Compression of optical pulses

Fork R L, Brito Cruz C H, Becker P C and Shank C V 1987 Compression of optical pulses to six femtoseconds by using cubic phase compensation Qpt. Lett. 12 483-5... 

R.L. Fork, C.H. Brito Cruz, P.C. Becker, and C.V. Shank, Compression of Optical Pulses to Six Femtoseconds by Using Cubic Phase Compensation , Opt. Lett. 12, 483 (1987). 

Since the principle lower limit ATmin = l/Sv of the optical pulse is given by the spectral bandwidth (5v of the gain medium, it is desirable to make as large as possible. The idea of spectral broadening of optical pulses by self-phase modulation in optical fibers with subsequent pulse compression represented a breakthrough... 

Kuhl J and Heppner J 1986 Compression of femtosecond optical pulses with dielectric multilayer interferometers IEEE J. Quantum. Electron. 22 182-5... 

To carry out a spectroscopy, that is the structural and dynamical determination, of elementary processes in real time at a molecular level necessitates the application of laser pulses with durations of tens, or at most hundreds, of femtoseconds to resolve in time the molecular motions. Sub-100 fs laser pulses were realised for the first time from a colliding-pulse mode-locked dye laser in the early 1980s at AT T Bell Laboratories by Shank and coworkers by 1987 these researchers had succeeded in producing record-breaking pulses as short as 6fs by optical pulse compression of the output of mode-locked dye laser. In the decade since 1987 there has only been a slight improvement in the minimum possible pulse width, but there have been truly major developments in the ease of generating and characterising ultrashort laser pulses. 

This technique will allow compression of a 100-femtosecond pulse down to 12 femtoseconds or even to 8 femtoseconds. (A femtosecond is a millionth of a billionth of a second or 1 x 10-15 s.) Pulse compression can be used to study chemical reactions, particularly intermediate states, at very high speeds. Alternatively, these optical pulses can be converted to electrical pulses to study electrical phenomena. This aspect, of course, is of great interest to people in the electronics industry because of their concern with the operation of high-speed electronic devices. It also is of great interest to people who are trying to understand the motion of biological objects such as bacteria. 

Verluise, R, Laude, V., Cheng, Z., Spiehnann, C., and Toumois, P. 2000. Amplitude and phase control of ultrashort pulses by use of an acousto-optic programmable dispersive filter Pulse compression and shaping. Opt. Lett. 25(8) 575-77. 

D. Strickland, G. Mourou, Compression of amplified chirped optical pulses, Optics Communications 56, 219 (1985)... 

In conclusion, it is worth reiterating that the anomalous absorption effects described here may be manifest in any experiments that employ sufficiently high-intensity broadband radiation. To this extent, anomalies may be observable in experiments not specifically involving USES light. In particular, the continued advances in techniques of laser pulse compression have now resulted in the production of femtosecond pulses only a few optical cycles in duration (Knox et al. 1985 Brito Cruz et al. 1987 Fork et al. 1987) which necessarily have a very broad frequency spread, as the time/energy uncertainty principle shows. Thus, mean-frequency absorption may have a wider role to play in the absorption of femtosecond pulses. If this is correct, it raises further questions over the suitablity of absorption-based techniques for their characterization. 

In the experiments described here, two separate techniques have been used for interferometric characterization of the shocked material s motion frequency domain interferometry (FDI) [69, 80-81] and ultrafast 2-d spatial interferometric microscopy [82-83]. Frequency domain interferometry was used predominantly in our early experiments designed to measure free surface velocity rise times [70-71]. The present workhorse in the chemical reaction studies presented below is ultrafast interferometric microscopy [82], This method can be schematically represented as in Figure 6. A portion of the 800 nm compressed spectrally-modified pulse from the seeded, chirped pulse amplified Ti sapphire laser system (Spectra Physics) was used to perform interferometry. The remainder of this compressed pulse drives the optical parametric amplifier used to generate tunable fs infrared pulses (see below). 

Until recently, the pulses used in those experiments were the shortest optical pulses characterized. The transition-state spectroscopy of Zewail and Bernstein [16,17,18,19, 20,21 and 22] exploited an amplified CPM laser after frequency doubling and/or continuum generation. The chemical systems that were most easily studied, however, were those that could be stimulated either by the 620 nm output of the CPM directly or after frequency doubling to 310 nm. In addition, the CPM laser and its contemporary, more tunable alternative, the pulse-compressed, synchronously pumped dye laser [H], were tools that could be effectively used only by researchers with extensive backgrounds in lasers and optics. 

Deterministic non-periodic Fibonacci structures have a specific feature not present in periodic ones. Quarter-wave Fibonacci multilayers can contain more layers than periodic ones on the same length scale because they can have more layers with high index of refraction which are geometrically thinner. This allows to increase the dispersion of the structure and to decrease geometrical compression length for optical chirped pulses. Theoretical analysis has shown that this diminish can amount to as much as 10 times (compared to periodic stacks) if the refraction index contrast is high. Therefore these structures can minimize the size of compressors for chirped optical pulses. 

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