Showing papers on "Femtosecond pulse shaping published in 1970"
TL;DR: In this article, a complex Gaussian pulse is followed through one pass around the laser cavity to keep the pulse Gaussian, and the analysis is further extended to include effects of detuning of the modulator, in which case analytical expressions are obtained for the phase shift of the pulse within the modulation cycle, the shift of pulse spectrum off line center, the change in pulse length, and change in power output.
Abstract: A new general analysis for mode-locked operation of a homogeneously broadened laser with either internal phase (FM) or amplitude (AM) modulation is presented in this paper. In this analysis, a complex Gaussian pulse is followed through one pass around the laser cavity. Approximations are made to the line shape and modulation characteristics to keep the pulse Gaussian. After one round trip, a self-consistent solution is required. This yields simple analytic expressions for the pulse length, frequency chirp, and bandwidth of the mode-locked pulses. The analysis is further extended to include effects of detuning of the modulator, in which case analytical expressions are obtained for the phase shift of the pulse within the modulation cycle, the shift of the pulse spectrum off line center, the change in pulse length, and the change in power output. Numerical results for a typical Nd:YAG laser are given. In the case of the FM mode-locked laser it is found that there is a frequency chirp on the pulse and that this causes pulse compression and stretching when the modulator is detuned. Etalon effects and dispersion effects are also considered.
600 citations
TL;DR: In this article, the authors extended the theory of transient stimulated Raman scattering to include an arbitrary shape of the laser pump pulse and showed that the maximum Stokes gain depends on the total energy content per unit area of the pump pulse, not on the instantaneous intensity for an exciting pulse of short duration.
Abstract: : The theory of transient stimulated Raman scattering has been extended to include an arbitrary shape of the laser pump pulse. It is shown that the maximum Stokes gain depends on the total energy content per unit area of the pump pulse, and not on the instantaneous intensity for an exciting pulse of short duration. The Stokes pulse has a leading edge which rises sharply to a maximum, where the maximum occurs with some delay with respect to the maximum of the pump pulse. The trailing edge follows the decay of the pump. In a nondispersive medium, the gain is not reduced by frequency broadening of the laser output, while in a dispersive medium, considerable gain reduction is expected. Numerical results for various laser pulse shapes and spectral distributions are presented. (Author)
399 citations
TL;DR: In this paper, the authors describe a model of a light pulse in which a Gaussian random radiation field of limited spectral extent is modulated by a temporal pulse envelope, and show that predictions based on such a model are in excellent detailed agreement with published experimental results.
Abstract: In careful experimental measurements of mode‐locked laser pulses, using nonlinear media, a number of workers have found evidence for what appear to be coexisting subpicosecond pulses, and pulses in the range of 10–40 psec. In this letter we describe a model of a light pulse in which a Gaussian random‐radiation field (i.e., a thermal field) of limited spectral extent is modulated by a temporal pulse envelope, and we show that predictions based on such a model are in excellent detailed agreement with published experimental results. We also consider the case of a pulse of linearly chirped radiation, and show that a clear distinction can be made between this case and a pulse of Gaussian random radiation.
66 citations
TL;DR: Coherent pulse propagation in inhomogeneously broadened attenuator, examining degeneracy influence and connection with self induced transparency /SIT/ in non-degenerate system as mentioned in this paper.
Abstract: Coherent pulse propagation in inhomogeneously broadened attenuator, examining degeneracy influence and connection with self induced transparency /SIT/ in nondegenerate system
35 citations
TL;DR: In this article, a new method is proposed for measuring the widths, and possibly even the detailed shapes, of picosecond pulses in CW mode-locked lasers, where the pulses are passed through an electro-optic modulator, which is biased for zero transmission with zero applied voltage, and which is driven at a harmonic of the pulse-repetition frequency.
Abstract: A new method is proposed for measuring the widths, and possibly even the detailed shapes, of picosecond pulses in CW mode-locked lasers. The pulses are passed through an electro-optic modulator, which is biased for zero transmission with zero applied voltage, and which is driven at a harmonic of the pulse-repetition frequency. The variation in average light transmission through the modulator is monitored while the relative phase between the light pulses and the modulator drive is varied. The pulsewidth may be deduced from one such measurement made at a microwave light-modulation frequency sufficiently high that the pulsewidth is a finite fraction of a period at the modulation frequency. By making such measurements at a number of harmonics, the complete Fourier expansion (including both amplitudes and phases) of the picosecond pulse envelope can, at least in principle, be determined without ambiguity.
24 citations
TL;DR: In this article, spontaneous mode locking has been observed in a high pressure CO2 laser, and the mode-locked pulses were found to be separated by 2L/c. The pulse shapes suggest that two axial cavity modes dominate the laser behavior.
Abstract: Spontaneous mode locking has been observed in a high‐pressure CO2 laser. The mode‐locked pulses were found to be separated by 2L/c. Pulse separations as short as 11 nsec were achieved. The pulse shapes suggest that two axial cavity modes dominate the laser behavior.
