Pulse duration

About: Pulse duration is a research topic. Over the lifetime, 19429 publications have been published within this topic receiving 286507 citations.

Use of lasers to break down objects

Abstract: Calculi, stones, calcified tissue and other material are broken down for removal from within a body using laser pulses that are delivered via an optical fiber and have a wavelength, intensity, energy per pulse and pulse duration selected to break down the object into smaller particles without delivering energy sufficient to cause damage to other tissue.

Efficient conversion of picosecond laser pulses into second-harmonic frequency using group-velocity dispersion

Abstract: A computer model has been used to investigate frequency doubling of 1-psec duration high-power pulses in potassium dihydrogen phosphate (KDP) for type-II phase matching. It has been found that group-velocity dispersion can be used to advantage by predelaying the ordinary and extraordinary polarizations appropriately in a thin KDP crystal with its axes aligned at 90\ifmmode^\circ\else\textdegree\fi{} to the main conversion crystal. In that situation power conversion g100% from the fundamental to the second harmonic can be obtained with simultaneous ``compression'' of the output pulse duration by up to a factor of 5.

Arc fault circuit detector device detecting pulse width modulation of arc noise

Abstract: Briefly stated, and in accordance with a presently preferred embodiment of the invention, an arc fault detecting circuit using, a pulse width modulation, or PWM, technique is used to sense series or parallel arc faults. When arc faults occur, typically an arc step in current is followed by broad band arc noise which is caused by the random fluctuations in arc column resistance. In this invention, a logic signal is created which has a duration or width that corresponds to the time interval during which the broad band arc noise generated by the arc is present. Typically an arc fault randomly starts, generates broad band arc noise, and then extinguishes as the next current zero cross of the AC load current is approached. The random start causes PWM of the logic pulse whenever the start of the arc randomly moves with respect to the current zero cross. An arc fault that randomly starts, and then randomly stops, will also cause PWM with respect to the zero cross. The PWM logic pulse is coupled to the input of a microprocessor which measures and stores the length of the present PWM pulse under measurement, and compares that pulse to the pulse length of the last stored PWM pulse, and increments a counter if the difference in pulse length is greater than a predetermined amount. When the counter number is greater than or equal to a predetermined number held in the microprocessor memory, an output signal is sent to a controller which activates the circuit interrupter. Another input to the microprocessor, corresponding to the magnitude of the arc current, is used to adjust the predetermined number value down or up depending on the intensity of the arc fault for faster or slower interrupts respectively.

Role of rotational temperature in adiabatic molecular alignment

Abstract: One-dimensional alignment of molecules in the adiabatic limit, where the pulse duration greatly exceeds the molecular rotational periods, is studied experimentally Four different asymmetric top molecules (iodobenzene, p-diiodobenzene, 3,4-dibromothiophene, and 4,4′-dibromobiphenyl), rotationally cooled through a high pressure supersonic pulsed valve, are aligned by a 9-ns-long pulse Their orientations are measured through Coulomb explosion, induced by a 130-fs-long pulse, and by recording the direction of the recoiling ions The paper focuses on the crucial role of the initial rotational temperature for the degree of alignment In particular, we show that at molecular temperatures in the 1K range very strong alignment is obtained already at intensities of a few times 1011W∕cm2 for all four molecules At the highest intensities (∼1012W∕cm2) the molecules can tolerate without ionizing ⟨cos2θ⟩⩾092 in the case of iodobenzene This is the strongest degree of alignment ever reported for any molecule

Method of decorating a transparent plastics material article by means of a laser beam

Abstract: A method for the decoration of a transparent plastics material article comprising the steps of providing an article having a transparent plastics material body to be decorated, said article body to be decorated having internal stresses and having characteristic physical properties, and directing a pulsed laser beam having a pulse energy and a pulse duration into the body of said article, said laser beam being successively focussed by an optical focussing system in different regions within the body of said article, said pulse energy and said pulse duration being selected in dependence upon the desired extent of the decorative features.