3 ps with a clean single-peak spectrum results in a time-bandwidth product of ~1.72, more than four times below the input pump pulses.