Positive and negative chirping of laser pulses shorter than 100 fsec in a saturable absorber

Miranda, Rubens S.; Jacobovitz, G. R.; Cruz, Carlos Henrique de Brito; Scarparo, M. A. F.

doi:10.1364/ol.11.000224

Cited by 29 publications

(13 citation statements)

References 10 publications

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“…In this paper we report that, by the change of the incident angle to cavity mirrors instead of the exchange of mirrors in the last technique, up-chirp can be compensated. In addition, it is shown that the amount of the second-order dispersion obtained for the up-chirp compensation agrees well with a recent analytic result of chirp behaviors due to intracavity self-phase modulation [ 5 ] . Furthermore, the influence of the third-order disper- sion due to mirrors at the optimum amount of the secondorder dispersion on femtosecond pulses is estimated.…”

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confidence: 86%

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A chirp-compensation technique using incident-angle changes of cavity mirrors in a femtosecond pulse laser

Yamashita

Torizuka

Sato

1987

IEEE J. Quantum Electron.

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Abstract-A technique for chirp-compensation in a CPM laser is presented. By using the change of the incident angle to multilayef. dielectric cavity mirrors, the intracavity second-order dispersion d~ ( w ) is adjusted without any additional elements. It is confirmed that the optimum value of J(w) = +2.1 X lo-" sz obtained when up-chirp was compensated and pulses as short as 55 fs were generated is reasonable, by comparison to analytic results of chirp behaviors. In addition, the effect of the third-order dispersion & ( w ) at the optimum value of $ ( w ) on pulses is evaluated.R ECENT studies on a colliding-pulse mode-locked (CPM) CW dye laser showed that the most important thing for femtosecond pulse generation is to compensate for the frequency chirp arising from dispersion and selfphase modulation in the cavity. For the chirp compensation, there are presently four techniques as follows: 1) the down-chirp compensation by the adjustment of the optical path in a prism inserted in the cavity [l], 2) the up-chirp compensation by the adjustment of the distance between four prisms inserted in the cavity [2], 3) the up-chirp compensation by the adjustment of the incident angle to a pair of Gires-Tournois interferometers used as parts of cavity mirrors [3], and 4) the up-chirp compensation by the use of the optimum second-order dispersion (the details will be described below) due to ho/4 multilayer dielectric mirrors composing of the cavity [4]. The former three techniques necessitate the additional optical elements which furthermore complicate the optical alignment of the CPM ring laser. On the other hand, the last one has the inconvenience that cavity mirrors must be exchanged to other mirrors of different coatings to determine the optimum dispersion. In this paper we report that, by the change of the incident angle to cavity mirrors instead of the exchange of mirrors in the last technique, up-chirp can be compensated. In addition, it is shown that the amount of the second-order dispersion obtained for the up-chirp compensation agrees well with a recent analytic result of chirp behaviors due to intracavity self-phase modulation [ 5 ] . Furthermore, the influence of the third-order disper- sion due to mirrors at the optimum amount of the secondorder dispersion on femtosecond pulses is estimated.The simple CPM (R6G + DODCI) laser used without additional elements is nearly identical to the one we previously described [4], except for the following points. The intracavity second-order dispersion was varied by moving mirrors M6 and M7 to the opposite direction of each other, as shown by arrow bars in Fig. l(a). That is, the incident angles to mirrors M6 and M 7 , respectively, were varied from 45 to 60" and from 40 to 25". The details of the mirror coatings will be described below. The transmission of the output coupling mirrors ( M7 or MI ) is about 0.5 -1.0 percent around 630 nm. Pump powers of 2.4-3.2 W at 514.5 nm were provided by a CW Ar ion laser. The DODCI concentration was 5 X M/1 in a jet from a 39 pm wide noz...

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confidence: 86%

“…Miranda et al carried out a simplified analysis of frequency-chirp C ( t ) = daw ( t ) / d t imposed on femtosecond pulses interacting with a saturable absorber including the effect of nonlinear refractive index due to the solvent [5]. Their results showed that the chirp in a CPM laser remarkably depends on the intracavity pulse energy E,,.…”

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confidence: 99%

A chirp-compensation technique using incident-angle changes of cavity mirrors in a femtosecond pulse laser

Yamashita

Torizuka

Sato

1987

IEEE J. Quantum Electron.

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“…In contrast, in the SA section, the refractive index decreases as the absorption saturates [18]. Because the frequency shift increases with the degree of absorption saturation [19], this can balance the negative intracavity GVD. In the model of the saturation dynamics [19], the nonzero phase-relaxation time of the SA, T2, was not included assuming that pulse durations were longer than T2.…”

Section: Discussionmentioning

confidence: 99%

“…Because the frequency shift increases with the degree of absorption saturation [19], this can balance the negative intracavity GVD. In the model of the saturation dynamics [19], the nonzero phase-relaxation time of the SA, T2, was not included assuming that pulse durations were longer than T2. The carrier-carrier scattering time in GaN is reported to be less than 15 fs [20], so that the saturation dynamics in the SA can be applied to explain the frequency shift.…”

