Showing papers on "Femtosecond pulse shaping published in 1977"
Patent•
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19 Dec 1977
TL;DR: In this article, a system for temporal pulse shaping of laser radiation beams particularly for use as photoexcitation radiation in isotope separation is presented. Each pulse is temporally segmented into two or more sections, and the sections may be superimposed after a delay in the leading one to augment the pulse intensity.
Abstract: A system for temporal pulse shaping of laser radiation beams particularly for use as photoexcitation radiation in isotope separation. Each pulse of laser radiation is temporally segmented into two or more sections. The sections may be superimposed after a delay in the leading one to augment the pulse intensity, or the segmented pulses may be separately used as segments in a desired application, or the pulse rise time may be decreased by segmenting the pulse so as to permit rejection of the more slowly rising leading edge.
31 citations
Patent•
09 Sep 1977
TL;DR: In this article, the electrical pulse train is fed to circuitry which monitors the switch-on delay of the laser and controls the bias current, such that the switchon delay is maintained constant.
Abstract: Apparatus for stabilizing the output characteristics of an injection laser has a device for producing an electrical pulse train representative of an optical pulse train of the laser. The electrical pulse train is fed to circuitry which monitors the switch-on delay of the laser and controls the bias current of the laser such that the switch-on delay is maintained constant. Alternatively the pulse length can be monitored. The pulse amplitude or mean pulse energy can also be monitored and maintained constant.
20 citations
TL;DR: In this paper, a Fabry-Perot interferometer has been used to produce optical pulses of variable width from a short gaussian input pulse, which can be used for short-pulse spectroscopy.
10 citations
Patent•
19 Dec 1977
TL;DR: In this paper, a system for temporal pulse shaping of laser radiation beams particularly for use as photoexcitation radiation in isotope separation is presented, where each pulse is temporally segmented into two or more sections and superimposed after a delay in the leading one to augment the pulse intensity.
Abstract: A system for temporal pulse shaping of laser radiation beams particularly for use as photoexcitation radiation in isotope separation. Each pulse of laser radiation is temporally segmented into two or more sections. The sections are superimposed after a delay in the leading one to augment the pulse intensity.
7 citations
01 Jan 1977
TL;DR: In this article, a stroboscopic SEM is used to observe the dynamic voltage contrast image of semiconductor devices at a certain phase of repeating cycles, and the pulse gate which is inserted between the electron gun and the first condenser lens is avoided.
Abstract: The stroboscopic SEM is very usuful to observe the dynamic voltage contrast image of semiconductor devices at a certain phase of repeating cycles. It consists of the usual SEM and the pulse gate which is inserted between the electron gun and the first condenser lens. The effect which affects the pulse width in the picosecond region is avoided in the design of the pulse gate. The shortest half-width of pulse is 0.2 ps. The spot size at usual pulse operations (several ps - several ns) is smaller than 0.1 µm. Examples of the two-dimensional voltage contrast images are shown in cases of 1 GHz Gunn diode and of a Simple 8 MHz IC.
4 citations
3 citations
TL;DR: In this paper, the possibility of collapsing a train of pulses, by delayed superposition, into a single pulse using a grating to obtain a very high energy density is described, and the same principle can also be used to produce a pulse of desired shape out of a given single or a train.
Abstract: The possibility of collapsing a train of pulses, by delayed super-position, into a single pulse using a grating to obtain a very high energy density is described. The same principle can also be used to produce a pulse of desired shape out of a given single or a train of pulses.
3 citations
3 citations
TL;DR: In this paper, it has been shown, in experiments carried out with 10 ps pulses of 1.06 pm, that semiconductor reflection switching is capable of generating 100 ps, 10.6 pm pulses.
Abstract: switch situated within the cavity of a low power CW CO, oscillator. The switch is controlled by means of a short pulse of visible radiation selected from the mode-locked output of a high power dye laser oscillator. It has been shown, in experiments carried out with 10 ps pulses of 1.06 pm r a d i a t i ~ n , ~ that semiconductor reflection switchingis capable of generating 100 ps, 10.6 pm pulses. Illumination of the switch with ultrashort visible pulses should permit the production of 10 pm pulses of even shorter duration. Pulses generated in this manner are injected into the optical resonator of a 7 mm aperture multi-atmosphere CO, module through a small hole in a 10 m radius of curvature gold mirror. Detailed measurements of the resulting mode-locked 10.6 pm pulses are now in progress and will be presented along with the results of the 1 ns experiments. and to provide maximum pulse-to-pulse reproducibility. Data will be presented relating to the laser output characteristics, the details of the plasma expansion, and the evidence that recombination is the dominant source of excitation. In addition, the results obtained at pressures above 1 atmosphere, using a specially designed high-pressure cell, will be described.
3 citations
TL;DR: In this article, a tunable picosecond pulse laser source was proposed, which is a tapered distributed feedback laser excited by a single pulse of a single photon of a 2D laser.
