Folded-path atmospheric-pressure CO2laser

A folded-path transversely excited atmospheric-pressure CO2laser utilizing shower or brush discharges is described. The output pulse has an initial peak 0.4 μs wide followed by a tail2-3 mus long. A peak power of 0.2 MW with 4.4 percent efficiency is obtained. By rotating one of the mirrors of the resonator the tail is eliminated, yielding a pulse 0.2 μs wide of the same peak power.     

A new device converting optical analog signals to light pulse density signals for fiber-optic sensing system

Signal conversion of optical analog signals to light pulse density signals was accomplished using a p-n-p-n LED and a simple passive RCL circuit. The light pulse density was 0.69 Mbit/s. The variable ratio per 1 μW of incident light power was 0.8 kbit/s. The peak wavelength, half width, detecting wavelength range, and output light power of the p-n-p-n LED were 900, 60, 650-900 nm, and 1.2 mW/50 mA, respectively.     

A continuously tunable sequential Stokes Raman laser

We have obtained continuously tunable coherent radiation in the1-12 mum region via sequential Raman scattering of pulsed-dye-laser radiation in hydrogen. A multiple-pass-cell was used to enhance the Raman gain and produce an overall quantum conversion efficiency of at least 45 percent in the wavelength range from 0.9 to 5μm. At 5 μm, an energy output of 1 mj in a 7 ns pulse at a 10 Hz repetition rate has been obtained. Inherent four-wave mixing initiates the sequential Stokes conversion to the infrared and produces single transverse mode (TEM00) radiation in a 0.2 cm^-1bandwidth. We have developed a nonlinear model of the process that includes the effects of diffraction, four-wave mixing, and temporal pulse shape and gives numerical outputs in agreement with experiment.     

Picosecond pulse generation in optically pumped, ultrashort-cavity, InGaAsP, InP, and InGaAs film lasers

Ultrashort-cavity semiconductor film lasers made with InP, InGaAsP, and InGaAs have generated picosecond pulses over the wavelength range from 0.77 μm to 1.65 μm after optical pumping by an intense, 0.5 ps pulse at 0.625 μm. Each material composition operates over an energy range from just below the bandgap to more than 20 percent above the bandgap. For a given composition, pulse duration increases as wavelength increases; for different compositions, pulse durations increase as the bandgap energy decreases. Pulse durations range from 1.4 ps (for InP) to about 30 ps. Peak power is in the range of 1- 10 W. These unique properties of ultrashort-cavity film lasers are due to the combination of bandfilling caused by the intense photoexcitation and the ultrashort cavity, which provides widely spaced resonances to ensure single mode operation and also produces a short photon lifetime necessary for optical gain switching. The film lasers have a uniform, nearly Gaussian, spatial mode.     

Lasing properties of several near-IR dyes for a nitrogen laser-pumped dye laser with an optical amplifier

The energy per pulse as a function of wavelength was measured for several near-IR dyes (and dye mixtures) spanning the wavelength region from 650 to 950 nm using a 900 kW nitrogen laser (Molectron UV24) and a tunable dye laser-amplifier combination (Molectron DL14). The peak energy per pulse for each dye ranges from a low of 90 μJ at 855 nm (DTTC) to a high of 350 μJ at 702 nm [Oxazine 720P:Rhodamine 610P (1:1)]. Several new near-IR dye mixtures are discussed that make it possible to tune from 660 to 940 nm without having the energy per pulse drop below 50 μJ. Pulse widths (FWHM) for HITC and IR 125 were measured at various wavelengths and were observed to vary by as much as 40 percent over the tuning ranges of the dyes.     

Study of Lasing Action in a Pulsed Optically Pumped D<Subscript>2</Subscript>O Gas Terahertz Laser

A modified three-level laser kinetics model for a pulsed high-power optically pumped gas terahertz laser is introduced and used to model the lasing kinetics process of a gas terahertz laser system. We, for the first time to our knowledge, investigated the time evolution dynamics process of the pump intensity, population distribution among the energy levels, pump and THz signal gain coefficient, and the THz laser intensity within the pulsed D₂O gas THz laser. High-power THz pulse with peak power of about 7.4 kW and pulse width of 145 ns at wavelength of 385 μm were obtained in the simulation, using an incident pump pulse with peak power of 2.2 MW and pulse width of 110 ns. THz pulse delay of 40 ns and pulse broadening of 35 ns were quantitatively analyzed. In addition, the experimental results for the pulse profile, pulse width, pulse broadening, pulse energy, and peak power are in agreement with the theoretical simulation results.     