Section: Discussionmentioning

confidence: 99%

Intensity Correlation Analysis on Blue-Violet FemtosecondPulses from a Dispersion-Compensated GaInN Mode-LockedSemiconductor Laser Diode

Kono¹,

Koda²,

Watanabe³

et al. 2015

Applied Sciences

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Abstract:We investigated the spectral and temporal characteristics of blue-violet femtosecond optical pulses generated by a passively mode-locked GaInN laser diode in a dispersion-compensated external cavity. The output optical pulses at 400 nm were analyzed in detail by intensity auto-and cross-correlation measurements using second harmonic generation on the surface of a β-BaB2O4 crystal. The obtained results clarified wavelength-dependent chirp characteristics of the optical pulses. The analysis suggested that a large frequency shift due to saturation in the saturable absorber and gain sections played an important role in the generation of femtosecond optical pulses.

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“…In this Letter we demonstrate that the addition of high-NRI organic materials to a solution of the saturable absorber permits intracavity pulse compression in a simple CPM laser employing cavity-mirror dispersion adjustment. The NRI organic materials used have the following properties: (1) a higher NRI than that of the EG solution (n 2 = 3.0 X 10-16 cm 2 /W), 4 ' 9 (2) an ultrafast time-dependent index change by electronic hyperpolarizability, (3) high solubility for EG or a mixture of EG and benzylalcohol, (4) no absorption around the lasing wavelength region, and (5) good photochemical stability in the solution. Recent studies of high-NRI organic materials enabled us to find suitable materials that satisfy these properties.…”

mentioning

confidence: 99%

Intracavity femtosecond-pulse compression with the addition of highly nonlinear organic materials

Yamashita¹,

Torizuka²,

Sato³

1988

Opt. Lett.

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It is experimentally shown that using organic materials of high nonlinear refractive index dissolved in a saturableabsorber solution permits femtosecond-pulse compression in a simple colliding-pulse mode-locked laser employing cavity-mirror dispersion adjustment.Fast self-phase modulation 1 ' 2 (FSPM) arising from the nonlinear refractive index (NRI) of a solvent of a saturable absorber, ethylene glycol (EG), restricts direct generation of pulses shorter than 100 fsec from a colliding-pulse mode-locked (CPM) cw dye laser.3 - 6For shorter-pulse generation, therefore, compensation for the upchirp caused by the FSPM is always needed, and lossless dispersive elements are used. Furthermore, in order to compress pulses external to the laser, a dispersive NRI medium such as an optical fiber is used in conjunction with dispersive elements such as a grating pair. 7 ' 8 The NRI medium broadens the pulse spectrum without disturbing relative phases between modes, and the dispersive elements remove the chirp to generate transform-limited pulses.Recently Martinez et al. 9 theoretically showed that short, stable, solitonlike pulses are generated by. a CPM laser operating in the balance between the FSPM that is due to EG and cavity dispersion. They further concluded that the dependence of the pulse duration on its dispersion is remarkably asymmetric. More recently, Haus and Silberberg' 0 pointed out that a NRI medium introduced into a CPM laser with adjustable cavity dispersion leads to shorter, though non-soliton-like, pulses. In this case, the dependence of the pulse duration on the dispersion is symmetric.However, to the authors' knowledge, no one has experimentally investigated how the introduction of a NRI medium into a practical CPM laser influences the generation of femtosecond pulses. This may be because the additional insertion of the usual NRI medium, such as an optical fiber or a Selfoc lens, 10 gives rise to high optical losses, dispersion broadening, and further complication of the cavity configuration. In this Letter we demonstrate that the addition of high-NRI organic materials to a solution of the saturable absorber permits intracavity pulse compression in a simple CPM laser employing cavity-mirror dispersion adjustment.The NRI organic materials used have the following properties: (1) a higher NRI than that of the EG solution (n 2 = 3.0 X 10-16 cm 2 /W), 4 ' 9 (2) an ultrafast time-dependent index change by electronic hyperpolarizability, (3) high solubility for EG or a mixture of EG and benzylalcohol, (4) no absorption around the lasing wavelength region, and (5) good photochemical stability in the solution. Recent studies of high-NRI organic materials enabled us to find suitable materials that satisfy these properties."1 The third-order molecular hyperpolarizabilities, y, of paradimethylamino-3 nitrostyrenel 2 (DMA-NS) and 2'-4'-methyl nitroanilinell (MNA) are much larger than that of usual solvents (by a factor of -104).4,9 13 Therefore, from the NRI equation, 14 n 2 = 37rNy (n 2 + 2)4/81, where n is the lin...

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Positive and negative chirping of laser pulses shorter than 100 fsec in a saturable absorber

Cited by 29 publications

References 10 publications

A chirp-compensation technique using incident-angle changes of cavity mirrors in a femtosecond pulse laser

A chirp-compensation technique using incident-angle changes of cavity mirrors in a femtosecond pulse laser

Intensity Correlation Analysis on Blue-Violet FemtosecondPulses from a Dispersion-Compensated GaInN Mode-LockedSemiconductor Laser Diode

Intracavity femtosecond-pulse compression with the addition of highly nonlinear organic materials

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