Showing papers on "Femtosecond pulse shaping published in 1981"
TL;DR: The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse.
Abstract: The theory of pulse distortion in single-mode fibers is extended to include laser sources that suffer a linear wavelength sweep (chirp) during the duration of the pulse. The transmitted pulse is expressed as a Fourier integral whose spectral function is given by an analytical expression in closed form. The rms width of the transmitted pulse is also expressed in closed form. Numerical examples illustrate the influence of the chirp on the shape and rms width of the pulse. A somewhat paradoxical situation exists. A given input pulse can be made arbitrarily short by a sufficiently large amount of chirping, and, after a given fiber length, this chirped pulse returns to its original width. But at this particular distance an unchirped pulse would be only [equiation] times longer. Thus chirping can improve the rate of data transmission by only 40%.
120 citations
TL;DR: In this paper, the frequency dependence of the pulse width was obtained using a long cavity with multiple pulses in the cavity, and the experimental results were shown to be in good agreement with a theoretical description of mode locking.
Abstract: Proton bombarded stripe geometry lasers have been actively mode locked in an external cavity consisting of a lens, a Fabry‐Perot etalon, and a mirror. Under optimized conditions, pulses as short as 5.3 psec have been observed from measurement of the second harmonic autocorrelation function. The dependence of the pulse width on external parameters was studied in detail. The pulse width t1/2 decreases with increasing direct current. The functional dependence of the pulse width on current indicates that a saturable absorption mechanism is present in the laser which causes significant pulse shortening. The pulse width decreases with increasing rf current. The pulse width is a sensitive function of the frequency detuning of the applied rf current. The shortest pulses are observed when the applied frequency is less than the round trip frequency of the pulse in the cavity. The frequency dependence of the pulse width was obtained using a long cavity with multiple pulses in the cavity. The shortest pulses occur between 0.9 and 1.4 GHz. The Fabry‐Perot etalon limits the emission to a 1.9‐A spectral band. At optimum mode locking the band is ∼30 A below the peak of the multimode emission obtained without the etalon. The shift of the gain curve to lower enery indicates that additional loss is introduced by the feedback from the external cavity. The experimental results are shown to be in good agreement with a theoretical description of mode locking.
77 citations
TL;DR: In this paper, the authors reported the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser at a repetition frequency of 2.5 GHz.
Abstract: We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.
57 citations
TL;DR: In this article, the characteristics of the light output of InGaAsP laser pulses are reported, and results on stacking of pulses as close as 220 ps are also presented, with a duration of less than 66 ps.
Abstract: Picosecond optical pulses are generated from InGaAsP lasers by short electrical pulse pumping, Detection limited pulses with a duration of less than 66 ps are observed. In this paper, we report the characteristics of the light output. Results on the stacking of pulses as close as 220 ps are also presented.
49 citations
TL;DR: In this paper, a synchronized streak camera monitors the pulse profiles and reveals that the modulation frequency must be maintained stable to <10 kHz to avoid pulse broadening and substructures.
Abstract: Bandwidth-limited pulses (16 ps duration, \Delta t \Delta
u = 0.36 ) are obtained from an actively mode-locked GaAlAs CW diode laser. Replacing the 380 MHz sinewave modulation by repetitive ∼300 ps pumping pulses produces more stable operation at 1 W peak power output pulses. A synchronized streak camera monitors the pulse profiles and reveals that the modulation frequency must be maintained stable to <10 kHz to avoid pulse broadening and substructures.
44 citations
TL;DR: In this paper, an AlGaAs tandem-type laser with transverse junction stripe structure was used for ultrashort optical pulse generation by an ultrafast streak camera, while typical pulse widths were about 20 ps.
Abstract: Experimental results are presented for ultrashort optical pulse generation by an AlGaAs tandem-type laser with transverse junction stripe structure The shortest optical pulse width of 14 ps was observed by an ultrafast streak camera, while typical pulse widths were about 20 ps Further shorter pulses may be expected with this type of semiconductor laser by adequate control of the saturable absorber region
41 citations
TL;DR: In this paper, the temporal shape of laser pulses generated from an active passive mode-locked Nd3+: YAG oscillator was measured over ten orders of magnitude by measuring the third order correlation function of the laser pulse.
36 citations
TL;DR: In this article, the influence of pulse substructure on the determination of pulse envelope duration of a synchronously pumped dye laser within the noise burst model of Pike and Hersher was established.
Abstract: With the combination of precise autocorrelation and spectral measurements we have established the influence of pulse substructure on the determination of pulse envelope duration of a synchronously pumped dye laser within the noise burst model of Pike and Hersher. Our results make a single sided exponential pulse shape unlikely and we present evidence supporting pulses having Gaussian or skewed Gaussian temporal profiles.