21 citations
Patent•
06 Jul 1970
TL;DR: In this paper, a wide band tactical pulsed laser communication system capable of operating at high bit rates was proposed, where an incoming digital data stream, as for example, a multi-channel time division multiplexed pulse code modulated signal, first is converted into a pulse position modulation signal and the corresponding pulse position modulated pulses of each channel are applied by way of appropriate gating circuitry in sequence to an array of injection lasers, each capable of generating optical signals at relatively high peak power.
Abstract: A wide band tactical pulsed laser communication system capable of operating at high bit rates wherein an incoming digital data stream, as for example, a multi-channel time division multiplexed pulse code modulated signal, first is converted into a pulse position modulated signal and the corresponding pulse position modulated pulses of each channel are applied by way of appropriate gating circuitry in sequence to an array of injection lasers, each capable of generating optical signals at relatively high peak power.
20 citations
TL;DR: In this article, the shape of a mode-locked continuously pumped Nd:YAG laser has been studied using an optical correlation technique and the shape is found to be Gaussian under stable conditions with the phase modulator frequency tuned to the cavity difference frequency.
Abstract: The pulse shape of a mode‐locked continuously pumped Nd:YAG laser has been studied using an optical correlation technique The shape is found to be Gaussian under stable conditions with the phase‐modulator frequency tuned to the cavity‐mode difference frequency This result is consistent with the theory of mode locking in lasers with homogeneous broadening
15 citations
Patent•
23 Sep 1970
TL;DR: In this paper, a frequency dependent phase shift in the optical pulse is introduced, which is proportional to the difference between the frequency of each Fourier component of the pulse and the central frequency.
Abstract: An optical pulse position modulator is provided by a diffraction grating (or other optical spectrum resolution device) in combination with a suitable control device, such as a triangular electrooptic prism. This control device introduces a frequency dependent phase shift in the optical pulse which is proportional to the difference between the frequency of each Fourier component of the pulse and the central frequency. Thereby, upon reconstruction of the pulse by reflection back to the diffraction grating, the pulse position is shifted in time according to the controlled phase shift. Such a device has a relatively higher efficiency than conventional optical delay lines for picosecond pulses in the visible region of the spectrum, for example.
14 citations
Patent•
13 Nov 1970TL;DR: In this paper, a radar transmitting system is disclosed for transmitting an optical pulse to a target comprising an optical cavity containing a laser incorporating a mode-locking means to build up an optical pulses.
Abstract: A radar transmitting system is disclosed for transmitting an optical pulse to a target comprising an optical cavity containing a laser incorporating a mode-locking means to build up an optical pulse. An optical switch is also provided within the cavity to convert the polarization of the optical pulse generated within the cavity. The optical switch comprises an electro-optical crystal driven by a time delayed driver circuit which is triggered by a coincident signal made from an optical pulse signal and a gating pulse signal. Upon being energized, the electro-optical crystal functions to convert the polarization of the optical pulse as it passes through the crystal. This converted optical pulse then strikes a polarization sensitive prism and is deflected out of the cavity toward the pending target in the form of a pulse containing most of the optical energy generated by the laser in the pulse build-up period. After striking the target, the reflected energy is picked up by a transceiver with the total travel time of the pulse being recorded. This travel time is a measure of the distance from the transceiver to the target.
12 citations
TL;DR: In this paper, a technique for the measurement of the widths of ultrashort optical pulses which does not involve any non-linear optical processes is described, and it is shown that for a pulse with a small rise time this technique can be used to produce a pulse whose width is approximately equal to the rise time of the original pulse.
TL;DR: In this paper, a laser source suitable for plasma production is described, which involves the use of uncoated flats that act as mode selectors when inserted inside the laser cavity.
Abstract: A laser source suitable for plasma production is described The technique involves the use of uncoated flats that act as mode selectors when inserted inside the laser cavity Pulse widths of 15 to 30 and 60 to 70 ps were obtained with signal-to-noise ratios greater than 20 dB for 70 to 80 percent of the laser firings
01 Jan 1970
TL;DR: In this paper, the amplitude of a long duration pulse instead of its frequency is modulated using a zone plate, and the echoes are reconstructed optically, as in side-looking radar, thereby circumventing the need for the complicated matched filters of the chirp process.
Abstract: This letter discusses a pulse compression technique suggested earlier by Tuttle which modulates the amplitude of a long duration pulse instead of its frequency (as in the "chirp" process). The modulation code is that of a zone plate; the echoes are recorded photographically, and then reconstructed optically, as in side-looking radar, thereby circumventing the need for the complicated matched filters of the chirp process.
Patent•
22 Jul 1970
TL;DR: In this paper, a coherent, 13-bit phase reversal pulse modulator and pulse compression filter was used for increasing the range resolution of a coherent radar. But the modulation of the radar return signal in an approximation to a matched filter was not considered.