Long-pulse second-harmonic generation in KTP

Performance and limitations for doubling mode-locked, 1 μm pulse trains in KTP (potassium titanyl phosphate) was experimentally examined. The micropulse length was on the order of 200 ps and the macropulse length was on the order of 100 μs. Conversion efficiencies of 55 percent was achieved with a generated green energy of 190 mJ in 120 μs. An intensity regime for long-term damage-free operation was identified.     

Analysis and optimization of Q-switched operation of a Tm/sup 3+/-doped silica fiber laser operating at 2 /spl mu/m

Analysis and operation of a Q-switched Tm/sup 3+/-doped silica fiber laser in the wavelength region of 2 /spl mu/m is described when pumped with a Nd:YAG laser operating at 1.319 /spl mu/m. A large core of 17-/spl mu/m diameter was used to increase the laser gain volume, allowing high pump-power absorption and an output of high pulse energy and peak power. An acoustooptic modulator was used as Q-switching element and operated at repetition rates up to 30 kHz. A maximum peak output power of greater than 4 kW and a pulse duration at full-width at half-maximum of 150 ns has been obtained. This is the first report of high peak-power operation of the thulium-doped silica fiber laser.     

High-power output over 200 mW of 1.3 µm GaInAsP VIPS lasers

Maximum CW output power was investigated in GaInAsP 1.3μm V-grooved inner stripe on P-substrate (VIPS) lasers considering both cavity length and facet reflectivity. Long-cavity lasers show a strong dependence of maximum output power on front reflectivity. A CW light output over 200 mW was obtained at room temperature using a 700 μm long cavity laser with 5 and 98 percent reflectivity of the front and rear facets, respectively. The fundamental transverse mode operation was confirmed up to 170 mW. A coupled power over 110 mW into a single-mode fiber was achieved with a coupling efficiency of 58 percent. We have verified the high reliability under high power levels, as high as 75 percent of the maximum CW output powers at room temperature.     

Radio frequency pumped mid-infrared waveguide lasers

RF discharge waveguide laser technology has been extended from the 10.6 μm CO2laser to include 2.7 μm HF, 3.8 μm DF, and several rare gas mid-infrared lasers. The maximum achieved electrical efficiencies of 5.3 and 4.0 percent were demonstrated in pulsed HF and DF systems, respectively. These, as well as several low efficiency rare gas lasers were demonstrated in a 20 cm gain length device. The output power and spectral distribution were determined as a function of the gas composition, pressure, velocity, and the RF power, pulse length, and repetition rate.     

高能量全光纤结构被动锁模2.0μm掺铥超短脉冲光纤激光器

报道了高脉冲能量全光纤结构半导体可饱和吸收镜锁模的2.0μm波段掺铥超短脉冲光纤激光器。在抽运功率为1.8W时,开始得到稳定的重复频率为14.3MHz的锁模激光脉冲,平均输出功率为5mW;当抽运功率增加到3.8W时,最大平均输出功率达到59mW,相应的最高单脉冲能量为4.1nJ。此时测得锁模激光脉冲的脉宽为2.2ps,中心波长为2015nm,3dB光谱带宽为2.9nm。     

Efficient acoustooptic modulation at 3.39 and 10.6 µm in crystalline germanium

A Ge acoustooptic pulse modulator has been constructed and tested at 3.39 and 10.6 μm. A pulse rise time of 20 ns and deflection efficiency of 11 percent per watt of RF drive power when operating at 10.6 μm were realized.     

百皮秒激光脉冲的全光纤放大及应用

为了得到高单脉冲能量的百皮秒激光脉冲,采用自制的被动锁模掺镱光纤激光器获得了100ps的激光脉冲输出,在此基础上采用两级全光纤结构主振荡功率放大器进行功率放大,其中预放大级采用7m纤芯的双包层掺镱光纤做增益介质,得到平均功率160mW的稳定脉冲输出;主放大级采用20m纤芯的双包层掺镱光纤做增益介质,在抽运功率逐步增加到35.37W时,输出功率达到了16.60W,相应的单脉冲能量为1.63J,峰值功率为16.61kW。此外,主放大级输出的激光通过自制的模场转换器与光子晶体光纤(纤芯4.6m)成功熔接,得到了2.85W的白光超连续光谱,光谱波长覆盖了600nm~1700nm的检测范围。结果表明,此激光可用于超连续谱光源的产生。     

The infrared N2laser as a pump for IR dyes

An infrared molecular nitrogen laser cooled by liquid nitrogen was used to pump a simple grating tuned infrared dye laser in the wavelength range from 0.915 μm to 1.04 μm. Broad-band operation of the dye lasers produced efficiencies as high as 20 percent, and produced output at wavelengths as long as 1.096 μm.     