27 citations
15 citations
TL;DR: In this article, a system of equations is derived to describe the pulse shape in a train of ultrashort pulses in the active mode-locking regime, which allows for the multilevel properties of the active medium, for dispersion of the group velocities of the interacting pulses, and also for depletion of the pump pulse during propagation and for the transient nature of the polarization of the lasing transition.
Abstract: A system of equations is derived to describe the pulse shape in a train of ultrashort pulses in the active mode-locking regime. Unlike other investigations, this system allows for the multilevel properties of the active medium, for the dispersion of the group velocities of the interacting pulses, and also for depletion of the pump pulse during propagation and for the transient nature of the polarization of the lasing transition. In the degenerate case, theoretical analyses are made of these equations and analytic expressions are obtained for the parameters of the laser pulse. It is found that the minimum of the lasing pulse duration is shifted into the range of negative detunings as a result of mismatch of the group velocities and that there is a certain pump pulse energy for which the duration of the laser pulse has a minimum. Numerical investigations are made of the shape and parameters of ultrashort pulses for various mismatches of the resonator lengths.
14 citations
TL;DR: It is shown here that this kind of pulse shaper is usable on a power laser chain and several pulse shapes with durations up to 640- and 40-psec rise time have been obtained at different power levels.
Abstract: Synchronizing a picosecond laser pulse with a nanosecond one would be useful in laser fusion research. Amplitude modulation of a picosecond spectrum makes this possible; this passive technique has already been studied by C. Froehly and demonstrated by B. Colombeau. It is shown here that this kind of pulse shaper is usable on a power laser chain. Starting from a 40-psec pulse, several pulse shapes with durations up to 640- and 40-psec rise time have been obtained at different power levels. Efficiency and signal to noise ratio of the system have been studied. The diffraction-limited beam has been amplified in a power laser chain.
TL;DR: In this article, the influence of detuning on the second laser threshold as well as on the pulse solutions above this threshold was investigated, and the influence was shown to be independent of the detuning.
TL;DR: In this paper, the evolution of a tunable dye laser (TDL) pulse in an ultrashort cavity pumped by a monochromatic picosecond light pulse is described using the appropriate laser rate equations.
Abstract: The evolution of a tunable dye laser (TDL) pulse in an ultrashort cavity pumped by a monochromatic picosecond light pulse is described using the appropriate laser rate equations. The ultrashort duration of the excitation pulse typically reduces the treatment into one which is directly analogous to the giant pulse model of Wagner and Lengyel, applied previously to Q‐switching dynamics in solid‐state lasers. The spectral properties of the TDL pulse are calculated using an active etalon model, in which the bandwidth narrowing of the cavity axial modes is governed by the time‐dependent gain derived from the giant pulse model. Theoretical conditions are obtained for achieving operating regimes which correspond to extraction of high pump→TDL conversion efficiencies, to the minimization of TDL pulse durations, or to shot‐to‐shot stabilization of output properties. The feasibility of extracting ∼45% conversion of 531‐nm SHG pulses from the mode‐locked Nd3+ : glass oscillator using a 54‐nm rhodamine 6G cavity is confirmed experimentally.
TL;DR: In this article, a large-scale hydrogen-fluoride (HF) laser system was demonstrated with angular multiplexing (AM) for a train of two 24 ns pulses, and the essential elements of this scheme were evaluated as a function of interpulse separation time.
Abstract: Pulse compression using angular multiplexing is demonstrated on a large-scale hydrogen-fluoride (HF) laser system. For a train of two 24 ns pulses, the essential elements of this scheme are evaluated as a function of interpulse separation time. Included are energy-extraction efficiency, overall temporal pulse distortion, leading-edge contrast-ratio distortion, and suppression of amplified spontaneous emission (ASE) relative to a single long-duration input pulse. For appropriate interpulse delay time, we show that distortionless amplification is possible with energy-extraction efficiency, as is obtained using a single input beam having a pulsewidth equal to the duration of the amplifier gain.
TL;DR: In this paper, the effect of simmer discharge on the operation of the SZ laser has been investigated, and it has been shown that the more intense simmer discharge is effective in reducing the absorption by the S3 molecules.
