Chirping

These limitations have recently been eliminated using solid-state sources of femtosecond pulses. Most of the femtosecond dye laser teclmology that was in wide use in the late 1980s [11] has been rendered obsolete by tliree teclmical developments the self-mode-locked Ti-sapphire oscillator [23, 24, 25, 26 and 27], the chirped-pulse, solid-state amplifier (CPA) [28, 29, 30 and 31], and the non-collinearly pumped optical parametric amplifier (OPA) [32, 33 and 34]- Moreover, although a number of investigators still construct home-built systems with narrowly chosen capabilities, it is now possible to obtain versatile, nearly state-of-the-art apparatus of the type described below Ifom commercial sources. Just as home-built NMR spectrometers capable of multidimensional or solid-state spectroscopies were still being home built in the late 1970s and now are almost exclusively based on commercially prepared apparatus, it is reasonable to expect that ultrafast spectroscopy in the next decade will be conducted almost exclusively with apparatus ifom conmiercial sources based around entirely solid-state systems. 

The spectrum of the femtosecond pulse provides some infonnation on whether the input pulse is chirped, however, causing the temporal width of I(t) to be broader than expected from the Heisenberg indetenninancy relationship. 

As an example, a series of transient hole-bnming spectra obtained with a chirp-compensated continuum probe with a light-harvesting protein is shown in figure B2.1.7 [112]. As the probe delay increases, tire initially... 

Pessot M, Squier J, Mourou G and Harter D 1989 Chirped-pulse amplification of 100 fsec pulses Opt. Lett. 14 797-9... 

Le Blanc C, Grillon G, Chambaret J P, Migus A and Antonetti A 1993 Compact and efficient multipass Ti sapphire system for femtosecond chirped-pulse amplification at the terawatt level Opt. Lett. 18 140-... 

Yamaguchl S and Hamaguchl H 1995 Convenient method of measuring the chirp structure of femtosecond white-light continuum pulses App/. Spectrosc. 49 1513-15... 

Bardeen C J, Wang Q and Shank C V 1998 Femtosecond chirped pulse excitation of vibrational wave packets in bacteriorhodopsin J. Phys. Chem. A 102 2759-66... 

Belt noise can take the form of squeals and squeaks or chirps, both of which are generally more annoying than... 

The following are some of the reasons for belt squeaking, which is often described as sounding like a bird chirping ... 

The chirping rate of a cricket X, in chirps per minute near room temperature, is... 

The layout of the experimental set-up is shown in Figure 8-3. The laser source was a Ti sapphire laser system with chirped pulse amplification, which provided 140 fs pulses at 780 nm and 700 pJ energy at a repetition rate of 1 kHz. The excitation pulses at 390 nm were generated by the second harmonic of the fundamental beam in a 1-nun-thick LiB305 crystal. The pump beam was focused to a spot size of 80 pm and the excitation energy density was between 0.3 and 12 ntJ/crn2 per pulse. Pump-... 

The purpose of this work is to demonstrate that the techniques of quantum control, which were developed originally to study atoms and molecules, can be applied to the solid state. Previous work considered a simple example, the asymmetric double quantum well (ADQW). Results for this system showed that both the wave paeket dynamics and the THz emission can be controlled with simple, experimentally feasible laser pulses. This work extends the previous results to superlattices and chirped superlattices. These systems are considerably more complicated, because their dynamic phase space is much larger. They also have potential applications as solid-state devices, such as ultrafast switches or detectors. 

C15-0089. The rate at which tree crickets chirp is 190/min at 28 °C but only 39.6/min at 5 °C. From these data, calculate the energy of activation for the chirping process. 

The above set of conditions are complete in the sense that a transition from any initial state to any final state can be controlled perfectly. This idea can also be applied to multilevel problems. In the practical applications, the quadratic chirping, that is, one-period oscillation, is quite useful, as demonstrated by numerical applications given below. 

First, let us consider a selective and complete excitation in a three-level problem by quadratically chirping the laser frequency as shown in Fig. 28 [42] (the field parameter F is the laser frequency oa). The energy separation CO23... 

Figure 29. Complete excitation from 11 > to 2 > by one period of frequency chirping in the case of the three-level model. Upper part-time variation of the population. Middle part-time variation of laser frequency. Bottom part-envelope of the laser pulse. Taken from Ref. [42].

The laser frequency is a combination of three linear chirping ... 

In the above numerical examples the held parameter F is taken to be the laser frequency and the nonadiabatic transition used is the Landau-Zener type of curve-crossing. The periodic chirping method, however, can actually be more... 

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