Passive mode locking in widebandcwsolid-state lasers

Abstract

It has been conjectured that little string theories in six dimensions are holographic to critical string theory in a linear dilaton background. We test this conjecture for theories arising on the worldvolume of heterotic fivebranes. We compute the spectrum of chiral primaries in these theories and compare with results following from type-I-heterotic duality and the AdS/CFT correspondence. We also construct holographic duals for heterotic fivebranes near orbifold singularities. Finally we find several new little string theories which have Spin(32)/Z 2 or E 8 × E 8 global symmetry but do not have a simple interpretation either in heterotic or M-theory.

Mode locking in cw solid-state lasers by linear and nonlinear frequency shifts

“…This has been achieved [14] by introducing a KTP crystal into the laser system. Therefore, the main relationships governing the behaviour of ultrashort pulses in a system with SPM and a frequency drift, which follow from Eqns (4)- (7), are in agreement with the experimental observations. This justifies a detailed analysis of this regime.…”

“…4a), as a result of which undamped oscillations appear in a pulse. The oscillations of high-energy ultrashort pulses match the oscillations of the parameters of the laser system with frequencies 1-100 MHz when these parameters deviate from the values corresponding to the zone of maximum modelocking efficiency [17,18,21]. It is worth noting that, according to Fig.…”

“…The discrete nature of the regions of existence of ultrashort pulses can be attributed to the discrete nature of the regions of efficient mode locking, pointed out earlier [21]. Within a mode-locking region there are discrete sets of parameters for which the balance of the factors that govern the transformation of ultrashort pulses in a laser system is optimal from the point of view of maintenance of the stability of the process of generation of minimum-duration pulses.…”

“…The detuning of the carrier frequency of a pulse from the centre of the pass band of a frequency-selective component may occur not only because of the Doppler effect, but also as a result of the frequency shift of the pass band itself, which happens -for example -in a Fabry-Perot interferometer with a moving mirror [18] or when the laser cavity period is modulated by rotating a prism or an optical plate. Moreover, mode locking by SPM and frequency asymmetry of the losses can occur as a result of truncation of the edge of the spectrum of a luminescence band, which may be caused by a detuning of the transmission maximum of a frequency filter from the gain maximum due to the Stark effect [20], by inhomogeneous broadening of the gain profile [21], or by introduction of an optical knife-edge between two prisms [19].…”

“…This is particularly true of the third-order nonlinearity responsible for self-phase-modulation (SPM), self-focusing, and induced nonlinear birefringence. The dependence of the phase state of a field on its intensity, which is characteristic of these effects, makes it possible to construct amplitude modulators based on them and suitable for the generation of ultrashort pulses in solid-state lasers [1][2][3][4][5][6][7].…”