Abstract: (necessary for operation of the Sz laser), and thus a much lower temperature environment can be used. The beneficial effects of the simmer discharge are demonstrated in Fig. 1 where the laser output from a 10-cm sulfur tube in a 4OO0C oven is shown to increase with a more intense discharge. The tube is axially pumped with 308-nm radiation from a XeCl excimer laser. This radiation overlaps the v\" = 2 to v' = 5 absorption band and thus produces S2 laser oscillations on the v ' = 5 to v\" = 18-22 bands, which span the wavelength range x = 449-519 nm. The traces shown in Fig. 1 correspond to two different amplitudes of the rf voltage applied to ring electrodes located on the outside of the tube envelope. In Fig. l(b) the discharge is weak, and the corresponding S2 laser signal is weak; for Fig. l(a) the discharge is much stronger, and the Sp laser intensity is also larger. The rf discharge causes two phenomena which are beneficial to the operation of the SZ laser. Electron collisions in the discharge convert some higher-order molecules of sulfur (Sn, 3 5 n 5 8) to S2. It can do this by either direct electron impact dissociation of sulfur molecules or by thermal dissociation of these species due to the enhanced gas temperature6 in a discharge. Both effects, of course, increase the density of the active species Sz. Simultaneously, the presence of the discharge reduces the density of S3 whose absorption band7 is centered at -390 nm. This last benefit is shown in Fig. 2 where the transmission through a 30-cm sulfur cell at 440'C is measured for various intensities of the rf discharge. Clearly the more intense rf discharge is effective in reducing the absorption by the S3 molecules. (13 rnin)
15 May 1981
TL;DR: In this paper, a passively mode-locked TEM-00 Nd:YAG laser was investigated theoretically and experimentally in detail, taking into account spontaneous emission and the time dependent pumping light.
Abstract: A passively mode-locked TEM-00 Nd:YAG laser is investigated theoretically and experimentally in detail. The numerical calculations base on the refined Letokhov model, taking into account the spontaneous emission and the time dependent pumping light. The statistical noise pulses of the spontaneous emission are approximated by an average noise power and two single pulses which develop into the mode locking pulse and its satellite. By starting at t = 0 with all atoms in the ground state, the temporal behaviour of the following quantities is pursued: main pulse energy and width, energy of the satellite pulse, average noise power, and their dependence on absorber transmission, pumping rate, and resonator losses. Special importance is attached to a realistic model of the nonlinear absorber which compresses the mode-locking pulse and determines the resulting pulse width in conjunction with the amplifier. The gaussian structure of the pulse in time and space is taken into account. The numerical results were checked experimentally. Pulse width measurements were carried out with two photon fluorescence and a fast streak-camera. The results confirm the theory and demonstrate that the refined Letokhov-model is suitable to describe mode-locking quantitatively.
30 Dec 1981
TL;DR: In this article, it was shown that substantial temporal distortion of nanosecond 10.6 µm laser pulses occurs in traversing multiphoton saturable absorbers, and that the risetime and pulse delay effects appear to depend both on fluence and wavelength, and were qualitatively consistent with predictions of a simple two-level absorption model.
Abstract: It was shown that substantial temporal distortion of nanosecond 10.6 ..mu..m laser pulses occurs in traversing multiphoton saturable absorbers. The risetime and pulse delay effects appear to depend both on fluence and wavelength, and to be qualitatively consistent with predictions of a simple two-level absorption model.
TL;DR: In this paper, a closed-form solution for the pulses of an internally pumped mode-locked CW dye laser, where the mode locking is achieved by a fast saturable absorber, is presented.
Abstract: A closed-form solution for the pulses of an internally pumped mode-locked CW dye laser, where the mode locking is achieved by a fast saturable absorber, is presented. The pulse shape is found to be secant hyperbolic in time. The pulsewidth and the pulse power are expressed as functions of the system parameters. The pulses are found to be bandwidth limited by the amplifier of relatively longer relaxation time.
05 Apr 1981
TL;DR: In this article, a colliding pulse mode-locking (CPM) was proposed for passive mode locking in which a key pulse shortening mechanism is the interaction of two oppositely directed pulses in a thin saturable absorber.
Abstract: We report a new technique for passive mode-locking lasers in which a key pulse shortening mechanism is the interaction of two oppositely directed pulses in a thin saturable absorber. Because of the central role played by this interaction or collision, we refer to the process as colliding pulse mode-locking (CPM).
TL;DR: In this article, a study was made of a neodymium glass laser with control of the pulse shape and duration in the nanosecond and subnanosecond ranges.
Abstract: A study was made of a neodymium glass laser with control of the pulse shape and duration in the nanosecond and subnanosecond ranges. The laser consisted of a master oscillator and an amplifying system. The time profile of a radiation pulse was shaped with an electrooptic deflector made of lithium niobate and a Pockels switch with two DKDP crystals in the amplifying system. Small-scale self-focusing in the amplifiers was suppressed by spatial filtering of the radiation. Pulses of duration 3 nsec and with an intensity difference up to three orders of magnitude were obtained at the laser output. The duration of the sharpened part of the pulse was ~200 psec. The radiation energy at the output was as high as 10 J.
01 Jan 1981