Pumps optical

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. 

Optical pumping, 14 658. See also Pumping Optical recording, polymethine dyes in, 20 516... 

The large molar extinction coefficients of the spin-allowed CT transitions make them much easier to pump optically. The intense 454-nm visible band of Ru(bpy)32+is an MLCT transition. 

Chance and co-workers have designed a flow system where the protein is continuously pumped optically using a tungsten or xenon flash lamp (764 nm). Using continuous illumination for various times and temperatures. Chance et al. have observed three intermediate states upon MbCO photolysis. At 40 K, a state with a recombination rate constant of 2 x 10 /s has been identified from two slower states with rate constants of 10 /s. 

Khaydarov, J. D., Andrews, J. H., and Singer, K. D. 1994. Pulse compression in a synchronously pumped optical parametric oscillator from group-velocity mismatch. Opt. Lett. 19 831-33. 

The simplest and most straightforward idea for producing collisionally polarized molecules in a thermal cell consists of using collisions with the participation of particles which are polarized in the laboratory frame. It seems that the earliest one was the method based on collisions of atoms which have been optically pumped (optically oriented in their ground state) by the Kastler method see Section 1.1, Fig. 1.1. If the gas constitutes a mixture of a molecular and an atomic component, the conditions being specially created in such a way as to produce such optical orientation of the atoms, we must expect, from considerations of spin conservation in molecular reactions, that polarization of the molecular component must also emerge. 

An approach to full spectroscopic near-field imaging in the IR range was presented by Michaels et al. [62], whose illumination-mode a-SNOM set-up was based on a Ti sapphire-pumped optical parametric amplifier (OPA) coupled into a tapered fluoride glass optical fiber. The OPA system provides tunable broadband IR radiation with output powers in the miUi Watt range. After passing the thin film sample, the transmitted fight is collected by a Cap2 lens and coupled into a monochromator with a detector array. Broadband illumination with a bandwidth... 

A wide range of laboratory high-pressure equipment, such as vessels, pumps, optical cells, valves, and tubing, mostly to 4 kbar... 

Fig. 10 Cross-sectional outline of the microcavity fluidic dye laser. The laser dye is pumped through a microfluidic channel. The laser cavity is formed mside the microfluidic channel by metal mirrors, deposited on the top and bottom glass wafers. The microcavity fluidic dye laser is pumped optically by an external laser, and output is emitted through the semitransparent top mirror (Reprinted from [149] with permission of lOP Publishing)...

Pth is the pumping optical power necessary to reach threshold and is linearly proportional to the threshold generation rate of excitons, Gth- Thus, if the introduction of an analyte causes the overall relaxation rate (732) to change then the quenched laser power becomes... 

Doppler-free two-photon spectroscopy or with two-step excitation (Sect. 5.4). For illustration, Fig. 8.5 illustrates pressure broadening and shifts of a rotational transition to a Rydberg level of the Li2 molecule measured with Doppler-free OODR polarization spectroscopy (Sect. 5.5) in a lithium/argon heat pipe [980], where the intermediate level B(v, J ) was pumped optically by a circularly polarized pump laser. For the chosen temperature and pressure conditions the argon is confined to the cooled outer parts of the heat pipe, and the center of the heat pipe contains pure lithium vapor (98 % Li atoms and 2 % Li2 molecules) with a total vapor pressure p(Li) = p(Ar) up to argon pressures of 0.7 mbar. The observed pressure broadening and shift in this range p < 0.7 mbar are therefore caused by Li + Li collisions. 

Because the irradiating laser beam is pulsed, MALDI is optimally combined with a TOP mass analyzer. The unlimited mass range of TOP and its ability to acquire the entire spectrum from a single laser pulse event are other factors in favor of the MALDI/TOF-MS combination. MALDI-TOF has become a well-known acronym for many researchers. Quadrupole, ion trap, and Fourier transform ion cyclotron resonance (FT-ICR) instruments have also been modified to accommodate MALDI. A schematic diagram of MALDI/TOF-MS is presented in Figure 2.10. A variety of laser systems has found applications in MALDI analysis, and the most common ones use LTV lasers such as the N2 laser (337 nm), the frequency-tripled (355 nm) and frequency-quadrupled (266 nm) Nd YAG laser, and the ArF excimer laser (193 nm). IR lasers have also been used to produce the MALDI effect. The transversely excited atmospheric (TEA) CO2 laser (10.6 p,m), the Q-switched Er YAG laser (2.94 (im), and the CriLiSAF or Nd YAG pumped optical parametric oscillator (OPO) laser (3.28 p,m) are the common IR lasers. UV and IR lasers yield similar spectra for proteins, although better resolution has been obtained for some proteins with an IR laser. 