3 citations
TL;DR: In this article, a method to generate high power, short light pulses with a moderate iteration frequency was described, where the pulse train of the actively mode-locked Kr laser was sent into a dye-laser amplifier pumped by a N 2 laser.
TL;DR: In this paper, a "pulse stacker" was used to produce the desired pulse shape in 30 psec steps, and the stacked trains were monitored at various points along the laser system.
Abstract: High speed optical measurements in the picosecond regime play a crucial role in any laser .fusion program. At KMS Fusion,image converter streak cameras have been used to study a high power neodymium glass laser system and to observe target response to the laser pulse. Experimental techniques and results ©I several studies will be discussed. A "pulse stacker" produced the desired pulse shape in 30 psec steps. These stacked trains were monitored at various points along the laser system. Perturbations of the pulse train as it propagates through the laser are most evident at the final output where examples of pulse splitting and breakup, which occur in extreme situations, will be shown. Target diagnostic studies include incident and nonabsorbed laser energy pulse shape and blast-wave photographs to determine absorbed energy.
TL;DR: In this paper, an analysis of the effects associated with the propagation of an ultrashort pulse in a three-level resonance medium was made, and it was shown that the dynamics of the changes in the pulse during its propagation differs considerably from the usual self-induced transparency effect in a two-level medium.
Abstract: An analysis is made of the effects associated with the propagation of an ultrashort pulse in a three-level resonance medium. It is shown that the dynamics of the changes in the pulse during its propagation differs considerably from the usual self-induced transparency effect in a two-level medium. It is predicted theoretically that there should be a propagation regime accompanied by periodic variation of the pulse shape.
Patent•
19 Apr 1977
TL;DR: In this article, the authors proposed a method to enable simple and accurate measuring by making it possible to measure only the pulse laser light of laser light oscillating pulse, which can be used to measure the position of the laser.
Abstract: PURPOSE:To enable simple and accurate measuring by making it psssible to measure only the pulse laser light of laser light oscillating pulse.
TL;DR: In this article, a YAG:Nd pulse-periodic laser, assembled from commercially available units and comprising an oscillator and amplifier, is described. This laser can provide efficient frequency conversion and, in particular, generate an intense fourth harmonic with a peak output power of about S MW per pulse (pulse halfwidth 7 nsec) and an average power of 0.7 W when the pulse repetition frequency is 20 Hz
Abstract: A description is given of a YAG:Nd pulse-periodic laser, assembled from commercially available units and comprising an oscillator and amplifier. This laser can provide efficient frequency conversion and, in particular, generate an intense fourth harmonic with a peak output power of about S MW per pulse (pulse half-width 7 nsec) and an average power of 0.7 W when the pulse repetition frequency is 20 Hz.
TL;DR: In this paper, a pulse modulator for frequency-temperature monitoring of transferred electron devices is described, which has a fully variable pulse height with a stability of 150 mV for a current demand of up to 1 A.
Abstract: A pulse modulator is described for frequency-temperature monitoring of transferred electron devices. It has a fully variable pulse height with a stability of 150 mV for a current demand of up to 1 A and is largely unaffected by variations of pulse repetition frequency and pulse width.
TL;DR: In this paper, an investigation was made of temperature tuning of modes emitted from pulse lead-tin chalcogenide laser diodes in spectroscopy applications, where the mode tuning was due to the time dependence of the temperature of a diode during a current pulse.
Abstract: An investigation was made of temperature tuning of modes emitted from pulse lead-tin chalcogenide lasers. Estimates were obtained of the resolution attainable in such pulse lasers in the case when the mode tuning was due to the time dependence of the temperature of a diode during a current pulse. Potential applications of such laser diodes in spectroscopy are indicated.
DOI•
14 Sep 1977TL;DR: In this article, an actively mode-locked ring laser system was developed to produce a single 200 ps, 1.06 μm pulse synchronized to an intense 1 ns duration CO2 laser pulse.
Abstract: An actively mode-locked Nd:glass ring laser system has been developed to produce a single 200 ps, 1.06 μm pulse synchronized to an intense 1 ns duration CO2 laser pulse. By controlling the build-up of the ring laser pulse and phase locking the modulators of both lasers, synchronization of output pulses to better than 400 ps has been achieved. This arrangement thus permits optical diagnosis of the time development of the CO2 laser produced plasmas. The second harmonic of the Nd:glass laser pulse has been used in inter-ferometric measurements of the electron density and Faraday rotation studies of the spontaneous magnetic field in the CO 2 laser produced plasmas on solid targets. The system will be described together with some preliminary results.
TL;DR: In this paper, a new excitation method is proposed for shaping and lengthening the output pulse of TEA CO2 lasers, based on the independent excitation of two or more coaxial discharge systems contained in the same resonator.
Abstract: A new excitation method is proposed for shaping and lengthening the output pulse of TEA CO2 lasers, based on the independent excitation of two or more coaxial discharge systems contained in the same resonator. The shape of the TEA CO2 laser pulse is derived, from the rate equations, as a function of the delay time between the two discharge-current pulses. The first experimental results for a laser of this type are presented.
