Showing papers on "Femtosecond pulse shaping published in 1982"

Optical pulse compression based on enhanced frequency chirping

Abstract: Through numerical simulations, we show that, under relatively general conditions, passage of an intense picosecond pulse through a single‐mode optical fiber can cause the pulse to become strongly frequency broadened with a positive chirp (linear frequency sweep) describing essentially all of the energy of the output pulse. Also, because the optical fiber supports only a single transverse mode, the entire output beam profile has the same frequency modulation. These two features allow for unprecedented optical pulse compression.

Amplification of subpicosecond optical pulses: Theory and experiment

Abstract: Laser-pumped dye amplifiers are the most convenient way to amplify ultrashort light pulses. In this paper, we develop an analytical theory of a transverse-pumped dye amplifier and compute the steady-state distribution of the excited state population and the total stored energy. The equation for the traveling amplified pulse is then solved for a given distribution of excited state molecules. The efficiency of an amplification stage associated with the distortion of the temporal pulse shape is obtained as a function of the input and stored energy density, normalized to the saturation level. The theoretical results are then compared to measurements obtained from an experimental arrangement of a three-stage optically pumped dye laser amplifier, which amplifies subpicosecond pulses from a passively mode-locked CW dye laser, to produce pulses with a peak intensity of 3 GW while maintaining a 0.5 picosecond pulsewidth.

Optical pulse compression apparatus and method

Abstract: An optical pulse is passed through a nonlinear dispersive delay line, which chirps the pulse by the nonlinear process of self-phase modulation and simultaneously and interactively broadens the pulse by the process of group velocity dispersion. The broadened and chirped pulse is then passed through a linear dispersive delay line, which compresses the pulse to a width less than the original pulse. By making the optical pulse suitably intense, a single-mode optical fiber may act as the nonlinear dispersive delay line. A near-resonant atomic vapor cell or a grating pair may act as the linear dispersive delay line.

Chirp pulse transmission through a single-mode fibre

Abstract: A pulse-compression phenomenon of a chirp pulse transmitted through a long single-mode fibre is presented. The chirp pulse is obtained by using a carrier density change in a DFB laser diode. The pulse width is 1.7 ns at the single-mode-fibre input and is compressed to 0.35 ns after a 104 km transmission at 1.54 μm wavelength.

Generation of short optical pulses in semiconductor lasers by combined DC and microwave current injection

Abstract: We report picosecond pulse generation in low threshold buried optical guide lasers using combined direct and microwave current excitation. The pulse widths were obtained as a function of direct current for several levels of RF excitation using lasers 125 and 380 μm long. The pulses have a Gaussian shape with full widths at half maximum intensity ranging from 19 to 57 ps. The pulse widths were obtained from the second harmonic autocorrelation. The experimental results are in reasonable agreement with the theory of short pulse formation in sinusoidally modulated lasers. The pulse width decreases with increasing dc and microwave current, and decreasing laser length. The shortest pulses were obtained with a 125μm long laser using 0.25 W RF at 1 GHz and 35 mA de bias. Multiple pulses are emitted at high dc excitation levels. Using the above laser at the indicated current levels the emission consists of a burst of ∼10 pulses which are separated by 30 ps, and has an approximately exponentially decaying amplitude. Saturable absorption was introduced in the lasers by degradation and results in shortening the pulses. A comparison is made of the pulse widths obtained for sinusoidal microwave current modulation and for pulsed excitation where the excitation is obtained from a step recovery diode. Reduced pulse widths are obtained for short current pulse excitation.

Electrical excitation of an XeCl laser using magnetic pulse compression

Abstract: Excitation of a small repetitively pulsed XeCl laser by a magnetic pulse compressor (MPC) is reported. The MPC makes use of a saturable inductor constructed out of relatively low frequency ferrites. It compresses a 300‐ns pulse into a 50‐ns pulse, enabling a low di/dt, long life thyratron to drive a fast discharge laser. The laser has operated at 750 Hz for several hours with an average optical output power of 3.5 W.

Plasma KrF laser pulse compressor

Abstract: The use of a plasma medium for the compression of KrF laser light to pulse widths suitable for laser‐driven fusion applications is described. The results indicate that efficient pulse compression can be realized. A particular feature is the absence of the troublesome backward second‐Stokes wave found in gas cell compressors.