Typical optical power output levels in standard singlestripe diode lasers are on the order of several milliwatts. These power levels are adequate for many commercial applications that use diode lasers, such as fiber communications, optical discs, etc. However, for many other applications, such as optical pumping, optical time-domain re-flectometry, laser radar, and nonlinear optics, these power levels are not sufficient. 

Most of the optical isolators are designed to be functional with wavelength windows of 850, 1310, and 1550 nm for optical communication applications and with wavelength windows of 980 and 1480 nm for pumping optical amplifiers. Performances of an optical isolator are mainly determined by the insertion loss and isolation. An ideal optical isolator would have zero insertion loss and infinite isolation. There are two types of optical isolators one is a polarization-dependent optical isolator which only functions for a linearly polarized light in forward direction, and the other is a polarization-independent... 

Solid state lasers are especially of interest for laser ablation. The laser medium is a crystal or a glass, doped with a transition metal. The medium is pumped optically by flash-lamps (discharges of 100-1000 J over a few ms) or continuously with a tungsten - halogen lamp. The resonator may be the space between two flat mirrors, or an ellipsoid, with the laser rod at one focus and the flash-lamp at the other. The ruby laser emits in the visible region (694.3 nm). It is thermally very robust, but... 

K. Zhao, S. Jackson Highly efficient free-running cascaded Raman fiber laser that uses broadband pumping. Optics Express 13, 4731 (2005)... 

Fig. 2.2. Experimental setup (as used for the investigations on NasB). An argon ion laser (ps mode-locked fs all lines, visible) pumps either a femtosecond laser system (a) (OPO synchronously pumped optical parametric oscillator SHG second-harmonic generator) or a picosecond laser system (b) (taken from [178]). The pulse duration and spectral width of the laser pulses are measured by an autocorrelator (A) and a spectrometer (S) respectively. A Michelson arrangement allows the probe pulses to be delayed At) with respect to the pump pulses. A quadrupole mass filter (QMS) enables the selection of the ensemble of investigated molecules ionized by a pump probe cycle. A secondary electron multiplier (SEM) detects the intensity I of the ions as a function of the delay time At. A Langmuir-Taylor detector (LTD) measures the total intensity /o of the cluster beam. The ratio I/Iq as a function of the delay time At is called the real-time spectrum...

Here, the principal features and characteristics of the ultrafast laser systems used are briefly summarized. Besides the titanium sapphire laser which acts as the workhorse in nearly all of the discussed experiments, a synchronously pumped dye laser is employed to study the ultrafast dynamics of Nas on a picosecond timescale (see Sect. 3.2.2). For measurements with femtosecond time resolution and wavelengths located between 600 and 625 nm a synchronously titanium sapphire pumped optical parametric oscillator followed by frequency doubling is used. To investigate the Nas C state, two mode-locked titanium sapphire lasers have been synchronized. In all cases the essential parameter of the generated laser pulses, the pulse width, has to be determined. This problem is solved by an autocorrelation technique. Hence, the principles of an autocorrelator are briefly described at the end of this section. 

Synchronously Pumped Optical Parametric Oscillator. Optical parametric oscillators (OPOs) were first used in the mid-1960s as an alternative to dye lasers for generating coherent radiation tunable over a wide wavelength region [204, 205]. It is only recently, however, that OPOs have become a practical reality with the advent of new high-quality, nonlinear optical materials and high-power, mode-locked pump sources [206-211]. 

In order to produce wavelengths around 600 nm (as required for the Naa B state investigations, see Sect. 3.2.4), a synchronously pumped optical parametric oscillator (Spectra Physics model Opal) (Fig. 2.10) is used, generating... 

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