Oscillator, from amplifier

To make an oscillator from an amplifier requires, in the language of electronics, positive feedback. In lasers this is provided by the active medium being between two mirrors, both of them highly reflecting but one rather less so in order to allow some of the stimulated radiation to leak out and form the laser beam. The region bounded by the mirrors is called the laser cavity. Various mirror systems are used but that shown in Figure 9.1, consisting of... 

Townes s academic life continued. He served as provost of MIT from 1961 to 1966. In 1964, Townes received the Nobel Prize in physics for work in quantum electronics leading to construction of oscillators and amplifiers based on the maser-laser principle. He was named university professor at the University of California-Berkeley in 1967. There he worked for more than 20 years in astrophysics. Ironically, this field is one of many that were transformed by die laser, and Townes often tised lasers in his subsequent research. 

Two femtosecond laser pulses were used in the experiment of FS TR SEP ED. One pulse was used as a pump source to excite the molecule to the electronically excited state, to generate fluorescence. The other, with a specific delay time, was used to perform SEP from the electronic excited states to the ground state. The variation of the decrease in the fluorescence induced by the SEP with delay time reflects vibrational relaxation in the excited states. A homemade regenerative amplified self-mode-locking Ti sapphire femtosecond laser, whose oscillator and amplifier... 

Fig.7.43, Infrared Raman waveguide laser in compressed H2, pumped by a dye laser. The frequency doubled output beam from an Nd YAG laser is reduced in diameter by an inverted beam expander and partioned between the oscillator and amplifier dye cell. The dye oscillator resonator is composed of mirror M, grating G, and beam-expanding prism BEP [7.96]...

In order to achieve a reasonable signal strength from the nonlinear response of approximately one atomic monolayer at an interface, a laser source with high peak power is generally required. Conuuon sources include Q-switched ( 10 ns pulsewidth) and mode-locked ( 100 ps) Nd YAG lasers, and mode-locked ( 10 fs-1 ps) Ti sapphire lasers. Broadly tunable sources have traditionally been based on dye lasers. More recently, optical parametric oscillator/amplifier (OPO/OPA) systems are coming into widespread use for tunable sources of both visible and infrared radiation. 

Examples of such situations are very numerous perhaps the best known example is the transition of the performance of an electronic circuit from regenerative amplification to the generation of oscillations. The parameter A in this case is the coefficient of mutual inductance between the anode and the grid circuits. As long as A < A0, the circuit functions as amplifier whose coefficient of amplification gradually... 

This particular bifurcation exists in the example from electronics mentioned above the regenerative amplifier has as its phase portrait SUS and after the bifurcation it becomes simply US, that is, an ordinary oscillator. 

Figure 13.12. Images and electrical measurements of integrated circuits that use semiconductor wires and ribbons on plastic, (a) Silicon ribbon five-stage ring oscillator and (b) differential amplifier. (Reprinted with permission from Ref. 87. Copyright 2007 American Institute of Physics.) (c) GaAs logic gates. (Reprinted with permission from Ref. 86. Copyright 2006 Wiley-VCH Verlag.)...

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