Simulation of femtosecond pulse in a Kerr-lens mode locked Ti: sapphire laser (original) (raw)
Related papers
Pulse evolution dynamics of a femtosecond passively mode-locked Ti:sapphire laser
Optics Letters, 1992
The pulse-formation process in a femtosecond passively mode-locked Ti:sapphire laser with a saturable absorber is investigated. The time to reach the steady state is -200 As. The formation time dependence on the dye concentration and the coincidence of the steady-state pulse width with the self-mode-locked state without a saturable absorber indicate that the function of the saturable absorber is mainly to induce the initial modulation and to shorten the pulse-formation time.
2004
A full spatio-temporal model is used for analyzing the features of generation of femtosecond pulses in a Kerr-lens mode-locked laser. The developed algorithm involves the field decomposition in terms of Laguerre-Gaussian functions which are the modes of empty space. Polarization of the medium is calculated from the Bloch equations for the two-level transition. With allowance for the frequency-dependent diffraction, such a method allows us to describe generation of pulses with a duration of several femtoseconds. It is shown that diffraction results in a shift of the carrier frequency of sub-10-fs pulses toward shorter wavelengths. A multiple-pulse oscillation regime can be realized near zero group-velocity dispersion in the cavity. It is shown that such a regime can be realized in the absence of higher-order dispersion. Strong coupling between the spatial and temporal characteristics of the field is observed for the pulses with a duration of several femtoseconds. This leads to a complicated dependence of the beam size on its power and, therefore, to a complicated variation in power-dependent losses. Due to this feature, regimes of generation of ultrashort pulses cannot be correctly described by models in which power-dependent losses are introduced artificially. approximation yields good estimates for both Kerr-lens mode-locked lasers and lasers with additive mode locking . However, another scenario is observed for the high-intensity pulses with a duration of several femtoseconds. The spatial and temporal characteristics of the optical field become strongly coupled by virtue of diffraction and nonlinearity. Generation of ultrashort pulses is usually achieved near zero group-velocity dispersion. In this case, the influence of the nonlinear filtering by the aperture is comparable with the effect of soliton formation of pulses. A decrease in the pulse duration due to the joint effect of the aperture and Kerr self-focusing results in the fact that a KLM laser can generate pulses even if the group-velocity dispersion is positive . The spatial and temporal characteristics of the pulse are mutually related not only by the self-focusing but also due to diffraction in free space. Parts of a pulsed beam with different spot sizes are subjected to different phase incursions for the same propagation distance , which leads to beam-frequency modulation. In addition, diffraction of femtosecond pulses in free space is frequency-dependent . Allowance for such type of the spatio-temporal relation is required for clarifying minimum attainable durations of pulses in KLM lasers with specified configuration.
2011
The correlation between mode locked pulse and its corresponding femtosecond generation are reported. A non-self starting Ti:sapphire laser was aligned to induce mode locked pulse. The cavity length was adjusted in the range from 104 to 105 mm to stabilize the mode locked pulse train. The mode locked pulse was recorded via high speed oscilloscope at various cavity lengths in the stability region. The corresponding femtosecond pulse generation was simultaneously measured via autocorrelator. This is referred as conjugate method. The result shows that the femtosecond pulse found to be having a linear relationship with mode locked pulse with the conversion efficiency achieved up to 8%.
Group delay dispersion tuned femtosecond Kerr-lens mode-locked Ti:sapphire laser
Optics Continuum, 2022
We report on a new design for a femtosecond Ti:sapphire oscillator in which dispersion compensation is realized exclusively using mirrors, including special mirrors with third order dispersion. This makes the oscillator dynamically tunable over a spectral range of 45 nm using an intracavity wedge-pair; and it delivers 40 fs pulses at 80 MHz repetition rate. Due to the all-mirror design, the oscillator represents an attractive base for a tunable frequency comb for high precision spectroscopy applications.
