High Peak Power Output Research Articles

Continuous-wave and high-power pulsed operation of index-coupled distributed feedback quantum cascade laser at λ≈8.5 μm

High performance index-coupled quantum cascade distributed feedback (QC-DFB) lasers operating at λ≈8.5 μm are reported. Reliable dynamic single-mode emission with a side mode suppression ratio ⩾30 dB is obtained. The continuous single-mode tuning range is 140 nm. In pulsed operation a record high peak output power of 60 mW at 300 K is achieved. We further report on the first continuous-wave QC-DFB lasers. These devices display an output power of 10 mW at 120 K.

Output Characteristics of Coupled-Cavity Q-Switched Er, Yb: Glass Lasers.

The Q-switch, high peak power oscillation of a laser-diode pumped Er, Yb: glass laser at eye-safe wavelengthhas been realized using a three-mirror coupled-cavity, low-loss and fast piezoelectric actuator Q-switch. Highpeak power of 3 kW was obtained with a pulse width of 4 ns and output energy of 12 μJ. The resonancecondition of the threshold gain of the coupled-cavity laser was calculated. In the case where the free spectralrange (FSR) of the external cavity is selected to be equal to the gain cavity FSR, the multi-axial mode pulse canoscillate and resulted in a high peak output power. By scanning the external mirror, the single-axial modeoscillation was step-tunable from 1535 nm to 1565 nm.

PEM Fuel Cell System Optimization

Fuel cells offer the potential of providing clean and efficient energy in a wide variety of applications. This paper presents a methodology for optimizing the fuel conversion efficiency and peak power of a direct-hydrogen proton-exchange-membrane (PEM) automotive fuel cell system over a wide range of power output. It is shown that optimal system operation can provide significant benefits in terms of both increased efficiency (especially in low power operation) and high peak power output from the system.

Exercise prescription for sitting and supine exercise in subjects with quadriplegia

Although in able-bodied individuals heart rate (HR) indicates exercise intensity, the linearity of the HR/oxygen uptake (VO2) relationship has not been established in persons with quadriplegia with impaired sympathetic function. The HR/VO2 relationship and four ACSM recommended methods of exercise prescription were evaluated in 11 individuals with quadriplegia during intermittent progressive peak exercise tests. Tests were conducted in either a supine or sitting position using an arm ergometer. The HR response was highly variable, with HR/VO2 correlation coefficients ranging from 0.22 to 0.99. A 2 x 2 ANOVA revealed an interaction between injury level, high-level (above C7) vs low-level (C7 and below) and exercise position, with the high-level group exhibiting the lower coefficient (0.68) between the HR/VO2 relationship in the sitting position. For all subjects, the target of 55-90% peak HR (mean = 72.5%) corresponded to 34% peak power output (PO) in sitting and 44% peak PO in supine. Similarly, 70% peak VO2 corresponded to 46% and 50% of peak PO (sitting and supine, respectively). A rating of perceived exertion (RPE) of 10-12 corresponded to 50-60% peak PO and was associated with a higher PO than that predicted by the HR or VO2 methods. The results of this study indicate that exercise intensity for quadriplegics be based on 50-60% peak PO and/or an RPE of 10-12.

Blue light generation using a high power tapered amplifier mode-locked laser

Light at 430 nm is generated by frequency doubling the high peak power output of a mode-locked compound cavity laser based on a tapered GaAlAs amplifier. The laser generated a peak 860 nm power of 12.7 W and pulse energy of 450 pJ. Using a 7.1 mm KNbO3 crystal, 45 mW of average blue light power was produced with a peak power of 1.6 W, minimum pulse length of 8.5 ps, and pulse energy of 30 pJ.

The FELSTRON: an electrostatic accelerator FEL oscillator power source for linear colliders

Abstract Electrostatic free electron lasers (FELs) operating in the oscillator mode have been demonstrated to be extremely efficient sources of coherent electromagnetic (laser) radiation. Output wavelengths between tens of microns and a few centimeters are achievable. The average power of these devices can be quite large (100s of kW). Linear colliders require high peak power as well as high average power. By storing the laser energy of an electrostatic FEL oscillator in a resonant cavity, and then employing a cavity dump, extremely high peak output power is obtainable. The high efficiency, accessible wavelength range, large average power and high peak power make electrostatic accelerator FELs excellent candidates for linear collider power sources.

A semiconductor preionised DF laser

Semiconductor preionisation is used to stabilise the discharge in a SF6:D2 gas mixture. This results in good discharge stability in the electronegative gas mix and allows high input energy density resulting in good shot-shot stability, high output energy density and peak power from a DF laser.

An efficient laboratory Raman scattering system

The apparatus consists of an UV-preionization nitrogen TEA laser (giving high peak power output), multipass Raman cell and spectrograph. The scattered Raman spectra of ordinary atmospheric air obtained using this apparatus are given as an example.

Coupled TEM Microstrip Impedance Transformer for S-Band TRAPATT Amplifiers

A coupled TEM microstrip line circuit suitable for use in S-band TRAPATT amplifiers has been investigated. An analytical model of the coupled-line structure has been developed which properly accounts for diode positioning on the line. This model has been used to calculate the fundamental and harmonic impedances at the device terminals for various stub terminations and device locations. Measurements made with a Hewlett-Packard network analyzer are in good agreement with the calculated results. The use of this circuit for the development of a fixed-tuned MIC circuit for the TRAPATT amplifier on Duroid Substrate is discussed. The complete circuit incorporates a bias line filter with this coupled microstrip line and appropiate harmonic tuning stubs at two of its ports. It is capable of providing at least 6-percent 1-dB bandwith with high efficiency and high peak power output over pulsewidths up to 50 mu s and up to 1-percent duty cycle.