Pulse pumping an optically pumped laser

Abstract: An efficient power supply employs a high current switching transistor to pulse a flashlamp for optical pumping in lasers, such as an Nd:YAG laser at high pulse repetition frequencies. The pulsing circuit offers a simple, flexible, and precise means of pump pulse control. Flashlamp simmer current is provided from the constant dc voltage source with a resistor in parallel with the switching transistor.

Propagation of ultrashort optical pulse in a two-level laser amplifier

Abstract: The response of a long two-level laser amplifier is obtained, i.e., the structure of the pulse at the amplifier output is determined as a function of the waveform of the firing pulse. It is shown that the output pulse is always quasi-self-similar, and that the parameters of the long-amplifier solution are determined exclusively by the rise time of the firing pulse.

Theoretical analysis of the performance of an atomic iodine laser amplifier chain

Abstract: The performance of an atomic iodine laser amplifier chain with output pulse powers close to 2 TW is analyzed by a numerical solution of the Maxwell-Bloch equations. Two subjects are discussed in detail. The first one refers to the pulse compression occurring in the chain as a result of saturation and some related aspects such as damage to components, self-focusing, correlations between the input and output pulse shapes, and the means of pulse shape control. The second deals with various schemes suited for achieving extraction efficiencies of about or larger than 55 percent. These include the single-pass and double-pass schemes, pulses with two carrier frequencies, and a variation of the pulse carrier frequency. In addition, the response of the chain to a variation of those parameters which are most easily subject to change in a routine operation is investigated.

Ultrafast optoelectronic switching in Blumlein pulse generator

Abstract: Blumlein pulse generator has the potentiality of yielding pulse amplitude equal to the charging voltage By applying the technique of optoelectronic switching to Blumlein pulse generator, square pulses with ultrafast rise time have been generated In such cases, the rise time is essentially controlled by the temporal width of the picosecond laser pulse

Radiation-induced transient absorption in optical fibers

Abstract: Transient absorption in optical fibers has been studied with emphasis on fast absorption components. Radiation damage was induced with a Febetron 706 electron accelerator, modified to deliver an electron pulse width of 1.1 ns. Dye lasers were synchronized to the accelerator to provide a light pulse through the fiber during the radiation pulse. The output light pulse was detected with a biplanar vacuum photodiode. Four scope traces were used on each electron pulse to monitor the Febetron output, the input drive pulse, and two records of the output pulse on two sweep speeds. Detailed data were acquired for times less than 100ons after irradiation. An insulated enclosure was used to vary fiber temperature from -30 C to +250 C. Several fibers were studied with emphasis on ITT T303 PCS fiber. Data were acquired at 600 and 850 nm. Theoretical modeling of the data will be presented.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Temporal analysis of a mode-locked Nd-glass laser by four-wave mixing

Abstract: The duration, shape, and background intensity level of pulses of a passively modelocked Nd-glass laser are determined by noncollinear phase-matched four-photon frequency mixing of time-separated fundamental and second-harmonic pulses in a KI crystal. The pulse shape is found to be slightly asymmetric with slower trailing than rising parts. The background intensity level before and behind the main pulse is about 5¢10−6 the peak pulse intensity.

Short laser pulse generation: part two

Abstract: The status of short laser pulse generation is reviewed. Achievements, limitations and potential of techniques producing pulses shorter than 50 ns, from the ultra-violet to the infra-red, are examined. In this second half of the paper the physical principles underlying the generation of ultra-short pulses by gating, interferometric techniques, pulse compression and pulse shaping are considered.

A new method of measuring ultra-short coherent light pulses

Abstract: A new method of pulse width measurement based on the total energy response of an etalon is presented. The theory is developed and results for several pulse shapes are given. The method is unique because no fast response detector is required and there are practically no spectral region limitations.