哑铃形高功率全保偏大模场掺镱锁模光纤激光器

采用基于非线性光纤环形镜的哑铃形结构搭建了全光纤全保偏掺镱锁模激光器。通过使用全保偏大模场光纤、高功率光纤器件和优化的腔结构,实现了脉冲宽度在156 ps到8.1 ns范围内可调的高功率、大能量矩形耗散孤子共振脉冲输出,在最大泵浦功率22.7 W下激光器直接输出功率达到5.5 W,脉冲能量达到0.68μJ,峰值功率为84 W。得益于全保偏光纤结构,所设计的激光器具有出色的抗干扰性和稳定性。     

High contrast GaInAs:Fe photoconductive optical AND gate fortime-division demultiplexing

A high-contrast, three port optical AND gate based on the photoconductive effect in Ga_0.47In_0.53As:Fe and operating in the λ=1.3-5 μm wavelength range is demonstrated. A 250:1 optical power contrast ratio (or 48 dB in electrical power after detection) is obtained in an optical-to-optical time division demultiplexing of a 100 MHz pulse train by a 6.25 MHz clock, both at λ=1.3 μm, with the demultiplexed output pulses at λ=1.5 μm     

Scalable visible Nd:YAG pumped Raman laser source

Experimental and analytical studies of a 60 Hz, 0.45 W, 630 nm Raman laser source with a 12 ns pulse duration have demonstrated an overall electrical to optical efficiency of 0.12 percent. This is the first demonstration of a short pulse, high repetition rate red laser at such a high average output power without the need for a visible pump laser. Additional significance arises from the fact that simple extensions of the present work will produce many wavelengths in the visible and near infrared (IR) spectral region. A 1064 nm Nd:YAG pump laser operating at 60 Hz was used to pump a methane gas Raman laser operating at 1544 nm. This wavelength was mixed with the remaining 1064 nm laser output in noncritically phase matched lithium niobate to produce 630 nm radiation. The optical energy conversion efficiencies for the three steps were 1.4, 30, and 20 percent, respectively, for output energies of 86 mJ at 1064 nm, 15 mJ at 1544 nm, and 7.5 mJ at 630 nm. rms pulse amplitude variation measured 6 percent or less. A 10.7 million pulse life test was conducted, and the average output energy did not vary more than ±10 percent from its initial value.     

Millimeter-wave pulsed IMPATT diode oscillators

Double-drift silicon IMPATT diodes were fabricated for pulse source application at 35, 94, and 140 GHz. The diodes were operated with 300 ns pulsewidth and a 1.5 percent duty cycle. All sources exhibited a change in output frequency of >1 percent throughout the duration of the pulsewidth with <1 dB peak power variation. Peak pulse output power levels of 10, 2, and 0.7 W were achieved in each of the three frequency bands, respectively.     

Pulse-pumped operation of divalent transition-metal lasers

The pulse-pumped operating characteristics of liquid-nitrogen-cooled Ni:MgF2, Co:MgF2, and Ni:CaY2Mg2Ge3O12(CAMGAR) solid-state lasers have been studied. The internal quantum efficiency of the Ni:MgF2laser was found to be limited to approximately 40 percent, presumably because of excited-state absorption. The Co:MgF2laser operated with near-unity quantum efficiency, and generated 150 mJ of diffraction-limited output at repetition rates up to 50 Hz. A continuous tuning range from 1.6 to 2.3 μm was observed along withQ-switched peak output powers of 80 kW. Laser operation from the garnet-structured crystal Ni:CAMGAR was obtained at a wavelength of 1.46 μm.     

Inductive storage pulse-train generator

Utilization of inductive storage in production of intense charged particle beams, laser beams, and hot dense plasmas of interest in thermonuclear fusion studies and in other research areas is very attractive because of its inherent compactness associated with energy storage in the form of magnetic fields. A major problem in utilizing inductive energy sources with sufficient output power for such beams and plasmas is the development of an opening switch. In some instances, repetitive pulse output is required, so that switches must open repeatedly at a frequency determined by the needs of the experiment. If only a small number of pulses is needed, then use of one switch per pulse in the train becomes a practical method for generating pulse trains with peak power determined by the performance of individual switches. Formation of pulse trains with peak pulse power in the range of 10⁹to 10¹⁰W was studied. This study included the investigation of single-switch elements to determine methods for extending the operating power to higher levels.