A sealed, UV-pre-ionisation CO2TEA laser with high peak power output

A long-lived, UV-pre-ionisation CO2 TEA laser is described which provides pulses (single-transverse mode) of high-output peak power per unit volume of discharge. Peak powers of 1.3 MW in 30-35 ns (FWHM) are obtained from a 10 mm*10 mm*110 mm discharge, corresponding to a peak power output per unit volume eight times greater than that achieved with a trigger-wire-initiated, sealed CO2 TEA laser. This improvement results largely from the higher CO2 concentration and greater input energy density, made possible by UV-pre-ionisation of the discharge. Prolonged operation of the sealed laser is achieved at high output peak power levels, using a hot platinum wire catalyst to recombine the CO2 dissociation products of the discharge.

High peak power output, high PRF by cavity dumping a Nd:YAG laser

Intracavity modation of a Nd:YAG laser at high dumping efficiencies was achieved by driving an acoustooptic quartz modulator with 100 W of rf input power at 450 MHz. Stable output pulses of 25-nsec width and peak powers as high as 570 W were obtained at repetition frequencies up to 2 MHz. It is shown that the oscillation of the circulating laser power in the presence of a perturbation determines the dynamics of cavity dumping and sets a lower limit to the pulse repetition frequency of approximately 200 kHz.

Single longitudinal mode operation of a transversely excited CO2laser

High peak power output has been obtained from a transversely excited CO2 laser in a single longitudinal mode, operating on a single rotational line and the lowest order transverse mode at 9.3, 9.6 and 10.6 mu m. The laser was designed to operate with high efficiency at reduced pressures and low voltage. Mode selection was by means of an intracavity germanium etalon.

Single longitudinal mode operation of a transversely excited CO2laser

High peak-power output has been obtained from a transversely excited CO 2 laser in a single longitudinal and lowest order transverse mode. An intracavity etalon was used for mode selection in a laser system designed to operate effectively at reduced pressures.

Reaction of neoplasm and brain to laser.

LASER is an acronym for light amplification by the stimulated emission of radiation. The laser is an instrument in which atoms are stimulated to emit light in the same phase and direction at a given frequency. The process produces an unidirectional, coherent, intense, monochromatic beam of high energy content. When a solid-state system is utilized, a pulsed, high peak power output is achieved which can be focused through a lens to a spot to produce a maximum in power density. The laser used in the experiments to be reported was such a solid-state unit in which a ruby was employed to emit a wave length of 6,943 Angstroms. The laser head was fitted with a liquid nitrogen cooling system so that a nominal output of 8 joules was delivered over 0.0005 seconds from a maximum energy input of 800 joules at 2 kv. The laser was mounted on a

EFFECT OF LASER ON CARCINOMA IN MAN.

THIS report, preliminary in nature, concerns itself with the effect of laser on the exposed surface of in vivo carcinoma in man. LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation. It represents a technological advance in instrumentation by which atoms are stimulated to emit light in same phase and direction at a given frequency. This yields a unidirectional, coherent, intense, monochromatic beam of high energy content. When a solid-state system is used, a pulsed, high-peak power output is achieved which can be focused through a lens to an impact site, to produce a maximum in power density. Thus, the ruby laser used in this study was emitting light at a wave length of 6,943 Angstroms with the delivery of 1 to 3 joules of energy in a pulse duration of 0.0005 seconds. By calculation, this is a rated power output of 2,000 to 6,000 w.

Sub-bottom penetrations in Boston Harbor

Preliminary experiments in harbor at Boston, Mass., with a sonar that has a high peak power output (about 105 db) and a very short ping length (about 0.1 msec) show that penetration at 12 kc/s can be as much as 50 feet below the bottom. Bedrock is reached in a few places. Sediment layers, probably of glacial origin, are clearly shown in others. Two vehicular tunnels that connect Boston with the airport are shown at 10 feet under the mud. The depth resolution in the sediment is less than ½ meter because of the short length of the signal. The transducer is mounted on a fish so that it can be lowered over the bow or side of a small boat and towed for making surveys. Thus there is a greater coupling of energy into the bottom and a smaller target area to reflect the signal.

A 1.5 megawatt high efficiency, X-band CEM coaxial magnetion

A new type magnetron, known as the GEM coaxial magetron, has been developed which has several major advantages over the conventional magnetrons of today. High peak power at long pulse length can be obtained at both high efficiency and with light weight, making this device especially suitable where power availability and weight are at a premium. The frequency stability of this tube is approximately a factor of 4 better than conventional magnetrons as evidenced by extremely low pushing and pulling figures. The basic principles upon which the design of the CEM coaxial magnetron is based are discussed. The design philosophy of this tube is compared to that of conventional magnetrons. In the rising-sun magnetron mode separation is the design criterion, whereas in the CEM coaxial magnetron selective mode absorption is the key to a successful design. To obtain higher peak power output, the interaction area of the rising-sun magnetron is increased axially while in the CEM coaxial magnetron the interaction space area is increased circumferentially. The electrical performance is described and a performance chart is shown. The ease of tunability of such a design is discussed.