Pulse Energy Optimization in Multipass-Cavity Mode-Locked Femtosecond Lasers
We describe a comprehensive model, which accounts for reflection and clipping losses of notched multipass-cavity (MPC) mode-locked lasers and determines the optimum q-preserving MPC configuration, which maximizes the output pulse energy for a given pump power. In order to make realistic predictions , an initial experimental MPC resonator with negligible clipping losses was built and its power performance was measured in order to determine the values of the fixed model parameters such as the round-trip loss of the short cavity and reflection coefficient of the MPC mirrors. Then, by using these parameters and by taking into account all possible reflection and clipping loss mechanisms, the output pulse energy for various q-preserving configurations was calculated. The simulation results indicated that, a mode-locked Ti 3+ :Sapphire laser based on the optimum MPC configuration should produce 30 nJ of pulse energy with a 3% output coupler at the pump power of 2 W. The experimental setup constructed at the optimum MPC configuration generated nearly transform-limited 74 fs pulses with 33 nJ of output pulse energy, in very good agreement with the model predictions. We believe that the model and the experimental procedure described in this paper should prove very useful in the practical design and optimization of energy-efficient MPC mode-locked lasers. Index Terms—Solid-state lasers, multi-pass cavity (MPC) solid-state lasers, mode locking, ultrafast optics.
Quantum Electronics, 1999
An analysis is made, with the aid of the selfconsistent nonlinear ABCD matrix method, of the specific features of the mechanism of passive mode locking of a femtosecond Ti : sapphire laser under conditions of pulsed synchronous pumping. The conditions of stable laser operation are studied. It is proposed to use an additional aperture as an element of negative feedback for the stabilisation of passive mode locking. Practical recommendations concerning the optimisation of a femtosecond laser are given.
Characteristics of the extreme events observed in the Kerr-lens mode-locked Ti:sapphire laser
Physical Review A, 2015
Kerr lens-mode-locked Ti:Sapphire lasers are known to display three coexistent modes of operation: continuous wave (CW), transform limited pulses (P1) and positive chirped pulses (P2). Extreme events (sometimes also called optical rogue waves), in the form of pulses of high energy appearing much often than in a Gaussian distribution, are observed in the chaotic regime of the mode P2, but not of P1. The extreme events in P2 appear unpredictably, but their separation (measured in number of round trips) is a simple combination of the numbers 11 and 12 (which were named "magic numbers"). The existence of extreme events in P2 and not in P1, and also of the magic numbers, have been successfully reproduced by numerical simulations based on a five-variables iterative map, but the intuitive insight on the physical causes has been limited. In this paper, we present evidence that the extreme events in this laser appear if the amount of self-phase modulation on the pulses is above a certain threshold. Also, that the mode P1 becomes unstable before crossing that threshold. This explains why the extreme events are observed in P2, and not in P1. Remarkably, even though the values of self-phase modulation on all the pulses (in the chaotic regime) are widely spread, the values inside the set of extreme events are relatively well-defined. Finally, the magic numbers are found to be the residuals of the periodical orbits of the "cold" laser cavity when they are perturbed by the opposite effects of a dissipative term, due to the presence of transversal apertures, and an expansive term, due to the self-focusing. PACS: 42.65.Sf, 05.45.Tp, 05.45.Pq, 05.90.+m.
Generation of 11-fs pulses from a Ti:sapphire laser without the use of prisms
Optics Letters, 1994
The generation of highly stable optical pulses as short as 11 fs from a Kerr-lens mode-locked Ti:sapphire laser containing no intracavity prisms is demonstrated. In the femtosecond oscillator design reported, novel dielectric mirrors provide broadband dispersion control for solitonlike pulse formation.
Dispersion-managed mode-locking dynamics in a Ti:sapphire laser
Physical Review A, 2006
We present what is to our knowledge the most complete 1-D numerical analysis of the evolution and the propagation dynamics of an ultrashort laser pulse in a Ti:Sapphire laser oscillator. This study confirms the dispersion managed model of mode-locking, and emphasizes the role of the Kerr nonlinearity in generating mode-locked spectra with a smooth and well − behaved spectral phase. A very good agreement with preliminary experimental measurements is found.