TL;DR: In this article, the authors used the second-harmonic output of a CW Nd:YAG Oscillator to obtain an 8 nsec pulsewidth and a 10 mJ pulse energy.
Abstract: confirmed in an experiment which employed, as the pump pulse, second-harmonic pulses of the giant pulse output from a Pockels-cell-&switched Nd:YAG laser (Fig. 1). The secondharmonic pulses had an 8 nsec pulsewidth and a 10 mJ pulse energy. They were coaxially fed into the CW Nd:YAG laser, which was acoustooptically mode-locked at 300 MHz. The minimum pulsewidth attained in the CW modelocked condition was measured at 70 psec (FWHM) using an optical correlator (Type I1 SHG). Care was taken to attain the closest spatial matching of the pump beam to the CW Nd :YAG laser beam. Examples of the resulting amplified modelocked pulse trains are shown in Fig. 2. The excellent reproducibility of the output waveforms, as demonstrated in this figure. was obtained with a non-critical alignment process so long as the second-harmonic generation and the CW mode-locked laser are reasonably stabilized. No change in the pulsewidth was observed after the amplification, as was expected. The amplification factor attained was on the order of lo5, and output pulses with peak powers exceeding 1 MW were obtained. In conclusion, intracavity amplification of CW mode-locked pulses by gain switching of the laser has been demonstrated. This method is a promising one for reliable high-power, picosecond pulse generation. 14.2 Injection-Locked Nd:YAG Oscillator,l W. H. Lowdermilk and J. E. Murray, Lawrence Livermore Laboratory, Livermore, Gal$ 94550 (15 min)
DOI•
14 Sep 1977
TL;DR: In this paper, the authors describe a technique by which a very short light pulse can be produced by compressing a portion of the main laser pulse, which results in an instantaneous frequency displacement from the original laser frequency given by the sender.
Abstract: A very fast (- 10 psec) laser light source has been constructed which can be used tomake shadowgraph, interferometry, and other diagnostic photographs useful in laser fusionstudies. To produce this pulsed light source, a portion of the 100 psec main Nd:glasslaser pulse is split off, sent through CS2 cells to produce a frequency chirp, and thenoptically compressed by diffraction gratings. By frequency converting the output pulse,one can perform studies at frequencies other than the fundamental (i.e., harmonic orRaman -shifted frequencies). The compressed pulse is absolutely time -synchronized with themain laser pulse. Shadowgrams taken using this technique are shown.IntroductionA very important diagnostic technique in laser fusion studies is the use ofsubnanosecond optical observations of laser produced plasmas. Optical techniques utilizinga pulsed light source such as shadowgraphy, Schlieren photography, and interferometry l'2 have proven particularly valuable for measuring the plasma density, shape, and velocity;while the Faraday rotations method has been used to measure the magnetic field generatedin the plasma. These plasmas often have velocities greater than 107 cm /sec, densitiesgreater than 1021 particles /cm3, and steep density gradients, particularly in the vicinityof the critical surface. Thus the use of such techniques usually requires a spatial -resolution of less than 10 u.m and a time -resolution of less than 10 picosec.In this paper we describe a technique by which a very short light pulse can be producedby compressing a portion of the main laser pulse.4 Moreover, the frequency of thecompressed pulse can be modified to serve a particular diagnostic purpose. Although atechnique of synchronizing two independent oscillators to within 100 psec has beenreported, the pulse compression system has the advantage that the probe light signal isabsolutely time -synchronized with the main laser pulse, and has a pulse duration shortenough to prevent time -smearing in the photograph.Pulse CompressionThe technique of pulse compression to reduce optical pulse duration and increase laserpeak power has been used for some time. 8'7 In this technique a relatively long laserpulse is passed through a liquid with a large nonlinear index of refraction to produce afrequency "chirp "; i.e., an actual optical carrier frequency variation within a singlelaser pulse. The chirped pulse can then be temporally compressed by passing it through apair of diffraction gratings.° Compression will take place if those frequencies thatappear earliest in the long pulse are forced to undergo the greatest delay. This isindicated in Fig. 1 where an incoming chirped pulse of FWHM duration At is dispersed sothat the higher frequency component (wo + Aw) is seen to follow a shorter path (AS) afterreflection from the second grating than the lower frequency component (wo - Aw), whichappeared earlier in the incident pulse. The recollimated exiting beam is then time -compressed to width Atc « At if the chirp bandwidth is large and if AS - c(At - Atc),The frequency chirp with initial pulsewidths up to about 100 psec is best produced byself phase modulation in a liquid with a high nonlinear index of refraction,i.e., for CS2n2 = 1.3 x 10 -11 esu. For example, an intense laser pulse passing through a CS2 cell under-goes self phase modulation, which results in an instantaneous frequency displacementfrom the original laser frequency given byHere