Abstract: A coherent, 13 bit phase reversal pulse modulator and pulse compression filter for increasing the range resolution of a coherent radar. The transmitted pulse is subdivided into equal duration bits, and as the pulse is being formed each bit may or may not be shifted in phase determined by a digital code generator. The range resolution of which this pulse reversal modulated pulse is capable is achieved by processing the radar return signal in an approximation to a matched filter.
TL;DR: In this article, the authors measured the pulse velocity of a mode-locked 6328-A He-Ne laser pulse in a resonant absorber as a function of the pulse intensity.
Abstract: Experiments are reported that measure the pulse velocity of a mode-locked 6328-A He-Ne laser pulse in a resonant absorber as a function of the pulse intensity. At low intensities, pulse velocities greater than the velocity of light in the passive medium are observed. These results are compared with a simple theory based on the saturation of the dispersion associated with the absorption. At higher intensities where the pulse approaches a 2π pulse, pulse delays (that is pulse velocities less than the velocity of light in the passive medium) are observed.
TL;DR: In this article, an experimental comparison of the pulse and group velocities in a self-pulsing ring laser is presented, and it is shown that the group velo-cities are essentially equal near laser threshold, and the group velocity exceeds the pulse velocity by an increasing amount for increasing laser excitation.
Abstract: An experimental comparison of the pulse and group velocities in a self-pulsing ring laser is presented. It is found that the two velocities are essentially equal near laser threshold, and the group velocity exceeds the pulse velocity by an increasing amount for increasing laser excitation.
TL;DR: In this paper, the basic characteristics of an electrooptically Q-switched CO 2 laser are given, compared with solutions of classical rate equations, clarifying the role of various processes in determining the output characteristics.
Abstract: Basic characteristics of an electrooptically Q -switched CO 2 laser are given in this paper. Studies of the dynamics of Q switching using this system are compared with solutions of classical rate equations, clarifying the role of various processes in determining the output characteristics. Q switching was obtained with an intracavity GaAs modulator crystal. Outputs similar to those of other switching techniques are obtained but with greater time control and somewhat greater amplitude stability. The pulse shape and the delay between switching and pulse development are independent of the manner in which switching was obtained, due to the fast ( 2 molecule must be included in the rate equations.
01 Sep 1970
TL;DR: In this paper, the authors extend the concept to the compression of pulses reflected from zone plate gratings, and contrast this with the recently described use of zone plate envelopes for pulse compression.
Abstract: Lord Rayleigh noted that a short noise pulse, upon reflection from a periodic grating, is transformed into a chirped pulse. Conversely, an ascending frequency signal is, upon reflection, compressed into one of shorter length. This letter extends the concept to the compression of pulses reflected from zone plate gratings, and contrasts this with the recently described use of zone plate envelopes for pulse compression. The possibility of compressing laser pulses into shorter, more powerful pulses is discussed.
TL;DR: In this paper, the Gaussian pulse amplitude modulated with a sin x/x waveform was used for baseband pulse shaping, which produces less intersymbol interference than in the commonly used procedure employing gradual roll off in the frequency domain.
Abstract: The use of the Gaussian pulse amplitude modulated with a sin x/x waveform for baseband pulse shaping is suggested. This produces less intersymbol interference than in the commonly used procedure employing gradual roll off in the frequency domain. Further the frequency characteristic also falls off as fast as exp (−x2) asymptotically.
TL;DR: Using two Pockels cells, a singlepicosecond-duration light pulse generated by a mode-locked Nd:glass laser was time synchronized with a 50-100ns-duration Q-switched ruby-laser pulse as discussed by the authors.
Abstract: Using two Pockels cells, a single-picosecond-duration light pulse generated by a mode-locked Nd:glass laser was time synchronized with a 50-100-ns-duration Q -switched ruby-laser pulse. The picosecond pulse was reliably placed in the early part of the rise of the Q -switched pulse, and could be delayed to any later time.
01 Jan 1970
TL;DR: In this article, a complex Gaussian pulse is followed through one pass around the laser cavity to estimate the line shape and modulation characteristics to keep the pulse Gaussian, and the analysis is further extended to include effects of detuning of the modulator, in which case analytical expressions are obtained for the phase shift of the pulse within the modulation cycle.
Abstract: Abstracf-A new general analysis for mode-locked operation of a homogeneously broadened laser with either internal phase (FM) or amplitude (AM) modulation is presented in this paper. In this analysis, a complex Gaussian pulse is followed through one pass around the laser cavity. Approximations are made to the line shape and modulation characteristics to keep the pulse Gaussian. After one round trip, a self-consistent solution is required. This yields simple analytic expressions for the pulse length, frequency chirp, and bandwidth of the mode-locked pulses. The analysis is further extended to include effects of detuning of the modulator, in which case analytical expressions are obtained for the phase shift of the pulse within the modulation cycle, the shift of the pulse spectrum off line center, the change in pulse length, and the change in power output. Numerical results for a typical Nd:YAG laser are given. In the case of the FM mode-locked laser it is found that there is a frequency chirp on the pulse and that this causes pulse compression and stretching when the modulator is detuned. Etalon effects and dispersion effects are also considered.