Short pulse free electron laser amplifier

Abstract: Method and apparatus for amplification of a laser pulse in a free electron laser amplifier where the laser pulse duration may be a small fraction of the electron beam pulse duration used for amplification. An electron beam pulse is passed through a first wiggler magnet and a short laser pulse to be amplified is passed through the same wiggler so that only the energy of the last fraction, f, (f<1) of the electron beam pulse is consumed in amplifying the laser pulse. After suitable delay of the electron beam, the process is repeated in a second wiggler magnet, a third, . . . , where substantially the same fraction f of the remainder of the electron beam pulse is consumed in amplification of the given short laser pulse in each wiggler magnet region until the useful electron beam energy is substantially completely consumed by amplification of the laser pulse.

Gigabit optical pulse generation with FM mode-locked LiNdP 4 O 12 lasers

Abstract: FM mode locking of an LiNdP 4 O 12 (LNP) laser with an intracavity modulator is reported. Mode-locked optical pulses with a pulse width of 49 ps at a repetition rate of 960 MHz, corresponding to c/2L ( c :light velocity, L :cavity length), have been obtained. A pulse repetition rate as high as 2.88 GHz has been achieved with a multiple mode-locking technique.

Intensity dependence of classical and collective absorption processes in laser produced plasmas at 1.053 μm and 0.527 μm

Abstract: Intensity dependence of absorption efficiency in laser produced plasmas, at a pulse width of 100 ps, has been measured using an integrating spherical photometer at the laser irradiance of ≅-1014 ˜ 1016 W/cm2 for the laser wavelengths of 1.053 μm and 0.527 μm, respectively. For these experimental conditions, the observed experimental results are well explained in terms of classical and collective absorption processes. Specifically, we propose the formation of periodic density profile modification in the underdense region which results in enhanced resonance absorption efficiency at high laser irradiance.

Statistical analysis of instantaneous laser spectra

Abstract: A statistical description of the pulse to pulse spectral variations of a semiconductor laser has been made using a technique which records the true instantaneous spectrum. Mode selection caused by external feedback has been examined.

The Pulse Duration of a Distributed Feedback Dye Laser Under Single Pulse Conditions

Abstract: As we have shown recently [1–3], distributed feedback dye lasers (DFDLs) are a new type of source for the generation of picosecond light pulses. DFDLs are relatively simple in construction and produce stable single pulses without need for a special pulse selecting device. Their range of operation extends through the visible to the near uv part of the spectrum [4]. Smooth tuning can be achieved by several techniques [2]. It is easy to set up an oscillator-amplifier system for DFDL pulses which is pumped by a single N2-laser [5]. Synchronization is greatly facilitated this way.

Laser device having laser beam energy control

Abstract: A laser device has a pulse controlled laser oscillator. Said laser device includes means for setting pulse width, pulse period and pulse number and generating a control pulse signal having the set pulse width, the set pulse period and the set pulse number, to control said laser oscillator to thereby control a laser beam energy to a desired amount.

Time-dependent pulse amplification in a three level gas

Abstract: The density matrix equations have been solved in conjunction with the time-dependent field amplitude equations for a three level optically pumped gas. The solutions are valid in the limit in which the pumping pulse is longer than the dephasing time of the system and true coherence effects may be neglected. In order to obtain closed form solutions, it is assumed that the FIR field is smaller than the pump field and saturation effects associated with this field are absent. When the pump pulse is resonant with the absorbing FIR transition, particularly simple solutions for the time-dependent FIR field amplification are obtained. These solutions exhibit the specific dependence of the FIR output pulse on the shape of the input pulse and display certain pulse narrowing features.

Numerical analysis of ultrashort pulse generation using a Fabry-Perot interferometer

Abstract: It is shown that this technique yields an asymmetric pulse that can be as short as a few picoseconds wide, but continuously tunable up to around 1 ns. The authors have studied the effects of the mirror spacing reflectivity losses and resonance between laser frequency and transmission peaks of the interferometer on the generated pulse width, shape, peak power and signal to background ratio.

Influence of rotational relaxation in a CO2 amplifier on the shape of a short amplified pulse

Abstract: An investigation was made into the change in shape of a nanosecond radiation pulse as it propagated in a TEA CO2 amplifier having a 5-m long amplifying medium. It was shown experimentally and theoretically that under certain conditions there was a substantial change in the pulse shape; a second peak caused by rotational relaxation in the amplifying medium appeared at the trailing edge of a pulse.